avcodec/h264_parser: Factor get_avc_nalsize() out

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

1 files changed, 20 insertions, 0 deletions

diff --git a/libavcodec/h2645_parse.h b/libavcodec/h2645_parse.h
index 630235994e..3a60f3fb9b 100644
--- a/libavcodec/h2645_parse.h
+++ b/libavcodec/h2645_parse.h
@@ -90,4 +90,24 @@ int ff_h2645_packet_split(H2645Packet *pkt, const uint8_t *buf, int length,
  */
 void ff_h2645_packet_uninit(H2645Packet *pkt);
 
+static inline int get_nalsize(int nal_length_size, const uint8_t *buf,
+                              int buf_size, int *buf_index, void *logctx)
+{
+    int i, nalsize = 0;
+
+    if (*buf_index >= buf_size - nal_length_size) {
+        // the end of the buffer is reached, refill it
+        return AVERROR(EAGAIN);
+    }
+
+    for (i = 0; i < nal_length_size; i++)
+        nalsize = ((unsigned)nalsize << 8) | buf[(*buf_index)++];
+    if (nalsize <= 0 || nalsize > buf_size - *buf_index) {
+        av_log(logctx, AV_LOG_ERROR,
+               "Invalid nal size %d\n", nalsize);
+        return AVERROR_INVALIDDATA;
+    }
+    return nalsize;
+}
+
 #endif /* AVCODEC_H2645_PARSE_H */