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      1 /*
      2  * Copyright (C) 2010 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 #ifndef UTILS_BITSET_H
     18 #define UTILS_BITSET_H
     19 
     20 #include <stdint.h>
     21 #include <utils/TypeHelpers.h>
     22 
     23 /*
     24  * Contains some bit manipulation helpers.
     25  */
     26 
     27 namespace android {
     28 
     29 // A simple set of 32 bits that can be individually marked or cleared.
     30 struct BitSet32 {
     31     uint32_t value;
     32 
     33     inline BitSet32() : value(0) { }
     34     explicit inline BitSet32(uint32_t value) : value(value) { }
     35 
     36     // Gets the value associated with a particular bit index.
     37     static inline uint32_t valueForBit(uint32_t n) { return 0x80000000 >> n; }
     38 
     39     // Clears the bit set.
     40     inline void clear() { value = 0; }
     41 
     42     // Returns the number of marked bits in the set.
     43     inline uint32_t count() const { return __builtin_popcount(value); }
     44 
     45     // Returns true if the bit set does not contain any marked bits.
     46     inline bool isEmpty() const { return ! value; }
     47 
     48     // Returns true if the bit set does not contain any unmarked bits.
     49     inline bool isFull() const { return value == 0xffffffff; }
     50 
     51     // Returns true if the specified bit is marked.
     52     inline bool hasBit(uint32_t n) const { return value & valueForBit(n); }
     53 
     54     // Marks the specified bit.
     55     inline void markBit(uint32_t n) { value |= valueForBit(n); }
     56 
     57     // Clears the specified bit.
     58     inline void clearBit(uint32_t n) { value &= ~ valueForBit(n); }
     59 
     60     // Finds the first marked bit in the set.
     61     // Result is undefined if all bits are unmarked.
     62     inline uint32_t firstMarkedBit() const { return __builtin_clz(value); }
     63 
     64     // Finds the first unmarked bit in the set.
     65     // Result is undefined if all bits are marked.
     66     inline uint32_t firstUnmarkedBit() const { return __builtin_clz(~ value); }
     67 
     68     // Finds the last marked bit in the set.
     69     // Result is undefined if all bits are unmarked.
     70     inline uint32_t lastMarkedBit() const { return 31 - __builtin_ctz(value); }
     71 
     72     // Finds the first marked bit in the set and clears it.  Returns the bit index.
     73     // Result is undefined if all bits are unmarked.
     74     inline uint32_t clearFirstMarkedBit() {
     75         uint32_t n = firstMarkedBit();
     76         clearBit(n);
     77         return n;
     78     }
     79 
     80     // Finds the first unmarked bit in the set and marks it.  Returns the bit index.
     81     // Result is undefined if all bits are marked.
     82     inline uint32_t markFirstUnmarkedBit() {
     83         uint32_t n = firstUnmarkedBit();
     84         markBit(n);
     85         return n;
     86     }
     87 
     88     // Finds the last marked bit in the set and clears it.  Returns the bit index.
     89     // Result is undefined if all bits are unmarked.
     90     inline uint32_t clearLastMarkedBit() {
     91         uint32_t n = lastMarkedBit();
     92         clearBit(n);
     93         return n;
     94     }
     95 
     96     // Gets the index of the specified bit in the set, which is the number of
     97     // marked bits that appear before the specified bit.
     98     inline uint32_t getIndexOfBit(uint32_t n) const {
     99         return __builtin_popcount(value & ~(0xffffffffUL >> n));
    100     }
    101 
    102     inline bool operator== (const BitSet32& other) const { return value == other.value; }
    103     inline bool operator!= (const BitSet32& other) const { return value != other.value; }
    104     inline BitSet32 operator& (const BitSet32& other) const {
    105         return BitSet32(value & other.value);
    106     }
    107     inline BitSet32& operator&= (const BitSet32& other) {
    108         value &= other.value;
    109         return *this;
    110     }
    111     inline BitSet32 operator| (const BitSet32& other) const {
    112         return BitSet32(value | other.value);
    113     }
    114     inline BitSet32& operator|= (const BitSet32& other) {
    115         value |= other.value;
    116         return *this;
    117     }
    118 };
    119 
    120 ANDROID_BASIC_TYPES_TRAITS(BitSet32)
    121 
    122 } // namespace android
    123 
    124 #endif // UTILS_BITSET_H
    125