Port of Android platform gesture detection code to C++

ui/events/gesture_detection/bitset_32.h

Index: ui/events/gesture_detection/bitset_32.h
diff --git a/ui/events/gesture_detection/bitset_32.h b/ui/events/gesture_detection/bitset_32.h
new file mode 100644
index 0000000000000000000000000000000000000000..9cb9d48aee65fd3f03c24eb6a624d390dcb581aa
--- /dev/null
+++ b/ui/events/gesture_detection/bitset_32.h
@@ -0,0 +1,128 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef UI_EVENTS_GESTURE_DETECTION_BITSET_32_H_
+#define UI_EVENTS_GESTURE_DETECTION_BITSET_32_H_
+
+#include "base/basictypes.h"
+
+namespace ui {
+
+// Port of BitSet32 from Android
+// * platform/system/core/include/utils/BitSet.h
+// * Change-Id: I9bbf41f9d2d4a2593b0e6d7d8be7e283f985bade
+// * Please update the Change-Id as upstream Android changes are pulled.
+struct BitSet32 {
+  uint32_t value;
+
+  inline BitSet32() : value(0) {}
+  explicit inline BitSet32(uint32_t value) : value(value) {}
+
+  // Gets the value associated with a particular bit index.
+  static inline uint32_t value_for_bit(uint32_t n) { return 0x80000000 >> n; }
+
+  // Clears the bit set.
+  inline void clear() { value = 0; }
+
+  // Returns the number of marked bits in the set.
+  inline uint32_t count() const { return popcnt(value); }
+
+  // Returns true if the bit set does not contain any marked bits.
+  inline bool is_empty() const { return !value; }
+
+  // Returns true if the bit set does not contain any unmarked bits.
+  inline bool is_full() const { return value == 0xffffffff; }
+
+  // Returns true if the specified bit is marked.
+  inline bool has_bit(uint32_t n) const {
+    return (value & value_for_bit(n)) != 0;
+  }
+
+  // Marks the specified bit.
+  inline void mark_bit(uint32_t n) { value |= value_for_bit(n); }
+
+  // Clears the specified bit.
+  inline void clear_bit(uint32_t n) { value &= ~value_for_bit(n); }
+
+  // Finds the first marked bit in the set.
+  // Result is undefined if all bits are unmarked.
+  inline uint32_t first_marked_bit() const { return clz(value); }
+
+  // Finds the first unmarked bit in the set.
+  // Result is undefined if all bits are marked.
+  inline uint32_t first_unmarked_bit() const { return clz(~value); }
+
+  // Finds the last marked bit in the set.
+  // Result is undefined if all bits are unmarked.
+  inline uint32_t last_marked_bit() const { return 31 - ctz(value); }
+
+  // Finds the first marked bit in the set and clears it.  Returns the bit
+  // index.
+  // Result is undefined if all bits are unmarked.
+  inline uint32_t clear_first_marked_bit() {
+    uint32_t n = first_marked_bit();
+    clear_bit(n);
+    return n;
+  }
+
+  // Finds the first unmarked bit in the set and marks it.  Returns the bit
+  // index.
+  // Result is undefined if all bits are marked.
+  inline uint32_t mark_first_unmarked_bit() {
+    uint32_t n = first_unmarked_bit();
+    mark_bit(n);
+    return n;
+  }
+
+  // Finds the last marked bit in the set and clears it.  Returns the bit index.
+  // Result is undefined if all bits are unmarked.
+  inline uint32_t clear_last_marked_bit() {
+    uint32_t n = last_marked_bit();
+    clear_bit(n);
+    return n;
+  }
+
+  // Gets the inde of the specified bit in the set, which is the number of
+  // marked bits that appear before the specified bit.
+  inline uint32_t get_index_of_bit(uint32_t n) const {
+    return popcnt(value & ~(0xffffffffUL >> n));
+  }
+
+  inline bool operator==(const BitSet32& other) const {
+    return value == other.value;
+  }
+  inline bool operator!=(const BitSet32& other) const {
+    return value != other.value;
+  }
+
+ private:
+#if defined(COMPILER_GCC) || defined(__clang__)
+  static inline uint32_t popcnt(uint32_t v) { return __builtin_popcount(v); }
+  static inline uint32_t clz(uint32_t v) { return __builtin_clz(v); }
+  static inline uint32_t ctz(uint32_t v) { return __builtin_ctz(v); }
+#else
+  // http://graphics.stanford.edu/~seander/bithacks.html#CountBitsSetParallel
+  static inline uint32_t popcnt(uint32_t v) {
+    v = v - ((v >> 1) & 0x55555555);
+    v = (v & 0x33333333) + ((v >> 2) & 0x33333333);
+    return (((v + (v >> 4)) & 0x0F0F0F0F) * 0x01010101) >> 24;
+  }
+  // TODO(jdduke): Use intrinsics (BitScan{Forward,Reverse}) with MSVC.
+  static inline uint32_t clz(uint32_t v) {
+    v |= (v >> 1);
+    v |= (v >> 2);
+    v |= (v >> 4);
+    v |= (v >> 8);
+    v |= (v >> 16);
+    return 32 - popcnt(v);
+  }
+  static inline uint32_t ctz(uint32_t v) {
+    return popcnt((v & static_cast<uint32_t>(-static_cast<int>(v))) - 1);
+  }
+#endif
+};
+
+}  // namespace ui
+
+#endif  // UI_EVENTS_GESTURE_DETECTION_BITSET_32_H_