runtime/memory_region.h - platform/art - Git at Google

 /*
  * Copyright (C) 2011 The Android Open Source Project
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *      http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */

 #ifndef ART_RUNTIME_MEMORY_REGION_H_
 #define ART_RUNTIME_MEMORY_REGION_H_

 #include <stdint.h>
 #include <type_traits>

 #include "arch/instruction_set.h"
 #include "base/bit_utils.h"
 #include "base/casts.h"
 #include "base/logging.h"
 #include "base/macros.h"
 #include "base/value_object.h"
 #include "globals.h"

 namespace art {

 // Memory regions are useful for accessing memory with bounds check in
 // debug mode. They can be safely passed by value and do not assume ownership
 // of the region.
 class MemoryRegion FINAL : public ValueObject {
  public:
   struct ContentEquals {
     constexpr bool operator()(const MemoryRegion& lhs, const MemoryRegion& rhs) const {
       return lhs.size() == rhs.size() && memcmp(lhs.begin(), rhs.begin(), lhs.size()) == 0;
     }
   };

   MemoryRegion() : pointer_(nullptr), size_(0) {}
   MemoryRegion(void* pointer_in, uintptr_t size_in) : pointer_(pointer_in), size_(size_in) {}

   void* pointer() const { return pointer_; }
   size_t size() const { return size_; }
   size_t size_in_bits() const { return size_ * kBitsPerByte; }

   static size_t pointer_offset() {
     return OFFSETOF_MEMBER(MemoryRegion, pointer_);
   }

   uint8_t* begin() const { return reinterpret_cast<uint8_t*>(pointer_); }
   uint8_t* end() const { return begin() + size_; }

   // Load value of type `T` at `offset`.  The memory address corresponding
   // to `offset` should be word-aligned (on ARM, this is a requirement).
   template<typename T>
   ALWAYS_INLINE T Load(uintptr_t offset) const {
     T* address = ComputeInternalPointer<T>(offset);
     DCHECK(IsWordAligned(address));
     return *address;
   }

   // Store `value` (of type `T`) at `offset`.  The memory address
   // corresponding to `offset` should be word-aligned (on ARM, this is
   // a requirement).
   template<typename T>
   ALWAYS_INLINE void Store(uintptr_t offset, T value) const {
     T* address = ComputeInternalPointer<T>(offset);
     DCHECK(IsWordAligned(address));
     *address = value;
   }

   // Load value of type `T` at `offset`.  The memory address corresponding
   // to `offset` does not need to be word-aligned.
   template<typename T>
   ALWAYS_INLINE T LoadUnaligned(uintptr_t offset) const {
     // Equivalent unsigned integer type corresponding to T.
     typedef typename std::make_unsigned<T>::type U;
     U equivalent_unsigned_integer_value = 0;
     // Read the value byte by byte in a little-endian fashion.
     for (size_t i = 0; i < sizeof(U); ++i) {
       equivalent_unsigned_integer_value +=
           *ComputeInternalPointer<uint8_t>(offset + i) << (i * kBitsPerByte);
     }
     return bit_cast<T, U>(equivalent_unsigned_integer_value);
   }

   // Store `value` (of type `T`) at `offset`.  The memory address
   // corresponding to `offset` does not need to be word-aligned.
   template<typename T>
   ALWAYS_INLINE void StoreUnaligned(uintptr_t offset, T value) const {
     // Equivalent unsigned integer type corresponding to T.
     typedef typename std::make_unsigned<T>::type U;
     U equivalent_unsigned_integer_value = bit_cast<U, T>(value);
     // Write the value byte by byte in a little-endian fashion.
     for (size_t i = 0; i < sizeof(U); ++i) {
       *ComputeInternalPointer<uint8_t>(offset + i) =
           (equivalent_unsigned_integer_value >> (i * kBitsPerByte)) & 0xFF;
     }
   }

   template<typename T>
   ALWAYS_INLINE T* PointerTo(uintptr_t offset) const {
     return ComputeInternalPointer<T>(offset);
   }

   // Load a single bit in the region. The bit at offset 0 is the least
   // significant bit in the first byte.
   ALWAYS_INLINE bool LoadBit(uintptr_t bit_offset) const {
     uint8_t bit_mask;
     uint8_t byte = *ComputeBitPointer(bit_offset, &bit_mask);
     return byte & bit_mask;
   }

   ALWAYS_INLINE void StoreBit(uintptr_t bit_offset, bool value) const {
     uint8_t bit_mask;
     uint8_t* byte = ComputeBitPointer(bit_offset, &bit_mask);
     if (value) {
       *byte |= bit_mask;
     } else {
       *byte &= ~bit_mask;
     }
   }

   // Load `length` bits from the region starting at bit offset `bit_offset`.
   // The bit at the smallest offset is the least significant bit in the
   // loaded value.  `length` must not be larger than the number of bits
   // contained in the return value (32).
   ALWAYS_INLINE uint32_t LoadBits(uintptr_t bit_offset, size_t length) const {
     DCHECK_LE(length, BitSizeOf<uint32_t>());
     DCHECK_LE(bit_offset + length, size_in_bits());
     if (UNLIKELY(length == 0)) {
       // Do not touch any memory if the range is empty.
       return 0;
     }
     const uint8_t* address = begin() + bit_offset / kBitsPerByte;
     const uint32_t shift = bit_offset & (kBitsPerByte - 1);
     // Load the value (reading only the strictly needed bytes).
     const uint32_t load_bit_count = shift + length;
     uint32_t value = address[0] >> shift;
     if (load_bit_count > 8) {
       value |= static_cast<uint32_t>(address[1]) << (8 - shift);
       if (load_bit_count > 16) {
         value |= static_cast<uint32_t>(address[2]) << (16 - shift);
         if (load_bit_count > 24) {
           value |= static_cast<uint32_t>(address[3]) << (24 - shift);
           if (load_bit_count > 32) {
             value |= static_cast<uint32_t>(address[4]) << (32 - shift);
           }
         }
       }
     }
     // Clear unwanted most significant bits.
     uint32_t clear_bit_count = BitSizeOf(value) - length;
     value = (value << clear_bit_count) >> clear_bit_count;
     for (size_t i = 0; i < length; ++i) {
       DCHECK_EQ((value >> i) & 1, LoadBit(bit_offset + i));
     }
     return value;
   }

   // Store `value` on `length` bits in the region starting at bit offset
   // `bit_offset`.  The bit at the smallest offset is the least significant
   // bit of the stored `value`.  `value` must not be larger than `length`
   // bits.
   void StoreBits(uintptr_t bit_offset, uint32_t value, size_t length);

   void CopyFrom(size_t offset, const MemoryRegion& from) const;

   template<class Vector>
   void CopyFromVector(size_t offset, Vector& vector) const {
     if (!vector.empty()) {
       CopyFrom(offset, MemoryRegion(vector.data(), vector.size()));
     }
   }

   // Compute a sub memory region based on an existing one.
   ALWAYS_INLINE MemoryRegion Subregion(uintptr_t offset, uintptr_t size_in) const {
     CHECK_GE(this->size(), size_in);
     CHECK_LE(offset,  this->size() - size_in);
     return MemoryRegion(reinterpret_cast<void*>(begin() + offset), size_in);
   }

   // Compute an extended memory region based on an existing one.
   ALWAYS_INLINE void Extend(const MemoryRegion& region, uintptr_t extra) {
     pointer_ = region.pointer();
     size_ = (region.size() + extra);
   }

  private:
   template<typename T>
   ALWAYS_INLINE T* ComputeInternalPointer(size_t offset) const {
     CHECK_GE(size(), sizeof(T));
     CHECK_LE(offset, size() - sizeof(T));
     return reinterpret_cast<T*>(begin() + offset);
   }

   // Locate the bit with the given offset. Returns a pointer to the byte
   // containing the bit, and sets bit_mask to the bit within that byte.
   ALWAYS_INLINE uint8_t* ComputeBitPointer(uintptr_t bit_offset, uint8_t* bit_mask) const {
     uintptr_t bit_remainder = (bit_offset & (kBitsPerByte - 1));
     *bit_mask = (1U << bit_remainder);
     uintptr_t byte_offset = (bit_offset >> kBitsPerByteLog2);
     return ComputeInternalPointer<uint8_t>(byte_offset);
   }

   // Is `address` aligned on a machine word?
   template<typename T> static constexpr bool IsWordAligned(const T* address) {
     // Word alignment in bytes.
     size_t kWordAlignment = static_cast<size_t>(GetInstructionSetPointerSize(kRuntimeISA));
     return IsAlignedParam(address, kWordAlignment);
   }

   void* pointer_;
   size_t size_;
 };

 }  // namespace art

 #endif  // ART_RUNTIME_MEMORY_REGION_H_
	/*
	* Copyright (C) 2011 The Android Open Source Project
	*
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/

	#ifndef ART_RUNTIME_MEMORY_REGION_H_
	#define ART_RUNTIME_MEMORY_REGION_H_

	#include <stdint.h>
	#include <type_traits>

	#include "arch/instruction_set.h"
	#include "base/bit_utils.h"
	#include "base/casts.h"
	#include "base/logging.h"
	#include "base/macros.h"
	#include "base/value_object.h"
	#include "globals.h"

	namespace art {

	// Memory regions are useful for accessing memory with bounds check in
	// debug mode. They can be safely passed by value and do not assume ownership
	// of the region.
	class MemoryRegion FINAL : public ValueObject {
	public:
	struct ContentEquals {
	constexpr bool operator()(const MemoryRegion& lhs, const MemoryRegion& rhs) const {
	return lhs.size() == rhs.size() && memcmp(lhs.begin(), rhs.begin(), lhs.size()) == 0;
	}
	};

	MemoryRegion() : pointer_(nullptr), size_(0) {}
	MemoryRegion(void* pointer_in, uintptr_t size_in) : pointer_(pointer_in), size_(size_in) {}

	void* pointer() const { return pointer_; }
	size_t size() const { return size_; }
	size_t size_in_bits() const { return size_ * kBitsPerByte; }

	static size_t pointer_offset() {
	return OFFSETOF_MEMBER(MemoryRegion, pointer_);
	}

	uint8_t* begin() const { return reinterpret_cast<uint8_t*>(pointer_); }
	uint8_t* end() const { return begin() + size_; }

	// Load value of type `T` at `offset`. The memory address corresponding
	// to `offset` should be word-aligned (on ARM, this is a requirement).
	template<typename T>
	ALWAYS_INLINE T Load(uintptr_t offset) const {
	T* address = ComputeInternalPointer<T>(offset);
	DCHECK(IsWordAligned(address));
	return *address;
	}

	// Store `value` (of type `T`) at `offset`. The memory address
	// corresponding to `offset` should be word-aligned (on ARM, this is
	// a requirement).
	template<typename T>
	ALWAYS_INLINE void Store(uintptr_t offset, T value) const {
	T* address = ComputeInternalPointer<T>(offset);
	DCHECK(IsWordAligned(address));
	*address = value;
	}

	// Load value of type `T` at `offset`. The memory address corresponding
	// to `offset` does not need to be word-aligned.
	template<typename T>
	ALWAYS_INLINE T LoadUnaligned(uintptr_t offset) const {
	// Equivalent unsigned integer type corresponding to T.
	typedef typename std::make_unsigned<T>::type U;
	U equivalent_unsigned_integer_value = 0;
	// Read the value byte by byte in a little-endian fashion.
	for (size_t i = 0; i < sizeof(U); ++i) {
	equivalent_unsigned_integer_value +=
	ComputeInternalPointer<uint8_t>(offset + i) << (i kBitsPerByte);
	}
	return bit_cast<T, U>(equivalent_unsigned_integer_value);
	}

	// Store `value` (of type `T`) at `offset`. The memory address
	// corresponding to `offset` does not need to be word-aligned.
	template<typename T>
	ALWAYS_INLINE void StoreUnaligned(uintptr_t offset, T value) const {
	// Equivalent unsigned integer type corresponding to T.
	typedef typename std::make_unsigned<T>::type U;
	U equivalent_unsigned_integer_value = bit_cast<U, T>(value);
	// Write the value byte by byte in a little-endian fashion.
	for (size_t i = 0; i < sizeof(U); ++i) {
	*ComputeInternalPointer<uint8_t>(offset + i) =
	(equivalent_unsigned_integer_value >> (i * kBitsPerByte)) & 0xFF;
	}
	}

	template<typename T>
	ALWAYS_INLINE T* PointerTo(uintptr_t offset) const {
	return ComputeInternalPointer<T>(offset);
	}

	// Load a single bit in the region. The bit at offset 0 is the least
	// significant bit in the first byte.
	ALWAYS_INLINE bool LoadBit(uintptr_t bit_offset) const {
	uint8_t bit_mask;
	uint8_t byte = *ComputeBitPointer(bit_offset, &bit_mask);
	return byte & bit_mask;
	}

	ALWAYS_INLINE void StoreBit(uintptr_t bit_offset, bool value) const {
	uint8_t bit_mask;
	uint8_t* byte = ComputeBitPointer(bit_offset, &bit_mask);
	if (value) {
	*byte \|= bit_mask;
	} else {
	*byte &= ~bit_mask;
	}
	}

	// Load `length` bits from the region starting at bit offset `bit_offset`.
	// The bit at the smallest offset is the least significant bit in the
	// loaded value. `length` must not be larger than the number of bits
	// contained in the return value (32).
	ALWAYS_INLINE uint32_t LoadBits(uintptr_t bit_offset, size_t length) const {
	DCHECK_LE(length, BitSizeOf<uint32_t>());
	DCHECK_LE(bit_offset + length, size_in_bits());
	if (UNLIKELY(length == 0)) {
	// Do not touch any memory if the range is empty.
	return 0;
	}
	const uint8_t* address = begin() + bit_offset / kBitsPerByte;
	const uint32_t shift = bit_offset & (kBitsPerByte - 1);
	// Load the value (reading only the strictly needed bytes).
	const uint32_t load_bit_count = shift + length;
	uint32_t value = address[0] >> shift;
	if (load_bit_count > 8) {
	value \|= static_cast<uint32_t>(address[1]) << (8 - shift);
	if (load_bit_count > 16) {
	value \|= static_cast<uint32_t>(address[2]) << (16 - shift);
	if (load_bit_count > 24) {
	value \|= static_cast<uint32_t>(address[3]) << (24 - shift);
	if (load_bit_count > 32) {
	value \|= static_cast<uint32_t>(address[4]) << (32 - shift);
	}
	}
	}
	}
	// Clear unwanted most significant bits.
	uint32_t clear_bit_count = BitSizeOf(value) - length;
	value = (value << clear_bit_count) >> clear_bit_count;
	for (size_t i = 0; i < length; ++i) {
	DCHECK_EQ((value >> i) & 1, LoadBit(bit_offset + i));
	}
	return value;
	}

	// Store `value` on `length` bits in the region starting at bit offset
	// `bit_offset`. The bit at the smallest offset is the least significant
	// bit of the stored `value`. `value` must not be larger than `length`
	// bits.
	void StoreBits(uintptr_t bit_offset, uint32_t value, size_t length);

	void CopyFrom(size_t offset, const MemoryRegion& from) const;

	template<class Vector>
	void CopyFromVector(size_t offset, Vector& vector) const {
	if (!vector.empty()) {
	CopyFrom(offset, MemoryRegion(vector.data(), vector.size()));
	}
	}

	// Compute a sub memory region based on an existing one.
	ALWAYS_INLINE MemoryRegion Subregion(uintptr_t offset, uintptr_t size_in) const {
	CHECK_GE(this->size(), size_in);
	CHECK_LE(offset, this->size() - size_in);
	return MemoryRegion(reinterpret_cast<void*>(begin() + offset), size_in);
	}

	// Compute an extended memory region based on an existing one.
	ALWAYS_INLINE void Extend(const MemoryRegion& region, uintptr_t extra) {
	pointer_ = region.pointer();
	size_ = (region.size() + extra);
	}

	private:
	template<typename T>
	ALWAYS_INLINE T* ComputeInternalPointer(size_t offset) const {
	CHECK_GE(size(), sizeof(T));
	CHECK_LE(offset, size() - sizeof(T));
	return reinterpret_cast<T*>(begin() + offset);
	}

	// Locate the bit with the given offset. Returns a pointer to the byte
	// containing the bit, and sets bit_mask to the bit within that byte.
	ALWAYS_INLINE uint8_t* ComputeBitPointer(uintptr_t bit_offset, uint8_t* bit_mask) const {
	uintptr_t bit_remainder = (bit_offset & (kBitsPerByte - 1));
	*bit_mask = (1U << bit_remainder);
	uintptr_t byte_offset = (bit_offset >> kBitsPerByteLog2);
	return ComputeInternalPointer<uint8_t>(byte_offset);
	}

	// Is `address` aligned on a machine word?
	template<typename T> static constexpr bool IsWordAligned(const T* address) {
	// Word alignment in bytes.
	size_t kWordAlignment = static_cast<size_t>(GetInstructionSetPointerSize(kRuntimeISA));
	return IsAlignedParam(address, kWordAlignment);
	}

	void* pointer_;
	size_t size_;
	};

	} // namespace art

	#endif // ART_RUNTIME_MEMORY_REGION_H_