_ Git - BearSSL/blob - src/int/i31_decode.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_i31_decode(uint32_t *x, const void *src, size_t len)
  30 {
  31         const unsigned char *buf;
  32         size_t u, v;
  33         uint32_t acc;
  34         int acc_len;
  35
  36         buf = src;
  37         u = len;
  38         v = 1;
  39         acc = 0;
  40         acc_len = 0;
  41         while (u -- > 0) {
  42                 uint32_t b;
  43
  44                 b = buf[u];
  45                 acc |= (b << acc_len);
  46                 acc_len += 8;
  47                 if (acc_len >= 31) {
  48                         x[v ++] = acc & (uint32_t)0x7FFFFFFF;
  49                         acc_len -= 31;
  50                         acc = b >> (8 - acc_len);
  51                 }
  52         }
  53         if (acc_len != 0) {
  54                 x[v ++] = acc;
  55         }
  56         x[0] = br_i31_bit_length(x + 1, v - 1);
  57 }