153 lines
4.3 KiB
C
153 lines
4.3 KiB
C
/* This program will write six C routines for the calculation of
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* the following CRC's. */
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/* The CRC polynomial.
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* These 4 values define the crc-polynomial.
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* If you change them, you must change crctab[]'s initial value to what is
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* printed by initcrctab() [see 'compile with -DMAKETAB' above].
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*/
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/* This tables assumes CCITT is MSB first. Swapped means LSB first. In that
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* case the polynomial is also swapped
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*/
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/* 16 bit crc's */
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/* Value used by: CCITT KERMIT ARC BINHEX */
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/* the poly: 0x1021 0x8408 0xA001 0x1021 */
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/* original: 0x1021 0x1021 0x8005 0x1021 */
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/* init value: -1 0 0 0 */
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/* swapped: no yes yes no */
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/* bits in CRC: 16 16 16 16 */
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/* ARC used by LHARC, ZOO, STUFFIT */
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/* BINHEX used by XMODEM, PACKIT */
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/* 32 bit crc's */
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/* Value used by: CCITT32 ZIP */
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/* the poly: 0x04c11db7 0xedb88320 */
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/* original: 0x04c11db7 0x04c11db7 */
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/* init value: -1 -1 */
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/* swapped no yes */
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/* bits in CRC: 32 32 */
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/* ZIP used by COMPACTOR */
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#include <stdio.h>
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#include <stdint.h>
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#include <stdlib.h>
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#include <string.h>
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static void initcrctab(char *name, int poly, int init, int swapped, int bits);
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int
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main (void)
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{
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initcrctab("ccitt", 0x1021, 0xffff, 0, 16);
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initcrctab("kermit", 0x8408, 0, 1, 16);
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initcrctab("arc", 0xa001, 0, 1, 16);
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initcrctab("binhex", 0x1021, 0, 0, 16);
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initcrctab("ccitt32",0x04c11db7,0xffffffff,0,32);
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initcrctab("zip",0xedb88320,0xffffffff,1,32);
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exit(0);
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}
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static void
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initcrctab (char *name, int poly, int init, int swapped, int bits)
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{
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register int b, i;
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unsigned short v;
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uint32_t vv;
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FILE *fd;
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char buf[20];
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buf[0] = 0;
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(void)strcat(buf, name);
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(void)strcat(buf, ".c");
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if((fd = fopen(buf, "w")) == NULL) {
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(void)fprintf(stderr, "Cannot open %s for writing\n", buf);
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exit(1);
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}
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(void)fprintf(fd, "#include \"crc.h\"\n");
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(void)fprintf(fd, "uint32_t %s_crcinit = %d;\n", name, init);
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(void)fprintf(fd, "\n");
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if(bits == 16) {
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(void)fprintf(fd, "static uint16_t crctab[256] = {\n");
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} else {
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(void)fprintf(fd, "static uint32_t crctab[256] = {\n");
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}
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(void)fprintf(fd, " ");
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if(bits == 16) {
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for(b = 0; b < 256; ++b) {
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if(swapped) {
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for(v = b, i = 8; --i >= 0;)
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v = v & 1 ? (v>>1)^poly : v>>1;
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} else {
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for(v = b<<8, i = 8; --i >= 0;)
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v = v & 0x8000 ? (v<<1)^poly : v<<1;
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}
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(void)fprintf(fd, "0x%.4x,", v & 0xffff);
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if((b&7) == 7) {
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(void)fprintf(fd, "\n");
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if(b != 255) (void)fprintf(fd, " ");
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} else {
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(void)fprintf(fd, " ");
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}
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}
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} else {
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for(b = 0; b < 256; ++b) {
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if(swapped) {
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for(vv = b, i = 8; --i >= 0;)
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vv = vv & 1 ? (vv>>1)^poly : vv>>1;
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} else {
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for(vv = b<<24, i = 8; --i >= 0;)
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vv = vv & 0x80000000 ? (vv<<1)^poly : vv<<1;
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}
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(void)fprintf(fd, "0x%.8x,", vv & 0xffffffff);
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if((b&3) == 3) {
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(void)fprintf(fd, "\n");
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if(b != 255) (void)fprintf(fd, " ");
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} else {
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(void)fprintf(fd, " ");
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}
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}
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}
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(void)fprintf(fd, "};\n");
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(void)fprintf(fd, "\n");
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(void)fprintf(fd, "uint32_t %s_updcrc(uint32_t icrc, unsigned char *icp, int32_t icnt)\n", name);
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(void)fprintf(fd, "{\n");
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if(bits == 16) {
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(void)fprintf(fd, "#define M1 0xff\n");
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(void)fprintf(fd, "#define M2 0xff00\n");
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} else {
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(void)fprintf(fd, "#define M1 0xffffff\n");
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(void)fprintf(fd, "#define M2 0xffffff00\n");
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}
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(void)fprintf(fd, " register uint32_t crc = icrc;\n");
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(void)fprintf(fd, " register unsigned char *cp = icp;\n");
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(void)fprintf(fd, " register int32_t cnt = icnt;\n");
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(void)fprintf(fd, "\n");
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(void)fprintf(fd, " while(cnt--) {\n");
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if(bits == 16) {
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if (swapped) {
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(void)fprintf(fd,
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"\tcrc=((crc>>8)&M1)^crctab[(crc&0xff)^*cp++];\n");
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} else {
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(void)fprintf(fd,
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"\tcrc=((crc<<8)&M2)^crctab[((crc>>8)&0xff)^*cp++];\n");
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}
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} else {
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if(swapped) {
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(void)fprintf(fd,
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"\tcrc=((crc>>8)&M1)^crctab[(crc&0xff)^*cp++];\n");
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} else {
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(void)fprintf(fd,
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"\tcrc=((crc<<8)&M2)^crctab[((crc>>24)&0xff)^*cp++];\n");
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}
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}
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(void)fprintf(fd, " }\n");
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(void)fprintf(fd, "\n");
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(void)fprintf(fd, " return(crc);\n");
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(void)fprintf(fd, "}\n");
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(void)fprintf(fd, "\n");
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(void)fclose(fd);
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}
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