michael@0: /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
michael@0: /* vim: set ts=8 sts=2 et sw=2 tw=80: */
michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: /* Functions for reading and writing integers in various endiannesses. */
michael@0: 
michael@0: /*
michael@0:  * The classes LittleEndian and BigEndian expose static methods for
michael@0:  * reading and writing 16-, 32-, and 64-bit signed and unsigned integers
michael@0:  * in their respective endianness.  The naming scheme is:
michael@0:  *
michael@0:  * {Little,Big}Endian::{read,write}{Uint,Int}<bitsize>
michael@0:  *
michael@0:  * For instance, LittleEndian::readInt32 will read a 32-bit signed
michael@0:  * integer from memory in little endian format.  Similarly,
michael@0:  * BigEndian::writeUint16 will write a 16-bit unsigned integer to memory
michael@0:  * in big-endian format.
michael@0:  *
michael@0:  * The class NativeEndian exposes methods for conversion of existing
michael@0:  * data to and from the native endianness.  These methods are intended
michael@0:  * for cases where data needs to be transferred, serialized, etc.
michael@0:  * swap{To,From}{Little,Big}Endian byteswap a single value if necessary.
michael@0:  * Bulk conversion functions are also provided which optimize the
michael@0:  * no-conversion-needed case:
michael@0:  *
michael@0:  * - copyAndSwap{To,From}{Little,Big}Endian;
michael@0:  * - swap{To,From}{Little,Big}EndianInPlace.
michael@0:  *
michael@0:  * The *From* variants are intended to be used for reading data and the
michael@0:  * *To* variants for writing data.
michael@0:  *
michael@0:  * Methods on NativeEndian work with integer data of any type.
michael@0:  * Floating-point data is not supported.
michael@0:  *
michael@0:  * For clarity in networking code, "Network" may be used as a synonym
michael@0:  * for "Big" in any of the above methods or class names.
michael@0:  *
michael@0:  * As an example, reading a file format header whose fields are stored
michael@0:  * in big-endian format might look like:
michael@0:  *
michael@0:  * class ExampleHeader
michael@0:  * {
michael@0:  *   private:
michael@0:  *     uint32_t magic;
michael@0:  *     uint32_t length;
michael@0:  *     uint32_t totalRecords;
michael@0:  *     uint64_t checksum;
michael@0:  *
michael@0:  *   public:
michael@0:  *     ExampleHeader(const void* data) {
michael@0:  *       const uint8_t* ptr = static_cast<const uint8_t*>(data);
michael@0:  *       magic = BigEndian::readUint32(ptr); ptr += sizeof(uint32_t);
michael@0:  *       length = BigEndian::readUint32(ptr); ptr += sizeof(uint32_t);
michael@0:  *       totalRecords = BigEndian::readUint32(ptr); ptr += sizeof(uint32_t);
michael@0:  *       checksum = BigEndian::readUint64(ptr);
michael@0:  *     }
michael@0:  *     ...
michael@0:  * };
michael@0:  */
michael@0: 
michael@0: #ifndef mozilla_Endian_h
michael@0: #define mozilla_Endian_h
michael@0: 
michael@0: #include "mozilla/Assertions.h"
michael@0: #include "mozilla/Attributes.h"
michael@0: #include "mozilla/Compiler.h"
michael@0: #include "mozilla/DebugOnly.h"
michael@0: #include "mozilla/TypeTraits.h"
michael@0: 
michael@0: #include <stdint.h>
michael@0: #include <string.h>
michael@0: 
michael@0: #if defined(_MSC_VER) && _MSC_VER >= 1300
michael@0: #  include <stdlib.h>
michael@0: #  pragma intrinsic(_byteswap_ushort)
michael@0: #  pragma intrinsic(_byteswap_ulong)
michael@0: #  pragma intrinsic(_byteswap_uint64)
michael@0: #endif
michael@0: 
michael@0: #if defined(_WIN64)
michael@0: #  if defined(_M_X64) || defined(_M_AMD64) || defined(_AMD64_)
michael@0: #    define MOZ_LITTLE_ENDIAN 1
michael@0: #  else
michael@0: #    error "CPU type is unknown"
michael@0: #  endif
michael@0: #elif defined(_WIN32)
michael@0: #  if defined(_M_IX86)
michael@0: #    define MOZ_LITTLE_ENDIAN 1
michael@0: #  else
michael@0: #    error "CPU type is unknown"
michael@0: #  endif
michael@0: #elif defined(__APPLE__) || defined(__powerpc__) || defined(__ppc__)
michael@0: #  if __LITTLE_ENDIAN__
michael@0: #    define MOZ_LITTLE_ENDIAN 1
michael@0: #  elif __BIG_ENDIAN__
michael@0: #    define MOZ_BIG_ENDIAN 1
michael@0: #  endif
michael@0: #elif defined(__GNUC__) && \
michael@0:       defined(__BYTE_ORDER__) && \
michael@0:       defined(__ORDER_LITTLE_ENDIAN__) && \
michael@0:       defined(__ORDER_BIG_ENDIAN__)
michael@0:    /*
michael@0:     * Some versions of GCC provide architecture-independent macros for
michael@0:     * this.  Yes, there are more than two values for __BYTE_ORDER__.
michael@0:     */
michael@0: #  if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
michael@0: #    define MOZ_LITTLE_ENDIAN 1
michael@0: #  elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
michael@0: #    define MOZ_BIG_ENDIAN 1
michael@0: #  else
michael@0: #    error "Can't handle mixed-endian architectures"
michael@0: #  endif
michael@0: /*
michael@0:  * We can't include useful headers like <endian.h> or <sys/isa_defs.h>
michael@0:  * here because they're not present on all platforms.  Instead we have
michael@0:  * this big conditional that ideally will catch all the interesting
michael@0:  * cases.
michael@0:  */
michael@0: #elif defined(__sparc) || defined(__sparc__) || \
michael@0:       defined(_POWER) || defined(__hppa) || \
michael@0:       defined(_MIPSEB) || defined(__ARMEB__) || \
michael@0:       defined(__s390__) || defined(__AARCH64EB__) || \
michael@0:       (defined(__sh__) && defined(__LITTLE_ENDIAN__)) || \
michael@0:       (defined(__ia64) && defined(__BIG_ENDIAN__))
michael@0: #  define MOZ_BIG_ENDIAN 1
michael@0: #elif defined(__i386) || defined(__i386__) || \
michael@0:       defined(__x86_64) || defined(__x86_64__) || \
michael@0:       defined(_MIPSEL) || defined(__ARMEL__) || \
michael@0:       defined(__alpha__) || defined(__AARCH64EL__) || \
michael@0:       (defined(__sh__) && defined(__BIG_ENDIAN__)) || \
michael@0:       (defined(__ia64) && !defined(__BIG_ENDIAN__))
michael@0: #  define MOZ_LITTLE_ENDIAN 1
michael@0: #endif
michael@0: 
michael@0: #if MOZ_BIG_ENDIAN
michael@0: #  define MOZ_LITTLE_ENDIAN 0
michael@0: #elif MOZ_LITTLE_ENDIAN
michael@0: #  define MOZ_BIG_ENDIAN 0
michael@0: #else
michael@0: #  error "Cannot determine endianness"
michael@0: #endif
michael@0: 
michael@0: #if defined(__clang__)
michael@0: #  if __has_builtin(__builtin_bswap16)
michael@0: #    define MOZ_HAVE_BUILTIN_BYTESWAP16 __builtin_bswap16
michael@0: #  endif
michael@0: #elif defined(__GNUC__)
michael@0: #  if MOZ_GCC_VERSION_AT_LEAST(4, 8, 0)
michael@0: #    define MOZ_HAVE_BUILTIN_BYTESWAP16 __builtin_bswap16
michael@0: #  endif
michael@0: #elif defined(_MSC_VER)
michael@0: #    define MOZ_HAVE_BUILTIN_BYTESWAP16 _byteswap_ushort
michael@0: #endif
michael@0: 
michael@0: namespace mozilla {
michael@0: 
michael@0: namespace detail {
michael@0: 
michael@0: /*
michael@0:  * We need wrappers here because free functions with default template
michael@0:  * arguments and/or partial specialization of function templates are not
michael@0:  * supported by all the compilers we use.
michael@0:  */
michael@0: template<typename T, size_t Size = sizeof(T)>
michael@0: struct Swapper;
michael@0: 
michael@0: template<typename T>
michael@0: struct Swapper<T, 2>
michael@0: {
michael@0:   static T swap(T value)
michael@0:   {
michael@0: #if defined(MOZ_HAVE_BUILTIN_BYTESWAP16)
michael@0:     return MOZ_HAVE_BUILTIN_BYTESWAP16(value);
michael@0: #else
michael@0:     return T(((value & 0x00ff) << 8) | ((value & 0xff00) >> 8));
michael@0: #endif
michael@0:   }
michael@0: };
michael@0: 
michael@0: template<typename T>
michael@0: struct Swapper<T, 4>
michael@0: {
michael@0:   static T swap(T value)
michael@0:   {
michael@0: #if defined(__clang__) || defined(__GNUC__)
michael@0:     return T(__builtin_bswap32(value));
michael@0: #elif defined(_MSC_VER)
michael@0:     return T(_byteswap_ulong(value));
michael@0: #else
michael@0:     return T(((value & 0x000000ffU) << 24) |
michael@0:              ((value & 0x0000ff00U) << 8) |
michael@0:              ((value & 0x00ff0000U) >> 8) |
michael@0:              ((value & 0xff000000U) >> 24));
michael@0: #endif
michael@0:   }
michael@0: };
michael@0: 
michael@0: template<typename T>
michael@0: struct Swapper<T, 8>
michael@0: {
michael@0:   static inline T swap(T value)
michael@0:   {
michael@0: #if defined(__clang__) || defined(__GNUC__)
michael@0:     return T(__builtin_bswap64(value));
michael@0: #elif defined(_MSC_VER)
michael@0:     return T(_byteswap_uint64(value));
michael@0: #else
michael@0:     return T(((value & 0x00000000000000ffULL) << 56) |
michael@0:              ((value & 0x000000000000ff00ULL) << 40) |
michael@0:              ((value & 0x0000000000ff0000ULL) << 24) |
michael@0:              ((value & 0x00000000ff000000ULL) << 8) |
michael@0:              ((value & 0x000000ff00000000ULL) >> 8) |
michael@0:              ((value & 0x0000ff0000000000ULL) >> 24) |
michael@0:              ((value & 0x00ff000000000000ULL) >> 40) |
michael@0:              ((value & 0xff00000000000000ULL) >> 56));
michael@0: #endif
michael@0:   }
michael@0: };
michael@0: 
michael@0: enum Endianness { Little, Big };
michael@0: 
michael@0: #if MOZ_BIG_ENDIAN
michael@0: #  define MOZ_NATIVE_ENDIANNESS detail::Big
michael@0: #else
michael@0: #  define MOZ_NATIVE_ENDIANNESS detail::Little
michael@0: #endif
michael@0: 
michael@0: class EndianUtils
michael@0: {
michael@0:     /**
michael@0:      * Assert that the memory regions [dest, dest+count) and [src, src+count]
michael@0:      * do not overlap.  count is given in bytes.
michael@0:      */
michael@0:     static void assertNoOverlap(const void* dest, const void* src, size_t count)
michael@0:     {
michael@0:       DebugOnly<const uint8_t*> byteDestPtr = static_cast<const uint8_t*>(dest);
michael@0:       DebugOnly<const uint8_t*> byteSrcPtr = static_cast<const uint8_t*>(src);
michael@0:       MOZ_ASSERT((byteDestPtr <= byteSrcPtr &&
michael@0:                   byteDestPtr + count <= byteSrcPtr) ||
michael@0:                  (byteSrcPtr <= byteDestPtr &&
michael@0:                   byteSrcPtr + count <= byteDestPtr));
michael@0:     }
michael@0: 
michael@0:     template<typename T>
michael@0:     static void assertAligned(T* ptr)
michael@0:     {
michael@0:       MOZ_ASSERT((uintptr_t(ptr) % sizeof(T)) == 0, "Unaligned pointer!");
michael@0:     }
michael@0: 
michael@0:   protected:
michael@0:     /**
michael@0:      * Return |value| converted from SourceEndian encoding to DestEndian
michael@0:      * encoding.
michael@0:      */
michael@0:     template<Endianness SourceEndian, Endianness DestEndian, typename T>
michael@0:     static inline T maybeSwap(T value)
michael@0:     {
michael@0:       if (SourceEndian == DestEndian)
michael@0:         return value;
michael@0: 
michael@0:       return Swapper<T>::swap(value);
michael@0:     }
michael@0: 
michael@0:     /**
michael@0:      * Convert |count| elements at |ptr| from SourceEndian encoding to
michael@0:      * DestEndian encoding.
michael@0:      */
michael@0:     template<Endianness SourceEndian, Endianness DestEndian, typename T>
michael@0:     static inline void maybeSwapInPlace(T* ptr, size_t count)
michael@0:     {
michael@0:       assertAligned(ptr);
michael@0: 
michael@0:       if (SourceEndian == DestEndian)
michael@0:         return;
michael@0: 
michael@0:       for (size_t i = 0; i < count; i++)
michael@0:         ptr[i] = Swapper<T>::swap(ptr[i]);
michael@0:     }
michael@0: 
michael@0:     /**
michael@0:      * Write |count| elements to the unaligned address |dest| in DestEndian
michael@0:      * format, using elements found at |src| in SourceEndian format.
michael@0:      */
michael@0:     template<Endianness SourceEndian, Endianness DestEndian, typename T>
michael@0:     static void copyAndSwapTo(void* dest, const T* src, size_t count)
michael@0:     {
michael@0:       assertNoOverlap(dest, src, count * sizeof(T));
michael@0:       assertAligned(src);
michael@0: 
michael@0:       if (SourceEndian == DestEndian) {
michael@0:         memcpy(dest, src, count * sizeof(T));
michael@0:         return;
michael@0:       }
michael@0: 
michael@0:       uint8_t* byteDestPtr = static_cast<uint8_t*>(dest);
michael@0:       for (size_t i = 0; i < count; ++i) {
michael@0:         union {
michael@0:           T val;
michael@0:           uint8_t buffer[sizeof(T)];
michael@0:         } u;
michael@0:         u.val = maybeSwap<SourceEndian, DestEndian>(src[i]);
michael@0:         memcpy(byteDestPtr, u.buffer, sizeof(T));
michael@0:         byteDestPtr += sizeof(T);
michael@0:       }
michael@0:     }
michael@0: 
michael@0:     /**
michael@0:      * Write |count| elements to |dest| in DestEndian format, using elements
michael@0:      * found at the unaligned address |src| in SourceEndian format.
michael@0:      */
michael@0:     template<Endianness SourceEndian, Endianness DestEndian, typename T>
michael@0:     static void copyAndSwapFrom(T* dest, const void* src, size_t count)
michael@0:     {
michael@0:       assertNoOverlap(dest, src, count * sizeof(T));
michael@0:       assertAligned(dest);
michael@0: 
michael@0:       if (SourceEndian == DestEndian) {
michael@0:         memcpy(dest, src, count * sizeof(T));
michael@0:         return;
michael@0:       }
michael@0: 
michael@0:       const uint8_t* byteSrcPtr = static_cast<const uint8_t*>(src);
michael@0:       for (size_t i = 0; i < count; ++i) {
michael@0:         union {
michael@0:           T val;
michael@0:           uint8_t buffer[sizeof(T)];
michael@0:         } u;
michael@0:         memcpy(u.buffer, byteSrcPtr, sizeof(T));
michael@0:         dest[i] = maybeSwap<SourceEndian, DestEndian>(u.val);
michael@0:         byteSrcPtr += sizeof(T);
michael@0:       }
michael@0:     }
michael@0: };
michael@0: 
michael@0: template<Endianness ThisEndian>
michael@0: class Endian : private EndianUtils
michael@0: {
michael@0:   protected:
michael@0:     /** Read a uint16_t in ThisEndian endianness from |p| and return it. */
michael@0:     static MOZ_WARN_UNUSED_RESULT uint16_t readUint16(const void* p) {
michael@0:       return read<uint16_t>(p);
michael@0:     }
michael@0: 
michael@0:     /** Read a uint32_t in ThisEndian endianness from |p| and return it. */
michael@0:     static MOZ_WARN_UNUSED_RESULT uint32_t readUint32(const void* p) {
michael@0:       return read<uint32_t>(p);
michael@0:     }
michael@0: 
michael@0:     /** Read a uint64_t in ThisEndian endianness from |p| and return it. */
michael@0:     static MOZ_WARN_UNUSED_RESULT uint64_t readUint64(const void* p) {
michael@0:       return read<uint64_t>(p);
michael@0:     }
michael@0: 
michael@0:     /** Read an int16_t in ThisEndian endianness from |p| and return it. */
michael@0:     static MOZ_WARN_UNUSED_RESULT int16_t readInt16(const void* p) {
michael@0:       return read<int16_t>(p);
michael@0:     }
michael@0: 
michael@0:     /** Read an int32_t in ThisEndian endianness from |p| and return it. */
michael@0:     static MOZ_WARN_UNUSED_RESULT int32_t readInt32(const void* p) {
michael@0:       return read<uint32_t>(p);
michael@0:     }
michael@0: 
michael@0:     /** Read an int64_t in ThisEndian endianness from |p| and return it. */
michael@0:     static MOZ_WARN_UNUSED_RESULT int64_t readInt64(const void* p) {
michael@0:       return read<int64_t>(p);
michael@0:     }
michael@0: 
michael@0:     /** Write |val| to |p| using ThisEndian endianness. */
michael@0:     static void writeUint16(void* p, uint16_t val) {
michael@0:       write(p, val);
michael@0:     }
michael@0:     /** Write |val| to |p| using ThisEndian endianness. */
michael@0:     static void writeUint32(void* p, uint32_t val) {
michael@0:       write(p, val);
michael@0:     }
michael@0:     /** Write |val| to |p| using ThisEndian endianness. */
michael@0:     static void writeUint64(void* p, uint64_t val) {
michael@0:       write(p, val);
michael@0:     }
michael@0: 
michael@0:     /** Write |val| to |p| using ThisEndian endianness. */
michael@0:     static void writeInt16(void* p, int16_t val) {
michael@0:       write(p, val);
michael@0:     }
michael@0:     /** Write |val| to |p| using ThisEndian endianness. */
michael@0:     static void writeInt32(void* p, int32_t val) {
michael@0:       write(p, val);
michael@0:     }
michael@0:     /** Write |val| to |p| using ThisEndian endianness. */
michael@0:     static void writeInt64(void* p, int64_t val) {
michael@0:       write(p, val);
michael@0:     }
michael@0: 
michael@0:     /*
michael@0:      * Converts a value of type T to little-endian format.
michael@0:      *
michael@0:      * This function is intended for cases where you have data in your
michael@0:      * native-endian format and you need it to appear in little-endian
michael@0:      * format for transmission.
michael@0:      */
michael@0:     template<typename T>
michael@0:     MOZ_WARN_UNUSED_RESULT static T swapToLittleEndian(T value) {
michael@0:       return maybeSwap<ThisEndian, Little>(value);
michael@0:     }
michael@0:     /*
michael@0:      * Copies count values of type T starting at src to dest, converting
michael@0:      * them to little-endian format if ThisEndian is Big.
michael@0:      * As with memcpy, dest and src must not overlap.
michael@0:      */
michael@0:     template<typename T>
michael@0:     static void copyAndSwapToLittleEndian(void* dest, const T* src,
michael@0:                                           size_t count) {
michael@0:       copyAndSwapTo<ThisEndian, Little>(dest, src, count);
michael@0:     }
michael@0:     /*
michael@0:      * Likewise, but converts values in place.
michael@0:      */
michael@0:     template<typename T>
michael@0:     static void swapToLittleEndianInPlace(T* p, size_t count) {
michael@0:       maybeSwapInPlace<ThisEndian, Little>(p, count);
michael@0:     }
michael@0: 
michael@0:     /*
michael@0:      * Converts a value of type T to big-endian format.
michael@0:      */
michael@0:     template<typename T>
michael@0:     MOZ_WARN_UNUSED_RESULT static T swapToBigEndian(T value) {
michael@0:       return maybeSwap<ThisEndian, Big>(value);
michael@0:     }
michael@0:     /*
michael@0:      * Copies count values of type T starting at src to dest, converting
michael@0:      * them to big-endian format if ThisEndian is Little.
michael@0:      * As with memcpy, dest and src must not overlap.
michael@0:      */
michael@0:     template<typename T>
michael@0:     static void copyAndSwapToBigEndian(void* dest, const T* src, size_t count) {
michael@0:       copyAndSwapTo<ThisEndian, Big>(dest, src, count);
michael@0:     }
michael@0:     /*
michael@0:      * Likewise, but converts values in place.
michael@0:      */
michael@0:     template<typename T>
michael@0:     static void swapToBigEndianInPlace(T* p, size_t count) {
michael@0:       maybeSwapInPlace<ThisEndian, Big>(p, count);
michael@0:     }
michael@0: 
michael@0:     /*
michael@0:      * Synonyms for the big-endian functions, for better readability
michael@0:      * in network code.
michael@0:      */
michael@0:     template<typename T>
michael@0:     MOZ_WARN_UNUSED_RESULT static T swapToNetworkOrder(T value) {
michael@0:       return swapToBigEndian(value);
michael@0:     }
michael@0:     template<typename T>
michael@0:     static void
michael@0:     copyAndSwapToNetworkOrder(void* dest, const T* src, size_t count) {
michael@0:       copyAndSwapToBigEndian(dest, src, count);
michael@0:     }
michael@0:     template<typename T>
michael@0:     static void
michael@0:     swapToNetworkOrderInPlace(T* p, size_t count) {
michael@0:       swapToBigEndianInPlace(p, count);
michael@0:     }
michael@0: 
michael@0:     /*
michael@0:      * Converts a value of type T from little-endian format.
michael@0:      */
michael@0:     template<typename T>
michael@0:     MOZ_WARN_UNUSED_RESULT static T swapFromLittleEndian(T value) {
michael@0:       return maybeSwap<Little, ThisEndian>(value);
michael@0:     }
michael@0:     /*
michael@0:      * Copies count values of type T starting at src to dest, converting
michael@0:      * them to little-endian format if ThisEndian is Big.
michael@0:      * As with memcpy, dest and src must not overlap.
michael@0:      */
michael@0:     template<typename T>
michael@0:     static void copyAndSwapFromLittleEndian(T* dest, const void* src,
michael@0:                                             size_t count) {
michael@0:       copyAndSwapFrom<Little, ThisEndian>(dest, src, count);
michael@0:     }
michael@0:     /*
michael@0:      * Likewise, but converts values in place.
michael@0:      */
michael@0:     template<typename T>
michael@0:     static void swapFromLittleEndianInPlace(T* p, size_t count) {
michael@0:       maybeSwapInPlace<Little, ThisEndian>(p, count);
michael@0:     }
michael@0: 
michael@0:     /*
michael@0:      * Converts a value of type T from big-endian format.
michael@0:      */
michael@0:     template<typename T>
michael@0:     MOZ_WARN_UNUSED_RESULT static T swapFromBigEndian(T value) {
michael@0:       return maybeSwap<Big, ThisEndian>(value);
michael@0:     }
michael@0:     /*
michael@0:      * Copies count values of type T starting at src to dest, converting
michael@0:      * them to big-endian format if ThisEndian is Little.
michael@0:      * As with memcpy, dest and src must not overlap.
michael@0:      */
michael@0:     template<typename T>
michael@0:     static void copyAndSwapFromBigEndian(T* dest, const void* src,
michael@0:                                          size_t count) {
michael@0:       copyAndSwapFrom<Big, ThisEndian>(dest, src, count);
michael@0:     }
michael@0:     /*
michael@0:      * Likewise, but converts values in place.
michael@0:      */
michael@0:     template<typename T>
michael@0:     static void swapFromBigEndianInPlace(T* p, size_t count) {
michael@0:       maybeSwapInPlace<Big, ThisEndian>(p, count);
michael@0:     }
michael@0: 
michael@0:     /*
michael@0:      * Synonyms for the big-endian functions, for better readability
michael@0:      * in network code.
michael@0:      */
michael@0:     template<typename T>
michael@0:     MOZ_WARN_UNUSED_RESULT static T swapFromNetworkOrder(T value) {
michael@0:       return swapFromBigEndian(value);
michael@0:     }
michael@0:     template<typename T>
michael@0:     static void copyAndSwapFromNetworkOrder(T* dest, const void* src,
michael@0:                                             size_t count) {
michael@0:       copyAndSwapFromBigEndian(dest, src, count);
michael@0:     }
michael@0:     template<typename T>
michael@0:     static void swapFromNetworkOrderInPlace(T* p, size_t count) {
michael@0:       swapFromBigEndianInPlace(p, count);
michael@0:     }
michael@0: 
michael@0:   private:
michael@0:     /**
michael@0:      * Read a value of type T, encoded in endianness ThisEndian from |p|.
michael@0:      * Return that value encoded in native endianness.
michael@0:      */
michael@0:     template<typename T>
michael@0:     static T read(const void* p) {
michael@0:       union {
michael@0:         T val;
michael@0:         uint8_t buffer[sizeof(T)];
michael@0:       } u;
michael@0:       memcpy(u.buffer, p, sizeof(T));
michael@0:       return maybeSwap<ThisEndian, MOZ_NATIVE_ENDIANNESS>(u.val);
michael@0:     }
michael@0: 
michael@0:     /**
michael@0:      * Write a value of type T, in native endianness, to |p|, in ThisEndian
michael@0:      * endianness.
michael@0:      */
michael@0:     template<typename T>
michael@0:     static void write(void* p, T value) {
michael@0:       T tmp = maybeSwap<MOZ_NATIVE_ENDIANNESS, ThisEndian>(value);
michael@0:       memcpy(p, &tmp, sizeof(T));
michael@0:     }
michael@0: 
michael@0:     Endian() MOZ_DELETE;
michael@0:     Endian(const Endian& other) MOZ_DELETE;
michael@0:     void operator=(const Endian& other) MOZ_DELETE;
michael@0: };
michael@0: 
michael@0: template<Endianness ThisEndian>
michael@0: class EndianReadWrite : public Endian<ThisEndian>
michael@0: {
michael@0:   private:
michael@0:     typedef Endian<ThisEndian> super;
michael@0: 
michael@0:   public:
michael@0:     using super::readUint16;
michael@0:     using super::readUint32;
michael@0:     using super::readUint64;
michael@0:     using super::readInt16;
michael@0:     using super::readInt32;
michael@0:     using super::readInt64;
michael@0:     using super::writeUint16;
michael@0:     using super::writeUint32;
michael@0:     using super::writeUint64;
michael@0:     using super::writeInt16;
michael@0:     using super::writeInt32;
michael@0:     using super::writeInt64;
michael@0: };
michael@0: 
michael@0: } /* namespace detail */
michael@0: 
michael@0: class LittleEndian MOZ_FINAL : public detail::EndianReadWrite<detail::Little>
michael@0: {};
michael@0: 
michael@0: class BigEndian MOZ_FINAL : public detail::EndianReadWrite<detail::Big>
michael@0: {};
michael@0: 
michael@0: typedef BigEndian NetworkEndian;
michael@0: 
michael@0: class NativeEndian MOZ_FINAL : public detail::Endian<MOZ_NATIVE_ENDIANNESS>
michael@0: {
michael@0:   private:
michael@0:     typedef detail::Endian<MOZ_NATIVE_ENDIANNESS> super;
michael@0: 
michael@0:   public:
michael@0:     /*
michael@0:      * These functions are intended for cases where you have data in your
michael@0:      * native-endian format and you need the data to appear in the appropriate
michael@0:      * endianness for transmission, serialization, etc.
michael@0:      */
michael@0:     using super::swapToLittleEndian;
michael@0:     using super::copyAndSwapToLittleEndian;
michael@0:     using super::swapToLittleEndianInPlace;
michael@0:     using super::swapToBigEndian;
michael@0:     using super::copyAndSwapToBigEndian;
michael@0:     using super::swapToBigEndianInPlace;
michael@0:     using super::swapToNetworkOrder;
michael@0:     using super::copyAndSwapToNetworkOrder;
michael@0:     using super::swapToNetworkOrderInPlace;
michael@0: 
michael@0:     /*
michael@0:      * These functions are intended for cases where you have data in the
michael@0:      * given endianness (e.g. reading from disk or a file-format) and you
michael@0:      * need the data to appear in native-endian format for processing.
michael@0:      */
michael@0:     using super::swapFromLittleEndian;
michael@0:     using super::copyAndSwapFromLittleEndian;
michael@0:     using super::swapFromLittleEndianInPlace;
michael@0:     using super::swapFromBigEndian;
michael@0:     using super::copyAndSwapFromBigEndian;
michael@0:     using super::swapFromBigEndianInPlace;
michael@0:     using super::swapFromNetworkOrder;
michael@0:     using super::copyAndSwapFromNetworkOrder;
michael@0:     using super::swapFromNetworkOrderInPlace;
michael@0: };
michael@0: 
michael@0: #undef MOZ_NATIVE_ENDIANNESS
michael@0: 
michael@0: } /* namespace mozilla */
michael@0: 
michael@0: #endif /* mozilla_Endian_h */