308 lines
8.9 KiB
C++
308 lines
8.9 KiB
C++
/*
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* Copyright (C) 2013 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef ART_RUNTIME_BASE_BIT_VECTOR_H_
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#define ART_RUNTIME_BASE_BIT_VECTOR_H_
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#include <stdint.h>
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#include <iterator>
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#include "base/bit_utils.h"
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#include "globals.h"
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namespace art {
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class Allocator;
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/*
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* Expanding bitmap, used for tracking resources. Bits are numbered starting
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* from zero. All operations on a BitVector are unsynchronized.
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*/
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class BitVector {
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public:
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class IndexContainer;
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/**
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* @brief Convenient iterator across the indexes of the BitVector's set bits.
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*
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* @details IndexIterator is a Forward iterator (C++11: 24.2.5) from the lowest
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* to the highest index of the BitVector's set bits. Instances can be retrieved
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* only through BitVector::Indexes() which returns an IndexContainer wrapper
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* object with begin() and end() suitable for range-based loops:
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* for (uint32_t idx : bit_vector.Indexes()) {
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* // Use idx.
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* }
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*/
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class IndexIterator :
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std::iterator<std::forward_iterator_tag, uint32_t, ptrdiff_t, void, uint32_t> {
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public:
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bool operator==(const IndexIterator& other) const;
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bool operator!=(const IndexIterator& other) const {
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return !(*this == other);
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}
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uint32_t operator*() const;
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IndexIterator& operator++();
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IndexIterator operator++(int);
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// Helper function to check for end without comparing with bit_vector.Indexes().end().
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bool Done() const {
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return bit_index_ == BitSize();
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}
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private:
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struct begin_tag { };
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struct end_tag { };
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IndexIterator(const BitVector* bit_vector, begin_tag)
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: bit_storage_(bit_vector->GetRawStorage()),
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storage_size_(bit_vector->storage_size_),
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bit_index_(FindIndex(0u)) { }
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IndexIterator(const BitVector* bit_vector, end_tag)
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: bit_storage_(bit_vector->GetRawStorage()),
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storage_size_(bit_vector->storage_size_),
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bit_index_(BitSize()) { }
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uint32_t BitSize() const {
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return storage_size_ * kWordBits;
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}
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uint32_t FindIndex(uint32_t start_index) const;
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const uint32_t* const bit_storage_;
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const uint32_t storage_size_; // Size of vector in words.
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uint32_t bit_index_; // Current index (size in bits).
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friend class BitVector::IndexContainer;
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};
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/**
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* @brief BitVector wrapper class for iteration across indexes of set bits.
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*/
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class IndexContainer {
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public:
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explicit IndexContainer(const BitVector* bit_vector) : bit_vector_(bit_vector) { }
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IndexIterator begin() const {
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return IndexIterator(bit_vector_, IndexIterator::begin_tag());
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}
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IndexIterator end() const {
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return IndexIterator(bit_vector_, IndexIterator::end_tag());
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}
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private:
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const BitVector* const bit_vector_;
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};
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// MoveConstructible but not MoveAssignable, CopyConstructible or CopyAssignable.
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BitVector(const BitVector& other) = delete;
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BitVector& operator=(const BitVector& other) = delete;
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BitVector(BitVector&& other)
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: storage_(other.storage_),
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storage_size_(other.storage_size_),
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allocator_(other.allocator_),
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expandable_(other.expandable_) {
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other.storage_ = nullptr;
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other.storage_size_ = 0u;
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}
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BitVector(uint32_t start_bits,
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bool expandable,
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Allocator* allocator);
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BitVector(bool expandable,
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Allocator* allocator,
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uint32_t storage_size,
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uint32_t* storage);
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BitVector(const BitVector& src,
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bool expandable,
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Allocator* allocator);
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virtual ~BitVector();
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// The number of words necessary to encode bits.
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static constexpr uint32_t BitsToWords(uint32_t bits) {
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return RoundUp(bits, kWordBits) / kWordBits;
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}
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// Mark the specified bit as "set".
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void SetBit(uint32_t idx) {
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/*
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* TUNING: this could have pathologically bad growth/expand behavior. Make sure we're
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* not using it badly or change resize mechanism.
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*/
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if (idx >= storage_size_ * kWordBits) {
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EnsureSize(idx);
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}
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storage_[WordIndex(idx)] |= BitMask(idx);
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}
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// Mark the specified bit as "unset".
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void ClearBit(uint32_t idx) {
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// If the index is over the size, we don't have to do anything, it is cleared.
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if (idx < storage_size_ * kWordBits) {
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// Otherwise, go ahead and clear it.
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storage_[WordIndex(idx)] &= ~BitMask(idx);
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}
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}
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// Determine whether or not the specified bit is set.
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bool IsBitSet(uint32_t idx) const {
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// If the index is over the size, whether it is expandable or not, this bit does not exist:
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// thus it is not set.
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return (idx < (storage_size_ * kWordBits)) && IsBitSet(storage_, idx);
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}
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// Mark all bits bit as "clear".
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void ClearAllBits();
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// Mark specified number of bits as "set". Cannot set all bits like ClearAll since there might
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// be unused bits - setting those to one will confuse the iterator.
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void SetInitialBits(uint32_t num_bits);
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void Copy(const BitVector* src);
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// Intersect with another bit vector.
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void Intersect(const BitVector* src2);
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// Union with another bit vector.
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bool Union(const BitVector* src);
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// Set bits of union_with that are not in not_in.
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bool UnionIfNotIn(const BitVector* union_with, const BitVector* not_in);
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void Subtract(const BitVector* src);
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// Are we equal to another bit vector? Note: expandability attributes must also match.
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bool Equal(const BitVector* src) const;
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/**
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* @brief Are all the bits set the same?
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* @details expandability and size can differ as long as the same bits are set.
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*/
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bool SameBitsSet(const BitVector *src) const;
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bool IsSubsetOf(const BitVector *other) const;
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// Count the number of bits that are set.
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uint32_t NumSetBits() const;
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// Count the number of bits that are set in range [0, end).
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uint32_t NumSetBits(uint32_t end) const;
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IndexContainer Indexes() const {
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return IndexContainer(this);
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}
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uint32_t GetStorageSize() const {
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return storage_size_;
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}
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bool IsExpandable() const {
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return expandable_;
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}
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uint32_t GetRawStorageWord(size_t idx) const {
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return storage_[idx];
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}
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uint32_t* GetRawStorage() {
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return storage_;
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}
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const uint32_t* GetRawStorage() const {
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return storage_;
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}
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size_t GetSizeOf() const {
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return storage_size_ * kWordBytes;
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}
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/**
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* @return the highest bit set, -1 if none are set
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*/
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int GetHighestBitSet() const;
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// Minimum number of bits required to store this vector, 0 if none are set.
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size_t GetNumberOfBits() const {
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return GetHighestBitSet() + 1;
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}
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// Is bit set in storage. (No range check.)
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static bool IsBitSet(const uint32_t* storage, uint32_t idx) {
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return (storage[WordIndex(idx)] & BitMask(idx)) != 0;
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}
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// Number of bits set in range [0, end) in storage. (No range check.)
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static uint32_t NumSetBits(const uint32_t* storage, uint32_t end);
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// Fill given memory region with the contents of the vector and zero padding.
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void CopyTo(void* dst, size_t len) const {
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DCHECK_LE(static_cast<size_t>(GetHighestBitSet() + 1), len * kBitsPerByte);
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size_t vec_len = GetSizeOf();
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if (vec_len < len) {
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void* dst_padding = reinterpret_cast<uint8_t*>(dst) + vec_len;
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memcpy(dst, storage_, vec_len);
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memset(dst_padding, 0, len - vec_len);
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} else {
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memcpy(dst, storage_, len);
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}
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}
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void Dump(std::ostream& os, const char* prefix) const;
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Allocator* GetAllocator() const;
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private:
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/**
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* @brief Dump the bitvector into buffer in a 00101..01 format.
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* @param buffer the ostringstream used to dump the bitvector into.
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*/
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void DumpHelper(const char* prefix, std::ostringstream& buffer) const;
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// Ensure there is space for a bit at idx.
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void EnsureSize(uint32_t idx);
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// The index of the word within storage.
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static constexpr uint32_t WordIndex(uint32_t idx) {
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return idx >> 5;
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}
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// A bit mask to extract the bit for the given index.
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static constexpr uint32_t BitMask(uint32_t idx) {
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return 1 << (idx & 0x1f);
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}
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static constexpr uint32_t kWordBytes = sizeof(uint32_t);
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static constexpr uint32_t kWordBits = kWordBytes * 8;
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uint32_t* storage_; // The storage for the bit vector.
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uint32_t storage_size_; // Current size, in 32-bit words.
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Allocator* const allocator_; // Allocator if expandable.
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const bool expandable_; // Should the bitmap expand if too small?
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};
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} // namespace art
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#endif // ART_RUNTIME_BASE_BIT_VECTOR_H_
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