input_stream: size==-1 means unknown size

Define the special value "-1" as "unknown size".  Previously, there
was no indicator for streams with unknown size, which might confuse
some decoders.

src/decoder/aac_plugin.c

@@ -186,7 +186,7 @@ static void aac_parse_header(AacBuffer * b, float *length)
 	if (length)
 		*length = -1;
 
-	fileread = b->inStream->size;
+	fileread = b->inStream->size >= 0 ? b->inStream->size : 0;
 
 	fillAacBuffer(b);
 

src/decoder/flac_plugin.c

@@ -75,6 +75,9 @@ static flac_length_status flacLength(mpd_unused const flac_decoder * flacDec,
 {
 	FlacData *data = (FlacData *) fdata;
 
+	if (data->inStream->size < 0)
+		return flac_length_status_unsupported;
+
 	*length = (size_t) (data->inStream->size);
 
 	return flac_length_status_ok;

src/decoder/oggflac_plugin.c

@@ -92,6 +92,9 @@ static OggFLAC__SeekableStreamDecoderLengthStatus of_length_cb(mpd_unused const
 {
 	FlacData *data = (FlacData *) fdata;
 
+	if (data->inStream->size < 0)
+		return OggFLAC__SEEKABLE_STREAM_DECODER_LENGTH_STATUS_ERROR;
+
 	*length = (size_t) (data->inStream->size);
 
 	return OggFLAC__SEEKABLE_STREAM_DECODER_LENGTH_STATUS_OK;

src/decoder/wavpack_plugin.c

@@ -410,6 +410,9 @@ wavpack_input_push_back_byte(void *id, int c)
 static uint32_t
 wavpack_input_get_length(void *id)
 {
+	if (wpin(id)->is->size < 0)
+		return 0;
+
 	return wpin(id)->is->size;
 }