avcodec: Constify AVCodecParserContext.parser

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
Signed-off-by: James Almer <jamrial@gmail.com>

doc/APIchanges

@@ -14,6 +14,9 @@ libavutil:     2017-10-21
 
 API changes, most recent first:
 
+2021-04-27 - xxxxxxxxxx - lavc yyyyyyyyy - avcodec.h
+  Constified AVCodecParserContext.parser.
+
 2021-04-27 - xxxxxxxxxx - lavd yyyyyyyyy - avdevice.h
   The av_*_device_next API functions now accept and return
   pointers to const AVInputFormat resp. AVOutputFormat.

libavcodec/avcodec.h

@@ -2877,7 +2877,7 @@ enum AVPictureStructure {
 
 typedef struct AVCodecParserContext {
     void *priv_data;
-    struct AVCodecParser *parser;
+    const struct AVCodecParser *parser;
     int64_t frame_offset; /* offset of the current frame */
     int64_t cur_offset; /* current offset
                            (incremented by each av_parser_parse()) */

libavcodec/parser.c

@@ -55,7 +55,7 @@ found:
     s = av_mallocz(sizeof(AVCodecParserContext));
     if (!s)
         goto err_out;
-    s->parser = (AVCodecParser*)parser;
+    s->parser = parser;
     s->priv_data = av_mallocz(parser->priv_data_size);
     if (!s->priv_data)
         goto err_out;