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/*
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 (
"encoding/binary"
"fmt"
"io"
jpegstructure "github.com/superseriousbusiness/go-jpeg-image-structure/v2"
)
var markerLen = map[byte]int{
0x00: 0,
0x01: 0,
0xd0: 0,
0xd1: 0,
0xd2: 0,
0xd3: 0,
0xd4: 0,
0xd5: 0,
0xd6: 0,
0xd7: 0,
0xd8: 0,
0xd9: 0,
0xda: 0,
// J2C
0x30: 0,
0x31: 0,
0x32: 0,
0x33: 0,
0x34: 0,
0x35: 0,
0x36: 0,
0x37: 0,
0x38: 0,
0x39: 0,
0x3a: 0,
0x3b: 0,
0x3c: 0,
0x3d: 0,
0x3e: 0,
0x3f: 0,
0x4f: 0,
0x92: 0,
0x93: 0,
// J2C extensions
0x74: 4,
0x75: 4,
0x77: 4,
}
type jpegVisitor struct {
js *jpegstructure.JpegSplitter
writer io.Writer
}
// HandleSegment satisfies the visitor interface{} of the jpegstructure library.
//
// We don't really care about many of the parameters, since all we're interested
// in here is the very last segment that was scanned.
func (v *jpegVisitor) HandleSegment(segmentMarker byte, _ string, _ int, _ bool) error {
segmentList := v.js.Segments()
segments := segmentList.Segments()
mostRecentSegment := segments[len(segments)-1]
return v.writeSegment(mostRecentSegment)
}
func (v *jpegVisitor) writeSegment(s *jpegstructure.Segment) error {
w := v.writer
defer func() {
// whatever happens, when we finished then evict data from the segment;
// once we've written it we don't want it in memory anymore
s.Data = nil
}()
if s.IsExif() {
// Segment contains exif data, terminate!
if err := terminateEXIF(s); err != nil {
return err
}
}
// The scan-data will have a marker-ID of (0) because it doesn't have a marker-ID or length.
if s.MarkerId != 0 {
_, err := w.Write([]byte{0xff, s.MarkerId})
if err != nil {
return err
}
sizeLen, found := markerLen[s.MarkerId]
if !found || sizeLen == 2 {
sizeLen = 2
l := uint16(len(s.Data) + sizeLen)
if err := binary.Write(w, binary.BigEndian, &l); err != nil {
return err
}
} else if sizeLen == 4 {
l := uint32(len(s.Data) + sizeLen)
if err := binary.Write(w, binary.BigEndian, &l); err != nil {
return err
}
} else if sizeLen != 0 {
return fmt.Errorf("not a supported marker-size: MARKER-ID=(0x%02x) MARKER-SIZE-LEN=(%d)", s.MarkerId, sizeLen)
}
}
_, err := w.Write(s.Data)
return err
}
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