view toys/posix/cksum.c @ 1183:0752b2d58909 draft

Rename xmsprintf() to just xmprintf(). Partly because there's no supplied target string ala sprintf, and partly because I can never remember what order the m and s go in.
author Rob Landley <>
date Thu, 16 Jan 2014 09:26:50 -0600
parents 6cc69be43c42
children 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.

    -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&4) ? 0xffffffff : 0;
  uint64_t llen = 0, llen2;
  unsigned (*cksum)(unsigned crc, unsigned char c);

  cksum = (toys.optflags&2) ? 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&1)) {
    while (llen) {
      crc = cksum(crc, llen);
      llen >>= 8;

  printf("%u %"PRIu64, (toys.optflags&8) ? crc : ~crc, llen2);
  if (strcmp("-", name)) printf(" %s", name);

void cksum_main(void)
  crc_init(TT.crc_table, toys.optflags&2);
  loopfiles(toys.optargs, do_cksum);