text: /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
   * All rights reserved.
   *
   * This package is an SSL implementation written
   * by Eric Young (eay@cryptsoft.com).
   * The implementation was written so as to conform with Netscapes SSL.
   *
   * This library is free for commercial and non-commercial use as long as
   * the following conditions are aheared to.  The following conditions
   * apply to all code found in this distribution, be it the RC4, RSA,
   * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
   * included with this distribution is covered by the same copyright terms
   * except that the holder is Tim Hudson (tjh@cryptsoft.com).
   *
   * Copyright remains Eric Young's, and as such any Copyright notices in
   * the code are not to be removed.
   * If this package is used in a product, Eric Young should be given attribution
   * as the author of the parts of the library used.
   * This can be in the form of a textual message at program startup or
   * in documentation (online or textual) provided with the package.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   * 1. Redistributions of source code must retain the copyright
   *    notice, this list of conditions and the following disclaimer.
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in the
   *    documentation and/or other materials provided with the distribution.
   * 3. All advertising materials mentioning features or use of this software
   *    must display the following acknowledgement:
   *    "This product includes cryptographic software written by
   *     Eric Young (eay@cryptsoft.com)"
   *    The word 'cryptographic' can be left out if the rouines from the library
   *    being used are not cryptographic related :-).
   * 4. If you include any Windows specific code (or a derivative thereof) from
   *    the apps directory (application code) you must include an acknowledgement:
   *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
   *
   * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
   * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
   * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   * SUCH DAMAGE.
   *
   * The licence and distribution terms for any publically available version or
   * derivative of this code cannot be changed.  i.e. this code cannot simply be
   * copied and put under another distribution licence
   * [including the GNU Public Licence.] */
  
  #include <CCryptoBoringSSL_bn.h>
  
  #include <assert.h>
  #include <limits.h>
  
  #include "internal.h"
  
  
  BIGNUM *BN_bin2bn(const uint8_t *in, size_t len, BIGNUM *ret) {
    size_t num_words;
    unsigned m;
    BN_ULONG word = 0;
    BIGNUM *bn = NULL;
  
    if (ret == NULL) {
      ret = bn = BN_new();
    }
  
    if (ret == NULL) {
      return NULL;
    }
  
    if (len == 0) {
      ret->width = 0;
      return ret;
    }
  
    num_words = ((len - 1) / BN_BYTES) + 1;
    m = (len - 1) % BN_BYTES;
    if (!bn_wexpand(ret, num_words)) {
      if (bn) {
        BN_free(bn);
      }
      return NULL;
    }
  
    // |bn_wexpand| must check bounds on |num_words| to write it into
    // |ret->dmax|.
    assert(num_words <= INT_MAX);
    ret->width = (int)num_words;
    ret->neg = 0;
  
    while (len--) {
      word = (word << 8) | *(in++);
      if (m-- == 0) {
        ret->d[--num_words] = word;
        word = 0;
        m = BN_BYTES - 1;
      }
    }
  
    return ret;
  }
  
  BIGNUM *BN_le2bn(const uint8_t *in, size_t len, BIGNUM *ret) {
    BIGNUM *bn = NULL;
    if (ret == NULL) {
      bn = BN_new();
      ret = bn;
    }
  
    if (ret == NULL) {
      return NULL;
    }
  
    if (len == 0) {
      ret->width = 0;
      ret->neg = 0;
      return ret;
    }
  
    // Reserve enough space in |ret|.
    size_t num_words = ((len - 1) / BN_BYTES) + 1;
    if (!bn_wexpand(ret, num_words)) {
      BN_free(bn);
      return NULL;
    }
    ret->width = num_words;
  
    // Make sure the top bytes will be zeroed.
    ret->d[num_words - 1] = 0;
  
    // We only support little-endian platforms, so we can simply memcpy the
    // internal representation.
    OPENSSL_memcpy(ret->d, in, len);
    return ret;
  }
  
  size_t BN_bn2bin(const BIGNUM *in, uint8_t *out) {
    size_t n, i;
    BN_ULONG l;
  
    n = i = BN_num_bytes(in);
    while (i--) {
      l = in->d[i / BN_BYTES];
      *(out++) = (unsigned char)(l >> (8 * (i % BN_BYTES))) & 0xff;
    }
    return n;
  }
  
  static int fits_in_bytes(const uint8_t *bytes, size_t num_bytes, size_t len) {
    uint8_t mask = 0;
    for (size_t i = len; i < num_bytes; i++) {
      mask |= bytes[i];
    }
    return mask == 0;
  }
  
  int BN_bn2le_padded(uint8_t *out, size_t len, const BIGNUM *in) {
    const uint8_t *bytes = (const uint8_t *)in->d;
    size_t num_bytes = in->width * BN_BYTES;
    if (len < num_bytes) {
      if (!fits_in_bytes(bytes, num_bytes, len)) {
        return 0;
      }
      num_bytes = len;
    }
  
    // We only support little-endian platforms, so we can simply memcpy into the
    // internal representation.
    OPENSSL_memcpy(out, bytes, num_bytes);
    // Pad out the rest of the buffer with zeroes.
    OPENSSL_memset(out + num_bytes, 0, len - num_bytes);
    return 1;
  }
  
  int BN_bn2bin_padded(uint8_t *out, size_t len, const BIGNUM *in) {
    const uint8_t *bytes = (const uint8_t *)in->d;
    size_t num_bytes = in->width * BN_BYTES;
    if (len < num_bytes) {
      if (!fits_in_bytes(bytes, num_bytes, len)) {
        return 0;
      }
      num_bytes = len;
    }
  
    // We only support little-endian platforms, so we can simply write the buffer
    // in reverse.
    for (size_t i = 0; i < num_bytes; i++) {
      out[len - i - 1] = bytes[i];
    }
    // Pad out the rest of the buffer with zeroes.
    OPENSSL_memset(out, 0, len - num_bytes);
    return 1;
  }
  
  BN_ULONG BN_get_word(const BIGNUM *bn) {
    switch (bn_minimal_width(bn)) {
      case 0:
        return 0;
      case 1:
        return bn->d[0];
      default:
        return BN_MASK2;
    }
  }
  
  int BN_get_u64(const BIGNUM *bn, uint64_t *out) {
    switch (bn_minimal_width(bn)) {
      case 0:
        *out = 0;
        return 1;
      case 1:
        *out = bn->d[0];
        return 1;
  #if defined(OPENSSL_32_BIT)
      case 2:
        *out = (uint64_t) bn->d[0] | (((uint64_t) bn->d[1]) << 32);
        return 1;
  #endif
      default:
        return 0;
    }
  }
  