1 // Copyright 2014 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 UI_EVENTS_GESTURE_DETECTION_BITSET_32_H_ 6 #define UI_EVENTS_GESTURE_DETECTION_BITSET_32_H_ 7 8 #include "base/basictypes.h" 9 10 namespace ui { 11 12 // Port of BitSet32 from Android 13 // * platform/system/core/include/utils/BitSet.h 14 // * Change-Id: I9bbf41f9d2d4a2593b0e6d7d8be7e283f985bade 15 // * Please update the Change-Id as upstream Android changes are pulled. 16 struct BitSet32 { 17 uint32_t value; 18 19 inline BitSet32() : value(0) {} 20 explicit inline BitSet32(uint32_t value) : value(value) {} 21 22 // Gets the value associated with a particular bit index. 23 static inline uint32_t value_for_bit(uint32_t n) { return 0x80000000 >> n; } 24 25 // Clears the bit set. 26 inline void clear() { value = 0; } 27 28 // Returns the number of marked bits in the set. 29 inline uint32_t count() const { return popcnt(value); } 30 31 // Returns true if the bit set does not contain any marked bits. 32 inline bool is_empty() const { return !value; } 33 34 // Returns true if the bit set does not contain any unmarked bits. 35 inline bool is_full() const { return value == 0xffffffff; } 36 37 // Returns true if the specified bit is marked. 38 inline bool has_bit(uint32_t n) const { 39 return (value & value_for_bit(n)) != 0; 40 } 41 42 // Marks the specified bit. 43 inline void mark_bit(uint32_t n) { value |= value_for_bit(n); } 44 45 // Clears the specified bit. 46 inline void clear_bit(uint32_t n) { value &= ~value_for_bit(n); } 47 48 // Finds the first marked bit in the set. 49 // Result is undefined if all bits are unmarked. 50 inline uint32_t first_marked_bit() const { return clz(value); } 51 52 // Finds the first unmarked bit in the set. 53 // Result is undefined if all bits are marked. 54 inline uint32_t first_unmarked_bit() const { return clz(~value); } 55 56 // Finds the last marked bit in the set. 57 // Result is undefined if all bits are unmarked. 58 inline uint32_t last_marked_bit() const { return 31 - ctz(value); } 59 60 // Finds the first marked bit in the set and clears it. Returns the bit 61 // index. 62 // Result is undefined if all bits are unmarked. 63 inline uint32_t clear_first_marked_bit() { 64 uint32_t n = first_marked_bit(); 65 clear_bit(n); 66 return n; 67 } 68 69 // Finds the first unmarked bit in the set and marks it. Returns the bit 70 // index. 71 // Result is undefined if all bits are marked. 72 inline uint32_t mark_first_unmarked_bit() { 73 uint32_t n = first_unmarked_bit(); 74 mark_bit(n); 75 return n; 76 } 77 78 // Finds the last marked bit in the set and clears it. Returns the bit index. 79 // Result is undefined if all bits are unmarked. 80 inline uint32_t clear_last_marked_bit() { 81 uint32_t n = last_marked_bit(); 82 clear_bit(n); 83 return n; 84 } 85 86 // Gets the inde of the specified bit in the set, which is the number of 87 // marked bits that appear before the specified bit. 88 inline uint32_t get_index_of_bit(uint32_t n) const { 89 return popcnt(value & ~(0xffffffffUL >> n)); 90 } 91 92 inline bool operator==(const BitSet32& other) const { 93 return value == other.value; 94 } 95 inline bool operator!=(const BitSet32& other) const { 96 return value != other.value; 97 } 98 99 private: 100 #if defined(COMPILER_GCC) || defined(__clang__) 101 static inline uint32_t popcnt(uint32_t v) { return __builtin_popcount(v); } 102 static inline uint32_t clz(uint32_t v) { return __builtin_clz(v); } 103 static inline uint32_t ctz(uint32_t v) { return __builtin_ctz(v); } 104 #else 105 // http://graphics.stanford.edu/~seander/bithacks.html#CountBitsSetParallel 106 static inline uint32_t popcnt(uint32_t v) { 107 v = v - ((v >> 1) & 0x55555555); 108 v = (v & 0x33333333) + ((v >> 2) & 0x33333333); 109 return (((v + (v >> 4)) & 0x0F0F0F0F) * 0x01010101) >> 24; 110 } 111 // TODO(jdduke): Use intrinsics (BitScan{Forward,Reverse}) with MSVC. 112 static inline uint32_t clz(uint32_t v) { 113 v |= (v >> 1); 114 v |= (v >> 2); 115 v |= (v >> 4); 116 v |= (v >> 8); 117 v |= (v >> 16); 118 return 32 - popcnt(v); 119 } 120 static inline uint32_t ctz(uint32_t v) { 121 return popcnt((v & static_cast<uint32_t>(-static_cast<int>(v))) - 1); 122 } 123 #endif 124 }; 125 126 } // namespace ui 127 128 #endif // UI_EVENTS_GESTURE_DETECTION_BITSET_32_H_ 129
