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head/contrib/bearssl/src/int/i15_reduce.c
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svn:eol-style | null | native \ No newline at end of property |
svn:keywords | null | FreeBSD=%H \ No newline at end of property |
svn:mime-type | null | text/plain \ No newline at end of property |
/* | |||||
* Copyright (c) 2017 Thomas Pornin <pornin@bolet.org> | |||||
* | |||||
* Permission is hereby granted, free of charge, to any person obtaining | |||||
* a copy of this software and associated documentation files (the | |||||
* "Software"), to deal in the Software without restriction, including | |||||
* without limitation the rights to use, copy, modify, merge, publish, | |||||
* distribute, sublicense, and/or sell copies of the Software, and to | |||||
* permit persons to whom the Software is furnished to do so, subject to | |||||
* the following conditions: | |||||
* | |||||
* The above copyright notice and this permission notice shall be | |||||
* included in all copies or substantial portions of the Software. | |||||
* | |||||
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, | |||||
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF | |||||
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND | |||||
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS | |||||
* BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN | |||||
* ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN | |||||
* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE | |||||
* SOFTWARE. | |||||
*/ | |||||
#include "inner.h" | |||||
/* see inner.h */ | |||||
void | |||||
br_i15_reduce(uint16_t *x, const uint16_t *a, const uint16_t *m) | |||||
{ | |||||
uint32_t m_bitlen, a_bitlen; | |||||
size_t mlen, alen, u; | |||||
m_bitlen = m[0]; | |||||
mlen = (m_bitlen + 15) >> 4; | |||||
x[0] = m_bitlen; | |||||
if (m_bitlen == 0) { | |||||
return; | |||||
} | |||||
/* | |||||
* If the source is shorter, then simply copy all words from a[] | |||||
* and zero out the upper words. | |||||
*/ | |||||
a_bitlen = a[0]; | |||||
alen = (a_bitlen + 15) >> 4; | |||||
if (a_bitlen < m_bitlen) { | |||||
memcpy(x + 1, a + 1, alen * sizeof *a); | |||||
for (u = alen; u < mlen; u ++) { | |||||
x[u + 1] = 0; | |||||
} | |||||
return; | |||||
} | |||||
/* | |||||
* The source length is at least equal to that of the modulus. | |||||
* We must thus copy N-1 words, and input the remaining words | |||||
* one by one. | |||||
*/ | |||||
memcpy(x + 1, a + 2 + (alen - mlen), (mlen - 1) * sizeof *a); | |||||
x[mlen] = 0; | |||||
for (u = 1 + alen - mlen; u > 0; u --) { | |||||
br_i15_muladd_small(x, a[u], m); | |||||
} | |||||
} |