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/* crc32.c - the crc check algorithm for cksfv modified by oliver for easytag
Copyright (C) 2000 Bryan Call <bc@fodder.org>
Copyright (C) 2003 Oliver Schinagl <oliver@are-b.org>
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <stdio.h>
#include "crc32.h"
/*
* Initial crc32 function
* This function was renamed from crc32(...) to crc32_easytag(...) to avoid a
* strange problem with some gtk theme that may use the same name of function.
*/
int crc32_easytag(register int fd, unsigned long *main_val)
{
char buf[BUFFERSIZE], *p;
int nr;
unsigned long crc = ~0, crc32_total = ~0;
while ((nr = read(fd, &buf, sizeof(buf))) > 0)
for (p = buf; nr--; ++p)
{
crc = (crc >> 8) ^ crctable[(crc ^ *p) & 0xff];
crc32_total = (crc >> 8) ^ crctable[(crc32_total ^ *p) & 0xff];
}
if (nr < 0)
return 1;
*main_val = ~crc;
return 0;
}
/*
* Calculate the CRC-32 value of audio data (doesn't read the ID3v2 and ID3v1 tags).
* Return 0 if OK
*/
int crc32_file_with_ID3_tag(char *filename, unsigned long *main_val)
{
char buf[BUFFERSIZE], *p;
int nr;
unsigned long crc = ~0, crc32_total = ~0;
FILE *fd;
unsigned char tmp_id3[4];
int id3v2size = 0;
struct stat statbuf;
unsigned long size = 0;
int has_id3v1 = 0;
if (!filename)
return 1;
stat(filename,&statbuf);
size = statbuf.st_size;
if ( (fd = fopen(filename,"r"))==NULL )
return 1;
// Check if there is an ID3v1 tag...
fseek(fd, -128, SEEK_END);
if (fread(tmp_id3, 1, 3, fd) != 3)
return 1;
if (tmp_id3[0] == 'T' && tmp_id3[1] == 'A' && tmp_id3[2] == 'G')
has_id3v1 = 1;
// Check if there is an ID3v2 tag...
fseek(fd, 0L, SEEK_SET);
if (fread(tmp_id3, 1, 4, fd) != 4)
return 1;
// Calculate ID3v2 length
if (tmp_id3[0] == 'I' && tmp_id3[1] == 'D' && tmp_id3[2] == '3' && tmp_id3[3] < 0xFF)
{
// id3v2 tag skipeer $49 44 33 yy yy xx zz zz zz zz [zz size]
fseek(fd, 2, SEEK_CUR); // Size is 6-9 position
if (fread(tmp_id3, 1, 4, fd) != 4)
return 1;
id3v2size = 10 + ( (long)(tmp_id3[3]) | ((long)(tmp_id3[2]) << 7)
| ((long)(tmp_id3[1]) << 14) | ((long)(tmp_id3[0]) << 21) );
fseek(fd, id3v2size, SEEK_SET);
size = size - id3v2size;
}else
{
fseek(fd, 0L, SEEK_SET);
}
while ((nr = fread(buf, sizeof(char), sizeof(buf), fd)) > 0)
{
if (has_id3v1 && nr <= 128) // We are reading end of ID3v1 tag
break;
if ( has_id3v1 && ((size=size-nr) < 128) ) // ID3v1 tag is in the current buf
nr = nr - 128 + size;
for (p = buf; nr--; ++p)
{
crc = (crc >> 8) ^ crctable[(crc ^ *p) & 0xff];
crc32_total = (crc >> 8) ^ crctable[(crc32_total ^ *p) & 0xff];
}
}
fclose(fd);
if (nr < 0)
return 1;
*main_val = ~crc;
return 0;
}
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