[FFmpeg-cvslog] avcodec/apng: Add APNG_FCTL_CHUNK_SIZE define

[Andreas Rheinhardt]

ffmpeg | branch: master | Andreas Rheinhardt <andreas.rheinhardt at outlook.com> | Mon Jul  4 17:13:58 2022 +0200| [e4a10dd63783f80ed251e7bbf2550feff4c01306] | committer: Andreas Rheinhardt

avcodec/apng: Add APNG_FCTL_CHUNK_SIZE define

Also use it where appropriate.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at outlook.com>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=e4a10dd63783f80ed251e7bbf2550feff4c01306
---

 libavcodec/apng.h     | 3 +++
 libavcodec/pngdec.c   | 2 +-
 libavcodec/pngenc.c   | 6 +++---
 libavformat/apngdec.c | 4 ++--
 4 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/libavcodec/apng.h b/libavcodec/apng.h
index 41249e0df0..abd8795334 100644
--- a/libavcodec/apng.h
+++ b/libavcodec/apng.h
@@ -38,4 +38,7 @@ enum {
     APNG_BLEND_OP_OVER   = 1,
 };
 
+/* Only the payload data, not including length, fourcc and CRC-32. */
+#define APNG_FCTL_CHUNK_SIZE    26
+
 #endif /* AVCODEC_APNG_H */
diff --git a/libavcodec/pngdec.c b/libavcodec/pngdec.c
index 6b44af59f2..87b0c639e3 100644
--- a/libavcodec/pngdec.c
+++ b/libavcodec/pngdec.c
@@ -972,7 +972,7 @@ static int decode_fctl_chunk(AVCodecContext *avctx, PNGDecContext *s,
     uint32_t sequence_number;
     int cur_w, cur_h, x_offset, y_offset, dispose_op, blend_op;
 
-    if (bytestream2_get_bytes_left(gb) != 26)
+    if (bytestream2_get_bytes_left(gb) != APNG_FCTL_CHUNK_SIZE)
         return AVERROR_INVALIDDATA;
 
     if (!(s->hdr_state & PNG_IHDR)) {
diff --git a/libavcodec/pngenc.c b/libavcodec/pngenc.c
index d79b4e3895..93463dd341 100644
--- a/libavcodec/pngenc.c
+++ b/libavcodec/pngenc.c
@@ -988,7 +988,7 @@ static int encode_apng(AVCodecContext *avctx, AVPacket *pkt,
         // to have the image data write to the correct place in the buffer
         fctl_chunk.sequence_number = s->sequence_number;
         ++s->sequence_number;
-        s->bytestream += 26 + 12;
+        s->bytestream += APNG_FCTL_CHUNK_SIZE + 12;
 
         ret = apng_encode_frame(avctx, pict, &fctl_chunk, &s->last_frame_fctl);
         if (ret < 0)
@@ -1002,7 +1002,7 @@ static int encode_apng(AVCodecContext *avctx, AVPacket *pkt,
 
     if (s->last_frame) {
         uint8_t* last_fctl_chunk_start = pkt->data;
-        uint8_t buf[26];
+        uint8_t buf[APNG_FCTL_CHUNK_SIZE];
         if (!s->extra_data_updated) {
             uint8_t *side_data = av_packet_new_side_data(pkt, AV_PKT_DATA_NEW_EXTRADATA, s->extra_data_size);
             if (!side_data)
@@ -1020,7 +1020,7 @@ static int encode_apng(AVCodecContext *avctx, AVPacket *pkt,
         AV_WB16(buf + 22, s->last_frame_fctl.delay_den);
         buf[24] = s->last_frame_fctl.dispose_op;
         buf[25] = s->last_frame_fctl.blend_op;
-        png_write_chunk(&last_fctl_chunk_start, MKTAG('f', 'c', 'T', 'L'), buf, 26);
+        png_write_chunk(&last_fctl_chunk_start, MKTAG('f', 'c', 'T', 'L'), buf, sizeof(buf));
 
         *got_packet = 1;
     }
diff --git a/libavformat/apngdec.c b/libavformat/apngdec.c
index e84f74e9d0..47cdbfcbfb 100644
--- a/libavformat/apngdec.c
+++ b/libavformat/apngdec.c
@@ -222,7 +222,7 @@ static int apng_read_header(AVFormatContext *s)
                                     ctx->num_frames, ctx->num_play);
             break;
         case MKTAG('f', 'c', 'T', 'L'):
-            if (!acTL_found || len != 26) {
+            if (!acTL_found || len != APNG_FCTL_CHUNK_SIZE) {
                 return AVERROR_INVALIDDATA;
             }
             if ((ret = avio_seek(pb, -8, SEEK_CUR)) < 0)
@@ -336,7 +336,7 @@ static int apng_read_packet(AVFormatContext *s, AVPacket *pkt)
 
     switch (tag) {
     case MKTAG('f', 'c', 'T', 'L'):
-        if (len != 26)
+        if (len != APNG_FCTL_CHUNK_SIZE)
             return AVERROR_INVALIDDATA;
 
         if ((ret = decode_fctl_chunk(s, ctx, pkt)) < 0)