/* -*- 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 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 "mozilla/TypeTraits.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 #if defined(_WIN64) # if defined(_M_X64) || defined(_M_AMD64) || defined(_AMD64_) # define MOZ_LITTLE_ENDIAN 1 # else # error "CPU type is unknown" # endif #elif defined(_WIN32) # if defined(_M_IX86) # define MOZ_LITTLE_ENDIAN 1 # elif defined(_M_ARM) # define MOZ_LITTLE_ENDIAN 1 # else # error "CPU type is unknown" # endif #elif defined(__APPLE__) || defined(__powerpc__) || defined(__ppc__) # if __LITTLE_ENDIAN__ # define MOZ_LITTLE_ENDIAN 1 # elif __BIG_ENDIAN__ # define MOZ_BIG_ENDIAN 1 # endif #elif defined(__GNUC__) && \ defined(__BYTE_ORDER__) && \ defined(__ORDER_LITTLE_ENDIAN__) && \ defined(__ORDER_BIG_ENDIAN__) /* * Some versions of GCC provide architecture-independent macros for * this. Yes, there are more than two values for __BYTE_ORDER__. */ # if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__ # define MOZ_LITTLE_ENDIAN 1 # elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__ # define MOZ_BIG_ENDIAN 1 # else # error "Can't handle mixed-endian architectures" # endif /* * We can't include useful headers like <endian.h> or <sys/isa_defs.h> * here because they're not present on all platforms. Instead we have * this big conditional that ideally will catch all the interesting * cases. */ #elif defined(__sparc) || defined(__sparc__) || \ defined(_POWER) || defined(__hppa) || \ defined(_MIPSEB) || defined(__ARMEB__) || \ defined(__s390__) || defined(__AARCH64EB__) || \ (defined(__sh__) && defined(__LITTLE_ENDIAN__)) || \ (defined(__ia64) && defined(__BIG_ENDIAN__)) # define MOZ_BIG_ENDIAN 1 #elif defined(__i386) || defined(__i386__) || \ defined(__x86_64) || defined(__x86_64__) || \ defined(_MIPSEL) || defined(__ARMEL__) || \ defined(__alpha__) || defined(__AARCH64EL__) || \ (defined(__sh__) && defined(__BIG_ENDIAN__)) || \ (defined(__ia64) && !defined(__BIG_ENDIAN__)) # define MOZ_LITTLE_ENDIAN 1 #endif #if MOZ_BIG_ENDIAN # define MOZ_LITTLE_ENDIAN 0 #elif MOZ_LITTLE_ENDIAN # define MOZ_BIG_ENDIAN 0 #else # error "Cannot 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. */ static MOZ_MUST_USE uint16_t readUint16(const void* aPtr) { return read<uint16_t>(aPtr); } /** Read a uint32_t in ThisEndian endianness from |aPtr| and return it. */ static MOZ_MUST_USE uint32_t readUint32(const void* aPtr) { return read<uint32_t>(aPtr); } /** Read a uint64_t in ThisEndian endianness from |aPtr| and return it. */ static MOZ_MUST_USE uint64_t readUint64(const void* aPtr) { return read<uint64_t>(aPtr); } /** Read an int16_t in ThisEndian endianness from |aPtr| and return it. */ static MOZ_MUST_USE int16_t readInt16(const void* aPtr) { return read<int16_t>(aPtr); } /** Read an int32_t in ThisEndian endianness from |aPtr| and return it. */ static MOZ_MUST_USE int32_t readInt32(const void* aPtr) { return read<uint32_t>(aPtr); } /** Read an int64_t in ThisEndian endianness from |aPtr| and return it. */ static MOZ_MUST_USE int64_t readInt64(const void* aPtr) { return read<int64_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 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); } /* * 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> MOZ_MUST_USE 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. * 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> MOZ_MUST_USE 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. * 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> MOZ_MUST_USE 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> MOZ_MUST_USE 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. * 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> MOZ_MUST_USE 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. * 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> MOZ_MUST_USE 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::readUint16; using super::readUint32; using super::readUint64; using super::readInt16; using super::readInt32; using super::readInt64; using super::writeUint16; using super::writeUint32; using super::writeUint64; using super::writeInt16; using super::writeInt32; using super::writeInt64; }; } /* 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::swapToLittleEndian; using super::copyAndSwapToLittleEndian; using super::swapToLittleEndianInPlace; using super::swapToBigEndian; using super::copyAndSwapToBigEndian; using super::swapToBigEndianInPlace; using super::swapToNetworkOrder; using super::copyAndSwapToNetworkOrder; 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::swapFromLittleEndian; using super::copyAndSwapFromLittleEndian; using super::swapFromLittleEndianInPlace; using super::swapFromBigEndian; using super::copyAndSwapFromBigEndian; using super::swapFromBigEndianInPlace; using super::swapFromNetworkOrder; using super::copyAndSwapFromNetworkOrder; using super::swapFromNetworkOrderInPlace; }; #undef MOZ_NATIVE_ENDIANNESS } /* namespace mozilla */ #endif /* mozilla_EndianUtils_h */