lavc: add ff_bprint_to_extradata() helper and use it.

This commit also makes sure the extradata and subtitle_header are NUL
terminated, without taking into account the trailing '\0' in account in
the size.

At the same time, it should fix 'warning: dereferencing type-punned
pointer will break strict-aliasing rules' warning for compilers who
don't consider uint8_t** and char** compatibles.

4 files changed, 14 insertions, 19 deletions

diff --git a/libavformat/assdec.c b/libavformat/assdec.c
index 6c4614ec47..34229cb6f9 100644
--- a/libavformat/assdec.c
+++ b/libavformat/assdec.c
@@ -22,6 +22,7 @@
 #include "avformat.h"
 #include "internal.h"
 #include "subtitles.h"
+#include "libavcodec/internal.h"
 #include "libavutil/bprint.h"
 
 typedef struct ASSContext{
@@ -132,12 +133,9 @@ static int ass_read_header(AVFormatContext *s)
 
     av_bprint_finalize(&line, NULL);
 
-    av_bprint_finalize(&header, (char **)&st->codec->extradata);
-    if (!st->codec->extradata) {
-        res = AVERROR(ENOMEM);
+    res = ff_bprint_to_extradata(st->codec, &header);
+    if (res < 0)
         goto end;
-    }
-    st->codec->extradata_size = header.len + 1;
 
     ff_subtitles_queue_finalize(&ass->q);
 
diff --git a/libavformat/jacosubdec.c b/libavformat/jacosubdec.c
index 1c58e3bf25..153da4247a 100644
--- a/libavformat/jacosubdec.c
+++ b/libavformat/jacosubdec.c
@@ -28,6 +28,7 @@
 #include "avformat.h"
 #include "internal.h"
 #include "subtitles.h"
+#include "libavcodec/internal.h"
 #include "libavcodec/jacosub.h"
 #include "libavutil/avstring.h"
 #include "libavutil/bprint.h"
@@ -159,7 +160,7 @@ static int jacosub_read_header(AVFormatContext *s)
     JACOsubContext *jacosub = s->priv_data;
     int shift_set = 0; // only the first shift matters
     int merge_line = 0;
-    int i;
+    int i, ret;
 
     AVStream *st = avformat_new_stream(s, NULL);
     if (!st)
@@ -228,8 +229,9 @@ static int jacosub_read_header(AVFormatContext *s)
     }
 
     /* general/essential directives in the extradata */
-    av_bprint_finalize(&header, (char **)&st->codec->extradata);
-    st->codec->extradata_size = header.len + 1;
+    ret = ff_bprint_to_extradata(st->codec, &header);
+    if (ret < 0)
+        return ret;
 
     /* SHIFT and TIMERES affect the whole script so packet timing can only be
      * done in a second pass */
diff --git a/libavformat/samidec.c b/libavformat/samidec.c
index 85fd220f4a..bdde2f466f 100644
--- a/libavformat/samidec.c
+++ b/libavformat/samidec.c
@@ -27,6 +27,7 @@
 #include "avformat.h"
 #include "internal.h"
 #include "subtitles.h"
+#include "libavcodec/internal.h"
 #include "libavutil/avstring.h"
 #include "libavutil/bprint.h"
 #include "libavutil/intreadwrite.h"
@@ -91,13 +92,9 @@ static int sami_read_header(AVFormatContext *s)
         av_bprint_clear(&buf);
     }
 
-    st->codec->extradata_size = hdr_buf.len + 1;
-    av_bprint_finalize(&hdr_buf, (char **)&st->codec->extradata);
-    if (!st->codec->extradata) {
-        st->codec->extradata_size = 0;
-        res = AVERROR(ENOMEM);
+    res = ff_bprint_to_extradata(st->codec, &hdr_buf);
+    if (res < 0)
         goto end;
-    }
 
     ff_subtitles_queue_finalize(&sami->q);
 
diff --git a/libavformat/subviewerdec.c b/libavformat/subviewerdec.c
index 7691d82768..8ecc928817 100644
--- a/libavformat/subviewerdec.c
+++ b/libavformat/subviewerdec.c
@@ -27,6 +27,7 @@
 #include "avformat.h"
 #include "internal.h"
 #include "subtitles.h"
+#include "libavcodec/internal.h"
 #include "libavutil/avstring.h"
 #include "libavutil/bprint.h"
 #include "libavutil/intreadwrite.h"
@@ -99,12 +100,9 @@ static int subviewer_read_header(AVFormatContext *s)
                 av_bprintf(&header, "%s", line);
                 if (!strncmp(line, "[END INFORMATION]", 17) || !strncmp(line, "[SUBTITLE]", 10)) {
                     /* end of header */
-                    av_bprint_finalize(&header, (char **)&st->codec->extradata);
-                    if (!st->codec->extradata) {
-                        res = AVERROR(ENOMEM);
+                    res = ff_bprint_to_extradata(st->codec, &header);
+                    if (res < 0)
                         goto end;
-                    }
-                    st->codec->extradata_size = header.len + 1;
                 } else if (strncmp(line, "[INFORMATION]", 13)) {
                     /* assume file metadata at this point */
                     int i, j = 0;