coreutils/cksum.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * cksum - calculate the CRC32 checksum of a file
   4  *
   5  * Copyright (C) 2006 by Rob Sullivan, with ideas from code by Walter Harms
   6  *
   7  * Licensed under GPLv2 or later, see file LICENSE in this tarball for details. */
   8
   9 #include "libbb.h"
  10
  11 int cksum_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  12 int cksum_main(int argc UNUSED_PARAM, char **argv)
  13 {
  14         uint32_t *crc32_table = crc32_filltable(NULL, 1);
  15         uint32_t crc;
  16         off_t length, filesize;
  17         int bytes_read;
  18         uint8_t *cp;
  19
  20 #if ENABLE_DESKTOP
  21         getopt32(argv, ""); /* coreutils 6.9 compat */
  22         argv += optind;
  23 #else
  24         argv++;
  25 #endif
  26
  27         do {
  28                 int fd = open_or_warn_stdin(*argv ? *argv : bb_msg_standard_input);
  29
  30                 if (fd < 0)
  31                         continue;
  32                 crc = 0;
  33                 length = 0;
  34
  35 #define read_buf bb_common_bufsiz1
  36                 while ((bytes_read = safe_read(fd, read_buf, sizeof(read_buf))) > 0) {
  37                         cp = (uint8_t *) read_buf;
  38                         length += bytes_read;
  39                         do {
  40                                 crc = (crc << 8) ^ crc32_table[(crc >> 24) ^ *cp++];
  41                         } while (--bytes_read);
  42                 }
  43                 close(fd);
  44
  45                 filesize = length;
  46
  47                 while (length) {
  48                         crc = (crc << 8) ^ crc32_table[(uint8_t)(crc >> 24) ^ (uint8_t)length];
  49                         /* must ensure that shift is unsigned! */
  50                         if (sizeof(length) <= sizeof(unsigned))
  51                                 length = (unsigned)length >> 8;
  52                         else if (sizeof(length) <= sizeof(unsigned long))
  53                                 length = (unsigned long)length >> 8;
  54                         else
  55                                 length = (unsigned long long)length >> 8;
  56                 }
  57                 crc = ~crc;
  58
  59                 printf((*argv ? "%"PRIu32" %"OFF_FMT"i %s\n" : "%"PRIu32" %"OFF_FMT"i\n"),
  60                                 crc, filesize, *argv);
  61         } while (*argv && *++argv);
  62
  63         fflush_stdout_and_exit(EXIT_SUCCESS);
  64 }