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// Copyright 2013 The Flutter 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 FLUTTER_FML_ENDIANNESS_H_
#define FLUTTER_FML_ENDIANNESS_H_
#include <cstdint>
#include <type_traits>
#if defined(_MSC_VER)
#include "intrin.h"
#endif
#include "flutter/fml/build_config.h"
// Compiler intrinsics for flipping endianness.
#if defined(_MSC_VER)
#define FML_BYTESWAP_16(n) _byteswap_ushort(n)
#define FML_BYTESWAP_32(n) _byteswap_ulong(n)
#define FML_BYTESWAP_64(n) _byteswap_uint64(n)
#else
#define FML_BYTESWAP_16(n) __builtin_bswap16(n)
#define FML_BYTESWAP_32(n) __builtin_bswap32(n)
#define FML_BYTESWAP_64(n) __builtin_bswap64(n)
#endif
namespace fml {
template <typename T>
struct IsByteSwappable
: public std::
integral_constant<bool, std::is_integral_v<T> || std::is_enum_v<T>> {
};
template <typename T>
constexpr bool kIsByteSwappableV = IsByteSwappable<T>::value;
/// @brief Flips the endianness of the given value.
/// The given value must be an integral type of size 1, 2, 4, or 8.
template <typename T, class = std::enable_if_t<kIsByteSwappableV<T>>>
constexpr T ByteSwap(T n) {
if constexpr (sizeof(T) == 1) {
return n;
} else if constexpr (sizeof(T) == 2) {
return (T)FML_BYTESWAP_16((uint16_t)n);
} else if constexpr (sizeof(T) == 4) {
return (T)FML_BYTESWAP_32((uint32_t)n);
} else if constexpr (sizeof(T) == 8) {
return (T)FML_BYTESWAP_64((uint64_t)n);
} else {
static_assert(!sizeof(T), "Unsupported size");
}
}
/// @brief Convert a known big endian value to match the endianness of the
/// current architecture. This is effectively a cross platform
/// ntohl/ntohs (as network byte order is always Big Endian).
/// The given value must be an integral type of size 1, 2, 4, or 8.
template <typename T, class = std::enable_if_t<kIsByteSwappableV<T>>>
constexpr T BigEndianToArch(T n) {
#if FML_ARCH_CPU_LITTLE_ENDIAN
return ByteSwap<T>(n);
#else
return n;
#endif
}
/// @brief Convert a known little endian value to match the endianness of the
/// current architecture.
/// The given value must be an integral type of size 1, 2, 4, or 8.
template <typename T, class = std::enable_if_t<kIsByteSwappableV<T>>>
constexpr T LittleEndianToArch(T n) {
#if !FML_ARCH_CPU_LITTLE_ENDIAN
return ByteSwap<T>(n);
#else
return n;
#endif
}
} // namespace fml
#endif // FLUTTER_FML_ENDIANNESS_H_