// 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_BASE_MEMORY_H_ #define V8_BASE_MEMORY_H_ #include "src/base/macros.h" namespace v8 { namespace base { using Address = uintptr_t; using byte = uint8_t; // 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. template <class T> inline T& Memory(Address addr) { DCHECK(IsAligned(addr, alignof(T))); return *reinterpret_cast<T*>(addr); } template <class T> inline T& Memory(byte* addr) { return Memory<T>(reinterpret_cast<Address>(addr)); } template <typename V> static inline V ReadUnalignedValue(Address p) { ASSERT_TRIVIALLY_COPYABLE(V); V r; memcpy(&r, reinterpret_cast<void*>(p), sizeof(V)); return r; } template <typename V> static inline void WriteUnalignedValue(Address p, V value) { ASSERT_TRIVIALLY_COPYABLE(V); memcpy(reinterpret_cast<void*>(p), &value, sizeof(V)); } 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 } template <typename V> static inline V ReadLittleEndianValue(V* p) { return ReadLittleEndianValue<V>(reinterpret_cast<Address>(p)); } template <typename V> static inline void WriteLittleEndianValue(V* p, V value) { static_assert( !std::is_array<V>::value, "Passing an array decays to pointer, causing unexpected results."); WriteLittleEndianValue<V>(reinterpret_cast<Address>(p), value); } } // namespace base } // namespace v8 #endif // V8_BASE_MEMORY_H_