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make some improvements to the seek algo

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This commit is contained in:
Josh Coalson 2001-03-31 00:29:46 +00:00
parent c8c0fa70cb
commit 159ac6259e
1 changed files with 41 additions and 16 deletions
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57
src/libFLAC/file_decoder.c
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@ -21,6 +21,7 @@
#include <stdio.h>
#include <stdlib.h> /* for malloc() */
#include <string.h> /* for strcmp() */
#include <sys/stat.h> /* for stat() */
#include "FLAC/file_decoder.h"
#include "protected/stream_decoder.h"
#include "private/md5.h"
@ -31,6 +32,7 @@ typedef struct FLAC__FileDecoderPrivate {
void (*error_callback)(const FLAC__FileDecoder *decoder, FLAC__StreamDecoderErrorStatus status, void *client_data);
void *client_data;
FILE *file;
char *filename; /* == NULL if stdin */
FLAC__StreamDecoder *stream;
struct MD5Context md5context;
byte stored_md5sum[16]; /* this is what is stored in the metadata */
@ -101,11 +103,19 @@ FLAC__FileDecoderState FLAC__file_decoder_init(
decoder->guts->error_callback = error_callback;
decoder->guts->client_data = client_data;
decoder->guts->stream = 0;
decoder->guts->file = 0;
decoder->guts->filename = 0;
if(0 == strcmp(filename, "-"))
if(0 == strcmp(filename, "-")) {
decoder->guts->file = stdin;
else
}
else {
if(0 == (decoder->guts->filename = (char*)malloc(strlen(filename)+1)))
return decoder->state = FLAC__FILE_DECODER_MEMORY_ALLOCATION_ERROR;
strcpy(decoder->guts->filename, filename);
decoder->guts->file = fopen(filename, "rb");
}
if(decoder->guts->file == 0)
return decoder->state = FLAC__FILE_DECODER_ERROR_OPENING_FILE;
@ -113,7 +123,7 @@ FLAC__FileDecoderState FLAC__file_decoder_init(
* because check_md5 may be turned on to start and then turned off if a
* seek occurs. So we always init the context here and finalize it in
* FLAC__file_decoder_finish() to make sure things are always cleaned up
*properly.
* properly.
*/
MD5Init(&decoder->guts->md5context);
@ -134,6 +144,8 @@ bool FLAC__file_decoder_finish(FLAC__FileDecoder *decoder)
if(decoder->guts != 0) {
if(decoder->guts->file != 0 && decoder->guts->file != stdin)
fclose(decoder->guts->file);
if(0 != decoder->guts->filename)
free(decoder->guts->filename);
/* see the comment in FLAC__file_decoder_init() as to why we always
* call MD5Final()
*/
@ -236,10 +248,16 @@ bool FLAC__file_decoder_process_remaining_frames(FLAC__FileDecoder *decoder)
bool FLAC__file_decoder_seek_absolute(FLAC__FileDecoder *decoder, uint64 sample)
{
long filesize;
struct stat filestats;
assert(decoder != 0);
assert(decoder->state == FLAC__FILE_DECODER_OK);
if(decoder->guts->filename == 0) { /* means the file is stdin... */
decoder->state = FLAC__FILE_DECODER_SEEK_ERROR;
return false;
}
decoder->state = FLAC__FILE_DECODER_SEEKING;
/* turn off md5 checking if a seek is attempted */
@ -250,15 +268,11 @@ bool FLAC__file_decoder_seek_absolute(FLAC__FileDecoder *decoder, uint64 sample)
return false;
}
/* get the file length */
if(0 != fseek(decoder->guts->file, 0, SEEK_END)) {
decoder->state = FLAC__FILE_DECODER_SEEK_ERROR;
return false;
}
fflush(decoder->guts->file);
if(-1 == (filesize = ftell(decoder->guts->file))) {
if(stat(decoder->guts->filename, &filestats) != 0) {
decoder->state = FLAC__FILE_DECODER_SEEK_ERROR;
return false;
}
filesize = filestats.st_size;
/* rewind */
if(0 != fseek(decoder->guts->file, 0, SEEK_SET)) {
decoder->state = FLAC__FILE_DECODER_SEEK_ERROR;
@ -380,27 +394,40 @@ bool seek_to_absolute_sample_(FLAC__FileDecoder *decoder, long filesize, uint64
bool needs_seek;
const bool is_variable_blocksize_stream = (decoder->guts->stream_info.min_blocksize != decoder->guts->stream_info.max_blocksize);
if(!is_variable_blocksize_stream) {
/* we are just guessing here, but we want to guess high, not low */
/* we are just guessing here, but we want to guess high, not low */
if(decoder->guts->stream_info.max_framesize > 0) {
approx_bytes_per_frame = decoder->guts->stream_info.max_framesize + 64;
}
else if(!is_variable_blocksize_stream) {
/* note there are no () around 'decoder->guts->stream_info.bits_per_sample/8' to keep precision up since it's an integer calulation */
approx_bytes_per_frame = decoder->guts->stream_info.min_blocksize * decoder->guts->stream_info.channels * decoder->guts->stream_info.bits_per_sample/8 + 64;
}
else
approx_bytes_per_frame = 1152 * decoder->guts->stream_info.channels * decoder->guts->stream_info.bits_per_sample/8 + 64;
/* Now we need to use the metadata and the filelength to search to the frame with the correct sample */
/* The file pointer is currently at the first frame plus any read
ahead data, so first we get the file pointer, then subtract
uncomsumed bytes to get the position (l) of the first frame
in the file */
if(-1 == (l = ftell(decoder->guts->file))) {
decoder->state = FLAC__FILE_DECODER_SEEK_ERROR;
return false;
}
l -= FLAC__stream_decoder_input_bytes_unconsumed(decoder->guts->stream);
l -= FLAC__stream_decoder_input_bytes_unconsumed(decoder->guts->stream) + 1;
if(l < 0)
l = 0;
/* Now we need to use the metadata and the filelength to search to the frame with the correct sample */
#ifdef _MSC_VER
/* with VC++ you have to spoon feed it the casting */
pos = l + (long)((double)(int64)target_sample / (double)(int64)decoder->guts->stream_info.total_samples * (double)(filesize-l+1)) - approx_bytes_per_frame;
#else
pos = l + (long)((double)target_sample / (double)decoder->guts->stream_info.total_samples * (double)(filesize-l+1)) - approx_bytes_per_frame;
#endif
r = filesize - ((decoder->guts->stream_info.channels * decoder->guts->stream_info.bits_per_sample * FLAC__MAX_BLOCK_SIZE) / 8 + 64);
if(decoder->guts->stream_info.max_framesize > 0)
r = filesize - decoder->guts->stream_info.max_framesize - 2;
else
r = filesize - ((decoder->guts->stream_info.channels * decoder->guts->stream_info.bits_per_sample * FLAC__MAX_BLOCK_SIZE) / 8 + 64);
if(pos >= r)
pos = r-1;
if(pos < l)
@ -453,8 +480,6 @@ bool seek_to_absolute_sample_(FLAC__FileDecoder *decoder, long filesize, uint64
}
if(pos < l)
pos = l;
if(pos < 0)
pos = 0;
last_frame_sample = this_frame_sample;
}
}