src/v8memory.h

// Copyright 2011 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef V8_V8MEMORY_H_
#define V8_V8MEMORY_H_

#include "src/globals.h"

namespace v8 {
namespace internal {

// Memory provides an interface to 'raw' memory. It encapsulates the casts
// that typically are needed when incompatible pointer types are used.
// Note that this class currently relies on undefined behaviour. There is a
// proposal (http://wg21.link/p0593r2) to make it defined behaviour though.
class Memory {
 public:
  static uint8_t& uint8_at(Address addr) {
    return *reinterpret_cast<uint8_t*>(addr);
  }

  static uint16_t& uint16_at(Address addr)  {
    return *reinterpret_cast<uint16_t*>(addr);
  }

  static uint32_t& uint32_at(Address addr)  {
    return *reinterpret_cast<uint32_t*>(addr);
  }

  static int32_t& int32_at(Address addr)  {
    return *reinterpret_cast<int32_t*>(addr);
  }

  static uint64_t& uint64_at(Address addr)  {
    return *reinterpret_cast<uint64_t*>(addr);
  }

  static int64_t& int64_at(Address addr) {
    return *reinterpret_cast<int64_t*>(addr);
  }

  static int& int_at(Address addr)  {
    return *reinterpret_cast<int*>(addr);
  }

  static unsigned& unsigned_at(Address addr) {
    return *reinterpret_cast<unsigned*>(addr);
  }

  static intptr_t& intptr_at(Address addr)  {
    return *reinterpret_cast<intptr_t*>(addr);
  }

  static uintptr_t& uintptr_at(Address addr) {
    return *reinterpret_cast<uintptr_t*>(addr);
  }

  static float& float_at(Address addr) {
    return *reinterpret_cast<float*>(addr);
  }

  static double& double_at(Address addr)  {
    return *reinterpret_cast<double*>(addr);
  }

  static Address& Address_at(Address addr)  {
    return *reinterpret_cast<Address*>(addr);
  }

  static Object*& Object_at(Address addr)  {
    return *reinterpret_cast<Object**>(addr);
  }

  static Handle<Object>& Object_Handle_at(Address addr)  {
    return *reinterpret_cast<Handle<Object>*>(addr);
  }

  static bool IsAddressInRange(Address base, Address address, uint32_t size) {
    return base <= address && address < base + size;
  }
};

template <typename V>
static inline V ReadUnalignedValue(Address p) {
  ASSERT_TRIVIALLY_COPYABLE(V);
#if !(V8_TARGET_ARCH_MIPS || V8_TARGET_ARCH_MIPS64 || V8_TARGET_ARCH_ARM)
  return *reinterpret_cast<const V*>(p);
#else   // V8_TARGET_ARCH_MIPS || V8_TARGET_ARCH_MIPS64 || V8_TARGET_ARCH_ARM
  V r;
  memmove(&r, reinterpret_cast<void*>(p), sizeof(V));
  return r;
#endif  // V8_TARGET_ARCH_MIPS || V8_TARGET_ARCH_MIPS64 || V8_TARGET_ARCH_ARM
}

template <typename V>
static inline void WriteUnalignedValue(Address p, V value) {
  ASSERT_TRIVIALLY_COPYABLE(V);
#if !(V8_TARGET_ARCH_MIPS || V8_TARGET_ARCH_MIPS64 || V8_TARGET_ARCH_ARM)
  *(reinterpret_cast<V*>(p)) = value;
#else   // V8_TARGET_ARCH_MIPS || V8_TARGET_ARCH_MIPS64 || V8_TARGET_ARCH_ARM
  memmove(reinterpret_cast<void*>(p), &value, sizeof(V));
#endif  // V8_TARGET_ARCH_MIPS || V8_TARGET_ARCH_MIPS64 || V8_TARGET_ARCH_ARM
}

static inline double ReadFloatValue(Address p) {
  return ReadUnalignedValue<float>(p);
}

static inline double ReadDoubleValue(Address p) {
  return ReadUnalignedValue<double>(p);
}

static inline void WriteDoubleValue(Address p, double value) {
  WriteUnalignedValue(p, value);
}

static inline uint16_t ReadUnalignedUInt16(Address p) {
  return ReadUnalignedValue<uint16_t>(p);
}

static inline void WriteUnalignedUInt16(Address p, uint16_t value) {
  WriteUnalignedValue(p, value);
}

static inline uint32_t ReadUnalignedUInt32(Address p) {
  return ReadUnalignedValue<uint32_t>(p);
}

static inline void WriteUnalignedUInt32(Address p, uint32_t value) {
  WriteUnalignedValue(p, value);
}

template <typename V>
static inline V ReadLittleEndianValue(Address p) {
#if defined(V8_TARGET_LITTLE_ENDIAN)
  return ReadUnalignedValue<V>(p);
#elif defined(V8_TARGET_BIG_ENDIAN)
  V ret{};
  const byte* src = reinterpret_cast<const byte*>(p);
  byte* dst = reinterpret_cast<byte*>(&ret);
  for (size_t i = 0; i < sizeof(V); i++) {
    dst[i] = src[sizeof(V) - i - 1];
  }
  return ret;
#endif  // V8_TARGET_LITTLE_ENDIAN
}

template <typename V>
static inline void WriteLittleEndianValue(Address p, V value) {
#if defined(V8_TARGET_LITTLE_ENDIAN)
  WriteUnalignedValue<V>(p, value);
#elif defined(V8_TARGET_BIG_ENDIAN)
  byte* src = reinterpret_cast<byte*>(&value);
  byte* dst = reinterpret_cast<byte*>(p);
  for (size_t i = 0; i < sizeof(V); i++) {
    dst[i] = src[sizeof(V) - i - 1];
  }
#endif  // V8_TARGET_LITTLE_ENDIAN
}

}  // namespace internal
}  // namespace v8

#endif  // V8_V8MEMORY_H_