+++ /dev/null
-/* mpn_sub -- Subtract two low-level natural-number integers.
-
-Copyright (C) 1991 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 General Public License as published by
-the Free Software Foundation; either version 2, 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 General Public License for more details.
-
-You should have received a copy of the GNU General Public License
-along with the GNU MP Library; see the file COPYING. If not, write to
-the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. */
-
-#include "gmp.h"
-#include "gmp-impl.h"
-
-/* Subtract SUB_PTR/SUB_SIZE from MIN_PTR/MIN_SIZE and store the
- result (MIN_SIZE words) at DIF_PTR.
-
- Return 1 if min < sub (result is negative). Otherwise, return the
- negative difference between the number of words in dif and min.
- (I.e. return 0 if the result has MIN_SIZE words, -1 if it has
- MIN_SIZE - 1 words, etc.)
-
- Argument constraint: MIN_SIZE >= SUB_SIZE.
-
- The size of DIF can be calculated as MIN_SIZE + the return value. */
-
-mp_size
-#ifdef __STDC__
-mpn_sub (mp_ptr dif_ptr,
- mp_srcptr min_ptr, mp_size min_size,
- mp_srcptr sub_ptr, mp_size sub_size)
-#else
-mpn_sub (dif_ptr, min_ptr, min_size, sub_ptr, sub_size)
- mp_ptr dif_ptr;
- mp_srcptr min_ptr;
- mp_size min_size;
- mp_srcptr sub_ptr;
- mp_size sub_size;
-#endif
-{
- mp_limb m, s, dif;
- mp_size j;
-
- /* The loop counter and index J goes from some negative value to zero.
- This way the loops are faster. Need to offset the base pointers
- to take care of the negative indices. */
-
- j = -sub_size;
- if (j == 0)
- goto sub_finished;
-
- min_ptr -= j;
- sub_ptr -= j;
- dif_ptr -= j;
-
- /* There are two do-loops, marked NON-CARRY LOOP and CARRY LOOP that
- jump between each other. The first loop is for when the previous
- subtraction didn't produce a carry-out; the second is for the
- complementary case. */
-
- /* NON-CARRY LOOP */
- do
- {
- m = min_ptr[j];
- s = sub_ptr[j];
- dif = m - s;
- dif_ptr[j] = dif;
- if (dif > m)
- goto cy_loop;
- ncy_loop:
- j++;
- }
- while (j < 0);
-
- /* We have exhausted SUB, with no carry out. Copy remaining part of
- MIN to DIF. */
-
- sub_finished:
- j = sub_size - min_size;
-
- /* If there's no difference between the length of the operands, the
- last words might have become zero, and re-normalization is needed. */
- if (j == 0)
- goto normalize;
-
- min_ptr -= j;
- dif_ptr -= j;
-
- goto copy;
-
- /* CARRY LOOP */
- do
- {
- m = min_ptr[j];
- s = sub_ptr[j];
- dif = m - s - 1;
- dif_ptr[j] = dif;
- if (dif < m)
- goto ncy_loop;
- cy_loop:
- j++;
- }
- while (j < 0);
-
- /* We have exhausted SUB, but need to propagate carry. */
-
- j = sub_size - min_size;
- if (j == 0)
- return 1; /* min < sub. Flag it to the caller */
-
- min_ptr -= j;
- dif_ptr -= j;
-
- /* Propagate carry. Sooner or later the carry will cancel with a
- non-zero word, because the minuend is normalized. Considering this,
- there's no need to test the index J. */
- for (;;)
- {
- m = min_ptr[j];
- dif = m - 1;
- dif_ptr[j] = dif;
- j++;
- if (dif < m)
- break;
- }
-
- if (j == 0)
- goto normalize;
-
- copy:
- /* Don't copy the remaining words of MIN to DIF if MIN_PTR and DIF_PTR
- are equal. It would just be a no-op copying. Return 0, as the length
- of the result equals that of the minuend. */
- if (dif_ptr == min_ptr)
- return 0;
-
- do
- {
- dif_ptr[j] = min_ptr[j];
- j++;
- }
- while (j < 0);
- return 0;
-
- normalize:
- for (j = -1; j >= -min_size; j--)
- {
- if (dif_ptr[j] != 0)
- return j + 1;
- }
-
- return -min_size;
-}
projects / ghc-hetmet.git / blobdiff