Add optional syslog logrus hook (#343)

* add optional syslog logrus hook

* document syslog

vendor/gopkg.in/mcuadros/go-syslog.v2/internal/syslogparser/syslogparser.go

@@ -0,0 +1,213 @@
+package syslogparser
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+	"time"
+)
+
+const (
+	PRI_PART_START = '<'
+	PRI_PART_END   = '>'
+
+	NO_VERSION = -1
+)
+
+var (
+	ErrEOL     = &ParserError{"End of log line"}
+	ErrNoSpace = &ParserError{"No space found"}
+
+	ErrPriorityNoStart  = &ParserError{"No start char found for priority"}
+	ErrPriorityEmpty    = &ParserError{"Priority field empty"}
+	ErrPriorityNoEnd    = &ParserError{"No end char found for priority"}
+	ErrPriorityTooShort = &ParserError{"Priority field too short"}
+	ErrPriorityTooLong  = &ParserError{"Priority field too long"}
+	ErrPriorityNonDigit = &ParserError{"Non digit found in priority"}
+
+	ErrVersionNotFound = &ParserError{"Can not find version"}
+
+	ErrTimestampUnknownFormat = &ParserError{"Timestamp format unknown"}
+
+	ErrHostnameTooShort = &ParserError{"Hostname field too short"}
+)
+
+type LogParser interface {
+	Parse() error
+	Dump() LogParts
+	Location(*time.Location)
+}
+
+type ParserError struct {
+	ErrorString string
+}
+
+type Priority struct {
+	P int
+	F Facility
+	S Severity
+}
+
+type Facility struct {
+	Value int
+}
+
+type Severity struct {
+	Value int
+}
+
+type LogParts map[string]interface{}
+
+// https://tools.ietf.org/html/rfc3164#section-4.1
+func ParsePriority(buff []byte, cursor *int, l int) (Priority, error) {
+	pri := newPriority(0)
+
+	if l <= 0 {
+		return pri, ErrPriorityEmpty
+	}
+
+	if buff[*cursor] != PRI_PART_START {
+		return pri, ErrPriorityNoStart
+	}
+
+	i := 1
+	priDigit := 0
+
+	for i < l {
+		if i >= 5 {
+			return pri, ErrPriorityTooLong
+		}
+
+		c := buff[i]
+
+		if c == PRI_PART_END {
+			if i == 1 {
+				return pri, ErrPriorityTooShort
+			}
+
+			*cursor = i + 1
+			return newPriority(priDigit), nil
+		}
+
+		if IsDigit(c) {
+			v, e := strconv.Atoi(string(c))
+			if e != nil {
+				return pri, e
+			}
+
+			priDigit = (priDigit * 10) + v
+		} else {
+			return pri, ErrPriorityNonDigit
+		}
+
+		i++
+	}
+
+	return pri, ErrPriorityNoEnd
+}
+
+// https://tools.ietf.org/html/rfc5424#section-6.2.2
+func ParseVersion(buff []byte, cursor *int, l int) (int, error) {
+	if *cursor >= l {
+		return NO_VERSION, ErrVersionNotFound
+	}
+
+	c := buff[*cursor]
+	*cursor++
+
+	// XXX : not a version, not an error though as RFC 3164 does not support it
+	if !IsDigit(c) {
+		return NO_VERSION, nil
+	}
+
+	v, e := strconv.Atoi(string(c))
+	if e != nil {
+		*cursor--
+		return NO_VERSION, e
+	}
+
+	return v, nil
+}
+
+func IsDigit(c byte) bool {
+	return c >= '0' && c <= '9'
+}
+
+func newPriority(p int) Priority {
+	// The Priority value is calculated by first multiplying the Facility
+	// number by 8 and then adding the numerical value of the Severity.
+
+	return Priority{
+		P: p,
+		F: Facility{Value: p / 8},
+		S: Severity{Value: p % 8},
+	}
+}
+
+func FindNextSpace(buff []byte, from int, l int) (int, error) {
+	var to int
+
+	for to = from; to < l; to++ {
+		if buff[to] == ' ' {
+			to++
+			return to, nil
+		}
+	}
+
+	return 0, ErrNoSpace
+}
+
+func Parse2Digits(buff []byte, cursor *int, l int, min int, max int, e error) (int, error) {
+	digitLen := 2
+
+	if *cursor+digitLen > l {
+		return 0, ErrEOL
+	}
+
+	sub := string(buff[*cursor : *cursor+digitLen])
+
+	*cursor += digitLen
+
+	i, err := strconv.Atoi(sub)
+	if err != nil {
+		return 0, e
+	}
+
+	if i >= min && i <= max {
+		return i, nil
+	}
+
+	return 0, e
+}
+
+func ParseHostname(buff []byte, cursor *int, l int) (string, error) {
+	from := *cursor
+
+	if from >= l {
+		return "", ErrHostnameTooShort
+	}
+
+	var to int
+
+	for to = from; to < l; to++ {
+		if buff[to] == ' ' {
+			break
+		}
+	}
+
+	hostname := buff[from:to]
+
+	*cursor = to
+
+	return string(hostname), nil
+}
+
+func ShowCursorPos(buff []byte, cursor int) {
+	fmt.Println(string(buff))
+	padding := strings.Repeat("-", cursor)
+	fmt.Println(padding + "↑\n")
+}
+
+func (err *ParserError) Error() string {
+	return err.ErrorString
+}