Annotation of OpenXM/src/kan96xx/gmp-2.0.2-ssh-2/mpz/sub_ui.c, Revision 1.1
1.1 ! takayama 1: /* mpz_sub_ui -- Subtract an unsigned one-word integer from an MP_INT.
! 2:
! 3: Copyright (C) 1991, 1993, 1994, 1996 Free Software Foundation, Inc.
! 4:
! 5: This file is part of the GNU MP Library.
! 6:
! 7: The GNU MP Library is free software; you can redistribute it and/or modify
! 8: it under the terms of the GNU Library General Public License as published by
! 9: the Free Software Foundation; either version 2 of the License, or (at your
! 10: option) any later version.
! 11:
! 12: The GNU MP Library is distributed in the hope that it will be useful, but
! 13: WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
! 14: or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public
! 15: License for more details.
! 16:
! 17: You should have received a copy of the GNU Library General Public License
! 18: along with the GNU MP Library; see the file COPYING.LIB. If not, write to
! 19: the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
! 20: MA 02111-1307, USA. */
! 21:
! 22: #include "gmp.h"
! 23: #include "gmp-impl.h"
! 24:
! 25: void
! 26: #if __STDC__
! 27: mpz_sub_ui (mpz_ptr w, mpz_srcptr u, unsigned long int v)
! 28: #else
! 29: mpz_sub_ui (w, u, v)
! 30: mpz_ptr w;
! 31: mpz_srcptr u;
! 32: unsigned long int v;
! 33: #endif
! 34: {
! 35: mp_srcptr up;
! 36: mp_ptr wp;
! 37: mp_size_t usize, wsize;
! 38: mp_size_t abs_usize;
! 39:
! 40: usize = u->_mp_size;
! 41: abs_usize = ABS (usize);
! 42:
! 43: /* If not space for W (and possible carry), increase space. */
! 44: wsize = abs_usize + 1;
! 45: if (w->_mp_alloc < wsize)
! 46: _mpz_realloc (w, wsize);
! 47:
! 48: /* These must be after realloc (U may be the same as W). */
! 49: up = u->_mp_d;
! 50: wp = w->_mp_d;
! 51:
! 52: if (abs_usize == 0)
! 53: {
! 54: wp[0] = v;
! 55: w->_mp_size = -(v != 0);
! 56: return;
! 57: }
! 58:
! 59: if (usize < 0)
! 60: {
! 61: mp_limb_t cy;
! 62: cy = mpn_add_1 (wp, up, abs_usize, v);
! 63: wp[abs_usize] = cy;
! 64: wsize = -(abs_usize + cy);
! 65: }
! 66: else
! 67: {
! 68: /* The signs are different. Need exact comparison to determine
! 69: which operand to subtract from which. */
! 70: if (abs_usize == 1 && up[0] < v)
! 71: {
! 72: wp[0] = v - up[0];
! 73: wsize = -1;
! 74: }
! 75: else
! 76: {
! 77: mpn_sub_1 (wp, up, abs_usize, v);
! 78: /* Size can decrease with at most one limb. */
! 79: wsize = abs_usize - (wp[abs_usize - 1] == 0);
! 80: }
! 81: }
! 82:
! 83: w->_mp_size = wsize;
! 84: }
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