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// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "net/quic/quic_fec_group_interface.h"
#include <limits>
#include "base/logging.h"
#include "base/stl_util.h"
namespace net {
void QuicFecGroupInterface::XorBuffers(const char* input,
size_t size_in_bytes,
char* output) {
#if defined(__i386__) || defined(__x86_64__)
// On x86, alignment is not required and casting bytes to words is safe.
// size_t is a reasonable approximation of how large a general-purpose
// register is for the platforms and compilers Chrome is built on.
typedef size_t platform_word;
const size_t size_in_words = size_in_bytes / sizeof(platform_word);
const platform_word* input_words =
reinterpret_cast<const platform_word*>(input);
platform_word* output_words = reinterpret_cast<platform_word*>(output);
// Handle word-sized part of the buffer.
size_t offset_in_words = 0;
for (; offset_in_words < size_in_words; offset_in_words++) {
output_words[offset_in_words] ^= input_words[offset_in_words];
}
// Handle the tail which does not fit into the word.
for (size_t offset_in_bytes = offset_in_words * sizeof(platform_word);
offset_in_bytes < size_in_bytes; offset_in_bytes++) {
output[offset_in_bytes] ^= input[offset_in_bytes];
}
#else
// On ARM and most other plaforms, the code above could fail due to the
// alignment errors. Stick to byte-by-byte comparison.
for (size_t offset = 0; offset < size_in_bytes; offset++) {
output[offset] ^= input[offset];
}
#endif /* defined(__i386__) || defined(__x86_64__) */
}
} // namespace net
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