home
***
CD-ROM
|
disk
|
FTP
|
other
***
search
/
Usenet 1994 October
/
usenetsourcesnewsgroupsinfomagicoctober1994disk2.iso
/
misc
/
volume6
/
crc-check
/
crc.c
< prev
next >
Wrap
C/C++ Source or Header
|
1989-03-07
|
10KB
|
399 lines
/* updcrc(3), crc(1) - calculate crc polynomials
*
* Calculate, intelligently, the CRC of a dataset incrementally given a
* buffer full at a time.
*
* Usage:
* newcrc = updcrc( oldcrc, bufadr, buflen )
* unsigned int oldcrc, buflen;
* char *bufadr;
*
* Compiling with -DTEST creates a program to print the CRC of stdin to stdout.
* Compile with -DMAKETAB to print values for crctab to stdout. If you change
* the CRC polynomial parameters, be sure to do this and change
* crctab's initial value.
*
* Notes:
* Regards the data stream as an integer whose MSB is the MSB of the first
* byte recieved. This number is 'divided' (using xor instead of subtraction)
* by the crc-polynomial P.
* XMODEM does things a little differently, essentially treating the LSB of
* the first data byte as the MSB of the integer. Define SWAPPED to make
* things behave in this manner.
*
* Author: Mark G. Mendel, 7/86
* UUCP: ihnp4!umn-cs!hyper!mark, GEnie: mgm
*/
#define TEST
/* The CRC polynomial.
* These 4 values define the crc-polynomial.
* If you change them, you must change crctab[]'s initial value to what is
* printed by initcrctab() [see 'compile with -DMAKETAB' above].
*/
/* Value used by: CITT XMODEM ARC */
#define P 0xA001 /* the poly: 0x1021 0x1021 A001 */
#define INIT_CRC 0L /* init value: -1 0 0 */
#define SWAPPED /* bit order: undef defined defined */
#define W 16 /* bits in CRC:16 16 16 */
/* data type that holds a W-bit unsigned integer */
#if W <= 16
# define WTYPE unsigned short
#else
# define WTYPE unsigned long
#endif
/* the number of bits per char: don't change it. */
#define B 8
static WTYPE crctab[1<<B] = /* as calculated by initcrctab() */ {
0x0, 0xc0c1, 0xc181, 0x140, 0xc301, 0x3c0, 0x280, 0xc241,
0xc601, 0x6c0, 0x780, 0xc741, 0x500, 0xc5c1, 0xc481, 0x440,
0xcc01, 0xcc0, 0xd80, 0xcd41, 0xf00, 0xcfc1, 0xce81, 0xe40,
0xa00, 0xcac1, 0xcb81, 0xb40, 0xc901, 0x9c0, 0x880, 0xc841,
0xd801, 0x18c0, 0x1980, 0xd941, 0x1b00, 0xdbc1, 0xda81, 0x1a40,
0x1e00, 0xdec1, 0xdf81, 0x1f40, 0xdd01, 0x1dc0, 0x1c80, 0xdc41,
0x1400, 0xd4c1, 0xd581, 0x1540, 0xd701, 0x17c0, 0x1680, 0xd641,
0xd201, 0x12c0, 0x1380, 0xd341, 0x1100, 0xd1c1, 0xd081, 0x1040,
0xf001, 0x30c0, 0x3180, 0xf141, 0x3300, 0xf3c1, 0xf281, 0x3240,
0x3600, 0xf6c1, 0xf781, 0x3740, 0xf501, 0x35c0, 0x3480, 0xf441,
0x3c00, 0xfcc1, 0xfd81, 0x3d40, 0xff01, 0x3fc0, 0x3e80, 0xfe41,
0xfa01, 0x3ac0, 0x3b80, 0xfb41, 0x3900, 0xf9c1, 0xf881, 0x3840,
0x2800, 0xe8c1, 0xe981, 0x2940, 0xeb01, 0x2bc0, 0x2a80, 0xea41,
0xee01, 0x2ec0, 0x2f80, 0xef41, 0x2d00, 0xedc1, 0xec81, 0x2c40,
0xe401, 0x24c0, 0x2580, 0xe541, 0x2700, 0xe7c1, 0xe681, 0x2640,
0x2200, 0xe2c1, 0xe381, 0x2340, 0xe101, 0x21c0, 0x2080, 0xe041,
0xa001, 0x60c0, 0x6180, 0xa141, 0x6300, 0xa3c1, 0xa281, 0x6240,
0x6600, 0xa6c1, 0xa781, 0x6740, 0xa501, 0x65c0, 0x6480, 0xa441,
0x6c00, 0xacc1, 0xad81, 0x6d40, 0xaf01, 0x6fc0, 0x6e80, 0xae41,
0xaa01, 0x6ac0, 0x6b80, 0xab41, 0x6900, 0xa9c1, 0xa881, 0x6840,
0x7800, 0xb8c1, 0xb981, 0x7940, 0xbb01, 0x7bc0, 0x7a80, 0xba41,
0xbe01, 0x7ec0, 0x7f80, 0xbf41, 0x7d00, 0xbdc1, 0xbc81, 0x7c40,
0xb401, 0x74c0, 0x7580, 0xb541, 0x7700, 0xb7c1, 0xb681, 0x7640,
0x7200, 0xb2c1, 0xb381, 0x7340, 0xb101, 0x71c0, 0x7080, 0xb041,
0x5000, 0x90c1, 0x9181, 0x5140, 0x9301, 0x53c0, 0x5280, 0x9241,
0x9601, 0x56c0, 0x5780, 0x9741, 0x5500, 0x95c1, 0x9481, 0x5440,
0x9c01, 0x5cc0, 0x5d80, 0x9d41, 0x5f00, 0x9fc1, 0x9e81, 0x5e40,
0x5a00, 0x9ac1, 0x9b81, 0x5b40, 0x9901, 0x59c0, 0x5880, 0x9841,
0x8801, 0x48c0, 0x4980, 0x8941, 0x4b00, 0x8bc1, 0x8a81, 0x4a40,
0x4e00, 0x8ec1, 0x8f81, 0x4f40, 0x8d01, 0x4dc0, 0x4c80, 0x8c41,
0x4400, 0x84c1, 0x8581, 0x4540, 0x8701, 0x47c0, 0x4680, 0x8641,
0x8201, 0x42c0, 0x4380, 0x8341, 0x4100, 0x81c1, 0x8081, 0x4040,
};
void perror();
char *strcpy();
void exit();
WTYPE
updcrc( icrc, icp, icnt )
WTYPE icrc;
unsigned char *icp;
int icnt;
{
register WTYPE crc = icrc;
register unsigned char *cp = icp;
register int cnt = icnt;
while ( cnt--) {
#ifndef SWAPPED
crc = (crc << B) ^ crctab[(crc>>(W-B)) ^ *cp++];
#else
crc = (crc >> B) ^ crctab[(crc & ((1<<B)-1)) ^ *cp++];
#endif
}
return( crc );
}
#ifdef MAKETAB
#include <stdio.h>
main()
{
initcrctab();
}
initcrctab()
{
register int b, i;
WTYPE v;
for ( b = 0; b <= (1 << B) - 1; ++b ) {
#ifndef SWAPPED
for ( v = b << (W - B), i = B; --i >= 0; )
v = v & ((WTYPE)1 << (W - 1)) ? (v << 1) ^ P : v << 1;
#else
for ( v = b, i = B; --i >= 0; )
v = v & 1 ? (v >> 1) ^ P : v >> 1;
#endif
crctab[b] = v;
(void) printf( "0x%lx,", v & ((1L << W) - 1L));
if ( (b & 7) == 7 )
(void) printf("\n" );
else
(void) printf(" ");
}
}
#endif
#ifdef TEST
#include <stdio.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <pwd.h>
#include <grp.h>
#define MAXBUF 4096
#ifndef S_IRGRP
#define S_IRGRP (S_IREAD >> 3)
#define S_IWGRP (S_IWRITE >> 3)
#define S_IXGRP (S_IEXEC >> 3)
#define S_IROTH (S_IREAD >> 6)
#define S_IWOTH (S_IWRITE >> 6)
#define S_IXOTH (S_IEXEC >> 6)
#endif
struct stat stat_buf;
int initial_crc = INIT_CRC;
extern char *optarg;
extern int optind;
extern int opterr;
main( argc, argv )
int argc;
char **argv;
{
int stats_flag = 0;
int c;
if (argc == 1) {
print_crc((char *)0, 0);
return 0;
}
/* process all arguments */
while ((c = getopt(argc, argv, "VvI:i:")) != EOF) {
switch (c) {
case 'V':
case 'v':
stats_flag = 1;
break;
case 'I':
case 'i':
initial_crc = atoi(optarg);
break;
default:
(void) fprintf(stderr, "crc: -v (verbose listing)\n");
(void) fprintf(stderr, " -i value (initial crc value)\n");
exit(1);
}
}
for (; optind < argc ; optind++)
print_crc(argv[optind], stats_flag);
return 0;
}
print_crc(name, stat_flag)
char *name;
int stat_flag;
{
int fd;
int nr;
unsigned char buf[MAXBUF];
WTYPE crc;
#ifdef MAGICCHECK
WTYPE crc2;
#endif
fd = 0;
/* quietly ignore files we can't stat */
if (name != NULL && stat(name, &stat_buf) != 0)
return;
/* don't do a crc on strange files */
crc = nr = 0;
if (name == NULL || (stat_buf.st_mode & S_IFMT) == S_IFREG) {
/* open the file and do a crc on it */
if (name != NULL && (fd = open( name, O_RDONLY )) < 0 ) {
perror( name );
exit( -1 );
}
#ifdef MAGICCHECK
crc2 =
#endif
crc = initial_crc;
while ( (nr = read( fd, (char *)buf, MAXBUF )) > 0 ) {
crc = updcrc(crc, buf, nr );
}
(void) close(fd);
}
if ( nr != 0 ) {
perror( "read error" );
} else {
(void) printf("%4.4x", (unsigned) crc );
if (stat_flag)
stats(name);
else
(void) printf("\n");
}
#ifdef MAGICCHECK
/* tack one's complement of crc onto data stream, and
continue crc calculation. Should get a constant (magic number)
dependent only on P, not the data.
*/
crc2 = crc ^ -1L;
for ( nr = W - B; nr >= 0; nr -= B ) {
buf[0] = (crc2 >> nr);
crc = updcrc(crc, buf, 1);
}
/* crc should now equal magic */
buf[0] = buf[1] = buf[2] = buf[3] = 0;
(void) printf( "magic test: %lx =?= %lx\n", crc, updcrc((WTYPE) - 1, buf, W / B));
#endif
}
stats(name)
char *name;
{
struct passwd *entry;
struct group *group_entry;
static char owner[20];
static char group[20];
char a_time[50];
struct passwd *getpwuid();
struct group *getgrgid();
char *ctime();
static int prev_uid = -9999;
static int prev_gid = -9999;
if (stat_buf.st_uid != prev_uid) {
entry = getpwuid((int)stat_buf.st_uid);
if (entry)
(void) strcpy(owner, entry->pw_name);
else
(void) sprintf(owner, "%d", stat_buf.st_uid);
prev_uid = stat_buf.st_uid;
}
if (stat_buf.st_gid != prev_gid) {
group_entry = getgrgid((int)stat_buf.st_gid);
if (group_entry)
(void) strcpy(group, group_entry->gr_name);
else
(void) sprintf(group, "%d", stat_buf.st_gid);
prev_gid = stat_buf.st_gid;
}
(void) strcpy(a_time, ctime(&stat_buf.st_mtime));
a_time[24] = '\0';
print_perm(stat_buf.st_mode);
(void) printf(" %s\t%s\t%s %s\n", owner, group, a_time + 4, name);
}
print_perm(perm)
unsigned int perm;
{
char string[20];
(void) strcpy(string, "----------");
switch (perm & S_IFMT) {
case S_IFDIR:
string[0] = 'd';
break;
case S_IFBLK:
string[0] = 'b';
break;
case S_IFCHR:
string[0] = 'c';
break;
case S_IFIFO:
string[0] = 'p';
break;
}
if (perm & S_IREAD)
string[1] = 'r';
if (perm & S_IWRITE)
string[2] = 'w';
if (perm & S_ISUID && perm & S_IEXEC)
string[3] = 's';
else if (perm & S_IEXEC)
string[3] = 'x';
else if (perm & S_ISUID)
string[3] = 'S';
if (perm & S_IRGRP)
string[4] = 'r';
if (perm & S_IWGRP)
string[5] = 'w';
if (perm & S_ISUID && perm & S_IXGRP)
string[6] = 's';
else if (perm & S_IXGRP)
string[6] = 'x';
else if (perm & S_ISUID)
string[6] = 'l';
if (perm & S_IROTH)
string[7] = 'r';
if (perm & S_IWOTH)
string[8] = 'w';
if (perm & S_ISVTX && perm & S_IXOTH)
string[9] = 't';
else if (perm & S_IXOTH)
string[9] = 'x';
else if (perm & S_ISVTX)
string[9] = 'T';
(void) printf(" %s", string);
}
#endif