1 | // Copyright (c) 2011, Google Inc. |
2 | // All rights reserved. |
3 | // |
4 | // Redistribution and use in source and binary forms, with or without |
5 | // modification, are permitted provided that the following conditions are |
6 | // met: |
7 | // |
8 | // * Redistributions of source code must retain the above copyright |
9 | // notice, this list of conditions and the following disclaimer. |
10 | // * Redistributions in binary form must reproduce the above |
11 | // copyright notice, this list of conditions and the following disclaimer |
12 | // in the documentation and/or other materials provided with the |
13 | // distribution. |
14 | // * Neither the name of Google Inc. nor the names of its |
15 | // contributors may be used to endorse or promote products derived from |
16 | // this software without specific prior written permission. |
17 | // |
18 | // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
19 | // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
20 | // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR |
21 | // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT |
22 | // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
23 | // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT |
24 | // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
25 | // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
26 | // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
27 | // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE |
28 | // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
29 | |
30 | // memory_range.h: Define the google_breakpad::MemoryRange class, which |
31 | // is a lightweight wrapper with a pointer and a length to encapsulate |
32 | // a contiguous range of memory. |
33 | |
34 | #ifndef COMMON_MEMORY_RANGE_H_ |
35 | #define COMMON_MEMORY_RANGE_H_ |
36 | |
37 | #include <stddef.h> |
38 | |
39 | #include "google_breakpad/common/breakpad_types.h" |
40 | |
41 | namespace google_breakpad { |
42 | |
43 | // A lightweight wrapper with a pointer and a length to encapsulate a |
44 | // contiguous range of memory. It provides helper methods for checked |
45 | // access of a subrange of the memory. Its implemementation does not |
46 | // allocate memory or call into libc functions, and is thus safer to use |
47 | // in a crashed environment. |
48 | class MemoryRange { |
49 | public: |
50 | MemoryRange() : data_(NULL), length_(0) {} |
51 | |
52 | MemoryRange(const void* data, size_t length) { |
53 | Set(data, length); |
54 | } |
55 | |
56 | // Returns true if this memory range contains no data. |
57 | bool IsEmpty() const { |
58 | // Set() guarantees that |length_| is zero if |data_| is NULL. |
59 | return length_ == 0; |
60 | } |
61 | |
62 | // Resets to an empty range. |
63 | void Reset() { |
64 | data_ = NULL; |
65 | length_ = 0; |
66 | } |
67 | |
68 | // Sets this memory range to point to |data| and its length to |length|. |
69 | void Set(const void* data, size_t length) { |
70 | data_ = reinterpret_cast<const uint8_t*>(data); |
71 | // Always set |length_| to zero if |data_| is NULL. |
72 | length_ = data ? length : 0; |
73 | } |
74 | |
75 | // Returns true if this range covers a subrange of |sub_length| bytes |
76 | // at |sub_offset| bytes of this memory range, or false otherwise. |
77 | bool Covers(size_t sub_offset, size_t sub_length) const { |
78 | // The following checks verify that: |
79 | // 1. sub_offset is within [ 0 .. length_ - 1 ] |
80 | // 2. sub_offset + sub_length is within |
81 | // [ sub_offset .. length_ ] |
82 | return sub_offset < length_ && |
83 | sub_offset + sub_length >= sub_offset && |
84 | sub_offset + sub_length <= length_; |
85 | } |
86 | |
87 | // Returns a raw data pointer to a subrange of |sub_length| bytes at |
88 | // |sub_offset| bytes of this memory range, or NULL if the subrange |
89 | // is out of bounds. |
90 | const void* GetData(size_t sub_offset, size_t sub_length) const { |
91 | return Covers(sub_offset, sub_length) ? (data_ + sub_offset) : NULL; |
92 | } |
93 | |
94 | // Same as the two-argument version of GetData() but uses sizeof(DataType) |
95 | // as the subrange length and returns an |DataType| pointer for convenience. |
96 | template <typename DataType> |
97 | const DataType* GetData(size_t sub_offset) const { |
98 | return reinterpret_cast<const DataType*>( |
99 | GetData(sub_offset, sizeof(DataType))); |
100 | } |
101 | |
102 | // Returns a raw pointer to the |element_index|-th element of an array |
103 | // of elements of length |element_size| starting at |sub_offset| bytes |
104 | // of this memory range, or NULL if the element is out of bounds. |
105 | const void* GetArrayElement(size_t element_offset, |
106 | size_t element_size, |
107 | unsigned element_index) const { |
108 | size_t sub_offset = element_offset + element_index * element_size; |
109 | return GetData(sub_offset, element_size); |
110 | } |
111 | |
112 | // Same as the three-argument version of GetArrayElement() but deduces |
113 | // the element size using sizeof(ElementType) and returns an |ElementType| |
114 | // pointer for convenience. |
115 | template <typename ElementType> |
116 | const ElementType* GetArrayElement(size_t element_offset, |
117 | unsigned element_index) const { |
118 | return reinterpret_cast<const ElementType*>( |
119 | GetArrayElement(element_offset, sizeof(ElementType), element_index)); |
120 | } |
121 | |
122 | // Returns a subrange of |sub_length| bytes at |sub_offset| bytes of |
123 | // this memory range, or an empty range if the subrange is out of bounds. |
124 | MemoryRange Subrange(size_t sub_offset, size_t sub_length) const { |
125 | return Covers(sub_offset, sub_length) ? |
126 | MemoryRange(data_ + sub_offset, sub_length) : MemoryRange(); |
127 | } |
128 | |
129 | // Returns a pointer to the beginning of this memory range. |
130 | const uint8_t* data() const { return data_; } |
131 | |
132 | // Returns the length, in bytes, of this memory range. |
133 | size_t length() const { return length_; } |
134 | |
135 | private: |
136 | // Pointer to the beginning of this memory range. |
137 | const uint8_t* data_; |
138 | |
139 | // Length, in bytes, of this memory range. |
140 | size_t length_; |
141 | }; |
142 | |
143 | } // namespace google_breakpad |
144 | |
145 | #endif // COMMON_MEMORY_RANGE_H_ |
146 | |