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Side by Side Diff: net/disk_cache/blockfile/bitmap.h

Issue 992733002: Remove //net (except for Android test stuff) and sdch (Closed) Base URL: git@github.com:domokit/mojo.git@master
Patch Set: Created 5 years, 9 months ago
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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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