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mp3: moved dropSamplesAtEnd check out of the loop

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Simplifying loops for performance: why check dropSamplesAtEnd in every
iteration, when we could modify the loop boundary?  The (writable)
variable samplesLeft can be eliminated; add a write-once variable
pcm_length instead, which is used for the loop condition.
This commit is contained in:
Max Kellermann 2008-08-26 08:27:12 +02:00
parent e4c6c01903
commit e99536e8eb
1 changed files with 18 additions and 21 deletions
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39
src/inputPlugins/mp3_plugin.c
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@ -839,7 +839,7 @@ static int openMp3FromInputStream(InputStream * inStream, mp3DecodeData * data,
static int mp3Read(mp3DecodeData * data, struct decoder *decoder, static int mp3Read(mp3DecodeData * data, struct decoder *decoder,
ReplayGainInfo ** replayGainInfo) ReplayGainInfo ** replayGainInfo)
{ {
unsigned int samplesLeft; unsigned int pcm_length;
unsigned int i; unsigned int i;
int ret; int ret;
int skip; int skip;
@ -917,33 +917,24 @@ static int mp3Read(mp3DecodeData * data, struct decoder *decoder,
freeMpdTag(tag); freeMpdTag(tag);
} }
samplesLeft = (data->synth).pcm.length;
if (!data->decodedFirstFrame) { if (!data->decodedFirstFrame) {
if (data->dropSamplesAtStart >= samplesLeft) { i = data->dropSamplesAtStart;
i = samplesLeft;
samplesLeft = 0;
} else {
i = data->dropSamplesAtStart;
samplesLeft -= data->dropSamplesAtStart;
}
data->decodedFirstFrame = 1; data->decodedFirstFrame = 1;
} else } else
i = 0; i = 0;
for (; i < (data->synth).pcm.length; i++) { pcm_length = data->synth.pcm.length;
if (data->dropSamplesAtEnd &&
(data->currentFrame == data->maxFrames - data->dropFramesAtEnd)) {
if (data->dropSamplesAtEnd >= pcm_length)
pcm_length = 0;
else
pcm_length -= data->dropSamplesAtEnd;
}
for (; i < pcm_length; i++) {
unsigned int num_samples; unsigned int num_samples;
samplesLeft--;
if (data->dropSamplesAtEnd &&
(data->currentFrame == (data->maxFrames - data->dropFramesAtEnd)) &&
(samplesLeft < data->dropSamplesAtEnd)) {
/* stop decoding, effectively dropping
* all remaining samples */
return DECODE_BREAK;
}
num_samples = dither_buffer((mpd_sint16 *) data->outputPtr, num_samples = dither_buffer((mpd_sint16 *) data->outputPtr,
&data->synth, &data->dither, &data->synth, &data->dither,
i, i + 1, i, i + 1,
@ -968,6 +959,12 @@ static int mp3Read(mp3DecodeData * data, struct decoder *decoder,
} }
} }
if (data->dropSamplesAtEnd &&
(data->currentFrame == data->maxFrames - data->dropFramesAtEnd))
/* stop decoding, effectively dropping
* all remaining samples */
return DECODE_BREAK;
if (decoder_get_command(decoder) == DECODE_COMMAND_SEEK && if (decoder_get_command(decoder) == DECODE_COMMAND_SEEK &&
data->inStream->seekable) { data->inStream->seekable) {
unsigned long j = 0; unsigned long j = 0;