268 lines
7.0 KiB
C
268 lines
7.0 KiB
C
/* mpz_and -- Logical and.
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Copyright (C) 1991 Free Software Foundation, Inc.
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This file is part of the GNU MP Library.
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The GNU MP Library is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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The GNU MP Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with the GNU MP Library; see the file COPYING. If not, write to
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the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. */
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#include "gmp.h"
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#include "gmp-impl.h"
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#define min(l,o) ((l) < (o) ? (l) : (o))
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#define max(h,i) ((h) > (i) ? (h) : (i))
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void
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#ifdef __STDC__
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mpz_and (MP_INT *res, const MP_INT *op1, const MP_INT *op2)
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#else
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mpz_and (res, op1, op2)
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MP_INT *res;
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const MP_INT *op1;
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const MP_INT *op2;
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#endif
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{
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mp_srcptr op1_ptr, op2_ptr;
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mp_size op1_size, op2_size;
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mp_ptr res_ptr;
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mp_size res_size;
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mp_size i;
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op1_size = op1->size;
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op2_size = op2->size;
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op1_ptr = op1->d;
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op2_ptr = op2->d;
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res_ptr = res->d;
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if (op1_size >= 0)
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{
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if (op2_size >= 0)
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{
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res_size = min (op1_size, op2_size);
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/* First loop finds the size of the result. */
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for (i = res_size - 1; i >= 0; i--)
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if ((op1_ptr[i] & op2_ptr[i]) != 0)
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break;
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res_size = i + 1;
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/* Handle allocation, now when we know exactly how much space is
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needed for the result. */
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if (res->alloc < res_size)
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{
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_mpz_realloc (res, res_size);
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op1_ptr = op1->d;
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op2_ptr = op2->d;
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res_ptr = res->d;
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}
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/* Second loop computes the real result. */
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for (i = res_size - 1; i >= 0; i--)
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res_ptr[i] = op1_ptr[i] & op2_ptr[i];
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res->size = res_size;
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return;
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}
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else /* op2_size < 0 */
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/* Fall through to the code at the end of the function. */
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;
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}
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else
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{
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if (op2_size < 0)
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{
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mp_ptr opx;
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mp_limb cy;
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mp_limb one = 1;
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mp_size res_alloc;
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/* Both operands are negative, so will be the result.
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-((-OP1) & (-OP2)) = -(~(OP1 - 1) & ~(OP2 - 1)) =
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= ~(~(OP1 - 1) & ~(OP2 - 1)) + 1 =
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= ((OP1 - 1) | (OP2 - 1)) + 1 */
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op1_size = -op1_size;
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op2_size = -op2_size;
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res_alloc = 1 + max (op1_size, op2_size);
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opx = (mp_ptr) alloca (op1_size * BYTES_PER_MP_LIMB);
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op1_size += mpn_sub (opx, op1_ptr, op1_size, &one, 1);
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op1_ptr = opx;
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opx = (mp_ptr) alloca (op2_size * BYTES_PER_MP_LIMB);
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op2_size += mpn_sub (opx, op2_ptr, op2_size, &one, 1);
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op2_ptr = opx;
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if (res->alloc < res_alloc)
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{
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_mpz_realloc (res, res_alloc);
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res_ptr = res->d;
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/* Don't re-read OP1_PTR and OP2_PTR. They point to
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temporary space--never to the space RES->D used
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to point to before reallocation. */
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}
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if (op1_size >= op2_size)
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{
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MPN_COPY (res_ptr + op2_size, op1_ptr + op2_size,
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op1_size - op2_size);
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for (i = op2_size - 1; i >= 0; i--)
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res_ptr[i] = op1_ptr[i] | op2_ptr[i];
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res_size = op1_size;
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}
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else
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{
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MPN_COPY (res_ptr + op1_size, op2_ptr + op1_size,
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op2_size - op1_size);
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for (i = op1_size - 1; i >= 0; i--)
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res_ptr[i] = op1_ptr[i] | op2_ptr[i];
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res_size = op2_size;
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}
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if (res_size != 0)
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{
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cy = mpn_add (res_ptr, res_ptr, res_size, &one, 1);
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if (cy)
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{
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res_ptr[res_size] = cy;
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res_size++;
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}
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}
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else
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{
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res_ptr[0] = 1;
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res_size = 1;
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}
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res->size = -res_size;
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return;
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}
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else
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{
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/* We should compute -OP1 & OP2. Swap OP1 and OP2 and fall
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through to the code that handles OP1 & -OP2. */
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{const MP_INT *t = op1; op1 = op2; op2 = t;}
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{mp_srcptr t = op1_ptr; op1_ptr = op2_ptr; op2_ptr = t;}
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{mp_size t = op1_size; op1_size = op2_size; op2_size = t;}
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}
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}
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{
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#if 0
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mp_size op2_lim;
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/* OP2 must be negated as with infinite precision.
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Scan from the low end for a non-zero limb. The first non-zero
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limb is simply negated (two's complement). Any subsequent
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limbs are one's complemented. Of course, we don't need to
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handle more limbs than there are limbs in the other, positive
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operand as the result for those limbs is going to become zero
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anyway. */
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/* Scan for the least significant. non-zero OP2 limb, and zero the
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result meanwhile for those limb positions. (We will surely
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find a non-zero limb, so we can write the loop with one
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termination condition only.) */
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for (i = 0; op2_ptr[i] == 0; i++)
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res_ptr[i] = 0;
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op2_lim = i;
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op2_size = -op2_size;
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if (op1_size <= op2_size)
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{
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/* The ones-extended OP2 is >= than the zero-extended OP1.
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RES_SIZE <= OP1_SIZE. Find the exact size. */
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for (i = op1_size - 1; i > op2_lim; i--)
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if ((op1_ptr[i] & ~op2_ptr[i]) != 0)
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break;
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res_size = i + 1;
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}
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else
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{
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/* The ones-extended OP2 is < than the zero-extended OP1.
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RES_SIZE == OP1_SIZE, since OP1 is normalized. */
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res_size = op1_size;
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}
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#endif
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/* OP1 is positive and zero-extended,
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OP2 is negative and ones-extended.
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The result will be positive.
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OP1 & -OP2 = OP1 & ~(OP2 - 1). */
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mp_ptr opx;
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const mp_limb one = 1;
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op2_size = -op2_size;
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opx = (mp_ptr) alloca (op2_size * BYTES_PER_MP_LIMB);
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op2_size += mpn_sub (opx, op2_ptr, op2_size, &one, 1);
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op2_ptr = opx;
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if (op1_size > op2_size)
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{
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/* The result has the same size as OP1, since OP1 is normalized
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and longer than the ones-extended OP2. */
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res_size = op1_size;
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/* Handle allocation, now when we know exactly how much space is
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needed for the result. */
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if (res->alloc < res_size)
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{
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_mpz_realloc (res, res_size);
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res_ptr = res->d;
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op1_ptr = op1->d;
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/* Don't re-read OP2_PTR. It points to temporary space--never
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to the space RES->D used to point to before reallocation. */
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}
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MPN_COPY (res_ptr + op2_size, op1_ptr + op2_size,
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res_size - op2_size);
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for (i = op2_size - 1; i >= 0; i--)
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res_ptr[i] = op1_ptr[i] & ~op2_ptr[i];
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res->size = res_size;
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}
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else
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{
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/* Find out the exact result size. Ignore the high limbs of OP2,
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OP1 is zero-extended and would make the result zero. */
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for (i = op1_size - 1; i >= 0; i--)
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if ((op1_ptr[i] & ~op2_ptr[i]) != 0)
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break;
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res_size = i + 1;
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/* Handle allocation, now when we know exactly how much space is
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needed for the result. */
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if (res->alloc < res_size)
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{
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_mpz_realloc (res, res_size);
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res_ptr = res->d;
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op1_ptr = op1->d;
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/* Don't re-read OP2_PTR. It points to temporary space--never
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to the space RES->D used to point to before reallocation. */
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}
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for (i = res_size - 1; i >= 0; i--)
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res_ptr[i] = op1_ptr[i] & ~op2_ptr[i];
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res->size = res_size;
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}
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}
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}
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