_ Git - BearSSL/blob - src/int/i15_encode.c

   1 /*
   2  * Copyright (c) 2017 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_i15_encode(void *dst, size_t len, const uint16_t *x)
  30 {
  31         unsigned char *buf;
  32         size_t u, xlen;
  33         uint32_t acc;
  34         int acc_len;
  35
  36         xlen = (x[0] + 15) >> 4;
  37         if (xlen == 0) {
  38                 memset(dst, 0, len);
  39                 return;
  40         }
  41         u = 1;
  42         acc = 0;
  43         acc_len = 0;
  44         buf = dst;
  45         while (len -- > 0) {
  46                 if (acc_len < 8) {
  47                         if (u <= xlen) {
  48                                 acc += (uint32_t)x[u ++] << acc_len;
  49                         }
  50                         acc_len += 15;
  51                 }
  52                 buf[len] = (unsigned char)acc;
  53                 acc >>= 8;
  54                 acc_len -= 8;
  55         }
  56 }