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// Copyright 2019 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.
#ifndef QUICHE_COMMON_QUICHE_ENDIAN_H_
#define QUICHE_COMMON_QUICHE_ENDIAN_H_
#include <algorithm>
#include <cstdint>
#include <type_traits>
#include "common/platform/api/quiche_export.h"
namespace quiche {
enum Endianness {
NETWORK_BYTE_ORDER, // big endian
HOST_BYTE_ORDER // little endian
};
// Provide utility functions that convert from/to network order (big endian)
// to/from host order (can be either little or big endian depending on the
// platform).
class QUICHE_EXPORT_PRIVATE QuicheEndian {
public:
// Convert |x| from host order (little endian) to network order (big endian).
#if defined(__clang__) || \
(defined(__GNUC__) && \
((__GNUC__ == 4 && __GNUC_MINOR__ >= 8) || __GNUC__ >= 5))
static uint16_t HostToNet16(uint16_t x) { return __builtin_bswap16(x); }
static uint32_t HostToNet32(uint32_t x) { return __builtin_bswap32(x); }
static uint64_t HostToNet64(uint64_t x) { return __builtin_bswap64(x); }
#else
static uint16_t HostToNet16(uint16_t x) { return PortableByteSwap(x); }
static uint32_t HostToNet32(uint32_t x) { return PortableByteSwap(x); }
static uint64_t HostToNet64(uint64_t x) { return PortableByteSwap(x); }
#endif
// Convert |x| from network order (big endian) to host order (little endian).
static uint16_t NetToHost16(uint16_t x) { return HostToNet16(x); }
static uint32_t NetToHost32(uint32_t x) { return HostToNet32(x); }
static uint64_t NetToHost64(uint64_t x) { return HostToNet64(x); }
// Returns true if current host order is little endian.
static bool HostIsLittleEndian() { return true; }
// Left public for tests.
template <typename T>
static T PortableByteSwap(T input) {
static_assert(std::is_unsigned<T>::value, "T has to be uintNN_t");
union {
T number;
char bytes[sizeof(T)];
} value;
value.number = input;
std::reverse(std::begin(value.bytes), std::end(value.bytes));
return value.number;
}
};
} // namespace quiche
#endif // QUICHE_COMMON_QUICHE_ENDIAN_H_