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
  22 #if ENABLE_DESKTOP
  23         getopt32(argv, ""); /* coreutils 6.9 compat */
  24         argv += optind;
  25 #else
  26         argv++;
  27 #endif
  28
  29         do {
  30                 int fd = open_or_warn_stdin(*argv ? *argv : bb_msg_standard_input);
  31
  32                 if (fd < 0) {
  33                         exit_code = EXIT_FAILURE;
  34                         continue;
  35                 }
  36                 crc = 0;
  37                 length = 0;
  38
  39 #define read_buf bb_common_bufsiz1
  40                 while ((bytes_read = safe_read(fd, read_buf, sizeof(read_buf))) > 0) {
  41                         length += bytes_read;
  42                         crc = crc32_block_endian1(crc, read_buf, bytes_read, crc32_table);
  43                 }
  44                 close(fd);
  45
  46                 filesize = length;
  47
  48                 while (length) {
  49                         crc = (crc << 8) ^ crc32_table[(uint8_t)(crc >> 24) ^ (uint8_t)length];
  50                         /* must ensure that shift is unsigned! */
  51                         if (sizeof(length) <= sizeof(unsigned))
  52                                 length = (unsigned)length >> 8;
  53                         else if (sizeof(length) <= sizeof(unsigned long))
  54                                 length = (unsigned long)length >> 8;
  55                         else
  56                                 length = (unsigned long long)length >> 8;
  57                 }
  58                 crc = ~crc;
  59
  60                 printf((*argv ? "%"PRIu32" %"OFF_FMT"i %s\n" : "%"PRIu32" %"OFF_FMT"i\n"),
  61                                 crc, filesize, *argv);
  62         } while (*argv && *++argv);
  63
  64         fflush_stdout_and_exit(exit_code);
  65 }