runtime/base/bit_vector.h - platform/art - Git at Google

 /*
  * 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 <iterator>

 #include "base/bit_utils.h"
 #include "globals.h"

 namespace art {

 class Allocator;

 /*
  * 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;

     bool operator!=(const IndexIterator& other) const {
       return !(*this == other);
     }

     uint32_t operator*() const;

     IndexIterator& operator++();

     IndexIterator operator++(int);

     // 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;
     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);

   BitVector(bool expandable,
             Allocator* allocator,
             uint32_t storage_size,
             uint32_t* storage);

   BitVector(const BitVector& src,
             bool expandable,
             Allocator* allocator);

   virtual ~BitVector();

   // The number of words necessary to encode bits.
   static constexpr uint32_t BitsToWords(uint32_t bits) {
     return RoundUp(bits, kWordBits) / kWordBits;
   }

   // Mark the specified bit as "set".
   void SetBit(uint32_t idx) {
     /*
      * TUNING: this could have pathologically bad growth/expand behavior.  Make sure we're
      * not using it badly or change resize mechanism.
      */
     if (idx >= storage_size_ * kWordBits) {
       EnsureSize(idx);
     }
     storage_[WordIndex(idx)] |= BitMask(idx);
   }

   // Mark the specified bit as "unset".
   void ClearBit(uint32_t idx) {
     // If the index is over the size, we don't have to do anything, it is cleared.
     if (idx < storage_size_ * kWordBits) {
       // Otherwise, go ahead and clear it.
       storage_[WordIndex(idx)] &= ~BitMask(idx);
     }
   }

   // Determine whether or not the specified bit is set.
   bool IsBitSet(uint32_t idx) const {
     // If the index is over the size, whether it is expandable or not, this bit does not exist:
     // thus it is not set.
     return (idx < (storage_size_ * kWordBits)) && IsBitSet(storage_, idx);
   }

   // Mark all bits bit as "clear".
   void ClearAllBits();

   // Mark specified number of bits as "set". Cannot set all bits like ClearAll since there might
   // be unused bits - setting those to one will confuse the iterator.
   void SetInitialBits(uint32_t num_bits);

   void Copy(const BitVector* src);

   // Intersect with another bit vector.
   void Intersect(const BitVector* src2);

   // Union with another bit vector.
   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) const;

   /**
    * @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) const;

   bool IsSubsetOf(const BitVector *other) const;

   // Count the number of bits that are set.
   uint32_t NumSetBits() const;

   // Count the number of bits that are 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;

   // Minimum number of bits required to store this vector, 0 if none are set.
   size_t GetNumberOfBits() const {
     return GetHighestBitSet() + 1;
   }

   // Is bit set in storage. (No range check.)
   static bool IsBitSet(const uint32_t* storage, uint32_t idx) {
     return (storage[WordIndex(idx)] & BitMask(idx)) != 0;
   }

   // Number of bits set in range [0, end) in storage. (No range check.)
   static uint32_t NumSetBits(const uint32_t* storage, uint32_t end);

   // Fill given memory region with the contents of the vector and zero padding.
   void CopyTo(void* dst, size_t len) const {
     DCHECK_LE(static_cast<size_t>(GetHighestBitSet() + 1), len * kBitsPerByte);
     size_t vec_len = GetSizeOf();
     if (vec_len < len) {
       void* dst_padding = reinterpret_cast<uint8_t*>(dst) + vec_len;
       memcpy(dst, storage_, vec_len);
       memset(dst_padding, 0, len - vec_len);
     } else {
       memcpy(dst, storage_, len);
     }
   }

   void Dump(std::ostream& os, const char* prefix) const;

   Allocator* GetAllocator() const;

  private:
   /**
    * @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;

   // Ensure there is space for a bit at idx.
   void EnsureSize(uint32_t idx);

   // The index of the word within storage.
   static constexpr uint32_t WordIndex(uint32_t idx) {
     return idx >> 5;
   }

   // A bit mask to extract the bit for the given index.
   static constexpr uint32_t BitMask(uint32_t idx) {
     return 1 << (idx & 0x1f);
   }

   static constexpr uint32_t kWordBytes = sizeof(uint32_t);
   static constexpr uint32_t kWordBits = kWordBytes * 8;

   uint32_t*  storage_;            // The storage for the bit vector.
   uint32_t   storage_size_;       // Current size, in 32-bit words.
   Allocator* const allocator_;    // Allocator if expandable.
   const bool expandable_;         // Should the bitmap expand if too small?
 };


 }  // namespace art

 #endif  // ART_RUNTIME_BASE_BIT_VECTOR_H_
	/*
	* 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 <iterator>

	#include "base/bit_utils.h"
	#include "globals.h"

	namespace art {

	class Allocator;

	/*
	* 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;

	bool operator!=(const IndexIterator& other) const {
	return !(*this == other);
	}

	uint32_t operator*() const;

	IndexIterator& operator++();

	IndexIterator operator++(int);

	// 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;
	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);

	BitVector(bool expandable,
	Allocator* allocator,
	uint32_t storage_size,
	uint32_t* storage);

	BitVector(const BitVector& src,
	bool expandable,
	Allocator* allocator);

	virtual ~BitVector();

	// The number of words necessary to encode bits.
	static constexpr uint32_t BitsToWords(uint32_t bits) {
	return RoundUp(bits, kWordBits) / kWordBits;
	}

	// Mark the specified bit as "set".
	void SetBit(uint32_t idx) {
	/*
	* TUNING: this could have pathologically bad growth/expand behavior. Make sure we're
	* not using it badly or change resize mechanism.
	*/
	if (idx >= storage_size_ * kWordBits) {
	EnsureSize(idx);
	}
	storage_[WordIndex(idx)] \|= BitMask(idx);
	}

	// Mark the specified bit as "unset".
	void ClearBit(uint32_t idx) {
	// If the index is over the size, we don't have to do anything, it is cleared.
	if (idx < storage_size_ * kWordBits) {
	// Otherwise, go ahead and clear it.
	storage_[WordIndex(idx)] &= ~BitMask(idx);
	}
	}

	// Determine whether or not the specified bit is set.
	bool IsBitSet(uint32_t idx) const {
	// If the index is over the size, whether it is expandable or not, this bit does not exist:
	// thus it is not set.
	return (idx < (storage_size_ * kWordBits)) && IsBitSet(storage_, idx);
	}

	// Mark all bits bit as "clear".
	void ClearAllBits();

	// Mark specified number of bits as "set". Cannot set all bits like ClearAll since there might
	// be unused bits - setting those to one will confuse the iterator.
	void SetInitialBits(uint32_t num_bits);

	void Copy(const BitVector* src);

	// Intersect with another bit vector.
	void Intersect(const BitVector* src2);

	// Union with another bit vector.
	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) const;

	/**
	* @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) const;

	bool IsSubsetOf(const BitVector *other) const;

	// Count the number of bits that are set.
	uint32_t NumSetBits() const;

	// Count the number of bits that are 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;

	// Minimum number of bits required to store this vector, 0 if none are set.
	size_t GetNumberOfBits() const {
	return GetHighestBitSet() + 1;
	}

	// Is bit set in storage. (No range check.)
	static bool IsBitSet(const uint32_t* storage, uint32_t idx) {
	return (storage[WordIndex(idx)] & BitMask(idx)) != 0;
	}

	// Number of bits set in range [0, end) in storage. (No range check.)
	static uint32_t NumSetBits(const uint32_t* storage, uint32_t end);

	// Fill given memory region with the contents of the vector and zero padding.
	void CopyTo(void* dst, size_t len) const {
	DCHECK_LE(static_cast<size_t>(GetHighestBitSet() + 1), len * kBitsPerByte);
	size_t vec_len = GetSizeOf();
	if (vec_len < len) {
	void* dst_padding = reinterpret_cast<uint8_t*>(dst) + vec_len;
	memcpy(dst, storage_, vec_len);
	memset(dst_padding, 0, len - vec_len);
	} else {
	memcpy(dst, storage_, len);
	}
	}

	void Dump(std::ostream& os, const char* prefix) const;

	Allocator* GetAllocator() const;

	private:
	/**
	* @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;

	// Ensure there is space for a bit at idx.
	void EnsureSize(uint32_t idx);

	// The index of the word within storage.
	static constexpr uint32_t WordIndex(uint32_t idx) {
	return idx >> 5;
	}

	// A bit mask to extract the bit for the given index.
	static constexpr uint32_t BitMask(uint32_t idx) {
	return 1 << (idx & 0x1f);
	}

	static constexpr uint32_t kWordBytes = sizeof(uint32_t);
	static constexpr uint32_t kWordBits = kWordBytes * 8;

	uint32_t* storage_; // The storage for the bit vector.
	uint32_t storage_size_; // Current size, in 32-bit words.
	Allocator* const allocator_; // Allocator if expandable.
	const bool expandable_; // Should the bitmap expand if too small?
	};


	} // namespace art

	#endif // ART_RUNTIME_BASE_BIT_VECTOR_H_