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 #include "common_bufsiz.h"
  17
  18 /* This is a NOEXEC applet. Be very careful! */
  19
  20 int cksum_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  21 int cksum_main(int argc UNUSED_PARAM, char **argv)
  22 {
  23         uint32_t *crc32_table = crc32_filltable(NULL, 1);
  24         uint32_t crc;
  25         off_t length, filesize;
  26         int bytes_read;
  27         int exit_code = EXIT_SUCCESS;
  28
  29 #if ENABLE_DESKTOP
  30         getopt32(argv, ""); /* coreutils 6.9 compat */
  31         argv += optind;
  32 #else
  33         argv++;
  34 #endif
  35
  36         do {
  37                 int fd = open_or_warn_stdin(*argv ? *argv : bb_msg_standard_input);
  38
  39                 if (fd < 0) {
  40                         exit_code = EXIT_FAILURE;
  41                         continue;
  42                 }
  43                 crc = 0;
  44                 length = 0;
  45
  46 #define        read_buf bb_common_bufsiz1
  47 #define sizeof_read_buf COMMON_BUFSIZE
  48                 while ((bytes_read = safe_read(fd, read_buf, sizeof_read_buf)) > 0) {
  49                         length += bytes_read;
  50                         crc = crc32_block_endian1(crc, read_buf, bytes_read, crc32_table);
  51                 }
  52                 close(fd);
  53
  54                 filesize = length;
  55
  56                 while (length) {
  57                         crc = (crc << 8) ^ crc32_table[(uint8_t)(crc >> 24) ^ (uint8_t)length];
  58                         /* must ensure that shift is unsigned! */
  59                         if (sizeof(length) <= sizeof(unsigned))
  60                                 length = (unsigned)length >> 8;
  61                         else if (sizeof(length) <= sizeof(unsigned long))
  62                                 length = (unsigned long)length >> 8;
  63                         else
  64                                 length = (unsigned long long)length >> 8;
  65                 }
  66                 crc = ~crc;
  67
  68                 printf((*argv ? "%"PRIu32" %"OFF_FMT"i %s\n" : "%"PRIu32" %"OFF_FMT"i\n"),
  69                                 crc, filesize, *argv);
  70         } while (*argv && *++argv);
  71
  72         fflush_stdout_and_exit(exit_code);
  73 }