_ Git - BearSSL/blob - src/ec/ecdsa_i31_bits.c

   1 /*
   2  * Copyright (c) 2016 Thomas Pornin <pornin@bolet.org>
   3  *
   4  * Permission is hereby granted, free of charge, to any person obtaining
   5  * a copy of this software and associated documentation files (the
   6  * "Software"), to deal in the Software without restriction, including
   7  * without limitation the rights to use, copy, modify, merge, publish,
   8  * distribute, sublicense, and/or sell copies of the Software, and to
   9  * permit persons to whom the Software is furnished to do so, subject to
  10  * the following conditions:
  11  *
  12  * The above copyright notice and this permission notice shall be
  13  * included in all copies or substantial portions of the Software.
  14  *
  15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  16  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  17  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  18  * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
  19  * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
  20  * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  21  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  22  * SOFTWARE.
  23  */
  24
  25 #include "inner.h"
  26
  27 /* see inner.h */
  28 void
  29 br_ecdsa_i31_bits2int(uint32_t *x,
  30         const void *src, size_t len, uint32_t ebitlen)
  31 {
  32         uint32_t bitlen, hbitlen;
  33         int sc;
  34
  35         bitlen = ebitlen - (ebitlen >> 5);
  36         hbitlen = (uint32_t)len << 3;
  37         if (hbitlen > bitlen) {
  38                 len = (bitlen + 7) >> 3;
  39                 sc = (int)((hbitlen - bitlen) & 7);
  40         } else {
  41                 sc = 0;
  42         }
  43         br_i31_zero(x, ebitlen);
  44         br_i31_decode(x, src, len);
  45         br_i31_rshift(x, sc);
  46         x[0] = ebitlen;
  47 }