1/*
2 * Copyright (C) 2011 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#ifndef ART_RUNTIME_MEMORY_REGION_H_
18#define ART_RUNTIME_MEMORY_REGION_H_
19
20#include <stdint.h>
21
22#include "base/logging.h"
23#include "base/macros.h"
24#include "globals.h"
25
26namespace art {
27
28// Memory regions are useful for accessing memory with bounds check in
29// debug mode. They can be safely passed by value and do not assume ownership
30// of the region.
31class MemoryRegion {
32 public:
33  MemoryRegion() : pointer_(NULL), size_(0) {}
34  MemoryRegion(void* pointer, uword size) : pointer_(pointer), size_(size) {}
35
36  void* pointer() const { return pointer_; }
37  size_t size() const { return size_; }
38  size_t size_in_bits() const { return size_ * kBitsPerByte; }
39
40  static size_t pointer_offset() {
41    return OFFSETOF_MEMBER(MemoryRegion, pointer_);
42  }
43
44  byte* start() const { return reinterpret_cast<byte*>(pointer_); }
45  byte* end() const { return start() + size_; }
46
47  template<typename T> T Load(uintptr_t offset) const {
48    return *ComputeInternalPointer<T>(offset);
49  }
50
51  template<typename T> void Store(uintptr_t offset, T value) const {
52    *ComputeInternalPointer<T>(offset) = value;
53  }
54
55  template<typename T> T* PointerTo(uintptr_t offset) const {
56    return ComputeInternalPointer<T>(offset);
57  }
58
59  void CopyFrom(size_t offset, const MemoryRegion& from) const;
60
61  // Compute a sub memory region based on an existing one.
62  void Subregion(const MemoryRegion& from, uintptr_t offset, uintptr_t size) {
63    CHECK_GE(from.size(), size);
64    CHECK_LE(offset,  from.size() - size);
65    pointer_ = reinterpret_cast<void*>(from.start() + offset);
66    size_ = size;
67  }
68
69  // Compute an extended memory region based on an existing one.
70  void Extend(const MemoryRegion& region, uintptr_t extra) {
71    pointer_ = region.pointer();
72    size_ = (region.size() + extra);
73  }
74
75 private:
76  template<typename T> T* ComputeInternalPointer(size_t offset) const {
77    CHECK_GE(size(), sizeof(T));
78    CHECK_LE(offset, size() - sizeof(T));
79    return reinterpret_cast<T*>(start() + offset);
80  }
81
82  // Locate the bit with the given offset. Returns a pointer to the byte
83  // containing the bit, and sets bit_mask to the bit within that byte.
84  byte* ComputeBitPointer(uintptr_t bit_offset, byte* bit_mask) const {
85    uintptr_t bit_remainder = (bit_offset & (kBitsPerByte - 1));
86    *bit_mask = (1U << bit_remainder);
87    uintptr_t byte_offset = (bit_offset >> kBitsPerByteLog2);
88    return ComputeInternalPointer<byte>(byte_offset);
89  }
90
91  void* pointer_;
92  size_t size_;
93
94  DISALLOW_COPY_AND_ASSIGN(MemoryRegion);
95};
96
97}  // namespace art
98
99#endif  // ART_RUNTIME_MEMORY_REGION_H_
100