inp_raw.c
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上传日期:2022-08-06
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- /* 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;
- }