view toys/posix/cksum.c @ 1775:57f2a26fa92c draft toast

To ensure that toybox can be installed alongside busybox without confusing update-alternatives, the paths of the links installed by toybox should match those installed by busybox. This is accomplished by changing the flags of a few tools within toybox.
author Paul Barker <>
date Sat, 04 Apr 2015 11:58:06 -0500
parents 22739b6d5a0e
line wrap: on
line source

/* cksum.c - produce crc32 checksum value for each input
 * Copyright 2008 Rob Landley <>
 * See


config CKSUM
  bool "cksum"
  default y
    usage: cksum [-IPLN] [file...]

    For each file, output crc32 checksum value, length and name of file.
    If no files listed, copy from stdin.  Filename "-" is a synonym for stdin.

    -H	Hexadecimal checksum (defaults to decimal)
    -L	Little endian (defaults to big endian)
    -P	Pre-inversion
    -I	Skip post-inversion
    -N	Do not include length in CRC calculation

#define FOR_cksum
#include "toys.h"

  unsigned crc_table[256];

static unsigned cksum_be(unsigned crc, unsigned char c)
  return (crc<<8)^TT.crc_table[(crc>>24)^c];

static unsigned cksum_le(unsigned crc, unsigned char c)
  return TT.crc_table[(crc^c)&0xff] ^ (crc>>8);

static void do_cksum(int fd, char *name)
  unsigned crc = (toys.optflags & FLAG_P) ? 0xffffffff : 0;
  uint64_t llen = 0, llen2;
  unsigned (*cksum)(unsigned crc, unsigned char c);

  cksum = (toys.optflags & FLAG_L) ? cksum_le : cksum_be;
  // CRC the data

  for (;;) {
    int len, i;

    len = read(fd, toybuf, sizeof(toybuf));
    if (len<0) perror_msg("%s", name);
    if (len<1) break;

    llen += len;
    for (i=0; i<len; i++) crc=cksum(crc, toybuf[i]);

  // CRC the length

  llen2 = llen;
  if (!(toys.optflags & FLAG_N)) {
    while (llen) {
      crc = cksum(crc, llen);
      llen >>= 8;

  printf((toys.optflags & FLAG_H) ? "%x" : "%u",
    (toys.optflags & FLAG_I) ? crc : ~crc);
  printf(" %"PRIu64, llen2);
  if (strcmp("-", name)) printf(" %s", name);

void cksum_main(void)
  crc_init(TT.crc_table, toys.optflags & FLAG_L);
  loopfiles(toys.optargs, do_cksum);