100 lines
1.5 KiB
C
100 lines
1.5 KiB
C
#include <u.h>
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#include <libc.h>
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#include <libsec.h>
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u32int table[256];
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u32int xor = -1, init, poly = 0xedb88320;
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char *error;
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static void
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dotable(void)
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{
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u32int c;
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int n, k;
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for(n = 0; n < 256; n++){
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c = n;
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for(k = 0; k < 8; k++)
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if((c & 1) != 0)
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c = poly ^ c >> 1;
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else
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c >>= 1;
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table[n] = c;
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}
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}
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static u32int
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calc(u32int init, uchar *buf, ulong len)
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{
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u32int c;
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c = init;
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while(len-- != 0)
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c = table[(*buf++ ^ c) & 0xff] ^ c >> 8;
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return c;
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}
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static void
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sum(int fd, char *name)
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{
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int n;
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uchar buf[8192];
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u32int crc;
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crc = init ^ xor;
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while((n = read(fd, buf, sizeof buf)) > 0)
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crc = calc(crc, buf, n);
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if(n < 0){
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fprint(2, "reading %s: %r\n", name ? name : "stdin");
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error = "read";
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return;
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}
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crc ^= xor;
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if(name == nil)
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print("%ux\n", crc);
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else
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print("%ux\t%s\n", crc, name);
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}
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void
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usage(void)
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{
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fprint(2, "usage: %s [-x xorval] [-i initial] [-p poly] [file...]\n", argv0);
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exits("usage");
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}
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void
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main(int argc, char *argv[])
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{
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int i, fd;
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ARGBEGIN{
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case 'x':
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xor = strtol(EARGF(usage()), 0, 0);
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break;
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case 'i':
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init = strtol(EARGF(usage()), 0, 0);
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break;
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case 'p':
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poly = strtol(EARGF(usage()), 0, 0);
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break;
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default:
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usage();
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}ARGEND
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dotable();
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if(argc == 0)
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sum(0, nil);
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else for(i = 0; i < argc; i++){
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fd = open(argv[i], OREAD);
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if(fd < 0){
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fprint(2, "crc32: can't open %s: %r\n", argv[i]);
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error = "open";
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continue;
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}
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sum(fd, argv[i]);
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close(fd);
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}
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exits(error);
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}
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