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#pragma once
#include "base/assert.hpp"
#include "base/bits.hpp"
#include "base/macros.hpp"
#include <cstdint>
#include <iterator>
#include <sstream>
#include <string>
namespace base
{
// A set of nonnegative integers less than |UpperBound|.
//
// Requires UpperBound + O(1) bits of memory. All operations except
// Clear() and iteration are O(1). Clear() and iteration require
// O(UpperBound) steps.
//
// *NOTE* This class *IS NOT* thread safe.
template <uint64_t UpperBound>
class SmallSet
{
public:
static uint64_t constexpr kNumBlocks = (UpperBound + 63) / 64;
class Iterator
{
public:
using difference_type = uint64_t;
using value_type = uint64_t;
using pointer = void;
using reference = void;
using iterator_category = std::forward_iterator_tag;
Iterator(uint64_t const * blocks, uint64_t current_block_index)
: m_blocks(blocks), m_current_block_index(current_block_index), m_current_block(0)
{
ASSERT_LESS_OR_EQUAL(current_block_index, kNumBlocks, ());
if (current_block_index < kNumBlocks)
m_current_block = m_blocks[current_block_index];
SkipZeroes();
}
bool operator==(Iterator const & rhs) const
{
return m_blocks == rhs.m_blocks && m_current_block_index == rhs.m_current_block_index &&
m_current_block == rhs.m_current_block;
}
bool operator!=(Iterator const & rhs) const { return !(*this == rhs); }
uint64_t operator*() const
{
ASSERT_NOT_EQUAL(m_current_block, 0, ());
auto const bit = m_current_block & -m_current_block;
return bits::FloorLog(bit) + m_current_block_index * 64;
}
Iterator const & operator++()
{
ASSERT(m_current_block_index < kNumBlocks, ());
ASSERT_NOT_EQUAL(m_current_block, 0, ());
m_current_block = m_current_block & (m_current_block - 1);
SkipZeroes();
return *this;
}
private:
void SkipZeroes()
{
ASSERT_LESS_OR_EQUAL(m_current_block_index, kNumBlocks, ());
if (m_current_block != 0 || m_current_block_index == kNumBlocks)
return;
do
++m_current_block_index;
while (m_current_block_index < kNumBlocks && m_blocks[m_current_block_index] == 0);
if (m_current_block_index < kNumBlocks)
m_current_block = m_blocks[m_current_block_index];
else
m_current_block = 0;
}
uint64_t const * m_blocks;
uint64_t m_current_block_index;
uint64_t m_current_block;
};
#define DEFINE_BLOCK_OFFSET(value) \
uint64_t const block = value / 64; \
uint64_t const offset = value % 64
// This invalidates all iterators except end().
void Insert(uint64_t value)
{
ASSERT_LESS(value, UpperBound, ());
DEFINE_BLOCK_OFFSET(value);
auto const bit = kOne << offset;
m_size += (m_blocks[block] & bit) == 0;
m_blocks[block] |= bit;
}
// This invalidates all iterators except end().
void Remove(uint64_t value)
{
ASSERT_LESS(value, UpperBound, ());
DEFINE_BLOCK_OFFSET(value);
auto const bit = kOne << offset;
m_size -= (m_blocks[block] & bit) != 0;
m_blocks[block] &= ~bit;
}
bool Contains(uint64_t value) const
{
ASSERT_LESS(value, UpperBound, ());
DEFINE_BLOCK_OFFSET(value);
return m_blocks[block] & (kOne << offset);
}
#undef DEFINE_BLOCK_OFFSET
uint64_t Size() const { return m_size; }
// This invalidates all iterators except end().
void Clear()
{
std::fill(std::begin(m_blocks), std::end(m_blocks), static_cast<uint64_t>(0));
m_size = 0;
}
Iterator begin() const { return Iterator(m_blocks, 0); }
Iterator cbegin() const { return Iterator(m_blocks, 0); }
Iterator end() const { return Iterator(m_blocks, kNumBlocks); }
Iterator cend() const { return Iterator(m_blocks, kNumBlocks); }
private:
static uint64_t constexpr kOne = 1;
uint64_t m_blocks[kNumBlocks] = {};
uint64_t m_size = 0;
};
// static
template <uint64_t UpperBound>
uint64_t constexpr SmallSet<UpperBound>::kNumBlocks;
// static
template <uint64_t UpperBound>
uint64_t constexpr SmallSet<UpperBound>::kOne;
template <uint64_t UpperBound>
std::string DebugPrint(SmallSet<UpperBound> const & set)
{
std::ostringstream os;
os << "SmallSet<" << UpperBound << "> [" << set.Size() << ": ";
for (auto const & v : set)
os << v << " ";
os << "]";
return os.str();
}
// This is a delegate for SmallSet<>, that checks the validity of
// argument in Insert(), Remove() and Contains() methods and does
// nothing when the argument is not valid.
template <uint64_t UpperBound>
class SafeSmallSet
{
public:
using Set = SmallSet<UpperBound>;
using Iterator = typename Set::Iterator;
void Insert(uint64_t value)
{
if (IsValid(value))
m_set.Insert(value);
}
void Remove(uint64_t value)
{
if (IsValid(value))
m_set.Remove(value);
}
bool Contains(uint64_t value) const { return IsValid(value) && m_set.Contains(value); }
uint64_t Size() const { return m_set.Size(); }
void Clear() { m_set.Clear(); }
Iterator begin() const { return m_set.begin(); }
Iterator cbegin() const { return m_set.cbegin(); }
Iterator end() const { return m_set.end(); }
Iterator cend() const { return m_set.cend(); }
private:
bool IsValid(uint64_t value) const { return value < UpperBound; }
Set m_set;
};
template <uint64_t UpperBound>
std::string DebugPrint(SafeSmallSet<UpperBound> const & set)
{
std::ostringstream os;
os << "SafeSmallSet<" << UpperBound << "> [" << set.Size() << ": ";
for (auto const & v : set)
os << v << " ";
os << "]";
return os.str();
}
} // namespace base
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