1 files changed, 85 insertions, 0 deletions
diff --git a/vendor/codeberg.org/superseriousbusiness/exif-terminator/png.go b/vendor/codeberg.org/superseriousbusiness/exif-terminator/png.go
new file mode 100644
index 000000000..b8b94efb7
--- /dev/null
+++ b/vendor/codeberg.org/superseriousbusiness/exif-terminator/png.go
@@ -0,0 +1,85 @@
+/*
+   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 := v.lastWrittenChunk + 1; i < len(chunks); i++ {
+		chunk := chunks[i]
+
+		if chunk.Type == pngstructure.EXifChunkType {
+			// Finally, some exif data! Terminate it!!
+			if err := terminateEXIF(chunkSlice); err != nil {
+				return advance, token, err
+			}
+
+			// Update chunk crc.
+			chunk.UpdateCrc32()
+		}
+
+		// Write this new chunk.
+		if _, err := chunk.WriteTo(v.writer); err != nil {
+			return advance, token, err
+		}
+		v.lastWrittenChunk = i
+
+		// Zero data; here you
+		// go garbage collector.
+		chunk.Data = nil
+	}
+
+	return advance, token, err
+}