110 lines
2.4 KiB
C
110 lines
2.4 KiB
C
/* $NetBSD: is_tar.c,v 1.12 2000/09/22 16:35:00 pooka Exp $ */
|
|
|
|
/*
|
|
* is_tar() -- figure out whether file is a tar archive.
|
|
*
|
|
* Stolen (by the author!) from the public domain tar program:
|
|
* Public Domain version written 26 Aug 1985 John Gilmore (ihnp4!hoptoad!gnu).
|
|
*
|
|
* @(#)list.c 1.18 9/23/86 Public Domain - gnu
|
|
* Id: is_tar.c,v 1.13 2000/08/05 17:36:48 christos Exp
|
|
*
|
|
* Comments changed and some code/comments reformatted
|
|
* for file command by Ian Darwin.
|
|
*/
|
|
|
|
#include <string.h>
|
|
#include <ctype.h>
|
|
#include <sys/types.h>
|
|
#include "file.h"
|
|
#include "tar.h"
|
|
#include "file.h"
|
|
|
|
#include <sys/cdefs.h>
|
|
#ifndef lint
|
|
#if 0
|
|
FILE_RCSID("@(#)Id: is_tar.c,v 1.13 2000/08/05 17:36:48 christos Exp ")
|
|
#else
|
|
__RCSID("$NetBSD: is_tar.c,v 1.12 2000/09/22 16:35:00 pooka Exp $");
|
|
#endif
|
|
#endif
|
|
|
|
#define isodigit(c) ( ((c) >= '0') && ((c) <= '7') )
|
|
|
|
static int from_oct __P((int, char *)); /* Decode octal number */
|
|
|
|
/*
|
|
* Return
|
|
* 0 if the checksum is bad (i.e., probably not a tar archive),
|
|
* 1 for old UNIX tar file,
|
|
* 2 for Unix Std (POSIX) tar file.
|
|
*/
|
|
int
|
|
is_tar(buf, nbytes)
|
|
unsigned char *buf;
|
|
int nbytes;
|
|
{
|
|
union record *header = (union record *)buf;
|
|
int i;
|
|
int sum, recsum;
|
|
char *p;
|
|
|
|
if (nbytes < sizeof(union record))
|
|
return 0;
|
|
|
|
recsum = from_oct(8, header->header.chksum);
|
|
|
|
sum = 0;
|
|
p = header->charptr;
|
|
for (i = sizeof(union record); --i >= 0;) {
|
|
/*
|
|
* We can't use unsigned char here because of old compilers,
|
|
* e.g. V7.
|
|
*/
|
|
sum += 0xFF & *p++;
|
|
}
|
|
|
|
/* Adjust checksum to count the "chksum" field as blanks. */
|
|
for (i = sizeof(header->header.chksum); --i >= 0;)
|
|
sum -= 0xFF & header->header.chksum[i];
|
|
sum += ' '* sizeof header->header.chksum;
|
|
|
|
if (sum != recsum)
|
|
return 0; /* Not a tar archive */
|
|
|
|
if (0==strcmp(header->header.magic, TMAGIC))
|
|
return 2; /* Unix Standard tar archive */
|
|
|
|
return 1; /* Old fashioned tar archive */
|
|
}
|
|
|
|
|
|
/*
|
|
* Quick and dirty octal conversion.
|
|
*
|
|
* Result is -1 if the field is invalid (all blank, or nonoctal).
|
|
*/
|
|
static int
|
|
from_oct(digs, where)
|
|
int digs;
|
|
char *where;
|
|
{
|
|
int value;
|
|
|
|
while (isspace((unsigned char)*where)) { /* Skip spaces */
|
|
where++;
|
|
if (--digs <= 0)
|
|
return -1; /* All blank field */
|
|
}
|
|
value = 0;
|
|
while (digs > 0 && isodigit(*where)) { /* Scan til nonoctal */
|
|
value = (value << 3) | (*where++ - '0');
|
|
--digs;
|
|
}
|
|
|
|
if (digs > 0 && *where && !isspace((unsigned char)*where))
|
|
return -1; /* Ended on non-space/nul */
|
|
|
|
return value;
|
|
}
|