gcc/gmp/mpz/inp_raw.c

/* mpz_inp_raw -- read an mpz_t in raw format.

Copyright 2001, 2002, 2005 Free Software Foundation, Inc.

This file is part of the GNU MP Library.

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

The GNU MP Library 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 Lesser General Public
License for more details.

You should have received a copy of the GNU Lesser General Public License
along with the GNU MP Library.  If not, see http://www.gnu.org/licenses/.  */

#include <stdio.h>
#include "gmp.h"
#include "gmp-impl.h"


/* NTOH_LIMB_FETCH fetches a limb which is in network byte order (ie. big
   endian) and produces a normal host byte order result. */

#if HAVE_LIMB_BIG_ENDIAN
#define NTOH_LIMB_FETCH(limb, src)  do { (limb) = *(src); } while (0)
#endif

#if HAVE_LIMB_LITTLE_ENDIAN
#define NTOH_LIMB_FETCH(limb, src)  BSWAP_LIMB_FETCH (limb, src)
#endif

#ifndef NTOH_LIMB_FETCH
#define NTOH_LIMB_FETCH(limb, src)                              \
  do {                                                          \
    const unsigned char  *__p = (const unsigned char *) (src);  \
    mp_limb_t  __limb;                                          \
    int        __i;                                             \
    __limb = 0;                                                 \
    for (__i = 0; __i < BYTES_PER_MP_LIMB; __i++)               \
      __limb = (__limb << 8) | __p[__i];                        \
    (limb) = __limb;                                            \
  } while (0)
#endif


/* Enhancement: The byte swap loop ought to be safe to vectorize on Cray
   etc, but someone who knows what they're doing needs to check it.  */

size_t
mpz_inp_raw (mpz_ptr x, FILE *fp)
{
  unsigned char  csize_bytes[4];
  mp_size_t      csize, abs_xsize, i;
  size_t         abs_csize;
  char           *cp;
  mp_ptr         xp, sp, ep;
  mp_limb_t      slimb, elimb;

  if (fp == 0)
    fp = stdin;

  /* 4 bytes for size */
  if (fread (csize_bytes, sizeof (csize_bytes), 1, fp) != 1)
    return 0;

  csize =
    (  (mp_size_t) csize_bytes[0] << 24)
    + ((mp_size_t) csize_bytes[1] << 16)
    + ((mp_size_t) csize_bytes[2] << 8)
    + ((mp_size_t) csize_bytes[3]);

  /* Sign extend if necessary.
     Could write "csize -= ((csize & 0x80000000L) << 1)", but that tickles a
     bug in gcc 3.0 for powerpc64 on AIX.  */
  if (sizeof (csize) > 4 && csize & 0x80000000L)
    csize -= 0x80000000L << 1;

  abs_csize = ABS (csize);

  /* round up to a multiple of limbs */
  abs_xsize = (abs_csize*8 + GMP_NUMB_BITS-1) / GMP_NUMB_BITS;

  if (abs_xsize != 0)
    {
      MPZ_REALLOC (x, abs_xsize);
      xp = PTR(x);

      /* Get limb boundaries right in the read, for the benefit of the
         non-nails case.  */
      xp[0] = 0;
      cp = (char *) (xp + abs_xsize) - abs_csize;
      if (fread (cp, abs_csize, 1, fp) != 1)
        return 0;

      if (GMP_NAIL_BITS == 0)
        {
          /* Reverse limbs to least significant first, and byte swap.  If
             abs_xsize is odd then on the last iteration elimb and slimb are
             the same.  It doesn't seem extra code to handle that case
             separately, to save an NTOH.  */
          sp = xp;
          ep = xp + abs_xsize-1;
          for (i = 0; i < (abs_xsize+1)/2; i++)
            {
              NTOH_LIMB_FETCH (elimb, ep);
              NTOH_LIMB_FETCH (slimb, sp);
              *sp++ = elimb;
              *ep-- = slimb;
            }
        }
      else
        {
          /* It ought to be possible to do the transformation in-place, but
             for now it's easier to use an extra temporary area.  */
          mp_limb_t  byte, limb;
          int        bits;
          mp_size_t  tpos;
          mp_ptr     tp;
          TMP_DECL;

          TMP_MARK;
          tp = TMP_ALLOC_LIMBS (abs_xsize);
          limb = 0;
          bits = 0;
          tpos = 0;
          for (i = abs_csize-1; i >= 0; i--)
            {
              byte = (unsigned char) cp[i];
              limb |= (byte << bits);
              bits += 8;
              if (bits >= GMP_NUMB_BITS)
                {
                  ASSERT (tpos < abs_xsize);
                  tp[tpos++] = limb & GMP_NUMB_MASK;
                  bits -= GMP_NUMB_BITS;
                  ASSERT (bits < 8);
                  limb = byte >> (8 - bits);
                }
            }
          if (bits != 0)
            {
              ASSERT (tpos < abs_xsize);
              tp[tpos++] = limb;
            }
          ASSERT (tpos == abs_xsize);

          MPN_COPY (xp, tp, abs_xsize);
          TMP_FREE;
        }

      /* GMP 1.x mpz_out_raw wrote high zero bytes, strip any high zero
         limbs resulting from this.  Should be a non-zero value here, but
         for safety don't assume that. */
      MPN_NORMALIZE (xp, abs_xsize);
    }

  SIZ(x) = (csize >= 0 ? abs_xsize : -abs_xsize);
  return abs_csize + 4;
}