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 //config:config CKSUM
  10 //config:       bool "cksum (4.2 kb)"
  11 //config:       default y
  12 //config:       help
  13 //config:       cksum is used to calculate the CRC32 checksum of a file.
  14
  15 //applet:IF_CKSUM(APPLET_NOEXEC(cksum, cksum, BB_DIR_USR_BIN, BB_SUID_DROP, cksum))
  16
  17 //kbuild:lib-$(CONFIG_CKSUM) += cksum.o
  18
  19 //usage:#define cksum_trivial_usage
  20 //usage:       "FILE..."
  21 //usage:#define cksum_full_usage "\n\n"
  22 //usage:       "Calculate the CRC32 checksums of FILEs"
  23
  24 #include "libbb.h"
  25 #include "common_bufsiz.h"
  26
  27 /* This is a NOEXEC applet. Be very careful! */
  28
  29 int cksum_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  30 int cksum_main(int argc UNUSED_PARAM, char **argv)
  31 {
  32         uint32_t *crc32_table = crc32_filltable(NULL, 1);
  33         uint32_t crc;
  34         off_t length, filesize;
  35         int bytes_read;
  36         int exit_code = EXIT_SUCCESS;
  37
  38 #if ENABLE_DESKTOP
  39         getopt32(argv, ""); /* coreutils 6.9 compat */
  40         argv += optind;
  41 #else
  42         argv++;
  43 #endif
  44
  45         setup_common_bufsiz();
  46         do {
  47                 int fd = open_or_warn_stdin(*argv ? *argv : bb_msg_standard_input);
  48
  49                 if (fd < 0) {
  50                         exit_code = EXIT_FAILURE;
  51                         continue;
  52                 }
  53                 crc = 0;
  54                 length = 0;
  55
  56 #define read_buf bb_common_bufsiz1
  57                 while ((bytes_read = safe_read(fd, read_buf, COMMON_BUFSIZE)) > 0) {
  58                         length += bytes_read;
  59                         crc = crc32_block_endian1(crc, read_buf, bytes_read, crc32_table);
  60                 }
  61                 close(fd);
  62
  63                 filesize = length;
  64
  65                 while (length) {
  66                         crc = (crc << 8) ^ crc32_table[(uint8_t)(crc >> 24) ^ (uint8_t)length];
  67                         /* must ensure that shift is unsigned! */
  68                         if (sizeof(length) <= sizeof(unsigned))
  69                                 length = (unsigned)length >> 8;
  70                         else if (sizeof(length) <= sizeof(unsigned long))
  71                                 length = (unsigned long)length >> 8;
  72                         else
  73                                 length = (unsigned long long)length >> 8;
  74                 }
  75                 crc = ~crc;
  76
  77                 printf((*argv ? "%"PRIu32" %"OFF_FMT"i %s\n" : "%"PRIu32" %"OFF_FMT"i\n"),
  78                                 crc, filesize, *argv);
  79         } while (*argv && *++argv);
  80
  81         fflush_stdout_and_exit(exit_code);
  82 }