_ Git - BearSSL/blob - src/int/i32_encode.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_i32_encode(void *dst, size_t len, const uint32_t *x)
  30 {
  31         unsigned char *buf;
  32         size_t k;
  33
  34         buf = dst;
  35
  36         /*
  37          * Compute the announced size of x in bytes; extra bytes are
  38          * filled with zeros.
  39          */
  40         k = (x[0] + 7) >> 3;
  41         while (len > k) {
  42                 *buf ++ = 0;
  43                 len --;
  44         }
  45
  46         /*
  47          * Now we use k as index within x[]. That index starts at 1;
  48          * we initialize it to the topmost complete word, and process
  49          * any remaining incomplete word.
  50          */
  51         k = (len + 3) >> 2;
  52         switch (len & 3) {
  53         case 3:
  54                 *buf ++ = x[k] >> 16;
  55                 /* fall through */
  56         case 2:
  57                 *buf ++ = x[k] >> 8;
  58                 /* fall through */
  59         case 1:
  60                 *buf ++ = x[k];
  61                 k --;
  62         }
  63
  64         /*
  65          * Encode all complete words.
  66          */
  67         while (k > 0) {
  68                 br_enc32be(buf, x[k]);
  69                 k --;
  70                 buf += 4;
  71         }
  72 }