src/cksum.c

/* cksum -- calculate and print POSIX checksums and sizes of files
   Copyright (C) 1992-2025 Free Software Foundation, Inc.

   This program is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation, either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <https://www.gnu.org/licenses/>.  */

/* Written by Q. Frank Xia, qx@math.columbia.edu.
   Cosmetic changes and reorganization by David MacKenzie, djm@gnu.ai.mit.edu.

  Usage: cksum [file...]

  The code segment between "#ifdef CRCTAB" and "#else" is the code
  which generates crctab.c

  This software is compatible with neither the System V nor the BSD
  'sum' program.  It is supposed to conform to POSIX, except perhaps
  for foreign language support.  Any inconsistency with the standard
  (other than foreign language support) is a bug.  */

/* This include must be at the top of the file to satisfy
   sc_require_config_h_first.  */
#ifndef CRCTAB
# include <config.h>
#endif

#ifdef CRCTAB

# include <stdio.h>

# define BIT(x)	(1u << (x))
# define SBIT	BIT (31)

/* The generating polynomial is

          32   26   23   22   16   12   11   10   8   7   5   4   2   1
    G(X)=X  + X  + X  + X  + X  + X  + X  + X  + X + X + X + X + X + X + 1

  The i bit in GEN is set if X^i is a summand of G(X) except X^32.  */

# define GEN	(BIT (26) | BIT (23) | BIT (22) | BIT (16) | BIT (12) \
                 | BIT (11) | BIT (10) | BIT (8) | BIT (7) | BIT (5) \
                 | BIT (4) | BIT (2) | BIT (1) | BIT (0))

static unsigned int r[8];

static void
fill_r (void)
{
  r[0] = GEN;
  for (int i = 1; i < 8; i++)
    r[i] = (r[i - 1] << 1) ^ ((r[i - 1] & SBIT) ? GEN : 0);
}

static unsigned int
crc_remainder (int m)
{
  unsigned int rem = 0;

  for (int i = 0; i < 8; i++)
    if (BIT (i) & m)
      rem ^= r[i];

  return rem & 0xFFFFFFFF;	/* Make it run on 64-bit machine.  */
}

int
main (void)
{
  static unsigned int crctab[8][256];

  fill_r ();

  for (int i = 0; i < 256; i++)
    crctab[0][i] = crc_remainder (i);

  /* CRC(0x11 0x22 0x33 0x44)
     is equal to
     CRC(0x11 0x00 0x00 0x00) XOR CRC(0x22 0x00 0x00) XOR
     CRC(0x33 0x00) XOR CRC(0x44)
     We precompute the CRC values for the offset values into
     separate CRC tables. We can then use them to speed up
     CRC calculation by processing multiple bytes at the time. */
  for (int i = 0; i < 256; i++)
    {
      unsigned int crc = 0;

      crc = (crc << 8) ^ crctab[0][((crc >> 24) ^ i) & 0xFF];
      for (int offset = 1; offset < 8; offset++)
        {
          crc = (crc << 8) ^ crctab[0][((crc >> 24) ^ 0) & 0xFF];
          crctab[offset][i] = crc & 0xFFFFFFFF;
        }
    }

  printf ("#include <config.h>\n");
  printf ("#include \"cksum.h\"\n");
  printf ("\n");
  printf ("uint_fast32_t const crctab[8][256] = {\n");
  for (int y = 0; y < 8; y++)
    {
      printf ("{\n  0x%08x", crctab[y][0]);
      for (int i = 0; i < 51; i++)
        {
          printf (",\n  0x%08x, 0x%08x, 0x%08x, 0x%08x, 0x%08x",
                  crctab[y][i * 5 + 1], crctab[y][i * 5 + 2],
                  crctab[y][i * 5 + 3], crctab[y][i * 5 + 4],
                  crctab[y][i * 5 + 5]);
        }
        printf ("\n},\n");
    }
  printf ("};\n");
}

#else /* !CRCTAB */

# include "cksum.h"
# include <sys/types.h>
# include <endian.h>
# include "system.h"

# ifdef USE_VMULL_CRC32
#  include <sys/auxv.h>
#  include <asm/hwcap.h>
# endif

# include "crc.h"
# include "cpu-supports.h"

/* Number of bytes to read at once.  */
# define BUFLEN (1 << 16)

typedef bool (*cksum_fp_t) (FILE *, uint_fast32_t *, uintmax_t *);

static cksum_fp_t
pclmul_supported (void)
{
# if USE_PCLMUL_CRC32 || GL_CRC_X86_64_PCLMUL
  bool pclmul_enabled = (cpu_supports ("avx")
                         && cpu_supports ("pclmul"));
  if (cksum_debug)
    error (0, 0, "%s",
           (pclmul_enabled
            ? _("using pclmul hardware support")
            : _("pclmul support not detected")));
#  if USE_PCLMUL_CRC32
  if (pclmul_enabled)
    return cksum_pclmul;
#  endif
# endif

  return nullptr;
}

static cksum_fp_t
avx2_supported (void)
{
  /* AVX512 processors will not set vpclmulqdq unless they support
     the avx512 version, but it implies that the avx2 version
     is supported  */
# if USE_AVX2_CRC32
  bool avx2_enabled = (cpu_supports ("avx2")
                       && cpu_supports ("vpclmulqdq"));
  if (cksum_debug)
    error (0, 0, "%s",
           (avx2_enabled
            ? _("using avx2 hardware support")
            : _("avx2 support not detected")));
  if (avx2_enabled)
    return cksum_avx2;
# endif

  return nullptr;
}

static cksum_fp_t
avx512_supported (void)
{
  /* vpclmulqdq for multiplication
     mavx512f for most of the avx512 functions we're using
     mavx512bw for byte swapping  */
# if USE_AVX512_CRC32
  bool avx512_enabled = (cpu_supports ("avx512f")
                         && cpu_supports ("avx512bw")
                         && cpu_supports ("vpclmulqdq"));

  if (cksum_debug)
    error (0, 0, "%s",
           (avx512_enabled
            ? _("using avx512 hardware support")
            : _("avx512 support not detected")));
  if (avx512_enabled)
    return cksum_avx512;
# endif

  return nullptr;
}

static cksum_fp_t
vmull_supported (void)
{
  /* vmull for multiplication  */
# if USE_VMULL_CRC32
  bool vmull_enabled = (cpu_may_support ("pmull")
                        && (getauxval (AT_HWCAP) & HWCAP_PMULL) > 0);
  if (cksum_debug)
    error (0, 0, "%s",
           (vmull_enabled
            ? _("using vmull hardware support")
            : _("vmull support not detected")));
  if (vmull_enabled)
    return cksum_vmull;
# endif

  return nullptr;
}

static bool
cksum_slice8 (FILE *fp, uint_fast32_t *crc_out, uintmax_t *length_out)
{
  uint32_t buf[BUFLEN / sizeof (uint32_t)];
  uint_fast32_t crc = 0;
  uintmax_t length = 0;
  size_t bytes_read;

  if (!fp || !crc_out || !length_out)
    return false;

  while ((bytes_read = fread (buf, 1, BUFLEN, fp)) > 0)
    {
      uint32_t *datap;

      if (length + bytes_read < length)
        {
          errno = EOVERFLOW;
          return false;
        }
      length += bytes_read;

      /* Process multiples of 8 bytes */
      datap = (uint32_t *)buf;
      while (bytes_read >= 8)
        {
          uint32_t first = *datap++, second = *datap++;
          crc ^= htobe32 (first);
          second = htobe32 (second);
          crc = (crctab[7][(crc >> 24) & 0xFF]
                 ^ crctab[6][(crc >> 16) & 0xFF]
                 ^ crctab[5][(crc >> 8) & 0xFF]
                 ^ crctab[4][(crc) & 0xFF]
                 ^ crctab[3][(second >> 24) & 0xFF]
                 ^ crctab[2][(second >> 16) & 0xFF]
                 ^ crctab[1][(second >> 8) & 0xFF]
                 ^ crctab[0][(second) & 0xFF]);
          bytes_read -= 8;
        }

      /* And finish up last 0-7 bytes in a byte by byte fashion */
      unsigned char *cp = (unsigned char *)datap;
      while (bytes_read--)
        crc = (crc << 8) ^ crctab[0][((crc >> 24) ^ *cp++) & 0xFF];
      if (feof (fp))
        break;
    }

  *crc_out = crc;
  *length_out = length;

  return !ferror (fp);
}

/* Calculate the checksum and length in bytes of stream STREAM.
   Return -1 on error, 0 on success.  */

int
crc_sum_stream (FILE *stream, void *resstream, uintmax_t *length)
{
  uintmax_t total_bytes = 0;
  uint_fast32_t crc = 0;

  static cksum_fp_t cksum_fp;
  if (! cksum_fp)
    cksum_fp = avx512_supported ();
  if (! cksum_fp)
    cksum_fp = avx2_supported ();
  if (! cksum_fp)
    cksum_fp = pclmul_supported ();
  if (! cksum_fp)
    cksum_fp = vmull_supported ();
  if (! cksum_fp)
    cksum_fp = cksum_slice8;

  if (! cksum_fp (stream, &crc, &total_bytes))
    return -1;

  *length = total_bytes;

  for (; total_bytes; total_bytes >>= 8)
    crc = (crc << 8) ^ crctab[0][((crc >> 24) ^ total_bytes) & 0xFF];
  crc = ~crc & 0xFFFFFFFF;

  unsigned int crc_out = crc;
  memcpy (resstream, &crc_out, sizeof crc_out);

  return 0;
}

/* Calculate the crc32b checksum and length in bytes of stream STREAM.
   Return -1 on error, 0 on success.  */

int
crc32b_sum_stream (FILE *stream, void *resstream, uintmax_t *reslen)
{
  uint32_t buf[BUFLEN / sizeof (uint32_t)];
  uint32_t crc = 0;
  uintmax_t len = 0;
  size_t bytes_read;

  if (!stream || !resstream || !reslen)
    return -1;

# if GL_CRC_X86_64_PCLMUL
  if (cksum_debug)
    (void) pclmul_supported ();
# endif

  while ((bytes_read = fread (buf, 1, BUFLEN, stream)) > 0)
    {
      if (len + bytes_read < len)
        {
          errno = EOVERFLOW;
          return -1;
        }
      len += bytes_read;

      crc = crc32_update (crc, (char const *)buf, bytes_read);

      if (feof (stream))
        break;
    }

  unsigned int crc_out = crc;
  memcpy (resstream, &crc_out, sizeof crc_out);

  *reslen = len;

  return ferror (stream) ? -1 : 0;
}

/* Print the checksum and size to stdout.
   If ARGS is true, also print the FILE name.  */

void
output_crc (char const *file, MAYBE_UNUSED int binary_file,
            void const *digest, bool raw, MAYBE_UNUSED bool tagged,
            unsigned char delim, bool args, uintmax_t length)
{
  if (raw)
    {
      /* Output in network byte order (big endian).  */
      uint32_t out_int = htobe32 (*(uint32_t *)digest);
      fwrite (&out_int, 1, 32/8, stdout);
      return;
    }

  printf ("%u %ju", *(unsigned int *)digest, length);
  if (args)
    printf (" %s", file);
  putchar (delim);
}

#endif /* !CRCTAB */