Pg to bun (#148)

* start moving to bun

* changing more stuff

* more

* and yet more

* tests passing

* seems stable now

* more big changes

* small fix

* little fixes

vendor/golang.org/x/text/cases/cases.go

@@ -0,0 +1,162 @@
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:generate go run gen.go gen_trieval.go
+
+// Package cases provides general and language-specific case mappers.
+package cases // import "golang.org/x/text/cases"
+
+import (
+	"golang.org/x/text/language"
+	"golang.org/x/text/transform"
+)
+
+// References:
+// - Unicode Reference Manual Chapter 3.13, 4.2, and 5.18.
+// - https://www.unicode.org/reports/tr29/
+// - https://www.unicode.org/Public/6.3.0/ucd/CaseFolding.txt
+// - https://www.unicode.org/Public/6.3.0/ucd/SpecialCasing.txt
+// - https://www.unicode.org/Public/6.3.0/ucd/DerivedCoreProperties.txt
+// - https://www.unicode.org/Public/6.3.0/ucd/auxiliary/WordBreakProperty.txt
+// - https://www.unicode.org/Public/6.3.0/ucd/auxiliary/WordBreakTest.txt
+// - http://userguide.icu-project.org/transforms/casemappings
+
+// TODO:
+// - Case folding
+// - Wide and Narrow?
+// - Segmenter option for title casing.
+// - ASCII fast paths
+// - Encode Soft-Dotted property within trie somehow.
+
+// A Caser transforms given input to a certain case. It implements
+// transform.Transformer.
+//
+// A Caser may be stateful and should therefore not be shared between
+// goroutines.
+type Caser struct {
+	t transform.SpanningTransformer
+}
+
+// Bytes returns a new byte slice with the result of converting b to the case
+// form implemented by c.
+func (c Caser) Bytes(b []byte) []byte {
+	b, _, _ = transform.Bytes(c.t, b)
+	return b
+}
+
+// String returns a string with the result of transforming s to the case form
+// implemented by c.
+func (c Caser) String(s string) string {
+	s, _, _ = transform.String(c.t, s)
+	return s
+}
+
+// Reset resets the Caser to be reused for new input after a previous call to
+// Transform.
+func (c Caser) Reset() { c.t.Reset() }
+
+// Transform implements the transform.Transformer interface and transforms the
+// given input to the case form implemented by c.
+func (c Caser) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
+	return c.t.Transform(dst, src, atEOF)
+}
+
+// Span implements the transform.SpanningTransformer interface.
+func (c Caser) Span(src []byte, atEOF bool) (n int, err error) {
+	return c.t.Span(src, atEOF)
+}
+
+// Upper returns a Caser for language-specific uppercasing.
+func Upper(t language.Tag, opts ...Option) Caser {
+	return Caser{makeUpper(t, getOpts(opts...))}
+}
+
+// Lower returns a Caser for language-specific lowercasing.
+func Lower(t language.Tag, opts ...Option) Caser {
+	return Caser{makeLower(t, getOpts(opts...))}
+}
+
+// Title returns a Caser for language-specific title casing. It uses an
+// approximation of the default Unicode Word Break algorithm.
+func Title(t language.Tag, opts ...Option) Caser {
+	return Caser{makeTitle(t, getOpts(opts...))}
+}
+
+// Fold returns a Caser that implements Unicode case folding. The returned Caser
+// is stateless and safe to use concurrently by multiple goroutines.
+//
+// Case folding does not normalize the input and may not preserve a normal form.
+// Use the collate or search package for more convenient and linguistically
+// sound comparisons. Use golang.org/x/text/secure/precis for string comparisons
+// where security aspects are a concern.
+func Fold(opts ...Option) Caser {
+	return Caser{makeFold(getOpts(opts...))}
+}
+
+// An Option is used to modify the behavior of a Caser.
+type Option func(o options) options
+
+// TODO: consider these options to take a boolean as well, like FinalSigma.
+// The advantage of using this approach is that other providers of a lower-case
+// algorithm could set different defaults by prefixing a user-provided slice
+// of options with their own. This is handy, for instance, for the precis
+// package which would override the default to not handle the Greek final sigma.
+
+var (
+	// NoLower disables the lowercasing of non-leading letters for a title
+	// caser.
+	NoLower Option = noLower
+
+	// Compact omits mappings in case folding for characters that would grow the
+	// input. (Unimplemented.)
+	Compact Option = compact
+)
+
+// TODO: option to preserve a normal form, if applicable?
+
+type options struct {
+	noLower bool
+	simple  bool
+
+	// TODO: segmenter, max ignorable, alternative versions, etc.
+
+	ignoreFinalSigma bool
+}
+
+func getOpts(o ...Option) (res options) {
+	for _, f := range o {
+		res = f(res)
+	}
+	return
+}
+
+func noLower(o options) options {
+	o.noLower = true
+	return o
+}
+
+func compact(o options) options {
+	o.simple = true
+	return o
+}
+
+// HandleFinalSigma specifies whether the special handling of Greek final sigma
+// should be enabled. Unicode prescribes handling the Greek final sigma for all
+// locales, but standards like IDNA and PRECIS override this default.
+func HandleFinalSigma(enable bool) Option {
+	if enable {
+		return handleFinalSigma
+	}
+	return ignoreFinalSigma
+}
+
+func ignoreFinalSigma(o options) options {
+	o.ignoreFinalSigma = true
+	return o
+}
+
+func handleFinalSigma(o options) options {
+	o.ignoreFinalSigma = false
+	return o
+}

vendor/golang.org/x/text/cases/context.go

@@ -0,0 +1,376 @@
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package cases
+
+import "golang.org/x/text/transform"
+
+// A context is used for iterating over source bytes, fetching case info and
+// writing to a destination buffer.
+//
+// Casing operations may need more than one rune of context to decide how a rune
+// should be cased. Casing implementations should call checkpoint on context
+// whenever it is known to be safe to return the runes processed so far.
+//
+// It is recommended for implementations to not allow for more than 30 case
+// ignorables as lookahead (analogous to the limit in norm) and to use state if
+// unbounded lookahead is needed for cased runes.
+type context struct {
+	dst, src []byte
+	atEOF    bool
+
+	pDst int // pDst points past the last written rune in dst.
+	pSrc int // pSrc points to the start of the currently scanned rune.
+
+	// checkpoints safe to return in Transform, where nDst <= pDst and nSrc <= pSrc.
+	nDst, nSrc int
+	err        error
+
+	sz   int  // size of current rune
+	info info // case information of currently scanned rune
+
+	// State preserved across calls to Transform.
+	isMidWord bool // false if next cased letter needs to be title-cased.
+}
+
+func (c *context) Reset() {
+	c.isMidWord = false
+}
+
+// ret returns the return values for the Transform method. It checks whether
+// there were insufficient bytes in src to complete and introduces an error
+// accordingly, if necessary.
+func (c *context) ret() (nDst, nSrc int, err error) {
+	if c.err != nil || c.nSrc == len(c.src) {
+		return c.nDst, c.nSrc, c.err
+	}
+	// This point is only reached by mappers if there was no short destination
+	// buffer. This means that the source buffer was exhausted and that c.sz was
+	// set to 0 by next.
+	if c.atEOF && c.pSrc == len(c.src) {
+		return c.pDst, c.pSrc, nil
+	}
+	return c.nDst, c.nSrc, transform.ErrShortSrc
+}
+
+// retSpan returns the return values for the Span method. It checks whether
+// there were insufficient bytes in src to complete and introduces an error
+// accordingly, if necessary.
+func (c *context) retSpan() (n int, err error) {
+	_, nSrc, err := c.ret()
+	return nSrc, err
+}
+
+// checkpoint sets the return value buffer points for Transform to the current
+// positions.
+func (c *context) checkpoint() {
+	if c.err == nil {
+		c.nDst, c.nSrc = c.pDst, c.pSrc+c.sz
+	}
+}
+
+// unreadRune causes the last rune read by next to be reread on the next
+// invocation of next. Only one unreadRune may be called after a call to next.
+func (c *context) unreadRune() {
+	c.sz = 0
+}
+
+func (c *context) next() bool {
+	c.pSrc += c.sz
+	if c.pSrc == len(c.src) || c.err != nil {
+		c.info, c.sz = 0, 0
+		return false
+	}
+	v, sz := trie.lookup(c.src[c.pSrc:])
+	c.info, c.sz = info(v), sz
+	if c.sz == 0 {
+		if c.atEOF {
+			// A zero size means we have an incomplete rune. If we are atEOF,
+			// this means it is an illegal rune, which we will consume one
+			// byte at a time.
+			c.sz = 1
+		} else {
+			c.err = transform.ErrShortSrc
+			return false
+		}
+	}
+	return true
+}
+
+// writeBytes adds bytes to dst.
+func (c *context) writeBytes(b []byte) bool {
+	if len(c.dst)-c.pDst < len(b) {
+		c.err = transform.ErrShortDst
+		return false
+	}
+	// This loop is faster than using copy.
+	for _, ch := range b {
+		c.dst[c.pDst] = ch
+		c.pDst++
+	}
+	return true
+}
+
+// writeString writes the given string to dst.
+func (c *context) writeString(s string) bool {
+	if len(c.dst)-c.pDst < len(s) {
+		c.err = transform.ErrShortDst
+		return false
+	}
+	// This loop is faster than using copy.
+	for i := 0; i < len(s); i++ {
+		c.dst[c.pDst] = s[i]
+		c.pDst++
+	}
+	return true
+}
+
+// copy writes the current rune to dst.
+func (c *context) copy() bool {
+	return c.writeBytes(c.src[c.pSrc : c.pSrc+c.sz])
+}
+
+// copyXOR copies the current rune to dst and modifies it by applying the XOR
+// pattern of the case info. It is the responsibility of the caller to ensure
+// that this is a rune with a XOR pattern defined.
+func (c *context) copyXOR() bool {
+	if !c.copy() {
+		return false
+	}
+	if c.info&xorIndexBit == 0 {
+		// Fast path for 6-bit XOR pattern, which covers most cases.
+		c.dst[c.pDst-1] ^= byte(c.info >> xorShift)
+	} else {
+		// Interpret XOR bits as an index.
+		// TODO: test performance for unrolling this loop. Verify that we have
+		// at least two bytes and at most three.
+		idx := c.info >> xorShift
+		for p := c.pDst - 1; ; p-- {
+			c.dst[p] ^= xorData[idx]
+			idx--
+			if xorData[idx] == 0 {
+				break
+			}
+		}
+	}
+	return true
+}
+
+// hasPrefix returns true if src[pSrc:] starts with the given string.
+func (c *context) hasPrefix(s string) bool {
+	b := c.src[c.pSrc:]
+	if len(b) < len(s) {
+		return false
+	}
+	for i, c := range b[:len(s)] {
+		if c != s[i] {
+			return false
+		}
+	}
+	return true
+}
+
+// caseType returns an info with only the case bits, normalized to either
+// cLower, cUpper, cTitle or cUncased.
+func (c *context) caseType() info {
+	cm := c.info & 0x7
+	if cm < 4 {
+		return cm
+	}
+	if cm >= cXORCase {
+		// xor the last bit of the rune with the case type bits.
+		b := c.src[c.pSrc+c.sz-1]
+		return info(b&1) ^ cm&0x3
+	}
+	if cm == cIgnorableCased {
+		return cLower
+	}
+	return cUncased
+}
+
+// lower writes the lowercase version of the current rune to dst.
+func lower(c *context) bool {
+	ct := c.caseType()
+	if c.info&hasMappingMask == 0 || ct == cLower {
+		return c.copy()
+	}
+	if c.info&exceptionBit == 0 {
+		return c.copyXOR()
+	}
+	e := exceptions[c.info>>exceptionShift:]
+	offset := 2 + e[0]&lengthMask // size of header + fold string
+	if nLower := (e[1] >> lengthBits) & lengthMask; nLower != noChange {
+		return c.writeString(e[offset : offset+nLower])
+	}
+	return c.copy()
+}
+
+func isLower(c *context) bool {
+	ct := c.caseType()
+	if c.info&hasMappingMask == 0 || ct == cLower {
+		return true
+	}
+	if c.info&exceptionBit == 0 {
+		c.err = transform.ErrEndOfSpan
+		return false
+	}
+	e := exceptions[c.info>>exceptionShift:]
+	if nLower := (e[1] >> lengthBits) & lengthMask; nLower != noChange {
+		c.err = transform.ErrEndOfSpan
+		return false
+	}
+	return true
+}
+
+// upper writes the uppercase version of the current rune to dst.
+func upper(c *context) bool {
+	ct := c.caseType()
+	if c.info&hasMappingMask == 0 || ct == cUpper {
+		return c.copy()
+	}
+	if c.info&exceptionBit == 0 {
+		return c.copyXOR()
+	}
+	e := exceptions[c.info>>exceptionShift:]
+	offset := 2 + e[0]&lengthMask // size of header + fold string
+	// Get length of first special case mapping.
+	n := (e[1] >> lengthBits) & lengthMask
+	if ct == cTitle {
+		// The first special case mapping is for lower. Set n to the second.
+		if n == noChange {
+			n = 0
+		}
+		n, e = e[1]&lengthMask, e[n:]
+	}
+	if n != noChange {
+		return c.writeString(e[offset : offset+n])
+	}
+	return c.copy()
+}
+
+// isUpper writes the isUppercase version of the current rune to dst.
+func isUpper(c *context) bool {
+	ct := c.caseType()
+	if c.info&hasMappingMask == 0 || ct == cUpper {
+		return true
+	}
+	if c.info&exceptionBit == 0 {
+		c.err = transform.ErrEndOfSpan
+		return false
+	}
+	e := exceptions[c.info>>exceptionShift:]
+	// Get length of first special case mapping.
+	n := (e[1] >> lengthBits) & lengthMask
+	if ct == cTitle {
+		n = e[1] & lengthMask
+	}
+	if n != noChange {
+		c.err = transform.ErrEndOfSpan
+		return false
+	}
+	return true
+}
+
+// title writes the title case version of the current rune to dst.
+func title(c *context) bool {
+	ct := c.caseType()
+	if c.info&hasMappingMask == 0 || ct == cTitle {
+		return c.copy()
+	}
+	if c.info&exceptionBit == 0 {
+		if ct == cLower {
+			return c.copyXOR()
+		}
+		return c.copy()
+	}
+	// Get the exception data.
+	e := exceptions[c.info>>exceptionShift:]
+	offset := 2 + e[0]&lengthMask // size of header + fold string
+
+	nFirst := (e[1] >> lengthBits) & lengthMask
+	if nTitle := e[1] & lengthMask; nTitle != noChange {
+		if nFirst != noChange {
+			e = e[nFirst:]
+		}
+		return c.writeString(e[offset : offset+nTitle])
+	}
+	if ct == cLower && nFirst != noChange {
+		// Use the uppercase version instead.
+		return c.writeString(e[offset : offset+nFirst])
+	}
+	// Already in correct case.
+	return c.copy()
+}
+
+// isTitle reports whether the current rune is in title case.
+func isTitle(c *context) bool {
+	ct := c.caseType()
+	if c.info&hasMappingMask == 0 || ct == cTitle {
+		return true
+	}
+	if c.info&exceptionBit == 0 {
+		if ct == cLower {
+			c.err = transform.ErrEndOfSpan
+			return false
+		}
+		return true
+	}
+	// Get the exception data.
+	e := exceptions[c.info>>exceptionShift:]
+	if nTitle := e[1] & lengthMask; nTitle != noChange {
+		c.err = transform.ErrEndOfSpan
+		return false
+	}
+	nFirst := (e[1] >> lengthBits) & lengthMask
+	if ct == cLower && nFirst != noChange {
+		c.err = transform.ErrEndOfSpan
+		return false
+	}
+	return true
+}
+
+// foldFull writes the foldFull version of the current rune to dst.
+func foldFull(c *context) bool {
+	if c.info&hasMappingMask == 0 {
+		return c.copy()
+	}
+	ct := c.caseType()
+	if c.info&exceptionBit == 0 {
+		if ct != cLower || c.info&inverseFoldBit != 0 {
+			return c.copyXOR()
+		}
+		return c.copy()
+	}
+	e := exceptions[c.info>>exceptionShift:]
+	n := e[0] & lengthMask
+	if n == 0 {
+		if ct == cLower {
+			return c.copy()
+		}
+		n = (e[1] >> lengthBits) & lengthMask
+	}
+	return c.writeString(e[2 : 2+n])
+}
+
+// isFoldFull reports whether the current run is mapped to foldFull
+func isFoldFull(c *context) bool {
+	if c.info&hasMappingMask == 0 {
+		return true
+	}
+	ct := c.caseType()
+	if c.info&exceptionBit == 0 {
+		if ct != cLower || c.info&inverseFoldBit != 0 {
+			c.err = transform.ErrEndOfSpan
+			return false
+		}
+		return true
+	}
+	e := exceptions[c.info>>exceptionShift:]
+	n := e[0] & lengthMask
+	if n == 0 && ct == cLower {
+		return true
+	}
+	c.err = transform.ErrEndOfSpan
+	return false
+}

vendor/golang.org/x/text/cases/fold.go

@@ -0,0 +1,34 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package cases
+
+import "golang.org/x/text/transform"
+
+type caseFolder struct{ transform.NopResetter }
+
+// caseFolder implements the Transformer interface for doing case folding.
+func (t *caseFolder) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
+	c := context{dst: dst, src: src, atEOF: atEOF}
+	for c.next() {
+		foldFull(&c)
+		c.checkpoint()
+	}
+	return c.ret()
+}
+
+func (t *caseFolder) Span(src []byte, atEOF bool) (n int, err error) {
+	c := context{src: src, atEOF: atEOF}
+	for c.next() && isFoldFull(&c) {
+		c.checkpoint()
+	}
+	return c.retSpan()
+}
+
+func makeFold(o options) transform.SpanningTransformer {
+	// TODO: Special case folding, through option Language, Special/Turkic, or
+	// both.
+	// TODO: Implement Compact options.
+	return &caseFolder{}
+}

vendor/golang.org/x/text/cases/icu.go

@@ -0,0 +1,62 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build icu
+// +build icu
+
+package cases
+
+// Ideally these functions would be defined in a test file, but go test doesn't
+// allow CGO in tests. The build tag should ensure either way that these
+// functions will not end up in the package.
+
+// TODO: Ensure that the correct ICU version is set.
+
+/*
+#cgo LDFLAGS: -licui18n.57 -licuuc.57
+#include <stdlib.h>
+#include <unicode/ustring.h>
+#include <unicode/utypes.h>
+#include <unicode/localpointer.h>
+#include <unicode/ucasemap.h>
+*/
+import "C"
+
+import "unsafe"
+
+func doICU(tag, caser, input string) string {
+	err := C.UErrorCode(0)
+	loc := C.CString(tag)
+	cm := C.ucasemap_open(loc, C.uint32_t(0), &err)
+
+	buf := make([]byte, len(input)*4)
+	dst := (*C.char)(unsafe.Pointer(&buf[0]))
+	src := C.CString(input)
+
+	cn := C.int32_t(0)
+
+	switch caser {
+	case "fold":
+		cn = C.ucasemap_utf8FoldCase(cm,
+			dst, C.int32_t(len(buf)),
+			src, C.int32_t(len(input)),
+			&err)
+	case "lower":
+		cn = C.ucasemap_utf8ToLower(cm,
+			dst, C.int32_t(len(buf)),
+			src, C.int32_t(len(input)),
+			&err)
+	case "upper":
+		cn = C.ucasemap_utf8ToUpper(cm,
+			dst, C.int32_t(len(buf)),
+			src, C.int32_t(len(input)),
+			&err)
+	case "title":
+		cn = C.ucasemap_utf8ToTitle(cm,
+			dst, C.int32_t(len(buf)),
+			src, C.int32_t(len(input)),
+			&err)
+	}
+	return string(buf[:cn])
+}

vendor/golang.org/x/text/cases/info.go

@@ -0,0 +1,82 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package cases
+
+func (c info) cccVal() info {
+	if c&exceptionBit != 0 {
+		return info(exceptions[c>>exceptionShift]) & cccMask
+	}
+	return c & cccMask
+}
+
+func (c info) cccType() info {
+	ccc := c.cccVal()
+	if ccc <= cccZero {
+		return cccZero
+	}
+	return ccc
+}
+
+// TODO: Implement full Unicode breaking algorithm:
+// 1) Implement breaking in separate package.
+// 2) Use the breaker here.
+// 3) Compare table size and performance of using the more generic breaker.
+//
+// Note that we can extend the current algorithm to be much more accurate. This
+// only makes sense, though, if the performance and/or space penalty of using
+// the generic breaker is big. Extra data will only be needed for non-cased
+// runes, which means there are sufficient bits left in the caseType.
+// ICU prohibits breaking in such cases as well.
+
+// For the purpose of title casing we use an approximation of the Unicode Word
+// Breaking algorithm defined in Annex #29:
+// https://www.unicode.org/reports/tr29/#Default_Grapheme_Cluster_Table.
+//
+// For our approximation, we group the Word Break types into the following
+// categories, with associated rules:
+//
+// 1) Letter:
+//    ALetter, Hebrew_Letter, Numeric, ExtendNumLet, Extend, Format_FE, ZWJ.
+//    Rule: Never break between consecutive runes of this category.
+//
+// 2) Mid:
+//    MidLetter, MidNumLet, Single_Quote.
+//    (Cf. case-ignorable: MidLetter, MidNumLet, Single_Quote or cat is Mn,
+//    Me, Cf, Lm or Sk).
+//    Rule: Don't break between Letter and Mid, but break between two Mids.
+//
+// 3) Break:
+//    Any other category: NewLine, MidNum, CR, LF, Double_Quote, Katakana, and
+//    Other.
+//    These categories should always result in a break between two cased letters.
+//    Rule: Always break.
+//
+// Note 1: the Katakana and MidNum categories can, in esoteric cases, result in
+// preventing a break between two cased letters. For now we will ignore this
+// (e.g. [ALetter] [ExtendNumLet] [Katakana] [ExtendNumLet] [ALetter] and
+// [ALetter] [Numeric] [MidNum] [Numeric] [ALetter].)
+//
+// Note 2: the rule for Mid is very approximate, but works in most cases. To
+// improve, we could store the categories in the trie value and use a FA to
+// manage breaks. See TODO comment above.
+//
+// Note 3: according to the spec, it is possible for the Extend category to
+// introduce breaks between other categories grouped in Letter. However, this
+// is undesirable for our purposes. ICU prevents breaks in such cases as well.
+
+// isBreak returns whether this rune should introduce a break.
+func (c info) isBreak() bool {
+	return c.cccVal() == cccBreak
+}
+
+// isLetter returns whether the rune is of break type ALetter, Hebrew_Letter,
+// Numeric, ExtendNumLet, or Extend.
+func (c info) isLetter() bool {
+	ccc := c.cccVal()
+	if ccc == cccZero {
+		return !c.isCaseIgnorable()
+	}
+	return ccc != cccBreak
+}

vendor/golang.org/x/text/cases/map.go

@@ -0,0 +1,816 @@
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package cases
+
+// This file contains the definitions of case mappings for all supported
+// languages. The rules for the language-specific tailorings were taken and
+// modified from the CLDR transform definitions in common/transforms.
+
+import (
+	"strings"
+	"unicode"
+	"unicode/utf8"
+
+	"golang.org/x/text/internal"
+	"golang.org/x/text/language"
+	"golang.org/x/text/transform"
+	"golang.org/x/text/unicode/norm"
+)
+
+// A mapFunc takes a context set to the current rune and writes the mapped
+// version to the same context. It may advance the context to the next rune. It
+// returns whether a checkpoint is possible: whether the pDst bytes written to
+// dst so far won't need changing as we see more source bytes.
+type mapFunc func(*context) bool
+
+// A spanFunc takes a context set to the current rune and returns whether this
+// rune would be altered when written to the output. It may advance the context
+// to the next rune. It returns whether a checkpoint is possible.
+type spanFunc func(*context) bool
+
+// maxIgnorable defines the maximum number of ignorables to consider for
+// lookahead operations.
+const maxIgnorable = 30
+
+// supported lists the language tags for which we have tailorings.
+const supported = "und af az el lt nl tr"
+
+func init() {
+	tags := []language.Tag{}
+	for _, s := range strings.Split(supported, " ") {
+		tags = append(tags, language.MustParse(s))
+	}
+	matcher = internal.NewInheritanceMatcher(tags)
+	Supported = language.NewCoverage(tags)
+}
+
+var (
+	matcher *internal.InheritanceMatcher
+
+	Supported language.Coverage
+
+	// We keep the following lists separate, instead of having a single per-
+	// language struct, to give the compiler a chance to remove unused code.
+
+	// Some uppercase mappers are stateless, so we can precompute the
+	// Transformers and save a bit on runtime allocations.
+	upperFunc = []struct {
+		upper mapFunc
+		span  spanFunc
+	}{
+		{nil, nil},                  // und
+		{nil, nil},                  // af
+		{aztrUpper(upper), isUpper}, // az
+		{elUpper, noSpan},           // el
+		{ltUpper(upper), noSpan},    // lt
+		{nil, nil},                  // nl
+		{aztrUpper(upper), isUpper}, // tr
+	}
+
+	undUpper            transform.SpanningTransformer = &undUpperCaser{}
+	undLower            transform.SpanningTransformer = &undLowerCaser{}
+	undLowerIgnoreSigma transform.SpanningTransformer = &undLowerIgnoreSigmaCaser{}
+
+	lowerFunc = []mapFunc{
+		nil,       // und
+		nil,       // af
+		aztrLower, // az
+		nil,       // el
+		ltLower,   // lt
+		nil,       // nl
+		aztrLower, // tr
+	}
+
+	titleInfos = []struct {
+		title     mapFunc
+		lower     mapFunc
+		titleSpan spanFunc
+		rewrite   func(*context)
+	}{
+		{title, lower, isTitle, nil},                // und
+		{title, lower, isTitle, afnlRewrite},        // af
+		{aztrUpper(title), aztrLower, isTitle, nil}, // az
+		{title, lower, isTitle, nil},                // el
+		{ltUpper(title), ltLower, noSpan, nil},      // lt
+		{nlTitle, lower, nlTitleSpan, afnlRewrite},  // nl
+		{aztrUpper(title), aztrLower, isTitle, nil}, // tr
+	}
+)
+
+func makeUpper(t language.Tag, o options) transform.SpanningTransformer {
+	_, i, _ := matcher.Match(t)
+	f := upperFunc[i].upper
+	if f == nil {
+		return undUpper
+	}
+	return &simpleCaser{f: f, span: upperFunc[i].span}
+}
+
+func makeLower(t language.Tag, o options) transform.SpanningTransformer {
+	_, i, _ := matcher.Match(t)
+	f := lowerFunc[i]
+	if f == nil {
+		if o.ignoreFinalSigma {
+			return undLowerIgnoreSigma
+		}
+		return undLower
+	}
+	if o.ignoreFinalSigma {
+		return &simpleCaser{f: f, span: isLower}
+	}
+	return &lowerCaser{
+		first:   f,
+		midWord: finalSigma(f),
+	}
+}
+
+func makeTitle(t language.Tag, o options) transform.SpanningTransformer {
+	_, i, _ := matcher.Match(t)
+	x := &titleInfos[i]
+	lower := x.lower
+	if o.noLower {
+		lower = (*context).copy
+	} else if !o.ignoreFinalSigma {
+		lower = finalSigma(lower)
+	}
+	return &titleCaser{
+		title:     x.title,
+		lower:     lower,
+		titleSpan: x.titleSpan,
+		rewrite:   x.rewrite,
+	}
+}
+
+func noSpan(c *context) bool {
+	c.err = transform.ErrEndOfSpan
+	return false
+}
+
+// TODO: consider a similar special case for the fast majority lower case. This
+// is a bit more involved so will require some more precise benchmarking to
+// justify it.
+
+type undUpperCaser struct{ transform.NopResetter }
+
+// undUpperCaser implements the Transformer interface for doing an upper case
+// mapping for the root locale (und). It eliminates the need for an allocation
+// as it prevents escaping by not using function pointers.
+func (t undUpperCaser) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
+	c := context{dst: dst, src: src, atEOF: atEOF}
+	for c.next() {
+		upper(&c)
+		c.checkpoint()
+	}
+	return c.ret()
+}
+
+func (t undUpperCaser) Span(src []byte, atEOF bool) (n int, err error) {
+	c := context{src: src, atEOF: atEOF}
+	for c.next() && isUpper(&c) {
+		c.checkpoint()
+	}
+	return c.retSpan()
+}
+
+// undLowerIgnoreSigmaCaser implements the Transformer interface for doing
+// a lower case mapping for the root locale (und) ignoring final sigma
+// handling. This casing algorithm is used in some performance-critical packages
+// like secure/precis and x/net/http/idna, which warrants its special-casing.
+type undLowerIgnoreSigmaCaser struct{ transform.NopResetter }
+
+func (t undLowerIgnoreSigmaCaser) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
+	c := context{dst: dst, src: src, atEOF: atEOF}
+	for c.next() && lower(&c) {
+		c.checkpoint()
+	}
+	return c.ret()
+
+}
+
+// Span implements a generic lower-casing. This is possible as isLower works
+// for all lowercasing variants. All lowercase variants only vary in how they
+// transform a non-lowercase letter. They will never change an already lowercase
+// letter. In addition, there is no state.
+func (t undLowerIgnoreSigmaCaser) Span(src []byte, atEOF bool) (n int, err error) {
+	c := context{src: src, atEOF: atEOF}
+	for c.next() && isLower(&c) {
+		c.checkpoint()
+	}
+	return c.retSpan()
+}
+
+type simpleCaser struct {
+	context
+	f    mapFunc
+	span spanFunc
+}
+
+// simpleCaser implements the Transformer interface for doing a case operation
+// on a rune-by-rune basis.
+func (t *simpleCaser) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
+	c := context{dst: dst, src: src, atEOF: atEOF}
+	for c.next() && t.f(&c) {
+		c.checkpoint()
+	}
+	return c.ret()
+}
+
+func (t *simpleCaser) Span(src []byte, atEOF bool) (n int, err error) {
+	c := context{src: src, atEOF: atEOF}
+	for c.next() && t.span(&c) {
+		c.checkpoint()
+	}
+	return c.retSpan()
+}
+
+// undLowerCaser implements the Transformer interface for doing a lower case
+// mapping for the root locale (und) ignoring final sigma handling. This casing
+// algorithm is used in some performance-critical packages like secure/precis
+// and x/net/http/idna, which warrants its special-casing.
+type undLowerCaser struct{ transform.NopResetter }
+
+func (t undLowerCaser) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
+	c := context{dst: dst, src: src, atEOF: atEOF}
+
+	for isInterWord := true; c.next(); {
+		if isInterWord {
+			if c.info.isCased() {
+				if !lower(&c) {
+					break
+				}
+				isInterWord = false
+			} else if !c.copy() {
+				break
+			}
+		} else {
+			if c.info.isNotCasedAndNotCaseIgnorable() {
+				if !c.copy() {
+					break
+				}
+				isInterWord = true
+			} else if !c.hasPrefix("Σ") {
+				if !lower(&c) {
+					break
+				}
+			} else if !finalSigmaBody(&c) {
+				break
+			}
+		}
+		c.checkpoint()
+	}
+	return c.ret()
+}
+
+func (t undLowerCaser) Span(src []byte, atEOF bool) (n int, err error) {
+	c := context{src: src, atEOF: atEOF}
+	for c.next() && isLower(&c) {
+		c.checkpoint()
+	}
+	return c.retSpan()
+}
+
+// lowerCaser implements the Transformer interface. The default Unicode lower
+// casing requires different treatment for the first and subsequent characters
+// of a word, most notably to handle the Greek final Sigma.
+type lowerCaser struct {
+	undLowerIgnoreSigmaCaser
+
+	context
+
+	first, midWord mapFunc
+}
+
+func (t *lowerCaser) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
+	t.context = context{dst: dst, src: src, atEOF: atEOF}
+	c := &t.context
+
+	for isInterWord := true; c.next(); {
+		if isInterWord {
+			if c.info.isCased() {
+				if !t.first(c) {
+					break
+				}
+				isInterWord = false
+			} else if !c.copy() {
+				break
+			}
+		} else {
+			if c.info.isNotCasedAndNotCaseIgnorable() {
+				if !c.copy() {
+					break
+				}
+				isInterWord = true
+			} else if !t.midWord(c) {
+				break
+			}
+		}
+		c.checkpoint()
+	}
+	return c.ret()
+}
+
+// titleCaser implements the Transformer interface. Title casing algorithms
+// distinguish between the first letter of a word and subsequent letters of the
+// same word. It uses state to avoid requiring a potentially infinite lookahead.
+type titleCaser struct {
+	context
+
+	// rune mappings used by the actual casing algorithms.
+	title     mapFunc
+	lower     mapFunc
+	titleSpan spanFunc
+
+	rewrite func(*context)
+}
+
+// Transform implements the standard Unicode title case algorithm as defined in
+// Chapter 3 of The Unicode Standard:
+// toTitlecase(X): Find the word boundaries in X according to Unicode Standard
+// Annex #29, "Unicode Text Segmentation." For each word boundary, find the
+// first cased character F following the word boundary. If F exists, map F to
+// Titlecase_Mapping(F); then map all characters C between F and the following
+// word boundary to Lowercase_Mapping(C).
+func (t *titleCaser) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
+	t.context = context{dst: dst, src: src, atEOF: atEOF, isMidWord: t.isMidWord}
+	c := &t.context
+
+	if !c.next() {
+		return c.ret()
+	}
+
+	for {
+		p := c.info
+		if t.rewrite != nil {
+			t.rewrite(c)
+		}
+
+		wasMid := p.isMid()
+		// Break out of this loop on failure to ensure we do not modify the
+		// state incorrectly.
+		if p.isCased() {
+			if !c.isMidWord {
+				if !t.title(c) {
+					break
+				}
+				c.isMidWord = true
+			} else if !t.lower(c) {
+				break
+			}
+		} else if !c.copy() {
+			break
+		} else if p.isBreak() {
+			c.isMidWord = false
+		}
+
+		// As we save the state of the transformer, it is safe to call
+		// checkpoint after any successful write.
+		if !(c.isMidWord && wasMid) {
+			c.checkpoint()
+		}
+
+		if !c.next() {
+			break
+		}
+		if wasMid && c.info.isMid() {
+			c.isMidWord = false
+		}
+	}
+	return c.ret()
+}
+
+func (t *titleCaser) Span(src []byte, atEOF bool) (n int, err error) {
+	t.context = context{src: src, atEOF: atEOF, isMidWord: t.isMidWord}
+	c := &t.context
+
+	if !c.next() {
+		return c.retSpan()
+	}
+
+	for {
+		p := c.info
+		if t.rewrite != nil {
+			t.rewrite(c)
+		}
+
+		wasMid := p.isMid()
+		// Break out of this loop on failure to ensure we do not modify the
+		// state incorrectly.
+		if p.isCased() {
+			if !c.isMidWord {
+				if !t.titleSpan(c) {
+					break
+				}
+				c.isMidWord = true
+			} else if !isLower(c) {
+				break
+			}
+		} else if p.isBreak() {
+			c.isMidWord = false
+		}
+		// As we save the state of the transformer, it is safe to call
+		// checkpoint after any successful write.
+		if !(c.isMidWord && wasMid) {
+			c.checkpoint()
+		}
+
+		if !c.next() {
+			break
+		}
+		if wasMid && c.info.isMid() {
+			c.isMidWord = false
+		}
+	}
+	return c.retSpan()
+}
+
+// finalSigma adds Greek final Sigma handing to another casing function. It
+// determines whether a lowercased sigma should be σ or ς, by looking ahead for
+// case-ignorables and a cased letters.
+func finalSigma(f mapFunc) mapFunc {
+	return func(c *context) bool {
+		if !c.hasPrefix("Σ") {
+			return f(c)
+		}
+		return finalSigmaBody(c)
+	}
+}
+
+func finalSigmaBody(c *context) bool {
+	// Current rune must be ∑.
+
+	// ::NFD();
+	// # 03A3; 03C2; 03A3; 03A3; Final_Sigma; # GREEK CAPITAL LETTER SIGMA
+	// Σ } [:case-ignorable:]* [:cased:] → σ;
+	// [:cased:] [:case-ignorable:]* { Σ → ς;
+	// ::Any-Lower;
+	// ::NFC();
+
+	p := c.pDst
+	c.writeString("ς")
+
+	// TODO: we should do this here, but right now this will never have an
+	// effect as this is called when the prefix is Sigma, whereas Dutch and
+	// Afrikaans only test for an apostrophe.
+	//
+	// if t.rewrite != nil {
+	// 	t.rewrite(c)
+	// }
+
+	// We need to do one more iteration after maxIgnorable, as a cased
+	// letter is not an ignorable and may modify the result.
+	wasMid := false
+	for i := 0; i < maxIgnorable+1; i++ {
+		if !c.next() {
+			return false
+		}
+		if !c.info.isCaseIgnorable() {
+			// All Midword runes are also case ignorable, so we are
+			// guaranteed to have a letter or word break here. As we are
+			// unreading the run, there is no need to unset c.isMidWord;
+			// the title caser will handle this.
+			if c.info.isCased() {
+				// p+1 is guaranteed to be in bounds: if writing ς was
+				// successful, p+1 will contain the second byte of ς. If not,
+				// this function will have returned after c.next returned false.
+				c.dst[p+1]++ // ς → σ
+			}
+			c.unreadRune()
+			return true
+		}
+		// A case ignorable may also introduce a word break, so we may need
+		// to continue searching even after detecting a break.
+		isMid := c.info.isMid()
+		if (wasMid && isMid) || c.info.isBreak() {
+			c.isMidWord = false
+		}
+		wasMid = isMid
+		c.copy()
+	}
+	return true
+}
+
+// finalSigmaSpan would be the same as isLower.
+
+// elUpper implements Greek upper casing, which entails removing a predefined
+// set of non-blocked modifiers. Note that these accents should not be removed
+// for title casing!
+// Example: "Οδός" -> "ΟΔΟΣ".
+func elUpper(c *context) bool {
+	// From CLDR:
+	// [:Greek:] [^[:ccc=Not_Reordered:][:ccc=Above:]]*? { [\u0313\u0314\u0301\u0300\u0306\u0342\u0308\u0304] → ;
+	// [:Greek:] [^[:ccc=Not_Reordered:][:ccc=Iota_Subscript:]]*? { \u0345 → ;
+
+	r, _ := utf8.DecodeRune(c.src[c.pSrc:])
+	oldPDst := c.pDst
+	if !upper(c) {
+		return false
+	}
+	if !unicode.Is(unicode.Greek, r) {
+		return true
+	}
+	i := 0
+	// Take the properties of the uppercased rune that is already written to the
+	// destination. This saves us the trouble of having to uppercase the
+	// decomposed rune again.
+	if b := norm.NFD.Properties(c.dst[oldPDst:]).Decomposition(); b != nil {
+		// Restore the destination position and process the decomposed rune.
+		r, sz := utf8.DecodeRune(b)
+		if r <= 0xFF { // See A.6.1
+			return true
+		}
+		c.pDst = oldPDst
+		// Insert the first rune and ignore the modifiers. See A.6.2.
+		c.writeBytes(b[:sz])
+		i = len(b[sz:]) / 2 // Greek modifiers are always of length 2.
+	}
+
+	for ; i < maxIgnorable && c.next(); i++ {
+		switch r, _ := utf8.DecodeRune(c.src[c.pSrc:]); r {
+		// Above and Iota Subscript
+		case 0x0300, // U+0300 COMBINING GRAVE ACCENT
+			0x0301, // U+0301 COMBINING ACUTE ACCENT
+			0x0304, // U+0304 COMBINING MACRON
+			0x0306, // U+0306 COMBINING BREVE
+			0x0308, // U+0308 COMBINING DIAERESIS
+			0x0313, // U+0313 COMBINING COMMA ABOVE
+			0x0314, // U+0314 COMBINING REVERSED COMMA ABOVE
+			0x0342, // U+0342 COMBINING GREEK PERISPOMENI
+			0x0345: // U+0345 COMBINING GREEK YPOGEGRAMMENI
+			// No-op. Gobble the modifier.
+
+		default:
+			switch v, _ := trie.lookup(c.src[c.pSrc:]); info(v).cccType() {
+			case cccZero:
+				c.unreadRune()
+				return true
+
+			// We don't need to test for IotaSubscript as the only rune that
+			// qualifies (U+0345) was already excluded in the switch statement
+			// above. See A.4.
+
+			case cccAbove:
+				return c.copy()
+			default:
+				// Some other modifier. We're still allowed to gobble Greek
+				// modifiers after this.
+				c.copy()
+			}
+		}
+	}
+	return i == maxIgnorable
+}
+
+// TODO: implement elUpperSpan (low-priority: complex and infrequent).
+
+func ltLower(c *context) bool {
+	// From CLDR:
+	// # Introduce an explicit dot above when lowercasing capital I's and J's
+	// # whenever there are more accents above.
+	// # (of the accents used in Lithuanian: grave, acute, tilde above, and ogonek)
+	// # 0049; 0069 0307; 0049; 0049; lt More_Above; # LATIN CAPITAL LETTER I
+	// # 004A; 006A 0307; 004A; 004A; lt More_Above; # LATIN CAPITAL LETTER J
+	// # 012E; 012F 0307; 012E; 012E; lt More_Above; # LATIN CAPITAL LETTER I WITH OGONEK
+	// # 00CC; 0069 0307 0300; 00CC; 00CC; lt; # LATIN CAPITAL LETTER I WITH GRAVE
+	// # 00CD; 0069 0307 0301; 00CD; 00CD; lt; # LATIN CAPITAL LETTER I WITH ACUTE
+	// # 0128; 0069 0307 0303; 0128; 0128; lt; # LATIN CAPITAL LETTER I WITH TILDE
+	// ::NFD();
+	// I } [^[:ccc=Not_Reordered:][:ccc=Above:]]* [:ccc=Above:] → i \u0307;
+	// J } [^[:ccc=Not_Reordered:][:ccc=Above:]]* [:ccc=Above:] → j \u0307;
+	// I \u0328 (Į) } [^[:ccc=Not_Reordered:][:ccc=Above:]]* [:ccc=Above:] → i \u0328 \u0307;
+	// I \u0300 (Ì) → i \u0307 \u0300;
+	// I \u0301 (Í) → i \u0307 \u0301;
+	// I \u0303 (Ĩ) → i \u0307 \u0303;
+	// ::Any-Lower();
+	// ::NFC();
+
+	i := 0
+	if r := c.src[c.pSrc]; r < utf8.RuneSelf {
+		lower(c)
+		if r != 'I' && r != 'J' {
+			return true
+		}
+	} else {
+		p := norm.NFD.Properties(c.src[c.pSrc:])
+		if d := p.Decomposition(); len(d) >= 3 && (d[0] == 'I' || d[0] == 'J') {
+			// UTF-8 optimization: the decomposition will only have an above
+			// modifier if the last rune of the decomposition is in [U+300-U+311].
+			// In all other cases, a decomposition starting with I is always
+			// an I followed by modifiers that are not cased themselves. See A.2.
+			if d[1] == 0xCC && d[2] <= 0x91 { // A.2.4.
+				if !c.writeBytes(d[:1]) {
+					return false
+				}
+				c.dst[c.pDst-1] += 'a' - 'A' // lower
+
+				// Assumption: modifier never changes on lowercase. See A.1.
+				// Assumption: all modifiers added have CCC = Above. See A.2.3.
+				return c.writeString("\u0307") && c.writeBytes(d[1:])
+			}
+			// In all other cases the additional modifiers will have a CCC
+			// that is less than 230 (Above). We will insert the U+0307, if
+			// needed, after these modifiers so that a string in FCD form
+			// will remain so. See A.2.2.
+			lower(c)
+			i = 1
+		} else {
+			return lower(c)
+		}
+	}
+
+	for ; i < maxIgnorable && c.next(); i++ {
+		switch c.info.cccType() {
+		case cccZero:
+			c.unreadRune()
+			return true
+		case cccAbove:
+			return c.writeString("\u0307") && c.copy() // See A.1.
+		default:
+			c.copy() // See A.1.
+		}
+	}
+	return i == maxIgnorable
+}
+
+// ltLowerSpan would be the same as isLower.
+
+func ltUpper(f mapFunc) mapFunc {
+	return func(c *context) bool {
+		// Unicode:
+		// 0307; 0307; ; ; lt After_Soft_Dotted; # COMBINING DOT ABOVE
+		//
+		// From CLDR:
+		// # Remove \u0307 following soft-dotteds (i, j, and the like), with possible
+		// # intervening non-230 marks.
+		// ::NFD();
+		// [:Soft_Dotted:] [^[:ccc=Not_Reordered:][:ccc=Above:]]* { \u0307 → ;
+		// ::Any-Upper();
+		// ::NFC();
+
+		// TODO: See A.5. A soft-dotted rune never has an exception. This would
+		// allow us to overload the exception bit and encode this property in
+		// info. Need to measure performance impact of this.
+		r, _ := utf8.DecodeRune(c.src[c.pSrc:])
+		oldPDst := c.pDst
+		if !f(c) {
+			return false
+		}
+		if !unicode.Is(unicode.Soft_Dotted, r) {
+			return true
+		}
+
+		// We don't need to do an NFD normalization, as a soft-dotted rune never
+		// contains U+0307. See A.3.
+
+		i := 0
+		for ; i < maxIgnorable && c.next(); i++ {
+			switch c.info.cccType() {
+			case cccZero:
+				c.unreadRune()
+				return true
+			case cccAbove:
+				if c.hasPrefix("\u0307") {
+					// We don't do a full NFC, but rather combine runes for
+					// some of the common cases. (Returning NFC or
+					// preserving normal form is neither a requirement nor
+					// a possibility anyway).
+					if !c.next() {
+						return false
+					}
+					if c.dst[oldPDst] == 'I' && c.pDst == oldPDst+1 && c.src[c.pSrc] == 0xcc {
+						s := ""
+						switch c.src[c.pSrc+1] {
+						case 0x80: // U+0300 COMBINING GRAVE ACCENT
+							s = "\u00cc" // U+00CC LATIN CAPITAL LETTER I WITH GRAVE
+						case 0x81: // U+0301 COMBINING ACUTE ACCENT
+							s = "\u00cd" // U+00CD LATIN CAPITAL LETTER I WITH ACUTE
+						case 0x83: // U+0303 COMBINING TILDE
+							s = "\u0128" // U+0128 LATIN CAPITAL LETTER I WITH TILDE
+						case 0x88: // U+0308 COMBINING DIAERESIS
+							s = "\u00cf" // U+00CF LATIN CAPITAL LETTER I WITH DIAERESIS
+						default:
+						}
+						if s != "" {
+							c.pDst = oldPDst
+							return c.writeString(s)
+						}
+					}
+				}
+				return c.copy()
+			default:
+				c.copy()
+			}
+		}
+		return i == maxIgnorable
+	}
+}
+
+// TODO: implement ltUpperSpan (low priority: complex and infrequent).
+
+func aztrUpper(f mapFunc) mapFunc {
+	return func(c *context) bool {
+		// i→İ;
+		if c.src[c.pSrc] == 'i' {
+			return c.writeString("İ")
+		}
+		return f(c)
+	}
+}
+
+func aztrLower(c *context) (done bool) {
+	// From CLDR:
+	// # I and i-dotless; I-dot and i are case pairs in Turkish and Azeri
+	// # 0130; 0069; 0130; 0130; tr; # LATIN CAPITAL LETTER I WITH DOT ABOVE
+	// İ→i;
+	// # When lowercasing, remove dot_above in the sequence I + dot_above, which will turn into i.
+	// # This matches the behavior of the canonically equivalent I-dot_above
+	// # 0307; ; 0307; 0307; tr After_I; # COMBINING DOT ABOVE
+	// # When lowercasing, unless an I is before a dot_above, it turns into a dotless i.
+	// # 0049; 0131; 0049; 0049; tr Not_Before_Dot; # LATIN CAPITAL LETTER I
+	// I([^[:ccc=Not_Reordered:][:ccc=Above:]]*)\u0307 → i$1 ;
+	// I→ı ;
+	// ::Any-Lower();
+	if c.hasPrefix("\u0130") { // İ
+		return c.writeString("i")
+	}
+	if c.src[c.pSrc] != 'I' {
+		return lower(c)
+	}
+
+	// We ignore the lower-case I for now, but insert it later when we know
+	// which form we need.
+	start := c.pSrc + c.sz
+
+	i := 0
+Loop:
+	// We check for up to n ignorables before \u0307. As \u0307 is an
+	// ignorable as well, n is maxIgnorable-1.
+	for ; i < maxIgnorable && c.next(); i++ {
+		switch c.info.cccType() {
+		case cccAbove:
+			if c.hasPrefix("\u0307") {
+				return c.writeString("i") && c.writeBytes(c.src[start:c.pSrc]) // ignore U+0307
+			}
+			done = true
+			break Loop
+		case cccZero:
+			c.unreadRune()
+			done = true
+			break Loop
+		default:
+			// We'll write this rune after we know which starter to use.
+		}
+	}
+	if i == maxIgnorable {
+		done = true
+	}
+	return c.writeString("ı") && c.writeBytes(c.src[start:c.pSrc+c.sz]) && done
+}
+
+// aztrLowerSpan would be the same as isLower.
+
+func nlTitle(c *context) bool {
+	// From CLDR:
+	// # Special titlecasing for Dutch initial "ij".
+	// ::Any-Title();
+	// # Fix up Ij at the beginning of a "word" (per Any-Title, notUAX #29)
+	// [:^WB=ALetter:] [:WB=Extend:]* [[:WB=MidLetter:][:WB=MidNumLet:]]? { Ij } → IJ ;
+	if c.src[c.pSrc] != 'I' && c.src[c.pSrc] != 'i' {
+		return title(c)
+	}
+
+	if !c.writeString("I") || !c.next() {
+		return false
+	}
+	if c.src[c.pSrc] == 'j' || c.src[c.pSrc] == 'J' {
+		return c.writeString("J")
+	}
+	c.unreadRune()
+	return true
+}
+
+func nlTitleSpan(c *context) bool {
+	// From CLDR:
+	// # Special titlecasing for Dutch initial "ij".
+	// ::Any-Title();
+	// # Fix up Ij at the beginning of a "word" (per Any-Title, notUAX #29)
+	// [:^WB=ALetter:] [:WB=Extend:]* [[:WB=MidLetter:][:WB=MidNumLet:]]? { Ij } → IJ ;
+	if c.src[c.pSrc] != 'I' {
+		return isTitle(c)
+	}
+	if !c.next() || c.src[c.pSrc] == 'j' {
+		return false
+	}
+	if c.src[c.pSrc] != 'J' {
+		c.unreadRune()
+	}
+	return true
+}
+
+// Not part of CLDR, but see https://unicode.org/cldr/trac/ticket/7078.
+func afnlRewrite(c *context) {
+	if c.hasPrefix("'") || c.hasPrefix("’") {
+		c.isMidWord = true
+	}
+}

vendor/golang.org/x/text/cases/trieval.go

@@ -0,0 +1,214 @@
+// Code generated by running "go generate" in golang.org/x/text. DO NOT EDIT.
+
+package cases
+
+// This file contains definitions for interpreting the trie value of the case
+// trie generated by "go run gen*.go". It is shared by both the generator
+// program and the resultant package. Sharing is achieved by the generator
+// copying gen_trieval.go to trieval.go and changing what's above this comment.
+
+// info holds case information for a single rune. It is the value returned
+// by a trie lookup. Most mapping information can be stored in a single 16-bit
+// value. If not, for example when a rune is mapped to multiple runes, the value
+// stores some basic case data and an index into an array with additional data.
+//
+// The per-rune values have the following format:
+//
+//   if (exception) {
+//     15..4  unsigned exception index
+//   } else {
+//     15..8  XOR pattern or index to XOR pattern for case mapping
+//            Only 13..8 are used for XOR patterns.
+//         7  inverseFold (fold to upper, not to lower)
+//         6  index: interpret the XOR pattern as an index
+//            or isMid if case mode is cIgnorableUncased.
+//      5..4  CCC: zero (normal or break), above or other
+//   }
+//      3  exception: interpret this value as an exception index
+//         (TODO: is this bit necessary? Probably implied from case mode.)
+//   2..0  case mode
+//
+// For the non-exceptional cases, a rune must be either uncased, lowercase or
+// uppercase. If the rune is cased, the XOR pattern maps either a lowercase
+// rune to uppercase or an uppercase rune to lowercase (applied to the 10
+// least-significant bits of the rune).
+//
+// See the definitions below for a more detailed description of the various
+// bits.
+type info uint16
+
+const (
+	casedMask      = 0x0003
+	fullCasedMask  = 0x0007
+	ignorableMask  = 0x0006
+	ignorableValue = 0x0004
+
+	inverseFoldBit = 1 << 7
+	isMidBit       = 1 << 6
+
+	exceptionBit     = 1 << 3
+	exceptionShift   = 4
+	numExceptionBits = 12
+
+	xorIndexBit = 1 << 6
+	xorShift    = 8
+
+	// There is no mapping if all xor bits and the exception bit are zero.
+	hasMappingMask = 0xff80 | exceptionBit
+)
+
+// The case mode bits encodes the case type of a rune. This includes uncased,
+// title, upper and lower case and case ignorable. (For a definition of these
+// terms see Chapter 3 of The Unicode Standard Core Specification.) In some rare
+// cases, a rune can be both cased and case-ignorable. This is encoded by
+// cIgnorableCased. A rune of this type is always lower case. Some runes are
+// cased while not having a mapping.
+//
+// A common pattern for scripts in the Unicode standard is for upper and lower
+// case runes to alternate for increasing rune values (e.g. the accented Latin
+// ranges starting from U+0100 and U+1E00 among others and some Cyrillic
+// characters). We use this property by defining a cXORCase mode, where the case
+// mode (always upper or lower case) is derived from the rune value. As the XOR
+// pattern for case mappings is often identical for successive runes, using
+// cXORCase can result in large series of identical trie values. This, in turn,
+// allows us to better compress the trie blocks.
+const (
+	cUncased          info = iota // 000
+	cTitle                        // 001
+	cLower                        // 010
+	cUpper                        // 011
+	cIgnorableUncased             // 100
+	cIgnorableCased               // 101 // lower case if mappings exist
+	cXORCase                      // 11x // case is cLower | ((rune&1) ^ x)
+
+	maxCaseMode = cUpper
+)
+
+func (c info) isCased() bool {
+	return c&casedMask != 0
+}
+
+func (c info) isCaseIgnorable() bool {
+	return c&ignorableMask == ignorableValue
+}
+
+func (c info) isNotCasedAndNotCaseIgnorable() bool {
+	return c&fullCasedMask == 0
+}
+
+func (c info) isCaseIgnorableAndNotCased() bool {
+	return c&fullCasedMask == cIgnorableUncased
+}
+
+func (c info) isMid() bool {
+	return c&(fullCasedMask|isMidBit) == isMidBit|cIgnorableUncased
+}
+
+// The case mapping implementation will need to know about various Canonical
+// Combining Class (CCC) values. We encode two of these in the trie value:
+// cccZero (0) and cccAbove (230). If the value is cccOther, it means that
+// CCC(r) > 0, but not 230. A value of cccBreak means that CCC(r) == 0 and that
+// the rune also has the break category Break (see below).
+const (
+	cccBreak info = iota << 4
+	cccZero
+	cccAbove
+	cccOther
+
+	cccMask = cccBreak | cccZero | cccAbove | cccOther
+)
+
+const (
+	starter       = 0
+	above         = 230
+	iotaSubscript = 240
+)
+
+// The exceptions slice holds data that does not fit in a normal info entry.
+// The entry is pointed to by the exception index in an entry. It has the
+// following format:
+//
+// Header
+// byte 0:
+//  7..6  unused
+//  5..4  CCC type (same bits as entry)
+//     3  unused
+//  2..0  length of fold
+//
+// byte 1:
+//   7..6  unused
+//   5..3  length of 1st mapping of case type
+//   2..0  length of 2nd mapping of case type
+//
+//   case     1st    2nd
+//   lower -> upper, title
+//   upper -> lower, title
+//   title -> lower, upper
+//
+// Lengths with the value 0x7 indicate no value and implies no change.
+// A length of 0 indicates a mapping to zero-length string.
+//
+// Body bytes:
+//   case folding bytes
+//   lowercase mapping bytes
+//   uppercase mapping bytes
+//   titlecase mapping bytes
+//   closure mapping bytes (for NFKC_Casefold). (TODO)
+//
+// Fallbacks:
+//   missing fold  -> lower
+//   missing title -> upper
+//   all missing   -> original rune
+//
+// exceptions starts with a dummy byte to enforce that there is no zero index
+// value.
+const (
+	lengthMask = 0x07
+	lengthBits = 3
+	noChange   = 0
+)
+
+// References to generated trie.
+
+var trie = newCaseTrie(0)
+
+var sparse = sparseBlocks{
+	values:  sparseValues[:],
+	offsets: sparseOffsets[:],
+}
+
+// Sparse block lookup code.
+
+// valueRange is an entry in a sparse block.
+type valueRange struct {
+	value  uint16
+	lo, hi byte
+}
+
+type sparseBlocks struct {
+	values  []valueRange
+	offsets []uint16
+}
+
+// lookup returns the value from values block n for byte b using binary search.
+func (s *sparseBlocks) lookup(n uint32, b byte) uint16 {
+	lo := s.offsets[n]
+	hi := s.offsets[n+1]
+	for lo < hi {
+		m := lo + (hi-lo)/2
+		r := s.values[m]
+		if r.lo <= b && b <= r.hi {
+			return r.value
+		}
+		if b < r.lo {
+			hi = m
+		} else {
+			lo = m + 1
+		}
+	}
+	return 0
+}
+
+// lastRuneForTesting is the last rune used for testing. Everything after this
+// is boring.
+const lastRuneForTesting = rune(0x1FFFF)

vendor/golang.org/x/text/internal/internal.go

@@ -0,0 +1,49 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package internal contains non-exported functionality that are used by
+// packages in the text repository.
+package internal // import "golang.org/x/text/internal"
+
+import (
+	"sort"
+
+	"golang.org/x/text/language"
+)
+
+// SortTags sorts tags in place.
+func SortTags(tags []language.Tag) {
+	sort.Sort(sorter(tags))
+}
+
+type sorter []language.Tag
+
+func (s sorter) Len() int {
+	return len(s)
+}
+
+func (s sorter) Swap(i, j int) {
+	s[i], s[j] = s[j], s[i]
+}
+
+func (s sorter) Less(i, j int) bool {
+	return s[i].String() < s[j].String()
+}
+
+// UniqueTags sorts and filters duplicate tags in place and returns a slice with
+// only unique tags.
+func UniqueTags(tags []language.Tag) []language.Tag {
+	if len(tags) <= 1 {
+		return tags
+	}
+	SortTags(tags)
+	k := 0
+	for i := 1; i < len(tags); i++ {
+		if tags[k].String() < tags[i].String() {
+			k++
+			tags[k] = tags[i]
+		}
+	}
+	return tags[:k+1]
+}

vendor/golang.org/x/text/internal/match.go

@@ -0,0 +1,67 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package internal
+
+// This file contains matchers that implement CLDR inheritance.
+//
+//     See https://unicode.org/reports/tr35/#Locale_Inheritance.
+//
+// Some of the inheritance described in this document is already handled by
+// the cldr package.
+
+import (
+	"golang.org/x/text/language"
+)
+
+// TODO: consider if (some of the) matching algorithm needs to be public after
+// getting some feel about what is generic and what is specific.
+
+// NewInheritanceMatcher returns a matcher that matches based on the inheritance
+// chain.
+//
+// The matcher uses canonicalization and the parent relationship to find a
+// match. The resulting match will always be either Und or a language with the
+// same language and script as the requested language. It will not match
+// languages for which there is understood to be mutual or one-directional
+// intelligibility.
+//
+// A Match will indicate an Exact match if the language matches after
+// canonicalization and High if the matched tag is a parent.
+func NewInheritanceMatcher(t []language.Tag) *InheritanceMatcher {
+	tags := &InheritanceMatcher{make(map[language.Tag]int)}
+	for i, tag := range t {
+		ct, err := language.All.Canonicalize(tag)
+		if err != nil {
+			ct = tag
+		}
+		tags.index[ct] = i
+	}
+	return tags
+}
+
+type InheritanceMatcher struct {
+	index map[language.Tag]int
+}
+
+func (m InheritanceMatcher) Match(want ...language.Tag) (language.Tag, int, language.Confidence) {
+	for _, t := range want {
+		ct, err := language.All.Canonicalize(t)
+		if err != nil {
+			ct = t
+		}
+		conf := language.Exact
+		for {
+			if index, ok := m.index[ct]; ok {
+				return ct, index, conf
+			}
+			if ct == language.Und {
+				break
+			}
+			ct = ct.Parent()
+			conf = language.High
+		}
+	}
+	return language.Und, 0, language.No
+}

vendor/golang.org/x/text/runes/cond.go

@@ -0,0 +1,187 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package runes
+
+import (
+	"unicode/utf8"
+
+	"golang.org/x/text/transform"
+)
+
+// Note: below we pass invalid UTF-8 to the tIn and tNotIn transformers as is.
+// This is done for various reasons:
+// - To retain the semantics of the Nop transformer: if input is passed to a Nop
+//   one would expect it to be unchanged.
+// - It would be very expensive to pass a converted RuneError to a transformer:
+//   a transformer might need more source bytes after RuneError, meaning that
+//   the only way to pass it safely is to create a new buffer and manage the
+//   intermingling of RuneErrors and normal input.
+// - Many transformers leave ill-formed UTF-8 as is, so this is not
+//   inconsistent. Generally ill-formed UTF-8 is only replaced if it is a
+//   logical consequence of the operation (as for Map) or if it otherwise would
+//   pose security concerns (as for Remove).
+// - An alternative would be to return an error on ill-formed UTF-8, but this
+//   would be inconsistent with other operations.
+
+// If returns a transformer that applies tIn to consecutive runes for which
+// s.Contains(r) and tNotIn to consecutive runes for which !s.Contains(r). Reset
+// is called on tIn and tNotIn at the start of each run. A Nop transformer will
+// substitute a nil value passed to tIn or tNotIn. Invalid UTF-8 is translated
+// to RuneError to determine which transformer to apply, but is passed as is to
+// the respective transformer.
+func If(s Set, tIn, tNotIn transform.Transformer) Transformer {
+	if tIn == nil && tNotIn == nil {
+		return Transformer{transform.Nop}
+	}
+	if tIn == nil {
+		tIn = transform.Nop
+	}
+	if tNotIn == nil {
+		tNotIn = transform.Nop
+	}
+	sIn, ok := tIn.(transform.SpanningTransformer)
+	if !ok {
+		sIn = dummySpan{tIn}
+	}
+	sNotIn, ok := tNotIn.(transform.SpanningTransformer)
+	if !ok {
+		sNotIn = dummySpan{tNotIn}
+	}
+
+	a := &cond{
+		tIn:    sIn,
+		tNotIn: sNotIn,
+		f:      s.Contains,
+	}
+	a.Reset()
+	return Transformer{a}
+}
+
+type dummySpan struct{ transform.Transformer }
+
+func (d dummySpan) Span(src []byte, atEOF bool) (n int, err error) {
+	return 0, transform.ErrEndOfSpan
+}
+
+type cond struct {
+	tIn, tNotIn transform.SpanningTransformer
+	f           func(rune) bool
+	check       func(rune) bool               // current check to perform
+	t           transform.SpanningTransformer // current transformer to use
+}
+
+// Reset implements transform.Transformer.
+func (t *cond) Reset() {
+	t.check = t.is
+	t.t = t.tIn
+	t.t.Reset() // notIn will be reset on first usage.
+}
+
+func (t *cond) is(r rune) bool {
+	if t.f(r) {
+		return true
+	}
+	t.check = t.isNot
+	t.t = t.tNotIn
+	t.tNotIn.Reset()
+	return false
+}
+
+func (t *cond) isNot(r rune) bool {
+	if !t.f(r) {
+		return true
+	}
+	t.check = t.is
+	t.t = t.tIn
+	t.tIn.Reset()
+	return false
+}
+
+// This implementation of Span doesn't help all too much, but it needs to be
+// there to satisfy this package's Transformer interface.
+// TODO: there are certainly room for improvements, though. For example, if
+// t.t == transform.Nop (which will a common occurrence) it will save a bundle
+// to special-case that loop.
+func (t *cond) Span(src []byte, atEOF bool) (n int, err error) {
+	p := 0
+	for n < len(src) && err == nil {
+		// Don't process too much at a time as the Spanner that will be
+		// called on this block may terminate early.
+		const maxChunk = 4096
+		max := len(src)
+		if v := n + maxChunk; v < max {
+			max = v
+		}
+		atEnd := false
+		size := 0
+		current := t.t
+		for ; p < max; p += size {
+			r := rune(src[p])
+			if r < utf8.RuneSelf {
+				size = 1
+			} else if r, size = utf8.DecodeRune(src[p:]); size == 1 {
+				if !atEOF && !utf8.FullRune(src[p:]) {
+					err = transform.ErrShortSrc
+					break
+				}
+			}
+			if !t.check(r) {
+				// The next rune will be the start of a new run.
+				atEnd = true
+				break
+			}
+		}
+		n2, err2 := current.Span(src[n:p], atEnd || (atEOF && p == len(src)))
+		n += n2
+		if err2 != nil {
+			return n, err2
+		}
+		// At this point either err != nil or t.check will pass for the rune at p.
+		p = n + size
+	}
+	return n, err
+}
+
+func (t *cond) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
+	p := 0
+	for nSrc < len(src) && err == nil {
+		// Don't process too much at a time, as the work might be wasted if the
+		// destination buffer isn't large enough to hold the result or a
+		// transform returns an error early.
+		const maxChunk = 4096
+		max := len(src)
+		if n := nSrc + maxChunk; n < len(src) {
+			max = n
+		}
+		atEnd := false
+		size := 0
+		current := t.t
+		for ; p < max; p += size {
+			r := rune(src[p])
+			if r < utf8.RuneSelf {
+				size = 1
+			} else if r, size = utf8.DecodeRune(src[p:]); size == 1 {
+				if !atEOF && !utf8.FullRune(src[p:]) {
+					err = transform.ErrShortSrc
+					break
+				}
+			}
+			if !t.check(r) {
+				// The next rune will be the start of a new run.
+				atEnd = true
+				break
+			}
+		}
+		nDst2, nSrc2, err2 := current.Transform(dst[nDst:], src[nSrc:p], atEnd || (atEOF && p == len(src)))
+		nDst += nDst2
+		nSrc += nSrc2
+		if err2 != nil {
+			return nDst, nSrc, err2
+		}
+		// At this point either err != nil or t.check will pass for the rune at p.
+		p = nSrc + size
+	}
+	return nDst, nSrc, err
+}

vendor/golang.org/x/text/runes/runes.go

@@ -0,0 +1,355 @@
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package runes provide transforms for UTF-8 encoded text.
+package runes // import "golang.org/x/text/runes"
+
+import (
+	"unicode"
+	"unicode/utf8"
+
+	"golang.org/x/text/transform"
+)
+
+// A Set is a collection of runes.
+type Set interface {
+	// Contains returns true if r is contained in the set.
+	Contains(r rune) bool
+}
+
+type setFunc func(rune) bool
+
+func (s setFunc) Contains(r rune) bool {
+	return s(r)
+}
+
+// Note: using funcs here instead of wrapping types result in cleaner
+// documentation and a smaller API.
+
+// In creates a Set with a Contains method that returns true for all runes in
+// the given RangeTable.
+func In(rt *unicode.RangeTable) Set {
+	return setFunc(func(r rune) bool { return unicode.Is(rt, r) })
+}
+
+// In creates a Set with a Contains method that returns true for all runes not
+// in the given RangeTable.
+func NotIn(rt *unicode.RangeTable) Set {
+	return setFunc(func(r rune) bool { return !unicode.Is(rt, r) })
+}
+
+// Predicate creates a Set with a Contains method that returns f(r).
+func Predicate(f func(rune) bool) Set {
+	return setFunc(f)
+}
+
+// Transformer implements the transform.Transformer interface.
+type Transformer struct {
+	t transform.SpanningTransformer
+}
+
+func (t Transformer) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
+	return t.t.Transform(dst, src, atEOF)
+}
+
+func (t Transformer) Span(b []byte, atEOF bool) (n int, err error) {
+	return t.t.Span(b, atEOF)
+}
+
+func (t Transformer) Reset() { t.t.Reset() }
+
+// Bytes returns a new byte slice with the result of converting b using t.  It
+// calls Reset on t. It returns nil if any error was found. This can only happen
+// if an error-producing Transformer is passed to If.
+func (t Transformer) Bytes(b []byte) []byte {
+	b, _, err := transform.Bytes(t, b)
+	if err != nil {
+		return nil
+	}
+	return b
+}
+
+// String returns a string with the result of converting s using t. It calls
+// Reset on t. It returns the empty string if any error was found. This can only
+// happen if an error-producing Transformer is passed to If.
+func (t Transformer) String(s string) string {
+	s, _, err := transform.String(t, s)
+	if err != nil {
+		return ""
+	}
+	return s
+}
+
+// TODO:
+// - Copy: copying strings and bytes in whole-rune units.
+// - Validation (maybe)
+// - Well-formed-ness (maybe)
+
+const runeErrorString = string(utf8.RuneError)
+
+// Remove returns a Transformer that removes runes r for which s.Contains(r).
+// Illegal input bytes are replaced by RuneError before being passed to f.
+func Remove(s Set) Transformer {
+	if f, ok := s.(setFunc); ok {
+		// This little trick cuts the running time of BenchmarkRemove for sets
+		// created by Predicate roughly in half.
+		// TODO: special-case RangeTables as well.
+		return Transformer{remove(f)}
+	}
+	return Transformer{remove(s.Contains)}
+}
+
+// TODO: remove transform.RemoveFunc.
+
+type remove func(r rune) bool
+
+func (remove) Reset() {}
+
+// Span implements transform.Spanner.
+func (t remove) Span(src []byte, atEOF bool) (n int, err error) {
+	for r, size := rune(0), 0; n < len(src); {
+		if r = rune(src[n]); r < utf8.RuneSelf {
+			size = 1
+		} else if r, size = utf8.DecodeRune(src[n:]); size == 1 {
+			// Invalid rune.
+			if !atEOF && !utf8.FullRune(src[n:]) {
+				err = transform.ErrShortSrc
+			} else {
+				err = transform.ErrEndOfSpan
+			}
+			break
+		}
+		if t(r) {
+			err = transform.ErrEndOfSpan
+			break
+		}
+		n += size
+	}
+	return
+}
+
+// Transform implements transform.Transformer.
+func (t remove) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
+	for r, size := rune(0), 0; nSrc < len(src); {
+		if r = rune(src[nSrc]); r < utf8.RuneSelf {
+			size = 1
+		} else if r, size = utf8.DecodeRune(src[nSrc:]); size == 1 {
+			// Invalid rune.
+			if !atEOF && !utf8.FullRune(src[nSrc:]) {
+				err = transform.ErrShortSrc
+				break
+			}
+			// We replace illegal bytes with RuneError. Not doing so might
+			// otherwise turn a sequence of invalid UTF-8 into valid UTF-8.
+			// The resulting byte sequence may subsequently contain runes
+			// for which t(r) is true that were passed unnoticed.
+			if !t(utf8.RuneError) {
+				if nDst+3 > len(dst) {
+					err = transform.ErrShortDst
+					break
+				}
+				dst[nDst+0] = runeErrorString[0]
+				dst[nDst+1] = runeErrorString[1]
+				dst[nDst+2] = runeErrorString[2]
+				nDst += 3
+			}
+			nSrc++
+			continue
+		}
+		if t(r) {
+			nSrc += size
+			continue
+		}
+		if nDst+size > len(dst) {
+			err = transform.ErrShortDst
+			break
+		}
+		for i := 0; i < size; i++ {
+			dst[nDst] = src[nSrc]
+			nDst++
+			nSrc++
+		}
+	}
+	return
+}
+
+// Map returns a Transformer that maps the runes in the input using the given
+// mapping. Illegal bytes in the input are converted to utf8.RuneError before
+// being passed to the mapping func.
+func Map(mapping func(rune) rune) Transformer {
+	return Transformer{mapper(mapping)}
+}
+
+type mapper func(rune) rune
+
+func (mapper) Reset() {}
+
+// Span implements transform.Spanner.
+func (t mapper) Span(src []byte, atEOF bool) (n int, err error) {
+	for r, size := rune(0), 0; n < len(src); n += size {
+		if r = rune(src[n]); r < utf8.RuneSelf {
+			size = 1
+		} else if r, size = utf8.DecodeRune(src[n:]); size == 1 {
+			// Invalid rune.
+			if !atEOF && !utf8.FullRune(src[n:]) {
+				err = transform.ErrShortSrc
+			} else {
+				err = transform.ErrEndOfSpan
+			}
+			break
+		}
+		if t(r) != r {
+			err = transform.ErrEndOfSpan
+			break
+		}
+	}
+	return n, err
+}
+
+// Transform implements transform.Transformer.
+func (t mapper) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
+	var replacement rune
+	var b [utf8.UTFMax]byte
+
+	for r, size := rune(0), 0; nSrc < len(src); {
+		if r = rune(src[nSrc]); r < utf8.RuneSelf {
+			if replacement = t(r); replacement < utf8.RuneSelf {
+				if nDst == len(dst) {
+					err = transform.ErrShortDst
+					break
+				}
+				dst[nDst] = byte(replacement)
+				nDst++
+				nSrc++
+				continue
+			}
+			size = 1
+		} else if r, size = utf8.DecodeRune(src[nSrc:]); size == 1 {
+			// Invalid rune.
+			if !atEOF && !utf8.FullRune(src[nSrc:]) {
+				err = transform.ErrShortSrc
+				break
+			}
+
+			if replacement = t(utf8.RuneError); replacement == utf8.RuneError {
+				if nDst+3 > len(dst) {
+					err = transform.ErrShortDst
+					break
+				}
+				dst[nDst+0] = runeErrorString[0]
+				dst[nDst+1] = runeErrorString[1]
+				dst[nDst+2] = runeErrorString[2]
+				nDst += 3
+				nSrc++
+				continue
+			}
+		} else if replacement = t(r); replacement == r {
+			if nDst+size > len(dst) {
+				err = transform.ErrShortDst
+				break
+			}
+			for i := 0; i < size; i++ {
+				dst[nDst] = src[nSrc]
+				nDst++
+				nSrc++
+			}
+			continue
+		}
+
+		n := utf8.EncodeRune(b[:], replacement)
+
+		if nDst+n > len(dst) {
+			err = transform.ErrShortDst
+			break
+		}
+		for i := 0; i < n; i++ {
+			dst[nDst] = b[i]
+			nDst++
+		}
+		nSrc += size
+	}
+	return
+}
+
+// ReplaceIllFormed returns a transformer that replaces all input bytes that are
+// not part of a well-formed UTF-8 code sequence with utf8.RuneError.
+func ReplaceIllFormed() Transformer {
+	return Transformer{&replaceIllFormed{}}
+}
+
+type replaceIllFormed struct{ transform.NopResetter }
+
+func (t replaceIllFormed) Span(src []byte, atEOF bool) (n int, err error) {
+	for n < len(src) {
+		// ASCII fast path.
+		if src[n] < utf8.RuneSelf {
+			n++
+			continue
+		}
+
+		r, size := utf8.DecodeRune(src[n:])
+
+		// Look for a valid non-ASCII rune.
+		if r != utf8.RuneError || size != 1 {
+			n += size
+			continue
+		}
+
+		// Look for short source data.
+		if !atEOF && !utf8.FullRune(src[n:]) {
+			err = transform.ErrShortSrc
+			break
+		}
+
+		// We have an invalid rune.
+		err = transform.ErrEndOfSpan
+		break
+	}
+	return n, err
+}
+
+func (t replaceIllFormed) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
+	for nSrc < len(src) {
+		// ASCII fast path.
+		if r := src[nSrc]; r < utf8.RuneSelf {
+			if nDst == len(dst) {
+				err = transform.ErrShortDst
+				break
+			}
+			dst[nDst] = r
+			nDst++
+			nSrc++
+			continue
+		}
+
+		// Look for a valid non-ASCII rune.
+		if _, size := utf8.DecodeRune(src[nSrc:]); size != 1 {
+			if size != copy(dst[nDst:], src[nSrc:nSrc+size]) {
+				err = transform.ErrShortDst
+				break
+			}
+			nDst += size
+			nSrc += size
+			continue
+		}
+
+		// Look for short source data.
+		if !atEOF && !utf8.FullRune(src[nSrc:]) {
+			err = transform.ErrShortSrc
+			break
+		}
+
+		// We have an invalid rune.
+		if nDst+3 > len(dst) {
+			err = transform.ErrShortDst
+			break
+		}
+		dst[nDst+0] = runeErrorString[0]
+		dst[nDst+1] = runeErrorString[1]
+		dst[nDst+2] = runeErrorString[2]
+		nDst += 3
+		nSrc++
+	}
+	return nDst, nSrc, err
+}

vendor/golang.org/x/text/secure/precis/class.go

@@ -0,0 +1,36 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package precis
+
+import (
+	"unicode/utf8"
+)
+
+// TODO: Add contextual character rules from Appendix A of RFC5892.
+
+// A class is a set of characters that match certain derived properties. The
+// PRECIS framework defines two classes: The Freeform class and the Identifier
+// class. The freeform class should be used for profiles where expressiveness is
+// prioritized over safety such as nicknames or passwords. The identifier class
+// should be used for profiles where safety is the first priority such as
+// addressable network labels and usernames.
+type class struct {
+	validFrom property
+}
+
+// Contains satisfies the runes.Set interface and returns whether the given rune
+// is a member of the class.
+func (c class) Contains(r rune) bool {
+	b := make([]byte, 4)
+	n := utf8.EncodeRune(b, r)
+
+	trieval, _ := dpTrie.lookup(b[:n])
+	return c.validFrom <= property(trieval)
+}
+
+var (
+	identifier = &class{validFrom: pValid}
+	freeform   = &class{validFrom: idDisOrFreePVal}
+)

vendor/golang.org/x/text/secure/precis/context.go

@@ -0,0 +1,139 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package precis
+
+import "errors"
+
+// This file contains tables and code related to context rules.
+
+type catBitmap uint16
+
+const (
+	// These bits, once set depending on the current value, are never unset.
+	bJapanese catBitmap = 1 << iota
+	bArabicIndicDigit
+	bExtendedArabicIndicDigit
+
+	// These bits are set on each iteration depending on the current value.
+	bJoinStart
+	bJoinMid
+	bJoinEnd
+	bVirama
+	bLatinSmallL
+	bGreek
+	bHebrew
+
+	// These bits indicated which of the permanent bits need to be set at the
+	// end of the checks.
+	bMustHaveJapn
+
+	permanent = bJapanese | bArabicIndicDigit | bExtendedArabicIndicDigit | bMustHaveJapn
+)
+
+const finalShift = 10
+
+var errContext = errors.New("precis: contextual rule violated")
+
+func init() {
+	// Programmatically set these required bits as, manually setting them seems
+	// too error prone.
+	for i, ct := range categoryTransitions {
+		categoryTransitions[i].keep |= permanent
+		categoryTransitions[i].accept |= ct.term
+	}
+}
+
+var categoryTransitions = []struct {
+	keep catBitmap // mask selecting which bits to keep from the previous state
+	set  catBitmap // mask for which bits to set for this transition
+
+	// These bitmaps are used for rules that require lookahead.
+	// term&accept == term must be true, which is enforced programmatically.
+	term   catBitmap // bits accepted as termination condition
+	accept catBitmap // bits that pass, but not sufficient as termination
+
+	// The rule function cannot take a *context as an argument, as it would
+	// cause the context to escape, adding significant overhead.
+	rule func(beforeBits catBitmap) (doLookahead bool, err error)
+}{
+	joiningL:          {set: bJoinStart},
+	joiningD:          {set: bJoinStart | bJoinEnd},
+	joiningT:          {keep: bJoinStart, set: bJoinMid},
+	joiningR:          {set: bJoinEnd},
+	viramaModifier:    {set: bVirama},
+	viramaJoinT:       {set: bVirama | bJoinMid},
+	latinSmallL:       {set: bLatinSmallL},
+	greek:             {set: bGreek},
+	greekJoinT:        {set: bGreek | bJoinMid},
+	hebrew:            {set: bHebrew},
+	hebrewJoinT:       {set: bHebrew | bJoinMid},
+	japanese:          {set: bJapanese},
+	katakanaMiddleDot: {set: bMustHaveJapn},
+
+	zeroWidthNonJoiner: {
+		term:   bJoinEnd,
+		accept: bJoinMid,
+		rule: func(before catBitmap) (doLookAhead bool, err error) {
+			if before&bVirama != 0 {
+				return false, nil
+			}
+			if before&bJoinStart == 0 {
+				return false, errContext
+			}
+			return true, nil
+		},
+	},
+	zeroWidthJoiner: {
+		rule: func(before catBitmap) (doLookAhead bool, err error) {
+			if before&bVirama == 0 {
+				err = errContext
+			}
+			return false, err
+		},
+	},
+	middleDot: {
+		term: bLatinSmallL,
+		rule: func(before catBitmap) (doLookAhead bool, err error) {
+			if before&bLatinSmallL == 0 {
+				return false, errContext
+			}
+			return true, nil
+		},
+	},
+	greekLowerNumeralSign: {
+		set:  bGreek,
+		term: bGreek,
+		rule: func(before catBitmap) (doLookAhead bool, err error) {
+			return true, nil
+		},
+	},
+	hebrewPreceding: {
+		set: bHebrew,
+		rule: func(before catBitmap) (doLookAhead bool, err error) {
+			if before&bHebrew == 0 {
+				err = errContext
+			}
+			return false, err
+		},
+	},
+	arabicIndicDigit: {
+		set: bArabicIndicDigit,
+		rule: func(before catBitmap) (doLookAhead bool, err error) {
+			if before&bExtendedArabicIndicDigit != 0 {
+				err = errContext
+			}
+			return false, err
+		},
+	},
+	extendedArabicIndicDigit: {
+		set: bExtendedArabicIndicDigit,
+		rule: func(before catBitmap) (doLookAhead bool, err error) {
+			if before&bArabicIndicDigit != 0 {
+				err = errContext
+			}
+			return false, err
+		},
+	},
+}

vendor/golang.org/x/text/secure/precis/doc.go

@@ -0,0 +1,14 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package precis contains types and functions for the preparation,
+// enforcement, and comparison of internationalized strings ("PRECIS") as
+// defined in RFC 8264. It also contains several pre-defined profiles for
+// passwords, nicknames, and usernames as defined in RFC 8265 and RFC 8266.
+//
+// BE ADVISED: This package is under construction and the API may change in
+// backwards incompatible ways and without notice.
+package precis // import "golang.org/x/text/secure/precis"
+
+//go:generate go run gen.go gen_trieval.go

vendor/golang.org/x/text/secure/precis/nickname.go

@@ -0,0 +1,72 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package precis
+
+import (
+	"unicode"
+	"unicode/utf8"
+
+	"golang.org/x/text/transform"
+)
+
+type nickAdditionalMapping struct {
+	// TODO: This transformer needs to be stateless somehow…
+	notStart  bool
+	prevSpace bool
+}
+
+func (t *nickAdditionalMapping) Reset() {
+	t.prevSpace = false
+	t.notStart = false
+}
+
+func (t *nickAdditionalMapping) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
+	// RFC 8266 §2.1.  Rules
+	//
+	// 2.  Additional Mapping Rule: The additional mapping rule consists of
+	//     the following sub-rules.
+	//
+	//     a.  Map any instances of non-ASCII space to SPACE (U+0020); a
+	//         non-ASCII space is any Unicode code point having a general
+	//         category of "Zs", naturally with the exception of SPACE
+	//         (U+0020).  (The inclusion of only ASCII space prevents
+	//         confusion with various non-ASCII space code points, many of
+	//         which are difficult to reproduce across different input
+	//         methods.)
+	//
+	//     b.  Remove any instances of the ASCII space character at the
+	//         beginning or end of a nickname (e.g., "stpeter " is mapped to
+	//         "stpeter").
+	//
+	//     c.  Map interior sequences of more than one ASCII space character
+	//         to a single ASCII space character (e.g., "St  Peter" is
+	//         mapped to "St Peter").
+	for nSrc < len(src) {
+		r, size := utf8.DecodeRune(src[nSrc:])
+		if size == 0 { // Incomplete UTF-8 encoding
+			if !atEOF {
+				return nDst, nSrc, transform.ErrShortSrc
+			}
+			size = 1
+		}
+		if unicode.Is(unicode.Zs, r) {
+			t.prevSpace = true
+		} else {
+			if t.prevSpace && t.notStart {
+				dst[nDst] = ' '
+				nDst += 1
+			}
+			if size != copy(dst[nDst:], src[nSrc:nSrc+size]) {
+				nDst += size
+				return nDst, nSrc, transform.ErrShortDst
+			}
+			nDst += size
+			t.prevSpace = false
+			t.notStart = true
+		}
+		nSrc += size
+	}
+	return nDst, nSrc, nil
+}

vendor/golang.org/x/text/secure/precis/options.go

@@ -0,0 +1,157 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package precis
+
+import (
+	"golang.org/x/text/cases"
+	"golang.org/x/text/language"
+	"golang.org/x/text/runes"
+	"golang.org/x/text/transform"
+	"golang.org/x/text/unicode/norm"
+)
+
+// An Option is used to define the behavior and rules of a Profile.
+type Option func(*options)
+
+type options struct {
+	// Preparation options
+	foldWidth bool
+
+	// Enforcement options
+	asciiLower    bool
+	cases         transform.SpanningTransformer
+	disallow      runes.Set
+	norm          transform.SpanningTransformer
+	additional    []func() transform.SpanningTransformer
+	width         transform.SpanningTransformer
+	disallowEmpty bool
+	bidiRule      bool
+	repeat        bool
+
+	// Comparison options
+	ignorecase bool
+}
+
+func getOpts(o ...Option) (res options) {
+	for _, f := range o {
+		f(&res)
+	}
+	// Using a SpanningTransformer, instead of norm.Form prevents an allocation
+	// down the road.
+	if res.norm == nil {
+		res.norm = norm.NFC
+	}
+	return
+}
+
+var (
+	// The IgnoreCase option causes the profile to perform a case insensitive
+	// comparison during the PRECIS comparison step.
+	IgnoreCase Option = ignoreCase
+
+	// The FoldWidth option causes the profile to map non-canonical wide and
+	// narrow variants to their decomposition mapping. This is useful for
+	// profiles that are based on the identifier class which would otherwise
+	// disallow such characters.
+	FoldWidth Option = foldWidth
+
+	// The DisallowEmpty option causes the enforcement step to return an error if
+	// the resulting string would be empty.
+	DisallowEmpty Option = disallowEmpty
+
+	// The BidiRule option causes the Bidi Rule defined in RFC 5893 to be
+	// applied.
+	BidiRule Option = bidiRule
+)
+
+var (
+	ignoreCase = func(o *options) {
+		o.ignorecase = true
+	}
+	foldWidth = func(o *options) {
+		o.foldWidth = true
+	}
+	disallowEmpty = func(o *options) {
+		o.disallowEmpty = true
+	}
+	bidiRule = func(o *options) {
+		o.bidiRule = true
+	}
+	repeat = func(o *options) {
+		o.repeat = true
+	}
+)
+
+// TODO: move this logic to package transform
+
+type spanWrap struct{ transform.Transformer }
+
+func (s spanWrap) Span(src []byte, atEOF bool) (n int, err error) {
+	return 0, transform.ErrEndOfSpan
+}
+
+// TODO: allow different types? For instance:
+//     func() transform.Transformer
+//     func() transform.SpanningTransformer
+//     func([]byte) bool  // validation only
+//
+// Also, would be great if we could detect if a transformer is reentrant.
+
+// The AdditionalMapping option defines the additional mapping rule for the
+// Profile by applying Transformer's in sequence.
+func AdditionalMapping(t ...func() transform.Transformer) Option {
+	return func(o *options) {
+		for _, f := range t {
+			sf := func() transform.SpanningTransformer {
+				return f().(transform.SpanningTransformer)
+			}
+			if _, ok := f().(transform.SpanningTransformer); !ok {
+				sf = func() transform.SpanningTransformer {
+					return spanWrap{f()}
+				}
+			}
+			o.additional = append(o.additional, sf)
+		}
+	}
+}
+
+// The Norm option defines a Profile's normalization rule. Defaults to NFC.
+func Norm(f norm.Form) Option {
+	return func(o *options) {
+		o.norm = f
+	}
+}
+
+// The FoldCase option defines a Profile's case mapping rule. Options can be
+// provided to determine the type of case folding used.
+func FoldCase(opts ...cases.Option) Option {
+	return func(o *options) {
+		o.asciiLower = true
+		o.cases = cases.Fold(opts...)
+	}
+}
+
+// The LowerCase option defines a Profile's case mapping rule. Options can be
+// provided to determine the type of case folding used.
+func LowerCase(opts ...cases.Option) Option {
+	return func(o *options) {
+		o.asciiLower = true
+		if len(opts) == 0 {
+			o.cases = cases.Lower(language.Und, cases.HandleFinalSigma(false))
+			return
+		}
+
+		opts = append([]cases.Option{cases.HandleFinalSigma(false)}, opts...)
+		o.cases = cases.Lower(language.Und, opts...)
+	}
+}
+
+// The Disallow option further restricts a Profile's allowed characters beyond
+// what is disallowed by the underlying string class.
+func Disallow(set runes.Set) Option {
+	return func(o *options) {
+		o.disallow = set
+	}
+}

vendor/golang.org/x/text/secure/precis/profile.go

@@ -0,0 +1,412 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package precis
+
+import (
+	"bytes"
+	"errors"
+	"unicode/utf8"
+
+	"golang.org/x/text/cases"
+	"golang.org/x/text/language"
+	"golang.org/x/text/runes"
+	"golang.org/x/text/secure/bidirule"
+	"golang.org/x/text/transform"
+	"golang.org/x/text/width"
+)
+
+var (
+	errDisallowedRune = errors.New("precis: disallowed rune encountered")
+)
+
+var dpTrie = newDerivedPropertiesTrie(0)
+
+// A Profile represents a set of rules for normalizing and validating strings in
+// the PRECIS framework.
+type Profile struct {
+	options
+	class *class
+}
+
+// NewIdentifier creates a new PRECIS profile based on the Identifier string
+// class. Profiles created from this class are suitable for use where safety is
+// prioritized over expressiveness like network identifiers, user accounts, chat
+// rooms, and file names.
+func NewIdentifier(opts ...Option) *Profile {
+	return &Profile{
+		options: getOpts(opts...),
+		class:   identifier,
+	}
+}
+
+// NewFreeform creates a new PRECIS profile based on the Freeform string class.
+// Profiles created from this class are suitable for use where expressiveness is
+// prioritized over safety like passwords, and display-elements such as
+// nicknames in a chat room.
+func NewFreeform(opts ...Option) *Profile {
+	return &Profile{
+		options: getOpts(opts...),
+		class:   freeform,
+	}
+}
+
+// NewRestrictedProfile creates a new PRECIS profile based on an existing
+// profile.
+// If the parent profile already had the Disallow option set, the new rule
+// overrides the parents rule.
+func NewRestrictedProfile(parent *Profile, disallow runes.Set) *Profile {
+	p := *parent
+	Disallow(disallow)(&p.options)
+	return &p
+}
+
+// NewTransformer creates a new transform.Transformer that performs the PRECIS
+// preparation and enforcement steps on the given UTF-8 encoded bytes.
+func (p *Profile) NewTransformer() *Transformer {
+	var ts []transform.Transformer
+
+	// These transforms are applied in the order defined in
+	// https://tools.ietf.org/html/rfc7564#section-7
+
+	// RFC 8266 §2.1:
+	//
+	//     Implementation experience has shown that applying the rules for the
+	//     Nickname profile is not an idempotent procedure for all code points.
+	//     Therefore, an implementation SHOULD apply the rules repeatedly until
+	//     the output string is stable; if the output string does not stabilize
+	//     after reapplying the rules three (3) additional times after the first
+	//     application, the implementation SHOULD terminate application of the
+	//     rules and reject the input string as invalid.
+	//
+	// There is no known string that will change indefinitely, so repeat 4 times
+	// and rely on the Span method to keep things relatively performant.
+	r := 1
+	if p.options.repeat {
+		r = 4
+	}
+	for ; r > 0; r-- {
+		if p.options.foldWidth {
+			ts = append(ts, width.Fold)
+		}
+
+		for _, f := range p.options.additional {
+			ts = append(ts, f())
+		}
+
+		if p.options.cases != nil {
+			ts = append(ts, p.options.cases)
+		}
+
+		ts = append(ts, p.options.norm)
+
+		if p.options.bidiRule {
+			ts = append(ts, bidirule.New())
+		}
+
+		ts = append(ts, &checker{p: p, allowed: p.Allowed()})
+	}
+
+	// TODO: Add the disallow empty rule with a dummy transformer?
+
+	return &Transformer{transform.Chain(ts...)}
+}
+
+var errEmptyString = errors.New("precis: transformation resulted in empty string")
+
+type buffers struct {
+	src  []byte
+	buf  [2][]byte
+	next int
+}
+
+func (b *buffers) apply(t transform.SpanningTransformer) (err error) {
+	n, err := t.Span(b.src, true)
+	if err != transform.ErrEndOfSpan {
+		return err
+	}
+	x := b.next & 1
+	if b.buf[x] == nil {
+		b.buf[x] = make([]byte, 0, 8+len(b.src)+len(b.src)>>2)
+	}
+	span := append(b.buf[x][:0], b.src[:n]...)
+	b.src, _, err = transform.Append(t, span, b.src[n:])
+	b.buf[x] = b.src
+	b.next++
+	return err
+}
+
+// Pre-allocate transformers when possible. In some cases this avoids allocation.
+var (
+	foldWidthT transform.SpanningTransformer = width.Fold
+	lowerCaseT transform.SpanningTransformer = cases.Lower(language.Und, cases.HandleFinalSigma(false))
+)
+
+// TODO: make this a method on profile.
+
+func (b *buffers) enforce(p *Profile, src []byte, comparing bool) (str []byte, err error) {
+	b.src = src
+
+	ascii := true
+	for _, c := range src {
+		if c >= utf8.RuneSelf {
+			ascii = false
+			break
+		}
+	}
+	// ASCII fast path.
+	if ascii {
+		for _, f := range p.options.additional {
+			if err = b.apply(f()); err != nil {
+				return nil, err
+			}
+		}
+		switch {
+		case p.options.asciiLower || (comparing && p.options.ignorecase):
+			for i, c := range b.src {
+				if 'A' <= c && c <= 'Z' {
+					b.src[i] = c ^ 1<<5
+				}
+			}
+		case p.options.cases != nil:
+			b.apply(p.options.cases)
+		}
+		c := checker{p: p}
+		if _, err := c.span(b.src, true); err != nil {
+			return nil, err
+		}
+		if p.disallow != nil {
+			for _, c := range b.src {
+				if p.disallow.Contains(rune(c)) {
+					return nil, errDisallowedRune
+				}
+			}
+		}
+		if p.options.disallowEmpty && len(b.src) == 0 {
+			return nil, errEmptyString
+		}
+		return b.src, nil
+	}
+
+	// These transforms are applied in the order defined in
+	// https://tools.ietf.org/html/rfc8264#section-7
+
+	r := 1
+	if p.options.repeat {
+		r = 4
+	}
+	for ; r > 0; r-- {
+		// TODO: allow different width transforms options.
+		if p.options.foldWidth || (p.options.ignorecase && comparing) {
+			b.apply(foldWidthT)
+		}
+		for _, f := range p.options.additional {
+			if err = b.apply(f()); err != nil {
+				return nil, err
+			}
+		}
+		if p.options.cases != nil {
+			b.apply(p.options.cases)
+		}
+		if comparing && p.options.ignorecase {
+			b.apply(lowerCaseT)
+		}
+		b.apply(p.norm)
+		if p.options.bidiRule && !bidirule.Valid(b.src) {
+			return nil, bidirule.ErrInvalid
+		}
+		c := checker{p: p}
+		if _, err := c.span(b.src, true); err != nil {
+			return nil, err
+		}
+		if p.disallow != nil {
+			for i := 0; i < len(b.src); {
+				r, size := utf8.DecodeRune(b.src[i:])
+				if p.disallow.Contains(r) {
+					return nil, errDisallowedRune
+				}
+				i += size
+			}
+		}
+		if p.options.disallowEmpty && len(b.src) == 0 {
+			return nil, errEmptyString
+		}
+	}
+	return b.src, nil
+}
+
+// Append appends the result of applying p to src writing the result to dst.
+// It returns an error if the input string is invalid.
+func (p *Profile) Append(dst, src []byte) ([]byte, error) {
+	var buf buffers
+	b, err := buf.enforce(p, src, false)
+	if err != nil {
+		return nil, err
+	}
+	return append(dst, b...), nil
+}
+
+func processBytes(p *Profile, b []byte, key bool) ([]byte, error) {
+	var buf buffers
+	b, err := buf.enforce(p, b, key)
+	if err != nil {
+		return nil, err
+	}
+	if buf.next == 0 {
+		c := make([]byte, len(b))
+		copy(c, b)
+		return c, nil
+	}
+	return b, nil
+}
+
+// Bytes returns a new byte slice with the result of applying the profile to b.
+func (p *Profile) Bytes(b []byte) ([]byte, error) {
+	return processBytes(p, b, false)
+}
+
+// AppendCompareKey appends the result of applying p to src (including any
+// optional rules to make strings comparable or useful in a map key such as
+// applying lowercasing) writing the result to dst. It returns an error if the
+// input string is invalid.
+func (p *Profile) AppendCompareKey(dst, src []byte) ([]byte, error) {
+	var buf buffers
+	b, err := buf.enforce(p, src, true)
+	if err != nil {
+		return nil, err
+	}
+	return append(dst, b...), nil
+}
+
+func processString(p *Profile, s string, key bool) (string, error) {
+	var buf buffers
+	b, err := buf.enforce(p, []byte(s), key)
+	if err != nil {
+		return "", err
+	}
+	return string(b), nil
+}
+
+// String returns a string with the result of applying the profile to s.
+func (p *Profile) String(s string) (string, error) {
+	return processString(p, s, false)
+}
+
+// CompareKey returns a string that can be used for comparison, hashing, or
+// collation.
+func (p *Profile) CompareKey(s string) (string, error) {
+	return processString(p, s, true)
+}
+
+// Compare enforces both strings, and then compares them for bit-string identity
+// (byte-for-byte equality). If either string cannot be enforced, the comparison
+// is false.
+func (p *Profile) Compare(a, b string) bool {
+	var buf buffers
+
+	akey, err := buf.enforce(p, []byte(a), true)
+	if err != nil {
+		return false
+	}
+
+	buf = buffers{}
+	bkey, err := buf.enforce(p, []byte(b), true)
+	if err != nil {
+		return false
+	}
+
+	return bytes.Compare(akey, bkey) == 0
+}
+
+// Allowed returns a runes.Set containing every rune that is a member of the
+// underlying profile's string class and not disallowed by any profile specific
+// rules.
+func (p *Profile) Allowed() runes.Set {
+	if p.options.disallow != nil {
+		return runes.Predicate(func(r rune) bool {
+			return p.class.Contains(r) && !p.options.disallow.Contains(r)
+		})
+	}
+	return p.class
+}
+
+type checker struct {
+	p       *Profile
+	allowed runes.Set
+
+	beforeBits catBitmap
+	termBits   catBitmap
+	acceptBits catBitmap
+}
+
+func (c *checker) Reset() {
+	c.beforeBits = 0
+	c.termBits = 0
+	c.acceptBits = 0
+}
+
+func (c *checker) span(src []byte, atEOF bool) (n int, err error) {
+	for n < len(src) {
+		e, sz := dpTrie.lookup(src[n:])
+		d := categoryTransitions[category(e&catMask)]
+		if sz == 0 {
+			if !atEOF {
+				return n, transform.ErrShortSrc
+			}
+			return n, errDisallowedRune
+		}
+		doLookAhead := false
+		if property(e) < c.p.class.validFrom {
+			if d.rule == nil {
+				return n, errDisallowedRune
+			}
+			doLookAhead, err = d.rule(c.beforeBits)
+			if err != nil {
+				return n, err
+			}
+		}
+		c.beforeBits &= d.keep
+		c.beforeBits |= d.set
+		if c.termBits != 0 {
+			// We are currently in an unterminated lookahead.
+			if c.beforeBits&c.termBits != 0 {
+				c.termBits = 0
+				c.acceptBits = 0
+			} else if c.beforeBits&c.acceptBits == 0 {
+				// Invalid continuation of the unterminated lookahead sequence.
+				return n, errContext
+			}
+		}
+		if doLookAhead {
+			if c.termBits != 0 {
+				// A previous lookahead run has not been terminated yet.
+				return n, errContext
+			}
+			c.termBits = d.term
+			c.acceptBits = d.accept
+		}
+		n += sz
+	}
+	if m := c.beforeBits >> finalShift; c.beforeBits&m != m || c.termBits != 0 {
+		err = errContext
+	}
+	return n, err
+}
+
+// TODO: we may get rid of this transform if transform.Chain understands
+// something like a Spanner interface.
+func (c checker) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
+	short := false
+	if len(dst) < len(src) {
+		src = src[:len(dst)]
+		atEOF = false
+		short = true
+	}
+	nSrc, err = c.span(src, atEOF)
+	nDst = copy(dst, src[:nSrc])
+	if short && (err == transform.ErrShortSrc || err == nil) {
+		err = transform.ErrShortDst
+	}
+	return nDst, nSrc, err
+}

vendor/golang.org/x/text/secure/precis/profiles.go

@@ -0,0 +1,78 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package precis
+
+import (
+	"unicode"
+
+	"golang.org/x/text/runes"
+	"golang.org/x/text/transform"
+	"golang.org/x/text/unicode/norm"
+)
+
+var (
+	// Implements the Nickname profile specified in RFC 8266.
+	Nickname *Profile = nickname
+
+	// Implements the UsernameCaseMapped profile specified in RFC 8265.
+	UsernameCaseMapped *Profile = usernameCaseMap
+
+	// Implements the UsernameCasePreserved profile specified in RFC 8265.
+	UsernameCasePreserved *Profile = usernameNoCaseMap
+
+	// Implements the OpaqueString profile defined in RFC 8265 for passwords and
+	// other secure labels.
+	OpaqueString *Profile = opaquestring
+)
+
+var (
+	nickname = &Profile{
+		options: getOpts(
+			AdditionalMapping(func() transform.Transformer {
+				return &nickAdditionalMapping{}
+			}),
+			IgnoreCase,
+			Norm(norm.NFKC),
+			DisallowEmpty,
+			repeat,
+		),
+		class: freeform,
+	}
+	usernameCaseMap = &Profile{
+		options: getOpts(
+			FoldWidth,
+			LowerCase(),
+			Norm(norm.NFC),
+			BidiRule,
+		),
+		class: identifier,
+	}
+	usernameNoCaseMap = &Profile{
+		options: getOpts(
+			FoldWidth,
+			Norm(norm.NFC),
+			BidiRule,
+		),
+		class: identifier,
+	}
+	opaquestring = &Profile{
+		options: getOpts(
+			AdditionalMapping(func() transform.Transformer {
+				return mapSpaces
+			}),
+			Norm(norm.NFC),
+			DisallowEmpty,
+		),
+		class: freeform,
+	}
+)
+
+// mapSpaces is a shared value of a runes.Map transformer.
+var mapSpaces transform.Transformer = runes.Map(func(r rune) rune {
+	if unicode.Is(unicode.Zs, r) {
+		return ' '
+	}
+	return r
+})

vendor/golang.org/x/text/secure/precis/transformer.go

@@ -0,0 +1,32 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package precis
+
+import "golang.org/x/text/transform"
+
+// Transformer implements the transform.Transformer interface.
+type Transformer struct {
+	t transform.Transformer
+}
+
+// Reset implements the transform.Transformer interface.
+func (t Transformer) Reset() { t.t.Reset() }
+
+// Transform implements the transform.Transformer interface.
+func (t Transformer) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
+	return t.t.Transform(dst, src, atEOF)
+}
+
+// Bytes returns a new byte slice with the result of applying t to b.
+func (t Transformer) Bytes(b []byte) []byte {
+	b, _, _ = transform.Bytes(t, b)
+	return b
+}
+
+// String returns a string with the result of applying t to s.
+func (t Transformer) String(s string) string {
+	s, _, _ = transform.String(t, s)
+	return s
+}

vendor/golang.org/x/text/secure/precis/trieval.go

@@ -0,0 +1,64 @@
+// Code generated by running "go generate" in golang.org/x/text. DO NOT EDIT.
+
+package precis
+
+// entry is the entry of a trie table
+// 7..6   property (unassigned, disallowed, maybe, valid)
+// 5..0   category
+type entry uint8
+
+const (
+	propShift = 6
+	propMask  = 0xc0
+	catMask   = 0x3f
+)
+
+func (e entry) property() property { return property(e & propMask) }
+func (e entry) category() category { return category(e & catMask) }
+
+type property uint8
+
+// The order of these constants matter. A Profile may consider runes to be
+// allowed either from pValid or idDisOrFreePVal.
+const (
+	unassigned property = iota << propShift
+	disallowed
+	idDisOrFreePVal // disallowed for Identifier, pValid for FreeForm
+	pValid
+)
+
+// compute permutations of all properties and specialCategories.
+type category uint8
+
+const (
+	other category = iota
+
+	// Special rune types
+	joiningL
+	joiningD
+	joiningT
+	joiningR
+	viramaModifier
+	viramaJoinT // Virama + JoiningT
+	latinSmallL // U+006c
+	greek
+	greekJoinT // Greek + JoiningT
+	hebrew
+	hebrewJoinT // Hebrew + JoiningT
+	japanese    // hirigana, katakana, han
+
+	// Special rune types associated with contextual rules defined in
+	// https://tools.ietf.org/html/rfc5892#appendix-A.
+	// ContextO
+	zeroWidthNonJoiner // rule 1
+	zeroWidthJoiner    // rule 2
+	// ContextJ
+	middleDot                // rule 3
+	greekLowerNumeralSign    // rule 4
+	hebrewPreceding          // rule 5 and 6
+	katakanaMiddleDot        // rule 7
+	arabicIndicDigit         // rule 8
+	extendedArabicIndicDigit // rule 9
+
+	numCategories
+)

vendor/golang.org/x/text/width/kind_string.go

@@ -0,0 +1,28 @@
+// Code generated by "stringer -type=Kind"; DO NOT EDIT.
+
+package width
+
+import "strconv"
+
+func _() {
+	// An "invalid array index" compiler error signifies that the constant values have changed.
+	// Re-run the stringer command to generate them again.
+	var x [1]struct{}
+	_ = x[Neutral-0]
+	_ = x[EastAsianAmbiguous-1]
+	_ = x[EastAsianWide-2]
+	_ = x[EastAsianNarrow-3]
+	_ = x[EastAsianFullwidth-4]
+	_ = x[EastAsianHalfwidth-5]
+}
+
+const _Kind_name = "NeutralEastAsianAmbiguousEastAsianWideEastAsianNarrowEastAsianFullwidthEastAsianHalfwidth"
+
+var _Kind_index = [...]uint8{0, 7, 25, 38, 53, 71, 89}
+
+func (i Kind) String() string {
+	if i < 0 || i >= Kind(len(_Kind_index)-1) {
+		return "Kind(" + strconv.FormatInt(int64(i), 10) + ")"
+	}
+	return _Kind_name[_Kind_index[i]:_Kind_index[i+1]]
+}

vendor/golang.org/x/text/width/transform.go

@@ -0,0 +1,239 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package width
+
+import (
+	"unicode/utf8"
+
+	"golang.org/x/text/transform"
+)
+
+type foldTransform struct {
+	transform.NopResetter
+}
+
+func (foldTransform) Span(src []byte, atEOF bool) (n int, err error) {
+	for n < len(src) {
+		if src[n] < utf8.RuneSelf {
+			// ASCII fast path.
+			for n++; n < len(src) && src[n] < utf8.RuneSelf; n++ {
+			}
+			continue
+		}
+		v, size := trie.lookup(src[n:])
+		if size == 0 { // incomplete UTF-8 encoding
+			if !atEOF {
+				err = transform.ErrShortSrc
+			} else {
+				n = len(src)
+			}
+			break
+		}
+		if elem(v)&tagNeedsFold != 0 {
+			err = transform.ErrEndOfSpan
+			break
+		}
+		n += size
+	}
+	return n, err
+}
+
+func (foldTransform) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
+	for nSrc < len(src) {
+		if src[nSrc] < utf8.RuneSelf {
+			// ASCII fast path.
+			start, end := nSrc, len(src)
+			if d := len(dst) - nDst; d < end-start {
+				end = nSrc + d
+			}
+			for nSrc++; nSrc < end && src[nSrc] < utf8.RuneSelf; nSrc++ {
+			}
+			n := copy(dst[nDst:], src[start:nSrc])
+			if nDst += n; nDst == len(dst) {
+				nSrc = start + n
+				if nSrc == len(src) {
+					return nDst, nSrc, nil
+				}
+				if src[nSrc] < utf8.RuneSelf {
+					return nDst, nSrc, transform.ErrShortDst
+				}
+			}
+			continue
+		}
+		v, size := trie.lookup(src[nSrc:])
+		if size == 0 { // incomplete UTF-8 encoding
+			if !atEOF {
+				return nDst, nSrc, transform.ErrShortSrc
+			}
+			size = 1 // gobble 1 byte
+		}
+		if elem(v)&tagNeedsFold == 0 {
+			if size != copy(dst[nDst:], src[nSrc:nSrc+size]) {
+				return nDst, nSrc, transform.ErrShortDst
+			}
+			nDst += size
+		} else {
+			data := inverseData[byte(v)]
+			if len(dst)-nDst < int(data[0]) {
+				return nDst, nSrc, transform.ErrShortDst
+			}
+			i := 1
+			for end := int(data[0]); i < end; i++ {
+				dst[nDst] = data[i]
+				nDst++
+			}
+			dst[nDst] = data[i] ^ src[nSrc+size-1]
+			nDst++
+		}
+		nSrc += size
+	}
+	return nDst, nSrc, nil
+}
+
+type narrowTransform struct {
+	transform.NopResetter
+}
+
+func (narrowTransform) Span(src []byte, atEOF bool) (n int, err error) {
+	for n < len(src) {
+		if src[n] < utf8.RuneSelf {
+			// ASCII fast path.
+			for n++; n < len(src) && src[n] < utf8.RuneSelf; n++ {
+			}
+			continue
+		}
+		v, size := trie.lookup(src[n:])
+		if size == 0 { // incomplete UTF-8 encoding
+			if !atEOF {
+				err = transform.ErrShortSrc
+			} else {
+				n = len(src)
+			}
+			break
+		}
+		if k := elem(v).kind(); byte(v) == 0 || k != EastAsianFullwidth && k != EastAsianWide && k != EastAsianAmbiguous {
+		} else {
+			err = transform.ErrEndOfSpan
+			break
+		}
+		n += size
+	}
+	return n, err
+}
+
+func (narrowTransform) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
+	for nSrc < len(src) {
+		if src[nSrc] < utf8.RuneSelf {
+			// ASCII fast path.
+			start, end := nSrc, len(src)
+			if d := len(dst) - nDst; d < end-start {
+				end = nSrc + d
+			}
+			for nSrc++; nSrc < end && src[nSrc] < utf8.RuneSelf; nSrc++ {
+			}
+			n := copy(dst[nDst:], src[start:nSrc])
+			if nDst += n; nDst == len(dst) {
+				nSrc = start + n
+				if nSrc == len(src) {
+					return nDst, nSrc, nil
+				}
+				if src[nSrc] < utf8.RuneSelf {
+					return nDst, nSrc, transform.ErrShortDst
+				}
+			}
+			continue
+		}
+		v, size := trie.lookup(src[nSrc:])
+		if size == 0 { // incomplete UTF-8 encoding
+			if !atEOF {
+				return nDst, nSrc, transform.ErrShortSrc
+			}
+			size = 1 // gobble 1 byte
+		}
+		if k := elem(v).kind(); byte(v) == 0 || k != EastAsianFullwidth && k != EastAsianWide && k != EastAsianAmbiguous {
+			if size != copy(dst[nDst:], src[nSrc:nSrc+size]) {
+				return nDst, nSrc, transform.ErrShortDst
+			}
+			nDst += size
+		} else {
+			data := inverseData[byte(v)]
+			if len(dst)-nDst < int(data[0]) {
+				return nDst, nSrc, transform.ErrShortDst
+			}
+			i := 1
+			for end := int(data[0]); i < end; i++ {
+				dst[nDst] = data[i]
+				nDst++
+			}
+			dst[nDst] = data[i] ^ src[nSrc+size-1]
+			nDst++
+		}
+		nSrc += size
+	}
+	return nDst, nSrc, nil
+}
+
+type wideTransform struct {
+	transform.NopResetter
+}
+
+func (wideTransform) Span(src []byte, atEOF bool) (n int, err error) {
+	for n < len(src) {
+		// TODO: Consider ASCII fast path. Special-casing ASCII handling can
+		// reduce the ns/op of BenchmarkWideASCII by about 30%. This is probably
+		// not enough to warrant the extra code and complexity.
+		v, size := trie.lookup(src[n:])
+		if size == 0 { // incomplete UTF-8 encoding
+			if !atEOF {
+				err = transform.ErrShortSrc
+			} else {
+				n = len(src)
+			}
+			break
+		}
+		if k := elem(v).kind(); byte(v) == 0 || k != EastAsianHalfwidth && k != EastAsianNarrow {
+		} else {
+			err = transform.ErrEndOfSpan
+			break
+		}
+		n += size
+	}
+	return n, err
+}
+
+func (wideTransform) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
+	for nSrc < len(src) {
+		// TODO: Consider ASCII fast path. Special-casing ASCII handling can
+		// reduce the ns/op of BenchmarkWideASCII by about 30%. This is probably
+		// not enough to warrant the extra code and complexity.
+		v, size := trie.lookup(src[nSrc:])
+		if size == 0 { // incomplete UTF-8 encoding
+			if !atEOF {
+				return nDst, nSrc, transform.ErrShortSrc
+			}
+			size = 1 // gobble 1 byte
+		}
+		if k := elem(v).kind(); byte(v) == 0 || k != EastAsianHalfwidth && k != EastAsianNarrow {
+			if size != copy(dst[nDst:], src[nSrc:nSrc+size]) {
+				return nDst, nSrc, transform.ErrShortDst
+			}
+			nDst += size
+		} else {
+			data := inverseData[byte(v)]
+			if len(dst)-nDst < int(data[0]) {
+				return nDst, nSrc, transform.ErrShortDst
+			}
+			i := 1
+			for end := int(data[0]); i < end; i++ {
+				dst[nDst] = data[i]
+				nDst++
+			}
+			dst[nDst] = data[i] ^ src[nSrc+size-1]
+			nDst++
+		}
+		nSrc += size
+	}
+	return nDst, nSrc, nil
+}

vendor/golang.org/x/text/width/trieval.go

@@ -0,0 +1,30 @@
+// Code generated by running "go generate" in golang.org/x/text. DO NOT EDIT.
+
+package width
+
+// elem is an entry of the width trie. The high byte is used to encode the type
+// of the rune. The low byte is used to store the index to a mapping entry in
+// the inverseData array.
+type elem uint16
+
+const (
+	tagNeutral elem = iota << typeShift
+	tagAmbiguous
+	tagWide
+	tagNarrow
+	tagFullwidth
+	tagHalfwidth
+)
+
+const (
+	numTypeBits = 3
+	typeShift   = 16 - numTypeBits
+
+	// tagNeedsFold is true for all fullwidth and halfwidth runes except for
+	// the Won sign U+20A9.
+	tagNeedsFold = 0x1000
+
+	// The Korean Won sign is halfwidth, but SHOULD NOT be mapped to a wide
+	// variant.
+	wonSign rune = 0x20A9
+)

vendor/golang.org/x/text/width/width.go

@@ -0,0 +1,206 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:generate stringer -type=Kind
+//go:generate go run gen.go gen_common.go gen_trieval.go
+
+// Package width provides functionality for handling different widths in text.
+//
+// Wide characters behave like ideographs; they tend to allow line breaks after
+// each character and remain upright in vertical text layout. Narrow characters
+// are kept together in words or runs that are rotated sideways in vertical text
+// layout.
+//
+// For more information, see https://unicode.org/reports/tr11/.
+package width // import "golang.org/x/text/width"
+
+import (
+	"unicode/utf8"
+
+	"golang.org/x/text/transform"
+)
+
+// TODO
+// 1) Reduce table size by compressing blocks.
+// 2) API proposition for computing display length
+//    (approximation, fixed pitch only).
+// 3) Implement display length.
+
+// Kind indicates the type of width property as defined in https://unicode.org/reports/tr11/.
+type Kind int
+
+const (
+	// Neutral characters do not occur in legacy East Asian character sets.
+	Neutral Kind = iota
+
+	// EastAsianAmbiguous characters that can be sometimes wide and sometimes
+	// narrow and require additional information not contained in the character
+	// code to further resolve their width.
+	EastAsianAmbiguous
+
+	// EastAsianWide characters are wide in its usual form. They occur only in
+	// the context of East Asian typography. These runes may have explicit
+	// halfwidth counterparts.
+	EastAsianWide
+
+	// EastAsianNarrow characters are narrow in its usual form. They often have
+	// fullwidth counterparts.
+	EastAsianNarrow
+
+	// Note: there exist Narrow runes that do not have fullwidth or wide
+	// counterparts, despite what the definition says (e.g. U+27E6).
+
+	// EastAsianFullwidth characters have a compatibility decompositions of type
+	// wide that map to a narrow counterpart.
+	EastAsianFullwidth
+
+	// EastAsianHalfwidth characters have a compatibility decomposition of type
+	// narrow that map to a wide or ambiguous counterpart, plus U+20A9 ₩ WON
+	// SIGN.
+	EastAsianHalfwidth
+
+	// Note: there exist runes that have a halfwidth counterparts but that are
+	// classified as Ambiguous, rather than wide (e.g. U+2190).
+)
+
+// TODO: the generated tries need to return size 1 for invalid runes for the
+// width to be computed correctly (each byte should render width 1)
+
+var trie = newWidthTrie(0)
+
+// Lookup reports the Properties of the first rune in b and the number of bytes
+// of its UTF-8 encoding.
+func Lookup(b []byte) (p Properties, size int) {
+	v, sz := trie.lookup(b)
+	return Properties{elem(v), b[sz-1]}, sz
+}
+
+// LookupString reports the Properties of the first rune in s and the number of
+// bytes of its UTF-8 encoding.
+func LookupString(s string) (p Properties, size int) {
+	v, sz := trie.lookupString(s)
+	return Properties{elem(v), s[sz-1]}, sz
+}
+
+// LookupRune reports the Properties of rune r.
+func LookupRune(r rune) Properties {
+	var buf [4]byte
+	n := utf8.EncodeRune(buf[:], r)
+	v, _ := trie.lookup(buf[:n])
+	last := byte(r)
+	if r >= utf8.RuneSelf {
+		last = 0x80 + byte(r&0x3f)
+	}
+	return Properties{elem(v), last}
+}
+
+// Properties provides access to width properties of a rune.
+type Properties struct {
+	elem elem
+	last byte
+}
+
+func (e elem) kind() Kind {
+	return Kind(e >> typeShift)
+}
+
+// Kind returns the Kind of a rune as defined in Unicode TR #11.
+// See https://unicode.org/reports/tr11/ for more details.
+func (p Properties) Kind() Kind {
+	return p.elem.kind()
+}
+
+// Folded returns the folded variant of a rune or 0 if the rune is canonical.
+func (p Properties) Folded() rune {
+	if p.elem&tagNeedsFold != 0 {
+		buf := inverseData[byte(p.elem)]
+		buf[buf[0]] ^= p.last
+		r, _ := utf8.DecodeRune(buf[1 : 1+buf[0]])
+		return r
+	}
+	return 0
+}
+
+// Narrow returns the narrow variant of a rune or 0 if the rune is already
+// narrow or doesn't have a narrow variant.
+func (p Properties) Narrow() rune {
+	if k := p.elem.kind(); byte(p.elem) != 0 && (k == EastAsianFullwidth || k == EastAsianWide || k == EastAsianAmbiguous) {
+		buf := inverseData[byte(p.elem)]
+		buf[buf[0]] ^= p.last
+		r, _ := utf8.DecodeRune(buf[1 : 1+buf[0]])
+		return r
+	}
+	return 0
+}
+
+// Wide returns the wide variant of a rune or 0 if the rune is already
+// wide or doesn't have a wide variant.
+func (p Properties) Wide() rune {
+	if k := p.elem.kind(); byte(p.elem) != 0 && (k == EastAsianHalfwidth || k == EastAsianNarrow) {
+		buf := inverseData[byte(p.elem)]
+		buf[buf[0]] ^= p.last
+		r, _ := utf8.DecodeRune(buf[1 : 1+buf[0]])
+		return r
+	}
+	return 0
+}
+
+// TODO for Properties:
+// - Add Fullwidth/Halfwidth or Inverted methods for computing variants
+// mapping.
+// - Add width information (including information on non-spacing runes).
+
+// Transformer implements the transform.Transformer interface.
+type Transformer struct {
+	t transform.SpanningTransformer
+}
+
+// Reset implements the transform.Transformer interface.
+func (t Transformer) Reset() { t.t.Reset() }
+
+// Transform implements the transform.Transformer interface.
+func (t Transformer) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
+	return t.t.Transform(dst, src, atEOF)
+}
+
+// Span implements the transform.SpanningTransformer interface.
+func (t Transformer) Span(src []byte, atEOF bool) (n int, err error) {
+	return t.t.Span(src, atEOF)
+}
+
+// Bytes returns a new byte slice with the result of applying t to b.
+func (t Transformer) Bytes(b []byte) []byte {
+	b, _, _ = transform.Bytes(t, b)
+	return b
+}
+
+// String returns a string with the result of applying t to s.
+func (t Transformer) String(s string) string {
+	s, _, _ = transform.String(t, s)
+	return s
+}
+
+var (
+	// Fold is a transform that maps all runes to their canonical width.
+	//
+	// Note that the NFKC and NFKD transforms in golang.org/x/text/unicode/norm
+	// provide a more generic folding mechanism.
+	Fold Transformer = Transformer{foldTransform{}}
+
+	// Widen is a transform that maps runes to their wide variant, if
+	// available.
+	Widen Transformer = Transformer{wideTransform{}}
+
+	// Narrow is a transform that maps runes to their narrow variant, if
+	// available.
+	Narrow Transformer = Transformer{narrowTransform{}}
+)
+
+// TODO: Consider the following options:
+// - Treat Ambiguous runes that have a halfwidth counterpart as wide, or some
+//   generalized variant of this.
+// - Consider a wide Won character to be the default width (or some generalized
+//   variant of this).
+// - Filter the set of characters that gets converted (the preferred approach is
+//   to allow applying filters to transforms).