avcodec/ac3_parser: add avpriv_ac3_parse_header2() and use it in libavcodec

The new function has the ability to allocate the structure, allowing it to grow
without needing major bumps
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/ac3_parser.c

@@ -47,9 +47,16 @@ static const uint8_t center_levels[4] = { 4, 5, 6, 5 };
 static const uint8_t surround_levels[4] = { 4, 6, 7, 6 };
 
 
-int avpriv_ac3_parse_header(GetBitContext *gbc, AC3HeaderInfo *hdr)
+int avpriv_ac3_parse_header2(GetBitContext *gbc, AC3HeaderInfo **phdr)
 {
     int frame_size_code;
+    AC3HeaderInfo *hdr;
+
+    if (!*phdr)
+        *phdr = av_mallocz(sizeof(AC3HeaderInfo));
+    if (!*phdr)
+        return AVERROR(ENOMEM);
+    hdr = *phdr;
 
     memset(hdr, 0, sizeof(*hdr));
 
@@ -144,6 +151,15 @@ int avpriv_ac3_parse_header(GetBitContext *gbc, AC3HeaderInfo *hdr)
     return 0;
 }
 
+int avpriv_ac3_parse_header(GetBitContext *gbc, AC3HeaderInfo *hdr)
+{
+    AC3HeaderInfo tmp, *ptmp = &tmp;
+    int ret = avpriv_ac3_parse_header2(gbc, &ptmp);
+
+    memcpy(hdr, ptmp, ((intptr_t)&tmp.channel_layout) - ((intptr_t)&tmp) + sizeof(uint64_t));
+    return ret;
+}
+
 static int ac3_sync(uint64_t state, AACAC3ParseContext *hdr_info,
         int *need_next_header, int *new_frame_start)
 {
@@ -152,11 +168,11 @@ static int ac3_sync(uint64_t state, AACAC3ParseContext *hdr_info,
         uint64_t u64;
         uint8_t  u8[8];
     } tmp = { av_be2ne64(state) };
-    AC3HeaderInfo hdr;
+    AC3HeaderInfo hdr, *phdr = &hdr;
     GetBitContext gbc;
 
     init_get_bits(&gbc, tmp.u8+8-AC3_HEADER_SIZE, 54);
-    err = avpriv_ac3_parse_header(&gbc, &hdr);
+    err = avpriv_ac3_parse_header2(&gbc, &phdr);
 
     if(err < 0)
         return 0;

libavcodec/ac3_parser.h

@@ -31,11 +31,14 @@
  * Parse the header up to the lfeon element, which is the first 52 or 54 bits
  * depending on the audio coding mode.
  * @param[in]  gbc BitContext containing the first 54 bits of the frame.
- * @param[out] hdr Pointer to struct where header info is written.
+ * @param[out] hdr Pointer to Pointer to struct where header info is written.
+ *                 will be allocated if NULL
  * @return Returns 0 on success, -1 if there is a sync word mismatch,
  * -2 if the bsid (version) element is invalid, -3 if the fscod (sample rate)
  * element is invalid, or -4 if the frmsizecod (bit rate) element is invalid.
  */
+int avpriv_ac3_parse_header2(GetBitContext *gbc, AC3HeaderInfo **hdr);
+
 int avpriv_ac3_parse_header(GetBitContext *gbc, AC3HeaderInfo *hdr);
 
 #endif /* AVCODEC_AC3_PARSER_H */

libavcodec/ac3dec.c

@@ -274,10 +274,10 @@ static int ac3_parse_header(AC3DecodeContext *s)
  */
 static int parse_frame_header(AC3DecodeContext *s)
 {
-    AC3HeaderInfo hdr;
+    AC3HeaderInfo hdr, *phdr=&hdr;
     int err;
 
-    err = avpriv_ac3_parse_header(&s->gbc, &hdr);
+    err = avpriv_ac3_parse_header2(&s->gbc, &phdr);
     if (err)
         return err;