/*

 * Copyright (c) 2016 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_i31_encode(void *dst, size_t len, const uint32_t *x)

{

  unsigned char *buf;

  size_t k, xlen;

  uint32_t acc;

  int acc_len;

  xlen = (x[0] + 31) >> 5;

  if (xlen == 0) {

    memset(dst, 0, len);

    return;

  }

  buf = (unsigned char *)dst + len;

  k = 1;

  acc = 0;

  acc_len = 0;

  while (len != 0) {

    uint32_t w;

    w = (k <= xlen) ? x[k] : 0;

    k ++;

    if (acc_len == 0) {

      acc = w;

      acc_len = 31;

    } else {

      uint32_t z;

      z = acc | (w << acc_len);

      acc_len --;

      acc = w >> (31 - acc_len);

      if (len >= 4) {

        buf -= 4;

        len -= 4;

        br_enc32be(buf, z);

      } else {

        switch (len) {

        case 3:

          buf[-3] = (unsigned char)(z >> 16);

          /* fall through */

        case 2:

          buf[-2] = (unsigned char)(z >> 8);

          /* fall through */

        case 1:

          buf[-1] = (unsigned char)z;

          break;

        }

        return;

      }

    }

  }

}