mirror of
https://github.com/superseriousbusiness/gotosocial.git
synced 2024-05-20 09:18:13 +00:00
94 lines
2.4 KiB
Go
94 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 (
|
|
"io"
|
|
|
|
pngstructure "github.com/superseriousbusiness/go-png-image-structure/v2"
|
|
)
|
|
|
|
type pngVisitor struct {
|
|
ps *pngstructure.PngSplitter
|
|
writer io.Writer
|
|
lastWrittenChunk int
|
|
}
|
|
|
|
func (v *pngVisitor) split(data []byte, atEOF bool) (int, []byte, error) {
|
|
// execute the ps split function to read in data
|
|
advance, token, err := v.ps.Split(data, atEOF)
|
|
if err != nil {
|
|
return advance, token, err
|
|
}
|
|
|
|
// if we haven't written anything at all yet, then write the png header back into the writer first
|
|
if v.lastWrittenChunk == -1 {
|
|
if _, err := v.writer.Write(pngstructure.PngSignature[:]); err != nil {
|
|
return advance, token, err
|
|
}
|
|
}
|
|
|
|
// Check if the splitter now has
|
|
// any new chunks in it for us.
|
|
chunkSlice, err := v.ps.Chunks()
|
|
if err != nil {
|
|
return advance, token, err
|
|
}
|
|
|
|
// Write each chunk by passing it
|
|
// through our custom write func,
|
|
// which strips out exif and fixes
|
|
// the CRC of each chunk.
|
|
chunks := chunkSlice.Chunks()
|
|
for i, chunk := range chunks {
|
|
if i <= v.lastWrittenChunk {
|
|
// Skip already
|
|
// written chunks.
|
|
continue
|
|
}
|
|
|
|
// Write this new chunk.
|
|
if err := v.writeChunk(chunk); err != nil {
|
|
return advance, token, err
|
|
}
|
|
v.lastWrittenChunk = i
|
|
|
|
// Zero data; here you
|
|
// go garbage collector.
|
|
chunk.Data = nil
|
|
}
|
|
|
|
return advance, token, err
|
|
}
|
|
|
|
func (v *pngVisitor) writeChunk(chunk *pngstructure.Chunk) error {
|
|
if chunk.Type == pngstructure.EXifChunkType {
|
|
// Replace exif data
|
|
// with zero bytes.
|
|
clear(chunk.Data)
|
|
}
|
|
|
|
// Fix CRC of each chunk.
|
|
chunk.UpdateCrc32()
|
|
|
|
// finally, write chunk to writer.
|
|
_, err := chunk.WriteTo(v.writer)
|
|
return err
|
|
}
|