102 lines
2.4 KiB
Go
102 lines
2.4 KiB
Go
/*
|
|
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"
|
|
"errors"
|
|
"io"
|
|
)
|
|
|
|
const (
|
|
riffHeaderSize = 4 * 3
|
|
)
|
|
|
|
var (
|
|
riffHeader = [4]byte{'R', 'I', 'F', 'F'}
|
|
webpHeader = [4]byte{'W', 'E', 'B', 'P'}
|
|
exifFourcc = [4]byte{'E', 'X', 'I', 'F'}
|
|
xmpFourcc = [4]byte{'X', 'M', 'P', ' '}
|
|
|
|
errNoRiffHeader = errors.New("no RIFF header")
|
|
errNoWebpHeader = errors.New("not a WEBP file")
|
|
)
|
|
|
|
type webpVisitor struct {
|
|
writer io.Writer
|
|
doneHeader bool
|
|
}
|
|
|
|
func fourCC(b []byte) [4]byte {
|
|
return [4]byte{b[0], b[1], b[2], b[3]}
|
|
}
|
|
|
|
func (v *webpVisitor) split(data []byte, atEOF bool) (advance int, token []byte, err error) {
|
|
// parse/write the header first
|
|
if !v.doneHeader {
|
|
if len(data) < riffHeaderSize {
|
|
// need the full header
|
|
return
|
|
}
|
|
if fourCC(data) != riffHeader {
|
|
err = errNoRiffHeader
|
|
return
|
|
}
|
|
if fourCC(data[8:]) != webpHeader {
|
|
err = errNoWebpHeader
|
|
return
|
|
}
|
|
if _, err = v.writer.Write(data[:riffHeaderSize]); err != nil {
|
|
return
|
|
}
|
|
advance += riffHeaderSize
|
|
data = data[riffHeaderSize:]
|
|
v.doneHeader = true
|
|
}
|
|
|
|
// need enough for fourcc and size
|
|
if len(data) < 8 {
|
|
return
|
|
}
|
|
size := int64(binary.LittleEndian.Uint32(data[4:]))
|
|
if (size & 1) != 0 {
|
|
// odd chunk size - extra padding byte
|
|
size++
|
|
}
|
|
// wait until there is enough
|
|
if int64(len(data)-8) < size {
|
|
return
|
|
}
|
|
|
|
fourcc := fourCC(data)
|
|
rawChunkData := data[8 : 8+size]
|
|
if fourcc == exifFourcc || fourcc == xmpFourcc {
|
|
// replace exif/xmp with blank
|
|
rawChunkData = make([]byte, size)
|
|
}
|
|
|
|
if _, err = v.writer.Write(data[:8]); err == nil {
|
|
if _, err = v.writer.Write(rawChunkData); err == nil {
|
|
advance += 8 + int(size)
|
|
}
|
|
}
|
|
|
|
return
|
|
}
|