Bug 798172 - part 1 - add mfbt/Endian.h; r=Waldo
authorNathan Froyd <froydnj@mozilla.com>
Wed, 30 Jan 2013 16:45:39 -0500
changeset 127596 4b3a5c36598ccceb9b211fdeb74305fac9d267be
parent 127595 ab825d9e6d1658562b18379b750cb20e64ce59d8
child 127597 ea8ae9085ea16cf6931c7496f7a89b835dc52557
push id24509
push userryanvm@gmail.com
push dateFri, 05 Apr 2013 00:57:47 +0000
treeherdermozilla-central@55f9e3e3dae7 [default view] [failures only]
perfherder[talos] [build metrics] [platform microbench] (compared to previous push)
reviewersWaldo
bugs798172
milestone23.0a1
first release with
nightly linux32
nightly linux64
nightly mac
nightly win32
nightly win64
last release without
nightly linux32
nightly linux64
nightly mac
nightly win32
nightly win64
Bug 798172 - part 1 - add mfbt/Endian.h; r=Waldo
mfbt/Endian.h
mfbt/exported_headers.mk
new file mode 100644
--- /dev/null
+++ b/mfbt/Endian.h
@@ -0,0 +1,631 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* 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/StandardInteger.h"
+#include "mozilla/TypeTraits.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__)
+#  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(__powerpc__) || \
+      defined(__ppc__) || defined(__hppa) || \
+      defined(_MIPSEB) || defined(__ARMEB__) || \
+      defined(__s390__) || \
+      (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(__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
+
+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(__clang__)
+    return T(__builtin_bswap16(value));
+#elif defined(__GNUC__) && MOZ_GCC_VERSION_AT_LEAST(4, 8, 0)
+    return T(__builtin_bswap16(value));
+#elif defined(_MSC_VER)
+    return T(_byteswap_ushort(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_ */
--- a/mfbt/exported_headers.mk
+++ b/mfbt/exported_headers.mk
@@ -12,16 +12,17 @@ EXPORTS_mozilla += \
   Assertions.h \
   Attributes.h \
   BloomFilter.h \
   Char16.h \
   CheckedInt.h \
   Compiler.h \
   Constants.h \
   DebugOnly.h \
+  Endian.h \
   EnumSet.h \
   FloatingPoint.h \
   GuardObjects.h \
   HashFunctions.h \
   Likely.h \
   LinkedList.h \
   MathAlgorithms.h \
   MemoryChecking.h \