/*
* Copyright (C) 2013 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef ART_RUNTIME_BASE_BIT_VECTOR_H_
#define ART_RUNTIME_BASE_BIT_VECTOR_H_
#include <stdint.h>
#include <stddef.h>
#include "allocator.h"
#include "base/logging.h"
#include "utils.h"
namespace art {
/*
* Expanding bitmap, used for tracking resources. Bits are numbered starting
* from zero. All operations on a BitVector are unsynchronized.
*/
class BitVector {
public:
class IndexContainer;
/**
* @brief Convenient iterator across the indexes of the BitVector's set bits.
*
* @details IndexIterator is a Forward iterator (C++11: 24.2.5) from the lowest
* to the highest index of the BitVector's set bits. Instances can be retrieved
* only through BitVector::Indexes() which returns an IndexContainer wrapper
* object with begin() and end() suitable for range-based loops:
* for (uint32_t idx : bit_vector.Indexes()) {
* // Use idx.
* }
*/
class IndexIterator
: std::iterator<std::forward_iterator_tag, uint32_t, ptrdiff_t, void, uint32_t> {
public:
bool operator==(const IndexIterator& other) const {
DCHECK(bit_storage_ == other.bit_storage_);
DCHECK_EQ(storage_size_, other.storage_size_);
return bit_index_ == other.bit_index_;
}
bool operator!=(const IndexIterator& other) const {
return !(*this == other);
}
int operator*() const {
DCHECK_LT(bit_index_, BitSize());
return bit_index_;
}
IndexIterator& operator++() {
DCHECK_LT(bit_index_, BitSize());
bit_index_ = FindIndex(bit_index_ + 1u);
return *this;
}
IndexIterator operator++(int) {
IndexIterator result(*this);
++*this;
return result;
}
// Helper function to check for end without comparing with bit_vector.Indexes().end().
bool Done() const {
return bit_index_ == BitSize();
}
private:
struct begin_tag { };
struct end_tag { };
IndexIterator(const BitVector* bit_vector, begin_tag)
: bit_storage_(bit_vector->GetRawStorage()),
storage_size_(bit_vector->storage_size_),
bit_index_(FindIndex(0u)) { }
IndexIterator(const BitVector* bit_vector, end_tag)
: bit_storage_(bit_vector->GetRawStorage()),
storage_size_(bit_vector->storage_size_),
bit_index_(BitSize()) { }
uint32_t BitSize() const {
return storage_size_ * kWordBits;
}
uint32_t FindIndex(uint32_t start_index) const {
DCHECK_LE(start_index, BitSize());
uint32_t word_index = start_index / kWordBits;
if (UNLIKELY(word_index == storage_size_)) {
return start_index;
}
uint32_t word = bit_storage_[word_index];
// Mask out any bits in the first word we've already considered.
word &= static_cast<uint32_t>(-1) << (start_index & 0x1f);
while (word == 0u) {
++word_index;
if (UNLIKELY(word_index == storage_size_)) {
return BitSize();
}
word = bit_storage_[word_index];
}
return word_index * 32u + CTZ(word);
}
const uint32_t* const bit_storage_;
const uint32_t storage_size_; // Size of vector in words.
uint32_t bit_index_; // Current index (size in bits).
friend class BitVector::IndexContainer;
};
/**
* @brief BitVector wrapper class for iteration across indexes of set bits.
*/
class IndexContainer {
public:
explicit IndexContainer(const BitVector* bit_vector) : bit_vector_(bit_vector) { }
IndexIterator begin() const {
return IndexIterator(bit_vector_, IndexIterator::begin_tag());
}
IndexIterator end() const {
return IndexIterator(bit_vector_, IndexIterator::end_tag());
}
private:
const BitVector* const bit_vector_;
};
BitVector(uint32_t start_bits,
bool expandable,
Allocator* allocator,
uint32_t storage_size = 0,
uint32_t* storage = nullptr);
virtual ~BitVector();
void SetBit(uint32_t num);
void ClearBit(uint32_t num);
bool IsBitSet(uint32_t num) const;
void ClearAllBits();
void SetInitialBits(uint32_t num_bits);
void Copy(const BitVector* src);
void Intersect(const BitVector* src2);
bool Union(const BitVector* src);
// Set bits of union_with that are not in not_in.
bool UnionIfNotIn(const BitVector* union_with, const BitVector* not_in);
void Subtract(const BitVector* src);
// Are we equal to another bit vector? Note: expandability attributes must also match.
bool Equal(const BitVector* src) {
return (storage_size_ == src->GetStorageSize()) &&
(expandable_ == src->IsExpandable()) &&
(memcmp(storage_, src->GetRawStorage(), storage_size_ * sizeof(uint32_t)) == 0);
}
/**
* @brief Are all the bits set the same?
* @details expandability and size can differ as long as the same bits are set.
*/
bool SameBitsSet(const BitVector *src);
uint32_t NumSetBits() const;
// Number of bits set in range [0, end).
uint32_t NumSetBits(uint32_t end) const;
IndexContainer Indexes() const {
return IndexContainer(this);
}
uint32_t GetStorageSize() const { return storage_size_; }
bool IsExpandable() const { return expandable_; }
uint32_t GetRawStorageWord(size_t idx) const { return storage_[idx]; }
uint32_t* GetRawStorage() { return storage_; }
const uint32_t* GetRawStorage() const { return storage_; }
size_t GetSizeOf() const { return storage_size_ * kWordBytes; }
/**
* @return the highest bit set, -1 if none are set
*/
int GetHighestBitSet() const;
// Is bit set in storage. (No range check.)
static bool IsBitSet(const uint32_t* storage, uint32_t num);
// Number of bits set in range [0, end) in storage. (No range check.)
static uint32_t NumSetBits(const uint32_t* storage, uint32_t end);
bool EnsureSizeAndClear(unsigned int num);
void Dump(std::ostream& os, const char* prefix) const;
/**
* @brief last_entry is this the last entry for the dot dumping
* @details if not, a "|" is appended to the dump.
*/
void DumpDot(FILE* file, const char* prefix, bool last_entry = false) const;
/**
* @brief last_entry is this the last entry for the dot dumping
* @details if not, a "|" is appended to the dump.
*/
void DumpIndicesDot(FILE* file, const char* prefix, bool last_entry = false) const;
protected:
/**
* @brief Dump the bitvector into buffer in a 00101..01 format.
* @param buffer the ostringstream used to dump the bitvector into.
*/
void DumpHelper(const char* prefix, std::ostringstream& buffer) const;
/**
* @brief Dump the bitvector in a 1 2 5 8 format, where the numbers are the bit set.
* @param buffer the ostringstream used to dump the bitvector into.
*/
void DumpIndicesHelper(const char* prefix, std::ostringstream& buffer) const;
/**
* @brief Wrapper to perform the bitvector dumping with the .dot format.
* @param buffer the ostringstream used to dump the bitvector into.
*/
void DumpDotHelper(bool last_entry, FILE* file, std::ostringstream& buffer) const;
private:
static constexpr uint32_t kWordBytes = sizeof(uint32_t);
static constexpr uint32_t kWordBits = kWordBytes * 8;
Allocator* const allocator_;
const bool expandable_; // expand bitmap if we run out?
uint32_t storage_size_; // current size, in 32-bit words.
uint32_t* storage_;
};
} // namespace art
#endif // ART_RUNTIME_BASE_BIT_VECTOR_H_