60 lines
2.0 KiB
C
60 lines
2.0 KiB
C
/*
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Copyright 2009, 2011 William Hart. All rights reserved.
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Redistribution and use in source and binary forms, with or without modification, are
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permitted provided that the following conditions are met:
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1. Redistributions of source code must retain the above copyright notice, this list of
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conditions and the following disclaimer.
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2. Redistributions in binary form must reproduce the above copyright notice, this list
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of conditions and the following disclaimer in the documentation and/or other materials
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provided with the distribution.
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THIS SOFTWARE IS PROVIDED BY William Hart ``AS IS'' AND ANY EXPRESS OR IMPLIED
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WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
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FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL William Hart OR
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CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
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ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
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NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
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ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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The views and conclusions contained in the software and documentation are those of the
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authors and should not be interpreted as representing official policies, either expressed
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or implied, of William Hart.
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*/
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#include "mpir.h"
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#include "gmp-impl.h"
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void
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mpn_normmod_2expp1(mp_ptr t, mp_size_t limbs)
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{
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mp_limb_signed_t hi = t[limbs];
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if (hi)
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{
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t[limbs] = 0;
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mpn_addmod_2expp1_1(t, limbs, -hi);
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/* hi will now be in [-1,1] */
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if ((hi = t[limbs]))
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{
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t[limbs] = 0;
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mpn_addmod_2expp1_1(t, limbs, -hi);
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if (t[limbs] == ~(mp_limb_signed_t) 0) /* if we now have -1 (very unlikely) */
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{
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t[limbs] = 0;
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mpn_addmod_2expp1_1(t, limbs, 1);
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}
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}
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}
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}
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