1 files changed, 158 insertions, 0 deletions
diff --git a/vendor/codeberg.org/superseriousbusiness/exif-terminator/terminator.go b/vendor/codeberg.org/superseriousbusiness/exif-terminator/terminator.go
new file mode 100644
index 000000000..7dd3d9ad7
--- /dev/null
+++ b/vendor/codeberg.org/superseriousbusiness/exif-terminator/terminator.go
@@ -0,0 +1,158 @@
+/*
+   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 "github.com/superseriousbusiness/go-jpeg-image-structure/v2"
+	pngstructure "github.com/superseriousbusiness/go-png-image-structure/v2"
+)
+
+func Terminate(in io.Reader, fileSize int, mediaType string) (io.Reader, error) {
+	// To avoid keeping too much stuff
+	// in memory we want to pipe data
+	// directly to the reader.
+	pipeReader, pipeWriter := io.Pipe()
+
+	// We don't know ahead of time how long
+	// segments might be: they could be as
+	// large as the file itself, so we need
+	// a buffer with generous overhead.
+	scanner := bufio.NewScanner(in)
+	scanner.Buffer([]byte{}, fileSize)
+
+	var err error
+	switch mediaType {
+	case "image/jpeg", "jpeg", "jpg":
+		err = terminateJpeg(scanner, pipeWriter, fileSize)
+
+	case "image/webp", "webp":
+		err = terminateWebp(scanner, pipeWriter)
+
+	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 {
+			err = headerError
+			break
+		}
+
+		if !bytes.Equal(header, pngstructure.PngSignature[:]) {
+			err = errors.New("could not decode png: invalid header")
+			break
+		}
+
+		err = terminatePng(scanner, pipeWriter)
+	default:
+		err = fmt.Errorf("mediaType %s cannot be processed", mediaType)
+	}
+
+	return pipeReader, err
+}
+
+func terminateJpeg(scanner *bufio.Scanner, writer *io.PipeWriter, expectedFileSize int) error {
+	v := &jpegVisitor{
+		writer:           writer,
+		expectedFileSize: expectedFileSize,
+	}
+
+	// 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)
+
+	go scanAndClose(scanner, writer)
+	return nil
+}
+
+func terminateWebp(scanner *bufio.Scanner, writer *io.PipeWriter) error {
+	v := &webpVisitor{
+		writer: writer,
+	}
+
+	// Webp visitor's 'split' function
+	// satisfies bufio.SplitFunc{}.
+	scanner.Split(v.split)
+
+	go scanAndClose(scanner, writer)
+	return nil
+}
+
+func terminatePng(scanner *bufio.Scanner, writer *io.PipeWriter) error {
+	ps := pngstructure.NewPngSplitter()
+
+	// Don't bother checking CRC;
+	// we're overwriting it anyway.
+	ps.DoCheckCrc(false)
+
+	v := &pngVisitor{
+		ps:               ps,
+		writer:           writer,
+		lastWrittenChunk: -1,
+	}
+
+	// Png visitor's 'split' function
+	// satisfies bufio.SplitFunc{}.
+	scanner.Split(v.split)
+
+	go scanAndClose(scanner, writer)
+	return nil
+}
+
+// scanAndClose scans through the given scanner until there's
+// nothing left to scan, and then closes the writer so that the
+// reader on the other side of the pipe knows that we're done.
+//
+// Any error encountered when scanning will be logged by terminator.
+//
+// Due to the nature of io.Pipe, writing won't actually work
+// until the pipeReader starts being read by the caller, which
+// is why this function should always be called asynchronously.
+func scanAndClose(scanner *bufio.Scanner, writer *io.PipeWriter) {
+	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).
+		writer.CloseWithError(err)
+	}()
+
+	for scanner.Scan() {
+	}
+
+	// Set error on return.
+	err = scanner.Err()
+}