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
  10 //usage:#define cksum_trivial_usage
  11 //usage:       "FILES..."
  12 //usage:#define cksum_full_usage "\n\n"
  13 //usage:       "Calculate the CRC32 checksums of FILES"
  14
  15 #include "libbb.h"
  16
  17 /* This is a NOEXEC applet. Be very careful! */
  18
  19 int cksum_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  20 int cksum_main(int argc UNUSED_PARAM, char **argv)
  21 {
  22         uint32_t *crc32_table = crc32_filltable(NULL, 1);
  23         uint32_t crc;
  24         off_t length, filesize;
  25         int bytes_read;
  26         int exit_code = EXIT_SUCCESS;
  27
  28 #if ENABLE_DESKTOP
  29         getopt32(argv, ""); /* coreutils 6.9 compat */
  30         argv += optind;
  31 #else
  32         argv++;
  33 #endif
  34
  35         do {
  36                 int fd = open_or_warn_stdin(*argv ? *argv : bb_msg_standard_input);
  37
  38                 if (fd < 0) {
  39                         exit_code = EXIT_FAILURE;
  40                         continue;
  41                 }
  42                 crc = 0;
  43                 length = 0;
  44
  45 #define read_buf bb_common_bufsiz1
  46                 while ((bytes_read = safe_read(fd, read_buf, sizeof(read_buf))) > 0) {
  47                         length += bytes_read;
  48                         crc = crc32_block_endian1(crc, read_buf, bytes_read, crc32_table);
  49                 }
  50                 close(fd);
  51
  52                 filesize = length;
  53
  54                 while (length) {
  55                         crc = (crc << 8) ^ crc32_table[(uint8_t)(crc >> 24) ^ (uint8_t)length];
  56                         /* must ensure that shift is unsigned! */
  57                         if (sizeof(length) <= sizeof(unsigned))
  58                                 length = (unsigned)length >> 8;
  59                         else if (sizeof(length) <= sizeof(unsigned long))
  60                                 length = (unsigned long)length >> 8;
  61                         else
  62                                 length = (unsigned long long)length >> 8;
  63                 }
  64                 crc = ~crc;
  65
  66                 printf((*argv ? "%"PRIu32" %"OFF_FMT"i %s\n" : "%"PRIu32" %"OFF_FMT"i\n"),
  67                                 crc, filesize, *argv);
  68         } while (*argv && *++argv);
  69
  70         fflush_stdout_and_exit(exit_code);
  71 }