1 // Copyright (c) 2009 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_BITMAP_H_ 6 #define NET_DISK_CACHE_BITMAP_H_ 7 #pragma once 8 9 #include "base/basictypes.h" 10 11 namespace disk_cache { 12 13 // This class provides support for simple maps of bits. 14 class Bitmap { 15 public: Bitmap()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. Size()37 int Size() const { return num_bits_; } 38 39 // Returns the number of 32-bit words in the bitmap. ArraySize()40 int ArraySize() const { return array_size_; } 41 42 // Sets all the bits to true or false. SetAll(bool value)43 void SetAll(bool value) { 44 memset(map_, (value ? 0xFF : 0x00), array_size_ * sizeof(*map_)); 45 } 46 47 // Clears all bits in the bitmap Clear()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. GetMap()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. FindNextSetBitBeforeLimit(int * index,int limit)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. FindNextSetBit(int * index)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|. RequiredArraySize(int 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_BITMAP_H_ 137