/* * 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_from_monty(uint16_t *x, const uint16_t *m, uint16_t m0i) { size_t len, u, v; len = (m[0] + 15) >> 4; for (u = 0; u < len; u ++) { uint32_t f, cc; f = MUL15(x[1], m0i) & 0x7FFF; cc = 0; for (v = 0; v < len; v ++) { uint32_t z; z = (uint32_t)x[v + 1] + MUL15(f, m[v + 1]) + cc; cc = z >> 15; if (v != 0) { x[v] = z & 0x7FFF; } } x[len] = cc; } /* * We may have to do an extra subtraction, but only if the * value in x[] is indeed greater than or equal to that of m[], * which is why we must do two calls (first call computes the * carry, second call performs the subtraction only if the carry * is 0). */ br_i15_sub(x, m, NOT(br_i15_sub(x, m, 0))); } |