boringssl/crypto/modes/ofb.c

/* ====================================================================
 * Copyright (c) 2008 The OpenSSL Project.  All rights reserved.
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 * Redistribution and use in source and binary forms, with or without
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 *    software must display the following acknowledgment:
 *    "This product includes software developed by the OpenSSL Project
 *    for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
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 *    openssl-core@openssl.org.
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 *    "This product includes software developed by the OpenSSL Project
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#include <openssl/modes.h>

#include <assert.h>

#include "internal.h"


void CRYPTO_ofb128_encrypt(const uint8_t *in, uint8_t *out, size_t len,
                           const void *key, uint8_t ivec[16], int *num,
                           block128_f block) {
  unsigned int n;

  assert(in && out && key && ivec && num);
  assert((16 % sizeof(size_t)) == 0);

  n = *num;

  while (n && len) {
    *(out++) = *(in++) ^ ivec[n];
    --len;
    n = (n + 1) % 16;
  }

#if STRICT_ALIGNMENT
  if (((size_t)in | (size_t)out | (size_t)ivec) % sizeof(size_t) != 0) {
    size_t l = 0;
    while (l < len) {
      if (n == 0) {
        (*block)(ivec, ivec, key);
      }
      out[l] = in[l] ^ ivec[n];
      ++l;
      n = (n + 1) % 16;
    }

    *num = n;
    return;
  }
#endif

  while (len >= 16) {
    (*block)(ivec, ivec, key);
    for (; n < 16; n += sizeof(size_t)) {
      *(size_t *)(out + n) = *(size_t *)(in + n) ^ *(size_t *)(ivec + n);
    }
    len -= 16;
    out += 16;
    in += 16;
    n = 0;
  }
  if (len) {
    (*block)(ivec, ivec, key);
    while (len--) {
      out[n] = in[n] ^ ivec[n];
      ++n;
    }
  }
  *num = n;
}