1 // Copyright 2011 The Chromium Authors 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 <stdint.h> 9 #include <string.h> 10 11 #include <memory> 12 13 #include "base/memory/raw_ptr.h" 14 #include "net/base/net_export.h" 15 16 namespace disk_cache { 17 18 // This class provides support for simple maps of bits. 19 class NET_EXPORT_PRIVATE Bitmap { 20 public: 21 Bitmap(); 22 23 // This constructor will allocate on a uint32_t boundary. If |clear_bits| is 24 // false, the bitmap bits will not be initialized. 25 Bitmap(int num_bits, bool clear_bits); 26 27 // Constructs a Bitmap with the actual storage provided by the caller. |map| 28 // has to be valid until this object destruction. |num_bits| is the number of 29 // bits in the bitmap, and |num_words| is the size of |map| in 32-bit words. 30 Bitmap(uint32_t* map, int num_bits, int num_words); 31 32 Bitmap(const Bitmap&) = delete; 33 Bitmap& operator=(const Bitmap&) = delete; 34 35 ~Bitmap(); 36 37 // Resizes the bitmap. 38 // If |num_bits| < Size(), the extra bits will be discarded. 39 // If |num_bits| > Size(), the extra bits will be filled with zeros if 40 // |clear_bits| is true. 41 // This object cannot be using memory provided during construction. 42 void Resize(int num_bits, bool clear_bits); 43 44 // Returns the number of bits in the bitmap. Size()45 int Size() const { return num_bits_; } 46 47 // Returns the number of 32-bit words in the bitmap. ArraySize()48 int ArraySize() const { return array_size_; } 49 50 // Sets all the bits to true or false. SetAll(bool value)51 void SetAll(bool value) { 52 memset(map_, (value ? 0xFF : 0x00), array_size_ * sizeof(*map_)); 53 } 54 55 // Clears all bits in the bitmap Clear()56 void Clear() { SetAll(false); } 57 58 // Sets the value, gets the value or toggles the value of a given bit. 59 void Set(int index, bool value); 60 bool Get(int index) const; 61 void Toggle(int index); 62 63 // Directly sets an element of the internal map. Requires |array_index| < 64 // ArraySize(); 65 void SetMapElement(int array_index, uint32_t value); 66 67 // Gets an entry of the internal map. Requires array_index < 68 // ArraySize() 69 uint32_t GetMapElement(int array_index) const; 70 71 // Directly sets the whole internal map. |size| is the number of 32-bit words 72 // to set from |map|. If |size| > array_size(), it ignores the end of |map|. 73 void SetMap(const uint32_t* map, int size); 74 75 // Gets a pointer to the internal map. GetMap()76 const uint32_t* GetMap() const { return map_; } 77 78 // Sets a range of bits to |value|. 79 void SetRange(int begin, int end, bool value); 80 81 // Returns true if any bit between begin inclusive and end exclusive is set. 82 // 0 <= |begin| <= |end| <= Size() is required. 83 bool TestRange(int begin, int end, bool value) const; 84 85 // Scans bits starting at bit *|index|, looking for a bit set to |value|. If 86 // it finds that bit before reaching bit index |limit|, sets *|index| to the 87 // bit index and returns true. Otherwise returns false. 88 // Requires |limit| <= Size(). 89 // 90 // Note that to use these methods in a loop you must increment the index 91 // after each use, as in: 92 // 93 // for (int index = 0 ; map.FindNextBit(&index, limit, value) ; ++index) { 94 // DoSomethingWith(index); 95 // } 96 bool FindNextBit(int* index, int limit, bool value) const; 97 98 // Finds the first offset >= *|index| and < |limit| that has its bit set. 99 // See FindNextBit() for more info. FindNextSetBitBeforeLimit(int * index,int limit)100 bool FindNextSetBitBeforeLimit(int* index, int limit) const { 101 return FindNextBit(index, limit, true); 102 } 103 104 // Finds the first offset >= *|index| that has its bit set. 105 // See FindNextBit() for more info. FindNextSetBit(int * index)106 bool FindNextSetBit(int *index) const { 107 return FindNextSetBitBeforeLimit(index, num_bits_); 108 } 109 110 // Scans bits starting at bit *|index|, looking for a bit set to |value|. If 111 // it finds that bit before reaching bit index |limit|, sets *|index| to the 112 // bit index and then counts the number of consecutive bits set to |value| 113 // (before reaching |limit|), and returns that count. If no bit is found 114 // returns 0. Requires |limit| <= Size(). 115 int FindBits(int* index, int limit, bool value) const; 116 117 // Returns number of allocated words required for a bitmap of size |num_bits|. RequiredArraySize(int num_bits)118 static int RequiredArraySize(int num_bits) { 119 // Force at least one allocated word. 120 if (num_bits <= kIntBits) 121 return 1; 122 123 return (num_bits + kIntBits - 1) >> kLogIntBits; 124 } 125 126 private: 127 static const int kIntBits = sizeof(uint32_t) * 8; 128 static const int kLogIntBits = 5; // 2^5 == 32 bits per word. 129 130 // Sets |len| bits from |start| to |value|. All the bits to be set should be 131 // stored in the same word, and len < kIntBits. 132 void SetWordBits(int start, int len, bool value); 133 134 int num_bits_ = 0; // The upper bound of the bitmap. 135 int array_size_ = 0; // The physical size (in uint32s) of the bitmap. 136 std::unique_ptr<uint32_t[]> allocated_map_; // The allocated data. 137 raw_ptr<uint32_t, AllowPtrArithmetic> map_ = nullptr; // The bitmap. 138 }; 139 140 } // namespace disk_cache 141 142 #endif // NET_DISK_CACHE_BLOCKFILE_BITMAP_H_ 143