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1 // Copyright (c) 2011 The Chromium Authors. All rights reserved. | |
2 // Use of this source code is governed by a BSD-style license that can be | |
3 // found in the LICENSE file. | |
4 | |
5 #ifndef NET_DISK_CACHE_BLOCKFILE_BITMAP_H_ | |
6 #define NET_DISK_CACHE_BLOCKFILE_BITMAP_H_ | |
7 | |
8 #include "base/basictypes.h" | |
9 #include "net/base/net_export.h" | |
10 | |
11 namespace disk_cache { | |
12 | |
13 // This class provides support for simple maps of bits. | |
14 class NET_EXPORT_PRIVATE Bitmap { | |
15 public: | |
16 Bitmap() : map_(NULL), num_bits_(0), array_size_(0), alloc_(false) {} | |
17 | |
18 // This constructor will allocate on a uint32 boundary. If |clear_bits| is | |
19 // false, the bitmap bits will not be initialized. | |
20 Bitmap(int num_bits, bool clear_bits); | |
21 | |
22 // Constructs a Bitmap with the actual storage provided by the caller. |map| | |
23 // has to be valid until this object destruction. |num_bits| is the number of | |
24 // bits in the bitmap, and |num_words| is the size of |map| in 32-bit words. | |
25 Bitmap(uint32* map, int num_bits, int num_words); | |
26 | |
27 ~Bitmap(); | |
28 | |
29 // Resizes the bitmap. | |
30 // If |num_bits| < Size(), the extra bits will be discarded. | |
31 // If |num_bits| > Size(), the extra bits will be filled with zeros if | |
32 // |clear_bits| is true. | |
33 // This object cannot be using memory provided during construction. | |
34 void Resize(int num_bits, bool clear_bits); | |
35 | |
36 // Returns the number of bits in the bitmap. | |
37 int Size() const { return num_bits_; } | |
38 | |
39 // Returns the number of 32-bit words in the bitmap. | |
40 int ArraySize() const { return array_size_; } | |
41 | |
42 // Sets all the bits to true or false. | |
43 void SetAll(bool value) { | |
44 memset(map_, (value ? 0xFF : 0x00), array_size_ * sizeof(*map_)); | |
45 } | |
46 | |
47 // Clears all bits in the bitmap | |
48 void Clear() { SetAll(false); } | |
49 | |
50 // Sets the value, gets the value or toggles the value of a given bit. | |
51 void Set(int index, bool value); | |
52 bool Get(int index) const; | |
53 void Toggle(int index); | |
54 | |
55 // Directly sets an element of the internal map. Requires |array_index| < | |
56 // ArraySize(); | |
57 void SetMapElement(int array_index, uint32 value); | |
58 | |
59 // Gets an entry of the internal map. Requires array_index < | |
60 // ArraySize() | |
61 uint32 GetMapElement(int array_index) const; | |
62 | |
63 // Directly sets the whole internal map. |size| is the number of 32-bit words | |
64 // to set from |map|. If |size| > array_size(), it ignores the end of |map|. | |
65 void SetMap(const uint32* map, int size); | |
66 | |
67 // Gets a pointer to the internal map. | |
68 const uint32* GetMap() const { return map_; } | |
69 | |
70 // Sets a range of bits to |value|. | |
71 void SetRange(int begin, int end, bool value); | |
72 | |
73 // Returns true if any bit between begin inclusive and end exclusive is set. | |
74 // 0 <= |begin| <= |end| <= Size() is required. | |
75 bool TestRange(int begin, int end, bool value) const; | |
76 | |
77 // Scans bits starting at bit *|index|, looking for a bit set to |value|. If | |
78 // it finds that bit before reaching bit index |limit|, sets *|index| to the | |
79 // bit index and returns true. Otherwise returns false. | |
80 // Requires |limit| <= Size(). | |
81 // | |
82 // Note that to use these methods in a loop you must increment the index | |
83 // after each use, as in: | |
84 // | |
85 // for (int index = 0 ; map.FindNextBit(&index, limit, value) ; ++index) { | |
86 // DoSomethingWith(index); | |
87 // } | |
88 bool FindNextBit(int* index, int limit, bool value) const; | |
89 | |
90 // Finds the first offset >= *|index| and < |limit| that has its bit set. | |
91 // See FindNextBit() for more info. | |
92 bool FindNextSetBitBeforeLimit(int* index, int limit) const { | |
93 return FindNextBit(index, limit, true); | |
94 } | |
95 | |
96 // Finds the first offset >= *|index| that has its bit set. | |
97 // See FindNextBit() for more info. | |
98 bool FindNextSetBit(int *index) const { | |
99 return FindNextSetBitBeforeLimit(index, num_bits_); | |
100 } | |
101 | |
102 // Scans bits starting at bit *|index|, looking for a bit set to |value|. If | |
103 // it finds that bit before reaching bit index |limit|, sets *|index| to the | |
104 // bit index and then counts the number of consecutive bits set to |value| | |
105 // (before reaching |limit|), and returns that count. If no bit is found | |
106 // returns 0. Requires |limit| <= Size(). | |
107 int FindBits(int* index, int limit, bool value) const; | |
108 | |
109 // Returns number of allocated words required for a bitmap of size |num_bits|. | |
110 static int RequiredArraySize(int num_bits) { | |
111 // Force at least one allocated word. | |
112 if (num_bits <= kIntBits) | |
113 return 1; | |
114 | |
115 return (num_bits + kIntBits - 1) >> kLogIntBits; | |
116 } | |
117 | |
118 private: | |
119 static const int kIntBits = sizeof(uint32) * 8; | |
120 static const int kLogIntBits = 5; // 2^5 == 32 bits per word. | |
121 | |
122 // Sets |len| bits from |start| to |value|. All the bits to be set should be | |
123 // stored in the same word, and len < kIntBits. | |
124 void SetWordBits(int start, int len, bool value); | |
125 | |
126 uint32* map_; // The bitmap. | |
127 int num_bits_; // The upper bound of the bitmap. | |
128 int array_size_; // The physical size (in uint32s) of the bitmap. | |
129 bool alloc_; // Whether or not we allocated the memory. | |
130 | |
131 DISALLOW_COPY_AND_ASSIGN(Bitmap); | |
132 }; | |
133 | |
134 } // namespace disk_cache | |
135 | |
136 #endif // NET_DISK_CACHE_BLOCKFILE_BITMAP_H_ | |
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