/* 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 . */ 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 { l := uint16(len(s.Data) + 2) b := make([]byte, 2) binary.BigEndian.PutUint16(b, l) if _, err := w.Write(b); err != nil { return err } } else if sizeLen == 4 { l := uint32(len(s.Data) + 4) b := make([]byte, 4) binary.BigEndian.PutUint32(b, l) if _, err := w.Write(b); 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 }