libartbase/base/bit_table.h - LeafOS-Project/android_art - Gitiles

 /*
  * Copyright (C) 2018 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_LIBARTBASE_BASE_BIT_TABLE_H_
 #define ART_LIBARTBASE_BASE_BIT_TABLE_H_

 #include <array>
 #include <initializer_list>
 #include <numeric>
 #include <string.h>
 #include <type_traits>
 #include <unordered_map>

 #include "base/bit_memory_region.h"
 #include "base/casts.h"
 #include "base/iteration_range.h"
 #include "base/memory_region.h"
 #include "base/scoped_arena_containers.h"
 #include "base/stl_util.h"

 namespace art {

 // Generic purpose table of uint32_t values, which are tightly packed at bit level.
 // It has its own header with the number of rows and the bit-widths of all columns.
 // The values are accessible by (row, column).  The value -1 is stored efficiently.
 template<uint32_t kNumColumns>
 class BitTableBase {
  public:
   static constexpr uint32_t kNoValue = std::numeric_limits<uint32_t>::max();  // == -1.
   static constexpr uint32_t kValueBias = kNoValue;  // Bias so that -1 is encoded as 0.

   BitTableBase() {}
   explicit BitTableBase(BitMemoryReader& reader) {
     Decode(reader);
   }

   ALWAYS_INLINE void Decode(BitMemoryReader& reader) {
     // Decode row count and column sizes from the table header.
     std::array<uint32_t, 1+kNumColumns> header = reader.ReadInterleavedVarints<1+kNumColumns>();
     num_rows_ = header[0];
     column_offset_[0] = 0;
     for (uint32_t i = 0; i < kNumColumns; i++) {
       size_t column_end = column_offset_[i] + header[i + 1];
       column_offset_[i + 1] = dchecked_integral_cast<uint16_t>(column_end);
     }

     // Record the region which contains the table data and skip past it.
     table_data_ = reader.ReadRegion(num_rows_ * NumRowBits());
   }

   ALWAYS_INLINE uint32_t Get(uint32_t row, uint32_t column = 0) const {
     DCHECK(table_data_.IsValid()) << "Table has not been loaded";
     DCHECK_LT(row, num_rows_);
     DCHECK_LT(column, kNumColumns);
     size_t offset = row * NumRowBits() + column_offset_[column];
     return table_data_.LoadBits(offset, NumColumnBits(column)) + kValueBias;
   }

   ALWAYS_INLINE BitMemoryRegion GetBitMemoryRegion(uint32_t row, uint32_t column = 0) const {
     DCHECK(table_data_.IsValid()) << "Table has not been loaded";
     DCHECK_LT(row, num_rows_);
     DCHECK_LT(column, kNumColumns);
     size_t offset = row * NumRowBits() + column_offset_[column];
     return table_data_.Subregion(offset, NumColumnBits(column));
   }

   uint32_t NumRows() const { return num_rows_; }

   uint32_t NumRowBits() const { return column_offset_[kNumColumns]; }

   constexpr uint32_t NumColumns() const { return kNumColumns; }

   uint32_t NumColumnBits(uint32_t column) const {
     return column_offset_[column + 1] - column_offset_[column];
   }

   size_t DataBitSize() const { return table_data_.size_in_bits(); }

   bool Equals(const BitTableBase& other) const {
     return num_rows_ == other.num_rows_ &&
         std::equal(column_offset_, column_offset_ + kNumColumns, other.column_offset_) &&
         BitMemoryRegion::Equals(table_data_, other.table_data_);
   }

  protected:
   BitMemoryRegion table_data_;
   uint32_t num_rows_ = 0;
   uint16_t column_offset_[kNumColumns + 1] = {};
 };

 // Helper class which can be used to create BitTable accessors with named getters.
 template<uint32_t NumColumns>
 class BitTableAccessor {
  public:
   static constexpr uint32_t kNumColumns = NumColumns;
   static constexpr uint32_t kNoValue = BitTableBase<kNumColumns>::kNoValue;

   BitTableAccessor() = default;
   BitTableAccessor(const BitTableBase<kNumColumns>* table, uint32_t row)
       : table_(table), row_(row) {
     DCHECK(table_ != nullptr);
   }

   ALWAYS_INLINE uint32_t Row() const { return row_; }

   ALWAYS_INLINE bool IsValid() const { return row_ < table_->NumRows(); }

   ALWAYS_INLINE bool Equals(const BitTableAccessor& other) {
     return this->table_ == other.table_ && this->row_ == other.row_;
   }

 // Helper macro to create constructors and per-table utilities in derived class.
 #define BIT_TABLE_HEADER(NAME)                                                       \
   using BitTableAccessor<kNumColumns>::BitTableAccessor; /* inherit constructors */  \
   template<int COLUMN, int UNUSED /*needed to compile*/> struct ColumnName;          \
   static constexpr const char* kTableName = #NAME;                                   \

 // Helper macro to create named column accessors in derived class.
 #define BIT_TABLE_COLUMN(COLUMN, NAME)                                               \
   static constexpr uint32_t k##NAME = COLUMN;                                        \
   ALWAYS_INLINE uint32_t Get##NAME() const { return table_->Get(row_, COLUMN); }     \
   ALWAYS_INLINE bool Has##NAME() const { return Get##NAME() != kNoValue; }           \
   template<int UNUSED> struct ColumnName<COLUMN, UNUSED> {                           \
     static constexpr const char* Value = #NAME;                                      \
   };                                                                                 \

  protected:
   const BitTableBase<kNumColumns>* table_ = nullptr;
   uint32_t row_ = -1;
 };

 // Template meta-programming helper.
 template<typename Accessor, size_t... Columns>
 static const char* const* GetBitTableColumnNamesImpl(std::index_sequence<Columns...>) {
   static const char* names[] = { Accessor::template ColumnName<Columns, 0>::Value... };
   return names;
 }

 // Wrapper which makes it easier to use named accessors for the individual rows.
 template<typename Accessor>
 class BitTable : public BitTableBase<Accessor::kNumColumns> {
  public:
   class const_iterator {
    public:
     using iterator_category = std::random_access_iterator_tag;
     using value_type = Accessor;
     using difference_type = int32_t;
     using pointer = void;
     using reference = void;
     const_iterator() {}
     const_iterator(const BitTable* table, uint32_t row) : table_(table), row_(row) {}
     const_iterator operator+(difference_type n) { return const_iterator(table_, row_ + n); }
     const_iterator operator-(difference_type n) { return const_iterator(table_, row_ - n); }
     difference_type operator-(const const_iterator& other) { return row_ - other.row_; }
     void operator+=(difference_type rows) { row_ += rows; }
     void operator-=(difference_type rows) { row_ -= rows; }
     const_iterator operator++() { return const_iterator(table_, ++row_); }
     const_iterator operator--() { return const_iterator(table_, --row_); }
     const_iterator operator++(int) { return const_iterator(table_, row_++); }
     const_iterator operator--(int) { return const_iterator(table_, row_--); }
     bool operator==(const_iterator i) const { DCHECK(table_ == i.table_); return row_ == i.row_; }
     bool operator!=(const_iterator i) const { DCHECK(table_ == i.table_); return row_ != i.row_; }
     bool operator<=(const_iterator i) const { DCHECK(table_ == i.table_); return row_ <= i.row_; }
     bool operator>=(const_iterator i) const { DCHECK(table_ == i.table_); return row_ >= i.row_; }
     bool operator<(const_iterator i) const { DCHECK(table_ == i.table_); return row_ < i.row_; }
     bool operator>(const_iterator i) const { DCHECK(table_ == i.table_); return row_ > i.row_; }
     Accessor operator*() {
       DCHECK_LT(row_, table_->NumRows());
       return Accessor(table_, row_);
     }
     Accessor operator->() {
       DCHECK_LT(row_, table_->NumRows());
       return Accessor(table_, row_);
     }
     Accessor operator[](size_t index) {
       DCHECK_LT(row_ + index, table_->NumRows());
       return Accessor(table_, row_ + index);
     }

    private:
     const BitTable* table_ = nullptr;
     uint32_t row_ = 0;
   };

   using BitTableBase<Accessor::kNumColumns>::BitTableBase;  // Constructors.

   ALWAYS_INLINE const_iterator begin() const { return const_iterator(this, 0); }
   ALWAYS_INLINE const_iterator end() const { return const_iterator(this, this->NumRows()); }

   ALWAYS_INLINE Accessor GetRow(uint32_t row) const {
     return Accessor(this, row);
   }

   ALWAYS_INLINE Accessor GetInvalidRow() const {
     return Accessor(this, static_cast<uint32_t>(-1));
   }

   const char* GetName() const {
     return Accessor::kTableName;
   }

   const char* const* GetColumnNames() const {
     return GetBitTableColumnNamesImpl<Accessor>(std::make_index_sequence<Accessor::kNumColumns>());
   }
 };

 template<typename Accessor>
 typename BitTable<Accessor>::const_iterator operator+(
     typename BitTable<Accessor>::const_iterator::difference_type n,
     typename BitTable<Accessor>::const_iterator a) {
   return a + n;
 }

 template<typename Accessor>
 class BitTableRange : public IterationRange<typename BitTable<Accessor>::const_iterator> {
  public:
   using const_iterator = typename BitTable<Accessor>::const_iterator;

   using IterationRange<const_iterator>::IterationRange;
   BitTableRange() : IterationRange<const_iterator>(const_iterator(), const_iterator()) { }

   bool empty() const { return this->begin() == this->end(); }
   size_t size() const { return this->end() - this->begin(); }

   Accessor operator[](size_t index) const {
     const_iterator it = this->begin() + index;
     DCHECK(it < this->end());
     return *it;
   }

   Accessor back() const {
     DCHECK(!empty());
     return *(this->end() - 1);
   }

   void pop_back() {
     DCHECK(!empty());
     --this->last_;
   }
 };

 // Helper class for encoding BitTable. It can optionally de-duplicate the inputs.
 template<uint32_t kNumColumns>
 class BitTableBuilderBase {
  public:
   static constexpr uint32_t kNoValue = BitTableBase<kNumColumns>::kNoValue;
   static constexpr uint32_t kValueBias = BitTableBase<kNumColumns>::kValueBias;

   class Entry {
    public:
     Entry() {
       // The definition of kLocalNoValue here is for host and target debug builds which
       // complain about missing a symbol definition for BitTableBase<N>::kNovValue when
       // optimization is off.
       static constexpr uint32_t kLocalNoValue = BitTableBase<kNumColumns>::kNoValue;
       std::fill_n(data_, kNumColumns, kLocalNoValue);
     }

     Entry(std::initializer_list<uint32_t> values) {
       DCHECK_EQ(values.size(), kNumColumns);
       std::copy(values.begin(), values.end(), data_);
     }

     uint32_t& operator[](size_t column) {
       DCHECK_LT(column, kNumColumns);
       return data_[column];
     }

     uint32_t operator[](size_t column) const {
       DCHECK_LT(column, kNumColumns);
       return data_[column];
     }

    private:
     uint32_t data_[kNumColumns];
   };

   explicit BitTableBuilderBase(ScopedArenaAllocator* allocator)
       : rows_(allocator->Adapter(kArenaAllocBitTableBuilder)),
         dedup_(8, allocator->Adapter(kArenaAllocBitTableBuilder)) {
   }

   Entry& operator[](size_t row) { return rows_[row]; }
   const Entry& operator[](size_t row) const { return rows_[row]; }
   const Entry& back() const { return rows_.back(); }
   size_t size() const { return rows_.size(); }

   // Append given value to the vector without de-duplication.
   // This will not add the element to the dedup map to avoid its associated costs.
   void Add(Entry value) {
     rows_.push_back(value);
   }

   // Append given list of values and return the index of the first value.
   // If the exact same set of values was already added, return the old index.
   uint32_t Dedup(Entry* values, size_t count = 1) {
     FNVHash<MemoryRegion> hasher;
     uint32_t hash = hasher(MemoryRegion(values, sizeof(Entry) * count));

     // Check if we have already added identical set of values.
     auto range = dedup_.equal_range(hash);
     for (auto it = range.first; it != range.second; ++it) {
       uint32_t index = it->second;
       if (count <= size() - index &&
           std::equal(values,
                      values + count,
                      rows_.begin() + index,
                      [](const Entry& lhs, const Entry& rhs) {
                        return memcmp(&lhs, &rhs, sizeof(Entry)) == 0;
                      })) {
         return index;
       }
     }

     // Add the set of values and add the index to the dedup map.
     uint32_t index = size();
     rows_.insert(rows_.end(), values, values + count);
     dedup_.emplace(hash, index);
     return index;
   }

   uint32_t Dedup(Entry value) {
     return Dedup(&value, /* count */ 1);
   }

   // Calculate the column bit widths based on the current data.
   void Measure(/*out*/ uint32_t* column_bits) const {
     uint32_t max_column_value[kNumColumns];
     std::fill_n(max_column_value, kNumColumns, 0);
     for (uint32_t r = 0; r < size(); r++) {
       for (uint32_t c = 0; c < kNumColumns; c++) {
         max_column_value[c] |= rows_[r][c] - kValueBias;
       }
     }
     for (uint32_t c = 0; c < kNumColumns; c++) {
       column_bits[c] = MinimumBitsToStore(max_column_value[c]);
     }
   }

   // Encode the stored data into a BitTable.
   template<typename Vector>
   void Encode(BitMemoryWriter<Vector>& out) const {
     size_t initial_bit_offset = out.NumberOfWrittenBits();

     // Write table header.
     std::array<uint32_t, 1 + kNumColumns> header;
     header[0] = size();
     uint32_t* column_bits = header.data() + 1;
     Measure(column_bits);
     out.WriteInterleavedVarints(header);

     // Write table data.
     for (uint32_t r = 0; r < size(); r++) {
       for (uint32_t c = 0; c < kNumColumns; c++) {
         out.WriteBits(rows_[r][c] - kValueBias, column_bits[c]);
       }
     }

     // Verify the written data.
     if (kIsDebugBuild) {
       BitTableBase<kNumColumns> table;
       BitMemoryReader reader(out.GetWrittenRegion().Subregion(initial_bit_offset));
       table.Decode(reader);
       DCHECK_EQ(size(), table.NumRows());
       for (uint32_t c = 0; c < kNumColumns; c++) {
         DCHECK_EQ(column_bits[c], table.NumColumnBits(c));
       }
       for (uint32_t r = 0; r < size(); r++) {
         for (uint32_t c = 0; c < kNumColumns; c++) {
           DCHECK_EQ(rows_[r][c], table.Get(r, c)) << " (" << r << ", " << c << ")";
         }
       }
     }
   }

  protected:
   ScopedArenaDeque<Entry> rows_;
   ScopedArenaUnorderedMultimap<uint32_t, uint32_t> dedup_;  // Hash -> row index.
 };

 template<typename Accessor>
 class BitTableBuilder : public BitTableBuilderBase<Accessor::kNumColumns> {
  public:
   using BitTableBuilderBase<Accessor::kNumColumns>::BitTableBuilderBase;  // Constructors.
 };

 // Helper class for encoding single-column BitTable of bitmaps (allows more than 32 bits).
 class BitmapTableBuilder {
  public:
   explicit BitmapTableBuilder(ScopedArenaAllocator* const allocator)
       : allocator_(allocator),
         rows_(allocator->Adapter(kArenaAllocBitTableBuilder)),
         dedup_(8, allocator_->Adapter(kArenaAllocBitTableBuilder)) {
   }

   MemoryRegion operator[](size_t row) { return rows_[row]; }
   const MemoryRegion operator[](size_t row) const { return rows_[row]; }
   size_t size() const { return rows_.size(); }

   // Add the given bitmap to the table and return its index.
   // If the bitmap was already added it will be deduplicated.
   // The last bit must be set and any padding bits in the last byte must be zero.
   uint32_t Dedup(const void* bitmap, size_t num_bits) {
     MemoryRegion region(const_cast<void*>(bitmap), BitsToBytesRoundUp(num_bits));
     DCHECK(num_bits == 0 || BitMemoryRegion(region).LoadBit(num_bits - 1) == 1);
     DCHECK_EQ(BitMemoryRegion(region).LoadBits(num_bits, region.size_in_bits() - num_bits), 0u);
     FNVHash<MemoryRegion> hasher;
     uint32_t hash = hasher(region);

     // Check if we have already added identical bitmap.
     auto range = dedup_.equal_range(hash);
     for (auto it = range.first; it != range.second; ++it) {
       if (MemoryRegion::ContentEquals()(region, rows_[it->second])) {
         return it->second;
       }
     }

     // Add the bitmap and add the index to the dedup map.
     uint32_t index = size();
     void* copy = allocator_->Alloc(region.size(), kArenaAllocBitTableBuilder);
     memcpy(copy, region.pointer(), region.size());
     rows_.push_back(MemoryRegion(copy, region.size()));
     dedup_.emplace(hash, index);
     max_num_bits_ = std::max(max_num_bits_, num_bits);
     return index;
   }

   // Encode the stored data into a BitTable.
   template<typename Vector>
   void Encode(BitMemoryWriter<Vector>& out) const {
     size_t initial_bit_offset = out.NumberOfWrittenBits();

     // Write table header.
     out.WriteInterleavedVarints(std::array<uint32_t, 2>{
       dchecked_integral_cast<uint32_t>(size()),
       dchecked_integral_cast<uint32_t>(max_num_bits_),
     });

     // Write table data.
     for (MemoryRegion row : rows_) {
       size_t bits_to_copy = std::min(max_num_bits_, row.size_in_bits());
       BitMemoryRegion src(row, /*bit_offset=*/ 0u, bits_to_copy);
       BitMemoryRegion dst = out.Allocate(max_num_bits_);
       dst.Subregion(/*bit_offset=*/ 0, bits_to_copy).CopyBits(src);
     }

     // Verify the written data.
     if (kIsDebugBuild) {
       BitTableBase<1> table;
       BitMemoryReader reader(out.GetWrittenRegion().Subregion(initial_bit_offset));
       table.Decode(reader);
       DCHECK_EQ(size(), table.NumRows());
       DCHECK_EQ(max_num_bits_, table.NumColumnBits(0));
       for (uint32_t r = 0; r < size(); r++) {
         BitMemoryRegion expected(rows_[r]);
         BitMemoryRegion seen = table.GetBitMemoryRegion(r);
         size_t num_bits = std::max(expected.size_in_bits(), seen.size_in_bits());
         for (size_t b = 0; b < num_bits; b++) {
           bool e = b < expected.size_in_bits() && expected.LoadBit(b);
           bool s = b < seen.size_in_bits() && seen.LoadBit(b);
           DCHECK_EQ(e, s) << " (" << r << ")[" << b << "]";
         }
       }
     }
   }

  private:
   ScopedArenaAllocator* const allocator_;
   ScopedArenaDeque<MemoryRegion> rows_;
   ScopedArenaUnorderedMultimap<uint32_t, uint32_t> dedup_;  // Hash -> row index.
   size_t max_num_bits_ = 0u;
 };

 }  // namespace art

 #endif  // ART_LIBARTBASE_BASE_BIT_TABLE_H_
	/*
	* Copyright (C) 2018 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_LIBARTBASE_BASE_BIT_TABLE_H_
	#define ART_LIBARTBASE_BASE_BIT_TABLE_H_

	#include <array>
	#include <initializer_list>
	#include <numeric>
	#include <string.h>
	#include <type_traits>
	#include <unordered_map>

	#include "base/bit_memory_region.h"
	#include "base/casts.h"
	#include "base/iteration_range.h"
	#include "base/memory_region.h"
	#include "base/scoped_arena_containers.h"
	#include "base/stl_util.h"

	namespace art {

	// Generic purpose table of uint32_t values, which are tightly packed at bit level.
	// It has its own header with the number of rows and the bit-widths of all columns.
	// The values are accessible by (row, column). The value -1 is stored efficiently.
	template<uint32_t kNumColumns>
	class BitTableBase {
	public:
	static constexpr uint32_t kNoValue = std::numeric_limits<uint32_t>::max(); // == -1.
	static constexpr uint32_t kValueBias = kNoValue; // Bias so that -1 is encoded as 0.

	BitTableBase() {}
	explicit BitTableBase(BitMemoryReader& reader) {
	Decode(reader);
	}

	ALWAYS_INLINE void Decode(BitMemoryReader& reader) {
	// Decode row count and column sizes from the table header.
	std::array<uint32_t, 1+kNumColumns> header = reader.ReadInterleavedVarints<1+kNumColumns>();
	num_rows_ = header[0];
	column_offset_[0] = 0;
	for (uint32_t i = 0; i < kNumColumns; i++) {
	size_t column_end = column_offset_[i] + header[i + 1];
	column_offset_[i + 1] = dchecked_integral_cast<uint16_t>(column_end);
	}

	// Record the region which contains the table data and skip past it.
	table_data_ = reader.ReadRegion(num_rows_ * NumRowBits());
	}

	ALWAYS_INLINE uint32_t Get(uint32_t row, uint32_t column = 0) const {
	DCHECK(table_data_.IsValid()) << "Table has not been loaded";
	DCHECK_LT(row, num_rows_);
	DCHECK_LT(column, kNumColumns);
	size_t offset = row * NumRowBits() + column_offset_[column];
	return table_data_.LoadBits(offset, NumColumnBits(column)) + kValueBias;
	}

	ALWAYS_INLINE BitMemoryRegion GetBitMemoryRegion(uint32_t row, uint32_t column = 0) const {
	DCHECK(table_data_.IsValid()) << "Table has not been loaded";
	DCHECK_LT(row, num_rows_);
	DCHECK_LT(column, kNumColumns);
	size_t offset = row * NumRowBits() + column_offset_[column];
	return table_data_.Subregion(offset, NumColumnBits(column));
	}

	uint32_t NumRows() const { return num_rows_; }

	uint32_t NumRowBits() const { return column_offset_[kNumColumns]; }

	constexpr uint32_t NumColumns() const { return kNumColumns; }

	uint32_t NumColumnBits(uint32_t column) const {
	return column_offset_[column + 1] - column_offset_[column];
	}

	size_t DataBitSize() const { return table_data_.size_in_bits(); }

	bool Equals(const BitTableBase& other) const {
	return num_rows_ == other.num_rows_ &&
	std::equal(column_offset_, column_offset_ + kNumColumns, other.column_offset_) &&
	BitMemoryRegion::Equals(table_data_, other.table_data_);
	}

	protected:
	BitMemoryRegion table_data_;
	uint32_t num_rows_ = 0;
	uint16_t column_offset_[kNumColumns + 1] = {};
	};

	// Helper class which can be used to create BitTable accessors with named getters.
	template<uint32_t NumColumns>
	class BitTableAccessor {
	public:
	static constexpr uint32_t kNumColumns = NumColumns;
	static constexpr uint32_t kNoValue = BitTableBase<kNumColumns>::kNoValue;

	BitTableAccessor() = default;
	BitTableAccessor(const BitTableBase<kNumColumns>* table, uint32_t row)
	: table_(table), row_(row) {
	DCHECK(table_ != nullptr);
	}

	ALWAYS_INLINE uint32_t Row() const { return row_; }

	ALWAYS_INLINE bool IsValid() const { return row_ < table_->NumRows(); }

	ALWAYS_INLINE bool Equals(const BitTableAccessor& other) {
	return this->table_ == other.table_ && this->row_ == other.row_;
	}

	// Helper macro to create constructors and per-table utilities in derived class.
	#define BIT_TABLE_HEADER(NAME) \
	using BitTableAccessor<kNumColumns>::BitTableAccessor; /* inherit constructors */ \
	template<int COLUMN, int UNUSED /needed to compile/> struct ColumnName; \
	static constexpr const char* kTableName = #NAME; \

	// Helper macro to create named column accessors in derived class.
	#define BIT_TABLE_COLUMN(COLUMN, NAME) \
	static constexpr uint32_t k##NAME = COLUMN; \
	ALWAYS_INLINE uint32_t Get##NAME() const { return table_->Get(row_, COLUMN); } \
	ALWAYS_INLINE bool Has##NAME() const { return Get##NAME() != kNoValue; } \
	template<int UNUSED> struct ColumnName<COLUMN, UNUSED> { \
	static constexpr const char* Value = #NAME; \
	}; \

	protected:
	const BitTableBase<kNumColumns>* table_ = nullptr;
	uint32_t row_ = -1;
	};

	// Template meta-programming helper.
	template<typename Accessor, size_t... Columns>
	static const char* const* GetBitTableColumnNamesImpl(std::index_sequence<Columns...>) {
	static const char* names[] = { Accessor::template ColumnName<Columns, 0>::Value... };
	return names;
	}

	// Wrapper which makes it easier to use named accessors for the individual rows.
	template<typename Accessor>
	class BitTable : public BitTableBase<Accessor::kNumColumns> {
	public:
	class const_iterator {
	public:
	using iterator_category = std::random_access_iterator_tag;
	using value_type = Accessor;
	using difference_type = int32_t;
	using pointer = void;
	using reference = void;
	const_iterator() {}
	const_iterator(const BitTable* table, uint32_t row) : table_(table), row_(row) {}
	const_iterator operator+(difference_type n) { return const_iterator(table_, row_ + n); }
	const_iterator operator-(difference_type n) { return const_iterator(table_, row_ - n); }
	difference_type operator-(const const_iterator& other) { return row_ - other.row_; }
	void operator+=(difference_type rows) { row_ += rows; }
	void operator-=(difference_type rows) { row_ -= rows; }
	const_iterator operator++() { return const_iterator(table_, ++row_); }
	const_iterator operator--() { return const_iterator(table_, --row_); }
	const_iterator operator++(int) { return const_iterator(table_, row_++); }
	const_iterator operator--(int) { return const_iterator(table_, row_--); }
	bool operator==(const_iterator i) const { DCHECK(table_ == i.table_); return row_ == i.row_; }
	bool operator!=(const_iterator i) const { DCHECK(table_ == i.table_); return row_ != i.row_; }
	bool operator<=(const_iterator i) const { DCHECK(table_ == i.table_); return row_ <= i.row_; }
	bool operator>=(const_iterator i) const { DCHECK(table_ == i.table_); return row_ >= i.row_; }
	bool operator<(const_iterator i) const { DCHECK(table_ == i.table_); return row_ < i.row_; }
	bool operator>(const_iterator i) const { DCHECK(table_ == i.table_); return row_ > i.row_; }
	Accessor operator*() {
	DCHECK_LT(row_, table_->NumRows());
	return Accessor(table_, row_);
	}
	Accessor operator->() {
	DCHECK_LT(row_, table_->NumRows());
	return Accessor(table_, row_);
	}
	Accessor operator[](size_t index) {
	DCHECK_LT(row_ + index, table_->NumRows());
	return Accessor(table_, row_ + index);
	}

	private:
	const BitTable* table_ = nullptr;
	uint32_t row_ = 0;
	};

	using BitTableBase<Accessor::kNumColumns>::BitTableBase; // Constructors.

	ALWAYS_INLINE const_iterator begin() const { return const_iterator(this, 0); }
	ALWAYS_INLINE const_iterator end() const { return const_iterator(this, this->NumRows()); }

	ALWAYS_INLINE Accessor GetRow(uint32_t row) const {
	return Accessor(this, row);
	}

	ALWAYS_INLINE Accessor GetInvalidRow() const {
	return Accessor(this, static_cast<uint32_t>(-1));
	}

	const char* GetName() const {
	return Accessor::kTableName;
	}

	const char* const* GetColumnNames() const {
	return GetBitTableColumnNamesImpl<Accessor>(std::make_index_sequence<Accessor::kNumColumns>());
	}
	};

	template<typename Accessor>
	typename BitTable<Accessor>::const_iterator operator+(
	typename BitTable<Accessor>::const_iterator::difference_type n,
	typename BitTable<Accessor>::const_iterator a) {
	return a + n;
	}

	template<typename Accessor>
	class BitTableRange : public IterationRange<typename BitTable<Accessor>::const_iterator> {
	public:
	using const_iterator = typename BitTable<Accessor>::const_iterator;

	using IterationRange<const_iterator>::IterationRange;
	BitTableRange() : IterationRange<const_iterator>(const_iterator(), const_iterator()) { }

	bool empty() const { return this->begin() == this->end(); }
	size_t size() const { return this->end() - this->begin(); }

	Accessor operator[](size_t index) const {
	const_iterator it = this->begin() + index;
	DCHECK(it < this->end());
	return *it;
	}

	Accessor back() const {
	DCHECK(!empty());
	return *(this->end() - 1);
	}

	void pop_back() {
	DCHECK(!empty());
	--this->last_;
	}
	};

	// Helper class for encoding BitTable. It can optionally de-duplicate the inputs.
	template<uint32_t kNumColumns>
	class BitTableBuilderBase {
	public:
	static constexpr uint32_t kNoValue = BitTableBase<kNumColumns>::kNoValue;
	static constexpr uint32_t kValueBias = BitTableBase<kNumColumns>::kValueBias;

	class Entry {
	public:
	Entry() {
	// The definition of kLocalNoValue here is for host and target debug builds which
	// complain about missing a symbol definition for BitTableBase<N>::kNovValue when
	// optimization is off.
	static constexpr uint32_t kLocalNoValue = BitTableBase<kNumColumns>::kNoValue;
	std::fill_n(data_, kNumColumns, kLocalNoValue);
	}

	Entry(std::initializer_list<uint32_t> values) {
	DCHECK_EQ(values.size(), kNumColumns);
	std::copy(values.begin(), values.end(), data_);
	}

	uint32_t& operator[](size_t column) {
	DCHECK_LT(column, kNumColumns);
	return data_[column];
	}

	uint32_t operator[](size_t column) const {
	DCHECK_LT(column, kNumColumns);
	return data_[column];
	}

	private:
	uint32_t data_[kNumColumns];
	};

	explicit BitTableBuilderBase(ScopedArenaAllocator* allocator)
	: rows_(allocator->Adapter(kArenaAllocBitTableBuilder)),
	dedup_(8, allocator->Adapter(kArenaAllocBitTableBuilder)) {
	}

	Entry& operator[](size_t row) { return rows_[row]; }
	const Entry& operator[](size_t row) const { return rows_[row]; }
	const Entry& back() const { return rows_.back(); }
	size_t size() const { return rows_.size(); }

	// Append given value to the vector without de-duplication.
	// This will not add the element to the dedup map to avoid its associated costs.
	void Add(Entry value) {
	rows_.push_back(value);
	}

	// Append given list of values and return the index of the first value.
	// If the exact same set of values was already added, return the old index.
	uint32_t Dedup(Entry* values, size_t count = 1) {
	FNVHash<MemoryRegion> hasher;
	uint32_t hash = hasher(MemoryRegion(values, sizeof(Entry) * count));

	// Check if we have already added identical set of values.
	auto range = dedup_.equal_range(hash);
	for (auto it = range.first; it != range.second; ++it) {
	uint32_t index = it->second;
	if (count <= size() - index &&
	std::equal(values,
	values + count,
	rows_.begin() + index,
	[](const Entry& lhs, const Entry& rhs) {
	return memcmp(&lhs, &rhs, sizeof(Entry)) == 0;
	})) {
	return index;
	}
	}

	// Add the set of values and add the index to the dedup map.
	uint32_t index = size();
	rows_.insert(rows_.end(), values, values + count);
	dedup_.emplace(hash, index);
	return index;
	}

	uint32_t Dedup(Entry value) {
	return Dedup(&value, /* count */ 1);
	}

	// Calculate the column bit widths based on the current data.
	void Measure(/out/ uint32_t* column_bits) const {
	uint32_t max_column_value[kNumColumns];
	std::fill_n(max_column_value, kNumColumns, 0);
	for (uint32_t r = 0; r < size(); r++) {
	for (uint32_t c = 0; c < kNumColumns; c++) {
	max_column_value[c] \|= rows_[r][c] - kValueBias;
	}
	}
	for (uint32_t c = 0; c < kNumColumns; c++) {
	column_bits[c] = MinimumBitsToStore(max_column_value[c]);
	}
	}

	// Encode the stored data into a BitTable.
	template<typename Vector>
	void Encode(BitMemoryWriter<Vector>& out) const {
	size_t initial_bit_offset = out.NumberOfWrittenBits();

	// Write table header.
	std::array<uint32_t, 1 + kNumColumns> header;
	header[0] = size();
	uint32_t* column_bits = header.data() + 1;
	Measure(column_bits);
	out.WriteInterleavedVarints(header);

	// Write table data.
	for (uint32_t r = 0; r < size(); r++) {
	for (uint32_t c = 0; c < kNumColumns; c++) {
	out.WriteBits(rows_[r][c] - kValueBias, column_bits[c]);
	}
	}

	// Verify the written data.
	if (kIsDebugBuild) {
	BitTableBase<kNumColumns> table;
	BitMemoryReader reader(out.GetWrittenRegion().Subregion(initial_bit_offset));
	table.Decode(reader);
	DCHECK_EQ(size(), table.NumRows());
	for (uint32_t c = 0; c < kNumColumns; c++) {
	DCHECK_EQ(column_bits[c], table.NumColumnBits(c));
	}
	for (uint32_t r = 0; r < size(); r++) {
	for (uint32_t c = 0; c < kNumColumns; c++) {
	DCHECK_EQ(rows_[r][c], table.Get(r, c)) << " (" << r << ", " << c << ")";
	}
	}
	}
	}

	protected:
	ScopedArenaDeque<Entry> rows_;
	ScopedArenaUnorderedMultimap<uint32_t, uint32_t> dedup_; // Hash -> row index.
	};

	template<typename Accessor>
	class BitTableBuilder : public BitTableBuilderBase<Accessor::kNumColumns> {
	public:
	using BitTableBuilderBase<Accessor::kNumColumns>::BitTableBuilderBase; // Constructors.
	};

	// Helper class for encoding single-column BitTable of bitmaps (allows more than 32 bits).
	class BitmapTableBuilder {
	public:
	explicit BitmapTableBuilder(ScopedArenaAllocator* const allocator)
	: allocator_(allocator),
	rows_(allocator->Adapter(kArenaAllocBitTableBuilder)),
	dedup_(8, allocator_->Adapter(kArenaAllocBitTableBuilder)) {
	}

	MemoryRegion operator[](size_t row) { return rows_[row]; }
	const MemoryRegion operator[](size_t row) const { return rows_[row]; }
	size_t size() const { return rows_.size(); }

	// Add the given bitmap to the table and return its index.
	// If the bitmap was already added it will be deduplicated.
	// The last bit must be set and any padding bits in the last byte must be zero.
	uint32_t Dedup(const void* bitmap, size_t num_bits) {
	MemoryRegion region(const_cast<void*>(bitmap), BitsToBytesRoundUp(num_bits));
	DCHECK(num_bits == 0 \|\| BitMemoryRegion(region).LoadBit(num_bits - 1) == 1);
	DCHECK_EQ(BitMemoryRegion(region).LoadBits(num_bits, region.size_in_bits() - num_bits), 0u);
	FNVHash<MemoryRegion> hasher;
	uint32_t hash = hasher(region);

	// Check if we have already added identical bitmap.
	auto range = dedup_.equal_range(hash);
	for (auto it = range.first; it != range.second; ++it) {
	if (MemoryRegion::ContentEquals()(region, rows_[it->second])) {
	return it->second;
	}
	}

	// Add the bitmap and add the index to the dedup map.
	uint32_t index = size();
	void* copy = allocator_->Alloc(region.size(), kArenaAllocBitTableBuilder);
	memcpy(copy, region.pointer(), region.size());
	rows_.push_back(MemoryRegion(copy, region.size()));
	dedup_.emplace(hash, index);
	max_num_bits_ = std::max(max_num_bits_, num_bits);
	return index;
	}

	// Encode the stored data into a BitTable.
	template<typename Vector>
	void Encode(BitMemoryWriter<Vector>& out) const {
	size_t initial_bit_offset = out.NumberOfWrittenBits();

	// Write table header.
	out.WriteInterleavedVarints(std::array<uint32_t, 2>{
	dchecked_integral_cast<uint32_t>(size()),
	dchecked_integral_cast<uint32_t>(max_num_bits_),
	});

	// Write table data.
	for (MemoryRegion row : rows_) {
	size_t bits_to_copy = std::min(max_num_bits_, row.size_in_bits());
	BitMemoryRegion src(row, /bit_offset=/ 0u, bits_to_copy);
	BitMemoryRegion dst = out.Allocate(max_num_bits_);
	dst.Subregion(/bit_offset=/ 0, bits_to_copy).CopyBits(src);
	}

	// Verify the written data.
	if (kIsDebugBuild) {
	BitTableBase<1> table;
	BitMemoryReader reader(out.GetWrittenRegion().Subregion(initial_bit_offset));
	table.Decode(reader);
	DCHECK_EQ(size(), table.NumRows());
	DCHECK_EQ(max_num_bits_, table.NumColumnBits(0));
	for (uint32_t r = 0; r < size(); r++) {
	BitMemoryRegion expected(rows_[r]);
	BitMemoryRegion seen = table.GetBitMemoryRegion(r);
	size_t num_bits = std::max(expected.size_in_bits(), seen.size_in_bits());
	for (size_t b = 0; b < num_bits; b++) {
	bool e = b < expected.size_in_bits() && expected.LoadBit(b);
	bool s = b < seen.size_in_bits() && seen.LoadBit(b);
	DCHECK_EQ(e, s) << " (" << r << ")[" << b << "]";
	}
	}
	}
	}

	private:
	ScopedArenaAllocator* const allocator_;
	ScopedArenaDeque<MemoryRegion> rows_;
	ScopedArenaUnorderedMultimap<uint32_t, uint32_t> dedup_; // Hash -> row index.
	size_t max_num_bits_ = 0u;
	};

	} // namespace art

	#endif // ART_LIBARTBASE_BASE_BIT_TABLE_H_