The Tor Browser / file revision

 /* -*- 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 magic;

  *     uint32_t length;

  *     uint32_t totalRecords;

  *     uint64_t checksum;

  *

  *   public:

  *     ExampleHeader(const void* data) {

  *       const uint8_t* ptr = static_cast<const uint8_t*>(data);

  *       magic = BigEndian::readUint32(ptr); ptr += sizeof(uint32_t);

  *       length = BigEndian::readUint32(ptr); ptr += sizeof(uint32_t);

  *       totalRecords = BigEndian::readUint32(ptr); ptr += sizeof(uint32_t);

  *       checksum = BigEndian::readUint64(ptr);

  *     }

  *     ...

  * };

  */

 #ifndef mozilla_Endian_h

 #define mozilla_Endian_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) && _MSC_VER >= 1300

 #  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

 #  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__)

 #  if MOZ_GCC_VERSION_AT_LEAST(4, 8, 0)

 #    define MOZ_HAVE_BUILTIN_BYTESWAP16 __builtin_bswap16

 #  endif

 #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 value)

   {

 #if defined(MOZ_HAVE_BUILTIN_BYTESWAP16)

     return MOZ_HAVE_BUILTIN_BYTESWAP16(value);

 #else

     return T(((value & 0x00ff) << 8) | ((value & 0xff00) >> 8));

 #endif

   }

 };

 template<typename T>

 struct Swapper<T, 4>

 {

   static T swap(T value)

   {

 #if defined(__clang__) || defined(__GNUC__)

     return T(__builtin_bswap32(value));

 #elif defined(_MSC_VER)

     return T(_byteswap_ulong(value));

 #else

     return T(((value & 0x000000ffU) << 24) |

              ((value & 0x0000ff00U) << 8) |

              ((value & 0x00ff0000U) >> 8) |

              ((value & 0xff000000U) >> 24));

 #endif

   }

 };

 template<typename T>

 struct Swapper<T, 8>

 {

   static inline T swap(T value)

   {

 #if defined(__clang__) || defined(__GNUC__)

     return T(__builtin_bswap64(value));

 #elif defined(_MSC_VER)

     return T(_byteswap_uint64(value));

 #else

     return T(((value & 0x00000000000000ffULL) << 56) |

              ((value & 0x000000000000ff00ULL) << 40) |

              ((value & 0x0000000000ff0000ULL) << 24) |

              ((value & 0x00000000ff000000ULL) << 8) |

              ((value & 0x000000ff00000000ULL) >> 8) |

              ((value & 0x0000ff0000000000ULL) >> 24) |

              ((value & 0x00ff000000000000ULL) >> 40) |

              ((value & 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 [dest, dest+count) and [src, src+count]

      * do not overlap.  count is given in bytes.

      */

     static void assertNoOverlap(const void* dest, const void* src, size_t count)

     {

       DebugOnly<const uint8_t*> byteDestPtr = static_cast<const uint8_t*>(dest);

       DebugOnly<const uint8_t*> byteSrcPtr = static_cast<const uint8_t*>(src);

       MOZ_ASSERT((byteDestPtr <= byteSrcPtr &&

                   byteDestPtr + count <= byteSrcPtr) ||

                  (byteSrcPtr <= byteDestPtr &&

                   byteSrcPtr + count <= byteDestPtr));

     }

     template<typename T>

     static void assertAligned(T* ptr)

     {

       MOZ_ASSERT((uintptr_t(ptr) % sizeof(T)) == 0, "Unaligned pointer!");

     }

   protected:

     /**

      * Return |value| converted from SourceEndian encoding to DestEndian

      * encoding.

      */

     template<Endianness SourceEndian, Endianness DestEndian, typename T>

     static inline T maybeSwap(T value)

     {

       if (SourceEndian == DestEndian)

         return value;

       return Swapper<T>::swap(value);

     }

     /**

      * Convert |count| elements at |ptr| from SourceEndian encoding to

      * DestEndian encoding.

      */

     template<Endianness SourceEndian, Endianness DestEndian, typename T>

     static inline void maybeSwapInPlace(T* ptr, size_t count)

     {

       assertAligned(ptr);

       if (SourceEndian == DestEndian)

         return;

       for (size_t i = 0; i < count; i++)

         ptr[i] = Swapper<T>::swap(ptr[i]);

     }

     /**

      * Write |count| elements to the unaligned address |dest| in DestEndian

      * format, using elements found at |src| in SourceEndian format.

      */

     template<Endianness SourceEndian, Endianness DestEndian, typename T>

     static void copyAndSwapTo(void* dest, const T* src, size_t count)

     {

       assertNoOverlap(dest, src, count * sizeof(T));

       assertAligned(src);

       if (SourceEndian == DestEndian) {

         memcpy(dest, src, count * sizeof(T));

         return;

       }

       uint8_t* byteDestPtr = static_cast<uint8_t*>(dest);

       for (size_t i = 0; i < count; ++i) {

         union {

           T val;

           uint8_t buffer[sizeof(T)];

         } u;

         u.val = maybeSwap<SourceEndian, DestEndian>(src[i]);

         memcpy(byteDestPtr, u.buffer, sizeof(T));

         byteDestPtr += sizeof(T);

       }

     }

     /**

      * Write |count| elements to |dest| in DestEndian format, using elements

      * found at the unaligned address |src| in SourceEndian format.

      */

     template<Endianness SourceEndian, Endianness DestEndian, typename T>

     static void copyAndSwapFrom(T* dest, const void* src, size_t count)

     {

       assertNoOverlap(dest, src, count * sizeof(T));

       assertAligned(dest);

       if (SourceEndian == DestEndian) {

         memcpy(dest, src, count * sizeof(T));

         return;

       }

       const uint8_t* byteSrcPtr = static_cast<const uint8_t*>(src);

       for (size_t i = 0; i < count; ++i) {

         union {

           T val;

           uint8_t buffer[sizeof(T)];

         } u;

         memcpy(u.buffer, byteSrcPtr, sizeof(T));

         dest[i] = maybeSwap<SourceEndian, DestEndian>(u.val);

         byteSrcPtr += sizeof(T);

       }

     }

 };

 template<Endianness ThisEndian>

 class Endian : private EndianUtils

 {

   protected:

     /** Read a uint16_t in ThisEndian endianness from |p| and return it. */

     static MOZ_WARN_UNUSED_RESULT uint16_t readUint16(const void* p) {

       return read<uint16_t>(p);

     }

     /** Read a uint32_t in ThisEndian endianness from |p| and return it. */

     static MOZ_WARN_UNUSED_RESULT uint32_t readUint32(const void* p) {

       return read<uint32_t>(p);

     }

     /** Read a uint64_t in ThisEndian endianness from |p| and return it. */

     static MOZ_WARN_UNUSED_RESULT uint64_t readUint64(const void* p) {

       return read<uint64_t>(p);

     }

     /** Read an int16_t in ThisEndian endianness from |p| and return it. */

     static MOZ_WARN_UNUSED_RESULT int16_t readInt16(const void* p) {

       return read<int16_t>(p);

     }

     /** Read an int32_t in ThisEndian endianness from |p| and return it. */

     static MOZ_WARN_UNUSED_RESULT int32_t readInt32(const void* p) {

       return read<uint32_t>(p);

     }

     /** Read an int64_t in ThisEndian endianness from |p| and return it. */

     static MOZ_WARN_UNUSED_RESULT int64_t readInt64(const void* p) {

       return read<int64_t>(p);

     }

     /** Write |val| to |p| using ThisEndian endianness. */

     static void writeUint16(void* p, uint16_t val) {

       write(p, val);

     }

     /** Write |val| to |p| using ThisEndian endianness. */

     static void writeUint32(void* p, uint32_t val) {

       write(p, val);

     }

     /** Write |val| to |p| using ThisEndian endianness. */

     static void writeUint64(void* p, uint64_t val) {

       write(p, val);

     }

     /** Write |val| to |p| using ThisEndian endianness. */

     static void writeInt16(void* p, int16_t val) {

       write(p, val);

     }

     /** Write |val| to |p| using ThisEndian endianness. */

     static void writeInt32(void* p, int32_t val) {

       write(p, val);

     }

     /** Write |val| to |p| using ThisEndian endianness. */

     static void writeInt64(void* p, int64_t val) {

       write(p, val);

     }

     /*

      * 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_WARN_UNUSED_RESULT static T swapToLittleEndian(T value) {

       return maybeSwap<ThisEndian, Little>(value);

     }

     /*

      * Copies count values of type T starting at src to dest, converting

      * them to little-endian format if ThisEndian is Big.

      * As with memcpy, dest and src must not overlap.

      */

     template<typename T>

     static void copyAndSwapToLittleEndian(void* dest, const T* src,

                                           size_t count) {

       copyAndSwapTo<ThisEndian, Little>(dest, src, count);

     }

     /*

      * Likewise, but converts values in place.

      */

     template<typename T>

     static void swapToLittleEndianInPlace(T* p, size_t count) {

       maybeSwapInPlace<ThisEndian, Little>(p, count);

     }

     /*

      * Converts a value of type T to big-endian format.

      */

     template<typename T>

     MOZ_WARN_UNUSED_RESULT static T swapToBigEndian(T value) {

       return maybeSwap<ThisEndian, Big>(value);

     }

     /*

      * Copies count values of type T starting at src to dest, converting

      * them to big-endian format if ThisEndian is Little.

      * As with memcpy, dest and src must not overlap.

      */

     template<typename T>

     static void copyAndSwapToBigEndian(void* dest, const T* src, size_t count) {

       copyAndSwapTo<ThisEndian, Big>(dest, src, count);

     }

     /*

      * Likewise, but converts values in place.

      */

     template<typename T>

     static void swapToBigEndianInPlace(T* p, size_t count) {

       maybeSwapInPlace<ThisEndian, Big>(p, count);

     }

     /*

      * Synonyms for the big-endian functions, for better readability

      * in network code.

      */

     template<typename T>

     MOZ_WARN_UNUSED_RESULT static T swapToNetworkOrder(T value) {

       return swapToBigEndian(value);

     }

     template<typename T>

     static void

     copyAndSwapToNetworkOrder(void* dest, const T* src, size_t count) {

       copyAndSwapToBigEndian(dest, src, count);

     }

     template<typename T>

     static void

     swapToNetworkOrderInPlace(T* p, size_t count) {

       swapToBigEndianInPlace(p, count);

     }

     /*

      * Converts a value of type T from little-endian format.

      */

     template<typename T>

     MOZ_WARN_UNUSED_RESULT static T swapFromLittleEndian(T value) {

       return maybeSwap<Little, ThisEndian>(value);

     }

     /*

      * Copies count values of type T starting at src to dest, converting

      * them to little-endian format if ThisEndian is Big.

      * As with memcpy, dest and src must not overlap.

      */

     template<typename T>

     static void copyAndSwapFromLittleEndian(T* dest, const void* src,

                                             size_t count) {

       copyAndSwapFrom<Little, ThisEndian>(dest, src, count);

     }

     /*

      * Likewise, but converts values in place.

      */

     template<typename T>

     static void swapFromLittleEndianInPlace(T* p, size_t count) {

       maybeSwapInPlace<Little, ThisEndian>(p, count);

     }

     /*

      * Converts a value of type T from big-endian format.

      */

     template<typename T>

     MOZ_WARN_UNUSED_RESULT static T swapFromBigEndian(T value) {

       return maybeSwap<Big, ThisEndian>(value);

     }

     /*

      * Copies count values of type T starting at src to dest, converting

      * them to big-endian format if ThisEndian is Little.

      * As with memcpy, dest and src must not overlap.

      */

     template<typename T>

     static void copyAndSwapFromBigEndian(T* dest, const void* src,

                                          size_t count) {

       copyAndSwapFrom<Big, ThisEndian>(dest, src, count);

     }

     /*

      * Likewise, but converts values in place.

      */

     template<typename T>

     static void swapFromBigEndianInPlace(T* p, size_t count) {

       maybeSwapInPlace<Big, ThisEndian>(p, count);

     }

     /*

      * Synonyms for the big-endian functions, for better readability

      * in network code.

      */

     template<typename T>

     MOZ_WARN_UNUSED_RESULT static T swapFromNetworkOrder(T value) {

       return swapFromBigEndian(value);

     }

     template<typename T>

     static void copyAndSwapFromNetworkOrder(T* dest, const void* src,

                                             size_t count) {

       copyAndSwapFromBigEndian(dest, src, count);

     }

     template<typename T>

     static void swapFromNetworkOrderInPlace(T* p, size_t count) {

       swapFromBigEndianInPlace(p, count);

     }

   private:

     /**

      * Read a value of type T, encoded in endianness ThisEndian from |p|.

      * Return that value encoded in native endianness.

      */

     template<typename T>

     static T read(const void* p) {

       union {

         T val;

         uint8_t buffer[sizeof(T)];

       } u;

       memcpy(u.buffer, p, sizeof(T));

       return maybeSwap<ThisEndian, MOZ_NATIVE_ENDIANNESS>(u.val);

     }

     /**

      * Write a value of type T, in native endianness, to |p|, in ThisEndian

      * endianness.

      */

     template<typename T>

     static void write(void* p, T value) {

       T tmp = maybeSwap<MOZ_NATIVE_ENDIANNESS, ThisEndian>(value);

       memcpy(p, &tmp, sizeof(T));

     }

     Endian() MOZ_DELETE;

     Endian(const Endian& other) MOZ_DELETE;

     void operator=(const Endian& other) MOZ_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 MOZ_FINAL : public detail::EndianReadWrite<detail::Little>

 {};

 class BigEndian MOZ_FINAL : public detail::EndianReadWrite<detail::Big>

 {};

 typedef BigEndian NetworkEndian;

 class NativeEndian MOZ_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_Endian_h */