avcodec/exif: remove GetByteContext usage from avpriv_exif_decode_ifd()

This prevents potential ABI issues with GetByteContext.
Reviewed-by: Paul B Mahol <onemda@gmail.com>
Signed-off-by: James Almer <jamrial@gmail.com>

libavcodec/exif.c

@@ -92,7 +92,7 @@ static int exif_decode_tag(void *logctx, GetByteContext *gbytes, int le,
     // store metadata or proceed with next IFD
     ret = ff_tis_ifd(id);
     if (ret) {
-        ret = avpriv_exif_decode_ifd(logctx, gbytes, le, depth + 1, metadata);
+        ret = ff_exif_decode_ifd(logctx, gbytes, le, depth + 1, metadata);
     } else {
         const char *name = exif_get_tag_name(id);
         char *use_name   = (char*) name;
@@ -119,8 +119,8 @@ static int exif_decode_tag(void *logctx, GetByteContext *gbytes, int le,
 }
 
 
-int avpriv_exif_decode_ifd(void *logctx, GetByteContext *gbytes, int le,
-                           int depth, AVDictionary **metadata)
+int ff_exif_decode_ifd(void *logctx, GetByteContext *gbytes,
+                       int le, int depth, AVDictionary **metadata)
 {
     int i, ret;
     int entries;
@@ -140,3 +140,13 @@ int avpriv_exif_decode_ifd(void *logctx, GetByteContext *gbytes, int le,
     // return next IDF offset or 0x000000000 or a value < 0 for failure
     return ff_tget_long(gbytes, le);
 }
+
+int avpriv_exif_decode_ifd(void *logctx, const uint8_t *buf, int size,
+                           int le, int depth, AVDictionary **metadata)
+{
+    GetByteContext gb;
+
+    bytestream2_init(&gb, buf, size);
+
+    return ff_exif_decode_ifd(logctx, &gb, le, depth, metadata);
+}

libavcodec/exif.h

@@ -164,7 +164,10 @@ static const struct exif_tag tag_list[] = { // JEITA CP-3451 EXIF specification:
 
 /** Recursively decodes all IFD's and
  *  adds included TAGS into the metadata dictionary. */
-int avpriv_exif_decode_ifd(void *logctx, GetByteContext *gbytes, int le,
+int avpriv_exif_decode_ifd(void *logctx, const uint8_t *buf, int size,
+                           int le, int depth, AVDictionary **metadata);
+
+int ff_exif_decode_ifd(void *logctx, GetByteContext *gbytes, int le,
                        int depth, AVDictionary **metadata);
 
 #endif /* AVCODEC_EXIF_H */

libavcodec/mjpegdec.c

@@ -1867,7 +1867,7 @@ static int mjpeg_decode_app(MJpegDecodeContext *s)
 
             // read 0th IFD and store the metadata
             // (return values > 0 indicate the presence of subimage metadata)
-            ret = avpriv_exif_decode_ifd(s->avctx, &gbytes, le, 0, &s->exif_metadata);
+            ret = ff_exif_decode_ifd(s->avctx, &gbytes, le, 0, &s->exif_metadata);
             if (ret < 0) {
                 av_log(s->avctx, AV_LOG_ERROR, "mjpeg: error decoding EXIF data\n");
             }

libavcodec/webp.c

@@ -1504,7 +1504,7 @@ static int webp_decode_frame(AVCodecContext *avctx, void *data, int *got_frame,
             }
 
             bytestream2_seek(&exif_gb, ifd_offset, SEEK_SET);
-            if (avpriv_exif_decode_ifd(avctx, &exif_gb, le, 0, &exif_metadata) < 0) {
+            if (ff_exif_decode_ifd(avctx, &exif_gb, le, 0, &exif_metadata) < 0) {
                 av_log(avctx, AV_LOG_ERROR, "error decoding Exif data\n");
                 goto exif_end;
             }

libavformat/avidec.c

@@ -401,10 +401,10 @@ static int avi_extract_stream_metadata(AVFormatContext *s, AVStream *st)
         // skip 4 byte padding
         bytestream2_skip(&gb, 4);
         offset = bytestream2_tell(&gb);
-        bytestream2_init(&gb, data + offset, data_size - offset);
 
         // decode EXIF tags from IFD, AVI is always little-endian
-        return avpriv_exif_decode_ifd(s, &gb, 1, 0, &st->metadata);
+        return avpriv_exif_decode_ifd(s, data + offset, data_size - offset,
+                                      1, 0, &st->metadata);
         break;
     case MKTAG('C', 'A', 'S', 'I'):
         avpriv_request_sample(s, "RIFF stream data tag type CASI (%u)", tag);