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 source tree.
   8  */
   9 #include "libbb.h"
  10
  11 /* This is a NOEXEC applet. Be very careful! */
  12
  13 int cksum_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  14 int cksum_main(int argc UNUSED_PARAM, char **argv)
  15 {
  16         uint32_t *crc32_table = crc32_filltable(NULL, 1);
  17         uint32_t crc;
  18         off_t length, filesize;
  19         int bytes_read;
  20         int exit_code = EXIT_SUCCESS;
  21         uint8_t *cp;
  22
  23 #if ENABLE_DESKTOP
  24         getopt32(argv, ""); /* coreutils 6.9 compat */
  25         argv += optind;
  26 #else
  27         argv++;
  28 #endif
  29
  30         do {
  31                 int fd = open_or_warn_stdin(*argv ? *argv : bb_msg_standard_input);
  32
  33                 if (fd < 0) {
  34                         exit_code = EXIT_FAILURE;
  35                         continue;
  36                 }
  37                 crc = 0;
  38                 length = 0;
  39
  40 #define read_buf bb_common_bufsiz1
  41                 while ((bytes_read = safe_read(fd, read_buf, sizeof(read_buf))) > 0) {
  42                         cp = (uint8_t *) read_buf;
  43                         length += bytes_read;
  44                         do {
  45                                 crc = (crc << 8) ^ crc32_table[(crc >> 24) ^ *cp++];
  46                         } while (--bytes_read);
  47                 }
  48                 close(fd);
  49
  50                 filesize = length;
  51
  52                 while (length) {
  53                         crc = (crc << 8) ^ crc32_table[(uint8_t)(crc >> 24) ^ (uint8_t)length];
  54                         /* must ensure that shift is unsigned! */
  55                         if (sizeof(length) <= sizeof(unsigned))
  56                                 length = (unsigned)length >> 8;
  57                         else if (sizeof(length) <= sizeof(unsigned long))
  58                                 length = (unsigned long)length >> 8;
  59                         else
  60                                 length = (unsigned long long)length >> 8;
  61                 }
  62                 crc = ~crc;
  63
  64                 printf((*argv ? "%"PRIu32" %"OFF_FMT"i %s\n" : "%"PRIu32" %"OFF_FMT"i\n"),
  65                                 crc, filesize, *argv);
  66         } while (*argv && *++argv);
  67
  68         fflush_stdout_and_exit(exit_code);
  69 }