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/containers/span.h" 14 #include "base/memory/raw_ptr.h" 15 #include "net/base/net_export.h" 16 17 namespace disk_cache { 18 19 // This class provides support for simple maps of bits. 20 class NET_EXPORT_PRIVATE Bitmap { 21 public: 22 Bitmap(); 23 24 // This constructor will allocate on a uint32_t boundary. If |clear_bits| is 25 // false, the bitmap bits will not be initialized. 26 Bitmap(int num_bits, bool clear_bits); 27 28 // Constructs a Bitmap with the actual storage provided by the caller. |map| 29 // has to be valid until this object destruction. |num_bits| is the number of 30 // bits in the bitmap, and |num_words| is the size of |map| in 32-bit words. 31 Bitmap(uint32_t* map, int num_bits, int num_words); 32 33 Bitmap(const Bitmap&) = delete; 34 Bitmap& operator=(const Bitmap&) = delete; 35 36 ~Bitmap(); 37 38 // Resizes the bitmap. 39 // If |num_bits| < Size(), the extra bits will be discarded. 40 // If |num_bits| > Size(), the extra bits will be filled with zeros if 41 // |clear_bits| is true. 42 // This object cannot be using memory provided during construction. 43 void Resize(int num_bits, bool clear_bits); 44 45 // Returns the number of bits in the bitmap. Size()46 int Size() const { return num_bits_; } 47 48 // Returns the number of 32-bit words in the bitmap. ArraySize()49 int ArraySize() const { return array_size_; } 50 51 // Sets all the bits to true or false. SetAll(bool value)52 void SetAll(bool value) { 53 memset(map_, (value ? 0xFF : 0x00), array_size_ * sizeof(*map_)); 54 } 55 56 // Clears all bits in the bitmap Clear()57 void Clear() { SetAll(false); } 58 59 // Sets the value, gets the value or toggles the value of a given bit. 60 void Set(int index, bool value); 61 bool Get(int index) const; 62 void Toggle(int index); 63 64 // Directly sets an element of the internal map. Requires |array_index| < 65 // ArraySize(); 66 void SetMapElement(int array_index, uint32_t value); 67 68 // Gets an entry of the internal map. Requires array_index < 69 // ArraySize() 70 uint32_t GetMapElement(int array_index) const; 71 72 // Directly sets the whole internal map. |size| is the number of 32-bit words 73 // to set from |map|. If |size| > array_size(), it ignores the end of |map|. 74 void SetMap(const uint32_t* map, int size); 75 76 // Gets a pointer to the internal map. GetMap()77 const uint32_t* GetMap() const { return map_; } 78 79 // Gets a span describing the internal map. GetSpan()80 base::span<const uint32_t> GetSpan() const { 81 return base::make_span(GetMap(), static_cast<size_t>(ArraySize())); 82 } 83 84 // Sets a range of bits to |value|. 85 void SetRange(int begin, int end, bool value); 86 87 // Returns true if any bit between begin inclusive and end exclusive is set. 88 // 0 <= |begin| <= |end| <= Size() is required. 89 bool TestRange(int begin, int end, bool value) const; 90 91 // Scans bits starting at bit *|index|, looking for a bit set to |value|. If 92 // it finds that bit before reaching bit index |limit|, sets *|index| to the 93 // bit index and returns true. Otherwise returns false. 94 // Requires |limit| <= Size(). 95 // 96 // Note that to use these methods in a loop you must increment the index 97 // after each use, as in: 98 // 99 // for (int index = 0 ; map.FindNextBit(&index, limit, value) ; ++index) { 100 // DoSomethingWith(index); 101 // } 102 bool FindNextBit(int* index, int limit, bool value) const; 103 104 // Finds the first offset >= *|index| and < |limit| that has its bit set. 105 // See FindNextBit() for more info. FindNextSetBitBeforeLimit(int * index,int limit)106 bool FindNextSetBitBeforeLimit(int* index, int limit) const { 107 return FindNextBit(index, limit, true); 108 } 109 110 // Finds the first offset >= *|index| that has its bit set. 111 // See FindNextBit() for more info. FindNextSetBit(int * index)112 bool FindNextSetBit(int *index) const { 113 return FindNextSetBitBeforeLimit(index, num_bits_); 114 } 115 116 // Scans bits starting at bit *|index|, looking for a bit set to |value|. If 117 // it finds that bit before reaching bit index |limit|, sets *|index| to the 118 // bit index and then counts the number of consecutive bits set to |value| 119 // (before reaching |limit|), and returns that count. If no bit is found 120 // returns 0. Requires |limit| <= Size(). 121 int FindBits(int* index, int limit, bool value) const; 122 123 // Returns number of allocated words required for a bitmap of size |num_bits|. RequiredArraySize(int num_bits)124 static int RequiredArraySize(int num_bits) { 125 // Force at least one allocated word. 126 if (num_bits <= kIntBits) 127 return 1; 128 129 return (num_bits + kIntBits - 1) >> kLogIntBits; 130 } 131 132 private: 133 static const int kIntBits = sizeof(uint32_t) * 8; 134 static const int kLogIntBits = 5; // 2^5 == 32 bits per word. 135 136 // Sets |len| bits from |start| to |value|. All the bits to be set should be 137 // stored in the same word, and len < kIntBits. 138 void SetWordBits(int start, int len, bool value); 139 140 int num_bits_ = 0; // The upper bound of the bitmap. 141 int array_size_ = 0; // The physical size (in uint32s) of the bitmap. 142 std::unique_ptr<uint32_t[]> allocated_map_; // The allocated data. 143 raw_ptr<uint32_t, AllowPtrArithmetic> map_ = nullptr; // The bitmap. 144 }; 145 146 } // namespace disk_cache 147 148 #endif // NET_DISK_CACHE_BLOCKFILE_BITMAP_H_ 149