#ifndef TieredMMapArray_h
#define TieredMMapArray_h
#include <wtf/OSAllocator.h>
namespace JSC {
template<typename T>
class TieredMMapArray {
static const size_t entriesPerBlock = 4096;
public:
TieredMMapArray()
: m_directoryCount(4096)
, m_directory(static_cast<T**>(OSAllocator::reserveAndCommit(m_directoryCount * sizeof(T*))))
, m_size(0)
{
for (size_t block = 0; block < m_directoryCount; ++block)
m_directory[block] = 0;
}
~TieredMMapArray()
{
size_t usedCount = (m_size + (entriesPerBlock - 1)) / entriesPerBlock;
ASSERT(usedCount == m_directoryCount || !m_directory[usedCount]);
for (size_t block = 0; block < usedCount; ++block) {
ASSERT(m_directory[block]);
OSAllocator::decommitAndRelease(m_directory[block], entriesPerBlock * sizeof(T));
}
OSAllocator::decommitAndRelease(m_directory, m_directoryCount * sizeof(T*));
}
T& operator[](size_t index)
{
ASSERT(index < m_size);
size_t block = index / entriesPerBlock;
size_t offset = index % entriesPerBlock;
ASSERT(m_directory[block]);
return m_directory[block][offset];
}
void append(const T& value)
{
if (m_size == m_directoryCount * entriesPerBlock) {
size_t oldDirectorySize = m_directoryCount * sizeof(T*);
size_t newDirectorySize = oldDirectorySize * 2;
RELEASE_ASSERT(newDirectorySize < oldDirectorySize);
m_directory = OSAllocator::reallocateCommitted(m_directory, oldDirectorySize, newDirectorySize);
size_t newDirectoryCount = m_directoryCount * 2;
for (size_t block = m_directoryCount; block < newDirectoryCount; ++block)
m_directory[block] = 0;
m_directoryCount = newDirectoryCount;
}
size_t index = m_size;
size_t block = index / entriesPerBlock;
size_t offset = index % entriesPerBlock;
if (!offset) {
ASSERT(!m_directory[block]);
m_directory[block] = static_cast<T*>(OSAllocator::reserveAndCommit(entriesPerBlock * sizeof(T)));
}
ASSERT(m_directory[block]);
++m_size;
m_directory[block][offset] = value;
}
size_t size() const { return m_size; }
private:
size_t m_directoryCount;
T** m_directory;
size_t m_size;
};
}
#endif // TieredMMapArray_h