avformat: add option to parse/store ID3 PRIV tags in metadata.

Enables getting access to ID3 PRIV tags from the command-line or metadata API
when demuxing. The PRIV owner is stored as the metadata key prepended with
"id3v2_priv.", and the data is stored as the metadata value. As PRIV tags may
contain arbitrary data, non-printable characters, including NULL bytes, are
escaped as \xXX.

Similarly, any metadata tags that begin with "id3v2_priv." are inserted as ID3
PRIV tags into the output (assuming the format supports ID3). \xXX sequences in
the value are un-escaped to their byte value.

Signed-off-by: wm4 <nfxjfg@googlemail.com>

1 files changed, 48 insertions, 0 deletions

diff --git a/libavformat/id3v2.c b/libavformat/id3v2.c
index 6c216ba7a2..b80178d67a 100644
--- a/libavformat/id3v2.c
+++ b/libavformat/id3v2.c
@@ -33,6 +33,7 @@
 #endif
 
 #include "libavutil/avstring.h"
+#include "libavutil/bprint.h"
 #include "libavutil/dict.h"
 #include "libavutil/intreadwrite.h"
 #include "avio_internal.h"
@@ -1224,3 +1225,50 @@ end:
     av_freep(&chapters);
     return ret;
 }
+
+int ff_id3v2_parse_priv_dict(AVDictionary **metadata, ID3v2ExtraMeta **extra_meta)
+{
+    ID3v2ExtraMeta *cur;
+    int dict_flags = AV_DICT_DONT_OVERWRITE | AV_DICT_DONT_STRDUP_KEY | AV_DICT_DONT_STRDUP_VAL;
+
+    for (cur = *extra_meta; cur; cur = cur->next) {
+        if (!strcmp(cur->tag, "PRIV")) {
+            ID3v2ExtraMetaPRIV *priv = cur->data;
+            AVBPrint bprint;
+            char *escaped, *key;
+            int i, ret;
+
+            if ((key = av_asprintf(ID3v2_PRIV_METADATA_PREFIX "%s", priv->owner)) == NULL) {
+                return AVERROR(ENOMEM);
+            }
+
+            av_bprint_init(&bprint, priv->datasize + 1, AV_BPRINT_SIZE_UNLIMITED);
+
+            for (i = 0; i < priv->datasize; i++) {
+                if (priv->data[i] < 32 || priv->data[i] > 126 || priv->data[i] == '\\') {
+                    av_bprintf(&bprint, "\\x%02x", priv->data[i]);
+                } else {
+                    av_bprint_chars(&bprint, priv->data[i], 1);
+                }
+            }
+
+            if ((ret = av_bprint_finalize(&bprint, &escaped)) < 0) {
+                av_free(key);
+                return ret;
+            }
+
+            if ((ret = av_dict_set(metadata, key, escaped, dict_flags)) < 0) {
+                av_free(key);
+                av_free(escaped);
+                return ret;
+            }
+        }
+    }
+
+    return 0;
+}
+
+int ff_id3v2_parse_priv(AVFormatContext *s, ID3v2ExtraMeta **extra_meta)
+{
+    return ff_id3v2_parse_priv_dict(&s->metadata, extra_meta);
+}