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/* bitfile.c
*
* Library routines for dealing with bit files, version 0.2
*
* Copyright 2001, 2002 by David Sullins
*
* This file is part of Bitinfo.
*
* Bitinfo 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, version 2 of the License.
*
* Bitinfo 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
* Bitinfo; if not, write to the Free Software Foundation, Inc., 59 Temple
* Place, Suite 330, Boston, MA 02111-1307 USA
*
* You may contact the author at djs@naspa.net.
*/
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include "bitfile.h"
#ifndef uchar
#define uchar unsigned char
#endif
/* first 13 bytes of a bit file */
static uchar head13[] = {0, 9, 15, 240, 15, 240, 15, 240, 15, 240, 0, 0, 1};
/* initbh
*
* Initialize the bithead struct
*/
void initbh(struct bithead *bh)
{
bh->filename = NULL;
bh->part = NULL;
bh->date = NULL;
bh->time = NULL;
bh->length = 0;
}
/* freebh
*
* Free up memory allocated for a bithead struct.
*/
void freebh(struct bithead *bh)
{
free(bh->filename);
free(bh->part);
free(bh->date);
free(bh->time);
initbh(bh);
}
/* readhead
*
* Read the entire bit file header. The file pointer will be advanced to
* point to the beginning of the bitstream, and the bitfile header struct
* will be filled with the appropriate data.
*
* Return -1 if an error occurs, 0 otherwise.
*/
int readhead(struct bithead *bh, FILE *f)
{
int t;
/* get first 13 bytes */
t = readhead13(f);
if (t) return t;
/* get filename */
t = readsecthead(NULL, f);
if (-1 == t) return -1;
bh->filename = malloc(t);
t = readsection(bh->filename, t, f);
/* get part name */
t = readsecthead(NULL, f);
if (-1 == t) return -1;
bh->part = malloc(t);
t = readsection(bh->part, t, f);
/* get file creation date */
t = readsecthead(NULL, f);
if (-1 == t) return -1;
bh->date = malloc(t);
t = readsection(bh->date, t, f);
/* get file creation time */
t = readsecthead(NULL, f);
if (-1 == t) return -1;
bh->time = malloc(t);
t = readsection(bh->time, t, f);
/* get bitstream length */
t = readlength(f);
if (-1 == t) return -1;
bh->length = t;
return 0;
}
/* readhead13
*
* Read the first 13 bytes of the bit file. Discards the 13 bytes but
* verifies that they are correct.
*
* Return -1 if an error occurs, 0 otherwise.
*/
int readhead13 (FILE *f)
{
int t;
uchar buf[13];
/* read header */
t = fread(buf, 1, 13, f);
if (t != 13)
{
return -1;
}
/* verify header is correct */
t = memcmp(buf, head13, 13);
if (t)
{
return -1;
}
return 0;
}
/* readsecthead
*
* Read the header of a bit file section. The section letter is placed in
* section buffer "buf" and the length of the following section is
* returned. If buf is NULL, the section letter is discarded.
*
* Return -1 if an error occurs, length of section otherwise.
*/
int readsecthead(char *buf, FILE *f)
{
int t;
char tbuf = 0;
char lenbuf[2];
/* if buf is NULL, use tbuf instead */
if (NULL == buf)
{
buf = &tbuf;
}
/* get section letter */
t = fread(buf, 1, 1, f);
if (t != 1)
{
return -1;
}
/* read length */
t = fread(lenbuf, 1, 2, f);
if (t != 2)
{
return -1;
}
/* convert 2-byte length to an int */
return (((int)lenbuf[0]) <<8) | lenbuf[1];
}
/* readsection
*
* Read a section of a bit file. The section contents are placed
* in the contents buffer "buf."
*
* Return -1 if an error occurs, 0 otherwise.
*/
int readsection(char *buf, int length, FILE *f)
{
int t;
/* get section data */
t = fread(buf, 1, length, f);
if ((t != length) || (buf[length-1] != 0))
{
return -1;
}
return 0;
}
/* readlength
*
* Read in the bitstream length. The section letter "e" is discarded
* and the length is returned.
*
* Return -1 if an error occurs, length otherwise.
*/
int readlength(FILE *f)
{
char s = 0;
uchar buf[4];
int length;
int t;
/* get section, make sure it's "e" */
t = fread(&s, 1, 1, f);
if ((t != 1) || (s != 'e'))
{
return -1;
}
/* get length */
t = fread(buf, 1, 4, f);
if (t != 4)
{
return -1;
}
/* convert 4-byte length to an int */
length = (((int)buf[0]) <<24) | (((int)buf[1]) <<16)
| (((int)buf[2]) <<8) | buf[3];
return length;
}
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