decoder/flac: validate the sample rate when scanning the tag

Don't calculate the song duration when the sample rate is 0 (division
by zero crash).

NEWS

@@ -1,6 +1,7 @@
 ver 0.16.4 (2010/??/??)
 * decoder:
   - ffmpeg: workaround for semantic API change in recent ffmpeg versions
+  - flac: validate the sample rate when scanning the tag
 
 
 ver 0.16.3 (2011/06/04)

src/decoder/flac_metadata.c

@@ -224,6 +224,7 @@ flac_tag_apply_metadata(struct tag *tag, const char *track,
 		break;
 
 	case FLAC__METADATA_TYPE_STREAMINFO:
+		if (block->data.stream_info.sample_rate > 0)
 			tag->time = flac_duration(&block->data.stream_info);
 		break;
 

src/decoder/flac_metadata.h

@@ -20,6 +20,7 @@
 #ifndef MPD_FLAC_METADATA_H
 #define MPD_FLAC_METADATA_H
 
+#include <assert.h>
 #include <stdbool.h>
 #include <FLAC/metadata.h>
 
@@ -29,6 +30,8 @@ struct replay_gain_info;
 static inline unsigned
 flac_duration(const FLAC__StreamMetadata_StreamInfo *stream_info)
 {
+	assert(stream_info->sample_rate > 0);
+
 	return (stream_info->total_samples + stream_info->sample_rate - 1) /
 		stream_info->sample_rate;
 }