88 lines
2.4 KiB
C
88 lines
2.4 KiB
C
/* mpz_sqrt(root, u) -- Set ROOT to floor(sqrt(U)).
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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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/* This code is just correct if "unsigned char" has at least 8 bits. It
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doesn't help to use CHAR_BIT from limits.h, as the real problem is
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the static arrays. */
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#include "gmp.h"
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#include "gmp-impl.h"
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void
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#ifdef __STDC__
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mpz_sqrt (MP_INT *root, const MP_INT *op)
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#else
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mpz_sqrt (root, op)
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MP_INT *root;
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const MP_INT *op;
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#endif
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{
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mp_size op_size, root_size;
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mp_ptr root_ptr, op_ptr;
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mp_ptr free_me = NULL;
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mp_size free_me_size;
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op_size = op->size;
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if (op_size < 0)
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op_size = 1 / op_size > 0; /* Divide by zero for negative OP. */
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/* The size of the root is accurate after this simple calculation. */
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root_size = (op_size + 1) / 2;
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root_ptr = root->d;
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op_ptr = op->d;
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if (root->alloc < root_size)
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{
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if (root_ptr == op_ptr)
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{
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free_me = root_ptr;
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free_me_size = root->alloc;
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}
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else
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(*_mp_free_func) (root_ptr, root->alloc * BYTES_PER_MP_LIMB);
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root->alloc = root_size;
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root_ptr = (mp_ptr) (*_mp_allocate_func) (root_size * BYTES_PER_MP_LIMB);
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root->d = root_ptr;
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}
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else
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{
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/* Make OP not overlap with ROOT. */
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if (root_ptr == op_ptr)
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{
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/* ROOT and OP are identical. Allocate temporary space for OP. */
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op_ptr = (mp_ptr) alloca (op_size * BYTES_PER_MP_LIMB);
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/* Copy to the temporary space. Hack: Avoid temporary variable
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by using ROOT_PTR. */
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MPN_COPY (op_ptr, root_ptr, op_size);
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}
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}
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mpn_sqrt (root_ptr, NULL, op_ptr, op_size);
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root->size = root_size;
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if (free_me != NULL)
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(*_mp_free_func) (free_me, free_me_size * BYTES_PER_MP_LIMB);
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alloca (0);
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}
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