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diff --git a/mfbt/EndianUtils.h b/mfbt/EndianUtils.h new file mode 100644 index 0000000000..b6f3e2c315 --- /dev/null +++ b/mfbt/EndianUtils.h @@ -0,0 +1,611 @@ +/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ +/* vim: set ts=8 sts=2 et sw=2 tw=80: */ +/* This Source Code Form is subject to the terms of the Mozilla Public + * License, v. 2.0. If a copy of the MPL was not distributed with this + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ + +/* Functions for reading and writing integers in various endiannesses. */ + +/* + * The classes LittleEndian and BigEndian expose static methods for + * reading and writing 16-, 32-, and 64-bit signed and unsigned integers + * in their respective endianness. The addresses read from or written + * to may be misaligned (although misaligned accesses may incur + * architecture-specific performance costs). The naming scheme is: + * + * {Little,Big}Endian::{read,write}{Uint,Int}<bitsize> + * + * For instance, LittleEndian::readInt32 will read a 32-bit signed + * integer from memory in little endian format. Similarly, + * BigEndian::writeUint16 will write a 16-bit unsigned integer to memory + * in big-endian format. + * + * The class NativeEndian exposes methods for conversion of existing + * data to and from the native endianness. These methods are intended + * for cases where data needs to be transferred, serialized, etc. + * swap{To,From}{Little,Big}Endian byteswap a single value if necessary. + * Bulk conversion functions are also provided which optimize the + * no-conversion-needed case: + * + * - copyAndSwap{To,From}{Little,Big}Endian; + * - swap{To,From}{Little,Big}EndianInPlace. + * + * The *From* variants are intended to be used for reading data and the + * *To* variants for writing data. + * + * Methods on NativeEndian work with integer data of any type. + * Floating-point data is not supported. + * + * For clarity in networking code, "Network" may be used as a synonym + * for "Big" in any of the above methods or class names. + * + * As an example, reading a file format header whose fields are stored + * in big-endian format might look like: + * + * class ExampleHeader + * { + * private: + * uint32_t mMagic; + * uint32_t mLength; + * uint32_t mTotalRecords; + * uint64_t mChecksum; + * + * public: + * ExampleHeader(const void* data) + * { + * const uint8_t* ptr = static_cast<const uint8_t*>(data); + * mMagic = BigEndian::readUint32(ptr); ptr += sizeof(uint32_t); + * mLength = BigEndian::readUint32(ptr); ptr += sizeof(uint32_t); + * mTotalRecords = BigEndian::readUint32(ptr); ptr += sizeof(uint32_t); + * mChecksum = BigEndian::readUint64(ptr); + * } + * ... + * }; + */ + +#ifndef mozilla_EndianUtils_h +#define mozilla_EndianUtils_h + +#include "mozilla/Assertions.h" +#include "mozilla/Attributes.h" +#include "mozilla/Compiler.h" +#include "mozilla/DebugOnly.h" + +#include <stdint.h> +#include <string.h> + +#if defined(_MSC_VER) +# include <stdlib.h> +# pragma intrinsic(_byteswap_ushort) +# pragma intrinsic(_byteswap_ulong) +# pragma intrinsic(_byteswap_uint64) +#endif + +/* + * Our supported compilers provide architecture-independent macros for this. + * Yes, there are more than two values for __BYTE_ORDER__. + */ +#if defined(__BYTE_ORDER__) && defined(__ORDER_LITTLE_ENDIAN__) && \ + defined(__ORDER_BIG_ENDIAN__) +# if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__ +# define MOZ_LITTLE_ENDIAN() 1 +# define MOZ_BIG_ENDIAN() 0 +# elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__ +# define MOZ_LITTLE_ENDIAN() 0 +# define MOZ_BIG_ENDIAN() 1 +# else +# error "Can't handle mixed-endian architectures" +# endif +#else +# error "Don't know how to determine endianness" +#endif + +#if defined(__clang__) +# if __has_builtin(__builtin_bswap16) +# define MOZ_HAVE_BUILTIN_BYTESWAP16 __builtin_bswap16 +# endif +#elif defined(__GNUC__) +# define MOZ_HAVE_BUILTIN_BYTESWAP16 __builtin_bswap16 +#elif defined(_MSC_VER) +# define MOZ_HAVE_BUILTIN_BYTESWAP16 _byteswap_ushort +#endif + +namespace mozilla { + +namespace detail { + +/* + * We need wrappers here because free functions with default template + * arguments and/or partial specialization of function templates are not + * supported by all the compilers we use. + */ +template <typename T, size_t Size = sizeof(T)> +struct Swapper; + +template <typename T> +struct Swapper<T, 2> { + static T swap(T aValue) { +#if defined(MOZ_HAVE_BUILTIN_BYTESWAP16) + return MOZ_HAVE_BUILTIN_BYTESWAP16(aValue); +#else + return T(((aValue & 0x00ff) << 8) | ((aValue & 0xff00) >> 8)); +#endif + } +}; + +template <typename T> +struct Swapper<T, 4> { + static T swap(T aValue) { +#if defined(__clang__) || defined(__GNUC__) + return T(__builtin_bswap32(aValue)); +#elif defined(_MSC_VER) + return T(_byteswap_ulong(aValue)); +#else + return T(((aValue & 0x000000ffU) << 24) | ((aValue & 0x0000ff00U) << 8) | + ((aValue & 0x00ff0000U) >> 8) | ((aValue & 0xff000000U) >> 24)); +#endif + } +}; + +template <typename T> +struct Swapper<T, 8> { + static inline T swap(T aValue) { +#if defined(__clang__) || defined(__GNUC__) + return T(__builtin_bswap64(aValue)); +#elif defined(_MSC_VER) + return T(_byteswap_uint64(aValue)); +#else + return T(((aValue & 0x00000000000000ffULL) << 56) | + ((aValue & 0x000000000000ff00ULL) << 40) | + ((aValue & 0x0000000000ff0000ULL) << 24) | + ((aValue & 0x00000000ff000000ULL) << 8) | + ((aValue & 0x000000ff00000000ULL) >> 8) | + ((aValue & 0x0000ff0000000000ULL) >> 24) | + ((aValue & 0x00ff000000000000ULL) >> 40) | + ((aValue & 0xff00000000000000ULL) >> 56)); +#endif + } +}; + +enum Endianness { Little, Big }; + +#if MOZ_BIG_ENDIAN() +# define MOZ_NATIVE_ENDIANNESS detail::Big +#else +# define MOZ_NATIVE_ENDIANNESS detail::Little +#endif + +class EndianUtils { + /** + * Assert that the memory regions [aDest, aDest+aCount) and + * [aSrc, aSrc+aCount] do not overlap. aCount is given in bytes. + */ + static void assertNoOverlap(const void* aDest, const void* aSrc, + size_t aCount) { + DebugOnly<const uint8_t*> byteDestPtr = static_cast<const uint8_t*>(aDest); + DebugOnly<const uint8_t*> byteSrcPtr = static_cast<const uint8_t*>(aSrc); + MOZ_ASSERT( + (byteDestPtr <= byteSrcPtr && byteDestPtr + aCount <= byteSrcPtr) || + (byteSrcPtr <= byteDestPtr && byteSrcPtr + aCount <= byteDestPtr)); + } + + template <typename T> + static void assertAligned(T* aPtr) { + MOZ_ASSERT((uintptr_t(aPtr) % sizeof(T)) == 0, "Unaligned pointer!"); + } + + protected: + /** + * Return |aValue| converted from SourceEndian encoding to DestEndian + * encoding. + */ + template <Endianness SourceEndian, Endianness DestEndian, typename T> + static inline T maybeSwap(T aValue) { + if (SourceEndian == DestEndian) { + return aValue; + } + return Swapper<T>::swap(aValue); + } + + /** + * Convert |aCount| elements at |aPtr| from SourceEndian encoding to + * DestEndian encoding. + */ + template <Endianness SourceEndian, Endianness DestEndian, typename T> + static inline void maybeSwapInPlace(T* aPtr, size_t aCount) { + assertAligned(aPtr); + + if (SourceEndian == DestEndian) { + return; + } + for (size_t i = 0; i < aCount; i++) { + aPtr[i] = Swapper<T>::swap(aPtr[i]); + } + } + + /** + * Write |aCount| elements to the unaligned address |aDest| in DestEndian + * format, using elements found at |aSrc| in SourceEndian format. + */ + template <Endianness SourceEndian, Endianness DestEndian, typename T> + static void copyAndSwapTo(void* aDest, const T* aSrc, size_t aCount) { + assertNoOverlap(aDest, aSrc, aCount * sizeof(T)); + assertAligned(aSrc); + + if (SourceEndian == DestEndian) { + memcpy(aDest, aSrc, aCount * sizeof(T)); + return; + } + + uint8_t* byteDestPtr = static_cast<uint8_t*>(aDest); + for (size_t i = 0; i < aCount; ++i) { + union { + T mVal; + uint8_t mBuffer[sizeof(T)]; + } u; + u.mVal = maybeSwap<SourceEndian, DestEndian>(aSrc[i]); + memcpy(byteDestPtr, u.mBuffer, sizeof(T)); + byteDestPtr += sizeof(T); + } + } + + /** + * Write |aCount| elements to |aDest| in DestEndian format, using elements + * found at the unaligned address |aSrc| in SourceEndian format. + */ + template <Endianness SourceEndian, Endianness DestEndian, typename T> + static void copyAndSwapFrom(T* aDest, const void* aSrc, size_t aCount) { + assertNoOverlap(aDest, aSrc, aCount * sizeof(T)); + assertAligned(aDest); + + if (SourceEndian == DestEndian) { + memcpy(aDest, aSrc, aCount * sizeof(T)); + return; + } + + const uint8_t* byteSrcPtr = static_cast<const uint8_t*>(aSrc); + for (size_t i = 0; i < aCount; ++i) { + union { + T mVal; + uint8_t mBuffer[sizeof(T)]; + } u; + memcpy(u.mBuffer, byteSrcPtr, sizeof(T)); + aDest[i] = maybeSwap<SourceEndian, DestEndian>(u.mVal); + byteSrcPtr += sizeof(T); + } + } +}; + +template <Endianness ThisEndian> +class Endian : private EndianUtils { + protected: + /** Read a uint16_t in ThisEndian endianness from |aPtr| and return it. */ + [[nodiscard]] static uint16_t readUint16(const void* aPtr) { + return read<uint16_t>(aPtr); + } + + /** Read a uint32_t in ThisEndian endianness from |aPtr| and return it. */ + [[nodiscard]] static uint32_t readUint32(const void* aPtr) { + return read<uint32_t>(aPtr); + } + + /** Read a uint64_t in ThisEndian endianness from |aPtr| and return it. */ + [[nodiscard]] static uint64_t readUint64(const void* aPtr) { + return read<uint64_t>(aPtr); + } + + /** Read a uintptr_t in ThisEndian endianness from |aPtr| and return it. */ + [[nodiscard]] static uintptr_t readUintptr(const void* aPtr) { + return read<uintptr_t>(aPtr); + } + + /** Read an int16_t in ThisEndian endianness from |aPtr| and return it. */ + [[nodiscard]] static int16_t readInt16(const void* aPtr) { + return read<int16_t>(aPtr); + } + + /** Read an int32_t in ThisEndian endianness from |aPtr| and return it. */ + [[nodiscard]] static int32_t readInt32(const void* aPtr) { + return read<uint32_t>(aPtr); + } + + /** Read an int64_t in ThisEndian endianness from |aPtr| and return it. */ + [[nodiscard]] static int64_t readInt64(const void* aPtr) { + return read<int64_t>(aPtr); + } + + /** Read an intptr_t in ThisEndian endianness from |aPtr| and return it. */ + [[nodiscard]] static intptr_t readIntptr(const void* aPtr) { + return read<intptr_t>(aPtr); + } + + /** Write |aValue| to |aPtr| using ThisEndian endianness. */ + static void writeUint16(void* aPtr, uint16_t aValue) { write(aPtr, aValue); } + + /** Write |aValue| to |aPtr| using ThisEndian endianness. */ + static void writeUint32(void* aPtr, uint32_t aValue) { write(aPtr, aValue); } + + /** Write |aValue| to |aPtr| using ThisEndian endianness. */ + static void writeUint64(void* aPtr, uint64_t aValue) { write(aPtr, aValue); } + + /** Write |aValue| to |aPtr| using ThisEndian endianness. */ + static void writeUintptr(void* aPtr, uintptr_t aValue) { + write(aPtr, aValue); + } + + /** Write |aValue| to |aPtr| using ThisEndian endianness. */ + static void writeInt16(void* aPtr, int16_t aValue) { write(aPtr, aValue); } + + /** Write |aValue| to |aPtr| using ThisEndian endianness. */ + static void writeInt32(void* aPtr, int32_t aValue) { write(aPtr, aValue); } + + /** Write |aValue| to |aPtr| using ThisEndian endianness. */ + static void writeInt64(void* aPtr, int64_t aValue) { write(aPtr, aValue); } + + /** Write |aValue| to |aPtr| using ThisEndian endianness. */ + static void writeIntptr(void* aPtr, intptr_t aValue) { write(aPtr, aValue); } + + /* + * Converts a value of type T to little-endian format. + * + * This function is intended for cases where you have data in your + * native-endian format and you need it to appear in little-endian + * format for transmission. + */ + template <typename T> + [[nodiscard]] static T swapToLittleEndian(T aValue) { + return maybeSwap<ThisEndian, Little>(aValue); + } + + /* + * Copies |aCount| values of type T starting at |aSrc| to |aDest|, converting + * them to little-endian format if ThisEndian is Big. |aSrc| as a typed + * pointer must be aligned; |aDest| need not be. + * + * As with memcpy, |aDest| and |aSrc| must not overlap. + */ + template <typename T> + static void copyAndSwapToLittleEndian(void* aDest, const T* aSrc, + size_t aCount) { + copyAndSwapTo<ThisEndian, Little>(aDest, aSrc, aCount); + } + + /* + * Likewise, but converts values in place. + */ + template <typename T> + static void swapToLittleEndianInPlace(T* aPtr, size_t aCount) { + maybeSwapInPlace<ThisEndian, Little>(aPtr, aCount); + } + + /* + * Converts a value of type T to big-endian format. + */ + template <typename T> + [[nodiscard]] static T swapToBigEndian(T aValue) { + return maybeSwap<ThisEndian, Big>(aValue); + } + + /* + * Copies |aCount| values of type T starting at |aSrc| to |aDest|, converting + * them to big-endian format if ThisEndian is Little. |aSrc| as a typed + * pointer must be aligned; |aDest| need not be. + * + * As with memcpy, |aDest| and |aSrc| must not overlap. + */ + template <typename T> + static void copyAndSwapToBigEndian(void* aDest, const T* aSrc, + size_t aCount) { + copyAndSwapTo<ThisEndian, Big>(aDest, aSrc, aCount); + } + + /* + * Likewise, but converts values in place. + */ + template <typename T> + static void swapToBigEndianInPlace(T* aPtr, size_t aCount) { + maybeSwapInPlace<ThisEndian, Big>(aPtr, aCount); + } + + /* + * Synonyms for the big-endian functions, for better readability + * in network code. + */ + + template <typename T> + [[nodiscard]] static T swapToNetworkOrder(T aValue) { + return swapToBigEndian(aValue); + } + + template <typename T> + static void copyAndSwapToNetworkOrder(void* aDest, const T* aSrc, + size_t aCount) { + copyAndSwapToBigEndian(aDest, aSrc, aCount); + } + + template <typename T> + static void swapToNetworkOrderInPlace(T* aPtr, size_t aCount) { + swapToBigEndianInPlace(aPtr, aCount); + } + + /* + * Converts a value of type T from little-endian format. + */ + template <typename T> + [[nodiscard]] static T swapFromLittleEndian(T aValue) { + return maybeSwap<Little, ThisEndian>(aValue); + } + + /* + * Copies |aCount| values of type T starting at |aSrc| to |aDest|, converting + * them to little-endian format if ThisEndian is Big. |aDest| as a typed + * pointer must be aligned; |aSrc| need not be. + * + * As with memcpy, |aDest| and |aSrc| must not overlap. + */ + template <typename T> + static void copyAndSwapFromLittleEndian(T* aDest, const void* aSrc, + size_t aCount) { + copyAndSwapFrom<Little, ThisEndian>(aDest, aSrc, aCount); + } + + /* + * Likewise, but converts values in place. + */ + template <typename T> + static void swapFromLittleEndianInPlace(T* aPtr, size_t aCount) { + maybeSwapInPlace<Little, ThisEndian>(aPtr, aCount); + } + + /* + * Converts a value of type T from big-endian format. + */ + template <typename T> + [[nodiscard]] static T swapFromBigEndian(T aValue) { + return maybeSwap<Big, ThisEndian>(aValue); + } + + /* + * Copies |aCount| values of type T starting at |aSrc| to |aDest|, converting + * them to big-endian format if ThisEndian is Little. |aDest| as a typed + * pointer must be aligned; |aSrc| need not be. + * + * As with memcpy, |aDest| and |aSrc| must not overlap. + */ + template <typename T> + static void copyAndSwapFromBigEndian(T* aDest, const void* aSrc, + size_t aCount) { + copyAndSwapFrom<Big, ThisEndian>(aDest, aSrc, aCount); + } + + /* + * Likewise, but converts values in place. + */ + template <typename T> + static void swapFromBigEndianInPlace(T* aPtr, size_t aCount) { + maybeSwapInPlace<Big, ThisEndian>(aPtr, aCount); + } + + /* + * Synonyms for the big-endian functions, for better readability + * in network code. + */ + template <typename T> + [[nodiscard]] static T swapFromNetworkOrder(T aValue) { + return swapFromBigEndian(aValue); + } + + template <typename T> + static void copyAndSwapFromNetworkOrder(T* aDest, const void* aSrc, + size_t aCount) { + copyAndSwapFromBigEndian(aDest, aSrc, aCount); + } + + template <typename T> + static void swapFromNetworkOrderInPlace(T* aPtr, size_t aCount) { + swapFromBigEndianInPlace(aPtr, aCount); + } + + private: + /** + * Read a value of type T, encoded in endianness ThisEndian from |aPtr|. + * Return that value encoded in native endianness. + */ + template <typename T> + static T read(const void* aPtr) { + union { + T mVal; + uint8_t mBuffer[sizeof(T)]; + } u; + memcpy(u.mBuffer, aPtr, sizeof(T)); + return maybeSwap<ThisEndian, MOZ_NATIVE_ENDIANNESS>(u.mVal); + } + + /** + * Write a value of type T, in native endianness, to |aPtr|, in ThisEndian + * endianness. + */ + template <typename T> + static void write(void* aPtr, T aValue) { + T tmp = maybeSwap<MOZ_NATIVE_ENDIANNESS, ThisEndian>(aValue); + memcpy(aPtr, &tmp, sizeof(T)); + } + + Endian() = delete; + Endian(const Endian& aTther) = delete; + void operator=(const Endian& aOther) = delete; +}; + +template <Endianness ThisEndian> +class EndianReadWrite : public Endian<ThisEndian> { + private: + typedef Endian<ThisEndian> super; + + public: + using super::readInt16; + using super::readInt32; + using super::readInt64; + using super::readIntptr; + using super::readUint16; + using super::readUint32; + using super::readUint64; + using super::readUintptr; + using super::writeInt16; + using super::writeInt32; + using super::writeInt64; + using super::writeIntptr; + using super::writeUint16; + using super::writeUint32; + using super::writeUint64; + using super::writeUintptr; +}; + +} /* namespace detail */ + +class LittleEndian final : public detail::EndianReadWrite<detail::Little> {}; + +class BigEndian final : public detail::EndianReadWrite<detail::Big> {}; + +typedef BigEndian NetworkEndian; + +class NativeEndian final : public detail::Endian<MOZ_NATIVE_ENDIANNESS> { + private: + typedef detail::Endian<MOZ_NATIVE_ENDIANNESS> super; + + public: + /* + * These functions are intended for cases where you have data in your + * native-endian format and you need the data to appear in the appropriate + * endianness for transmission, serialization, etc. + */ + using super::copyAndSwapToBigEndian; + using super::copyAndSwapToLittleEndian; + using super::copyAndSwapToNetworkOrder; + using super::swapToBigEndian; + using super::swapToBigEndianInPlace; + using super::swapToLittleEndian; + using super::swapToLittleEndianInPlace; + using super::swapToNetworkOrder; + using super::swapToNetworkOrderInPlace; + + /* + * These functions are intended for cases where you have data in the + * given endianness (e.g. reading from disk or a file-format) and you + * need the data to appear in native-endian format for processing. + */ + using super::copyAndSwapFromBigEndian; + using super::copyAndSwapFromLittleEndian; + using super::copyAndSwapFromNetworkOrder; + using super::swapFromBigEndian; + using super::swapFromBigEndianInPlace; + using super::swapFromLittleEndian; + using super::swapFromLittleEndianInPlace; + using super::swapFromNetworkOrder; + using super::swapFromNetworkOrderInPlace; +}; + +#undef MOZ_NATIVE_ENDIANNESS + +} /* namespace mozilla */ + +#endif /* mozilla_EndianUtils_h */ |