mirror of
https://github.com/superseriousbusiness/gotosocial.git
synced 2025-11-03 19:52:24 -06:00
109 lines
2.2 KiB
Go
109 lines
2.2 KiB
Go
/*
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exif-terminator
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Copyright (C) 2022 SuperSeriousBusiness admin@gotosocial.org
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU Affero General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU Affero General Public License for more details.
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You should have received a copy of the GNU Affero General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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package terminator
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import (
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"encoding/binary"
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"errors"
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"io"
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)
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const (
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riffHeader = "RIFF"
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webpHeader = "WEBP"
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exifFourcc = "EXIF"
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xmpFourcc = "XMP "
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)
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var (
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errNoRiffHeader = errors.New("no RIFF header")
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errNoWebpHeader = errors.New("not a WEBP file")
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errInvalidChunk = errors.New("invalid chunk")
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)
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type webpVisitor struct {
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writer io.Writer
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doneHeader bool
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}
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func (v *webpVisitor) split(data []byte, atEOF bool) (advance int, token []byte, err error) {
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// parse/write the header first
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if !v.doneHeader {
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// const rifHeaderSize = 12
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if len(data) < 12 {
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if atEOF {
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err = errNoRiffHeader
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}
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return
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}
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if string(data[:4]) != riffHeader {
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err = errNoRiffHeader
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return
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}
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if string(data[8:12]) != webpHeader {
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err = errNoWebpHeader
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return
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}
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if _, err = v.writer.Write(data[:12]); err != nil {
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return
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}
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advance += 12
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data = data[12:]
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v.doneHeader = true
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}
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for {
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// need enough for
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// fourcc and size
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if len(data) < 8 {
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return
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}
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size := int64(binary.LittleEndian.Uint32(data[4:]))
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if (size & 1) != 0 {
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// odd chunk size:
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// extra padding byte
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size++
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}
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// wait until there is enough
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if int64(len(data)) < 8+size {
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return
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}
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// replace exif/xmp with blank
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switch string(data[:4]) {
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case exifFourcc, xmpFourcc:
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clear(data[8 : 8+size])
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}
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if _, err = v.writer.Write(data[:8+size]); err != nil {
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return
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}
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advance += 8 + int(size)
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data = data[8+size:]
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}
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}
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