[chore] Move deps to code.superseriousbusiness.org (#4054)

vendor/code.superseriousbusiness.org/exif-terminator/terminator.go

@@ -0,0 +1,146 @@
+/*
+   exif-terminator
+   Copyright (C) 2022 SuperSeriousBusiness admin@gotosocial.org
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU Affero General Public License as published by
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU Affero General Public License for more details.
+
+   You should have received a copy of the GNU Affero General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+package terminator
+
+import (
+	"bufio"
+	"bytes"
+	"errors"
+	"fmt"
+	"io"
+
+	jpegstructure "code.superseriousbusiness.org/go-jpeg-image-structure/v2"
+	pngstructure "code.superseriousbusiness.org/go-png-image-structure/v2"
+)
+
+func Terminate(in io.Reader, mediaType string) (io.Reader, error) {
+	// To avoid keeping too much stuff
+	// in memory we want to pipe data
+	// directly to the reader.
+	pr, pw := io.Pipe()
+
+	// Setup scanner to terminate exif into pipe writer.
+	scanner, err := terminatingScanner(pw, in, mediaType)
+	if err != nil {
+		_ = pw.Close()
+		return nil, err
+	}
+
+	go func() {
+		var err error
+
+		defer func() {
+			// Always close writer, using returned
+			// scanner error (if any). If err is nil
+			// then the standard io.EOF will be used.
+			// (this will not overwrite existing).
+			pw.CloseWithError(err)
+		}()
+
+		// Scan through input.
+		for scanner.Scan() {
+		}
+
+		// Set error on return.
+		err = scanner.Err()
+	}()
+
+	return pr, nil
+}
+
+func TerminateInto(out io.Writer, in io.Reader, mediaType string) error {
+	// Setup scanner to terminate exif from 'in' to 'out'.
+	scanner, err := terminatingScanner(out, in, mediaType)
+	if err != nil {
+		return err
+	}
+
+	// Scan through input.
+	for scanner.Scan() {
+	}
+
+	// Return scan errors.
+	return scanner.Err()
+}
+
+func terminatingScanner(out io.Writer, in io.Reader, mediaType string) (*bufio.Scanner, error) {
+	scanner := bufio.NewScanner(in)
+
+	// 40mb buffer size should be enough
+	// to scan through most file chunks
+	// without running into issues, they're
+	// usually chunked smaller than this...
+	scanner.Buffer(nil, 40*1024*1024)
+
+	switch mediaType {
+	case "image/jpeg", "jpeg", "jpg":
+		v := &jpegVisitor{
+			writer: out,
+		}
+
+		// Provide the visitor to the splitter so
+		// that it triggers on every section scan.
+		js := jpegstructure.NewJpegSplitter(v)
+
+		// The visitor also needs to read back the
+		// list of segments: for this it needs to
+		// know what jpeg splitter it's attached to,
+		// so give it a pointer to the splitter.
+		v.js = js
+
+		// Jpeg visitor's 'split' function
+		// satisfies bufio.SplitFunc{}.
+		scanner.Split(js.Split)
+
+	case "image/webp", "webp":
+		// Webp visitor's 'split' function
+		// satisfies bufio.SplitFunc{}.
+		scanner.Split((&webpVisitor{
+			writer: out,
+		}).split)
+
+	case "image/png", "png":
+		// For pngs we need to skip the header bytes, so read
+		// them in and check we're really dealing with a png.
+		header := make([]byte, len(pngstructure.PngSignature))
+		if _, headerError := in.Read(header); headerError != nil {
+			return nil, headerError
+		} else if !bytes.Equal(header, pngstructure.PngSignature[:]) {
+			return nil, errors.New("could not decode png: invalid header")
+		}
+
+		// Don't bother checking CRC;
+		// we're overwriting it anyway.
+		ps := pngstructure.NewPngSplitter()
+		ps.DoCheckCrc(false)
+
+		// Png visitor's 'split' function
+		// satisfies bufio.SplitFunc{}.
+		scanner.Split((&pngVisitor{
+			ps:               ps,
+			writer:           out,
+			lastWrittenChunk: -1,
+		}).split)
+
+	default:
+		return nil, fmt.Errorf("mediaType %s cannot be processed", mediaType)
+	}
+
+	return scanner, nil
+}