bitset_32.h revision a1401311d1ab56c4ed0a474bd38c108f75cb0cd9 
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
10namespace 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.
16struct 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