greenplumn CSyncHashtableAccessByIter 代码
文件路径：/src/backend/gporca/libgpos/include/gpos/common/CSyncHashtableAccessByIter.h
/---------------------------------------------------------------------------
/ Greenplum Database
/ Copyright (C) 2011 EMC Corp.
/
/ @filename:
/ CSyncHashtableAccessByIter.h
/
/ @doc:
/ Iterator's accessor provides protected access to hashtable elements
/ during iteration.
/---------------------------------------------------------------------------
#ifndef GPOS_CSyncHashtableAccessByIter_H
#define GPOS_CSyncHashtableAccessByIter_H
#include "gpos/common/CSyncHashtableAccessorBase.h"
#include "gpos/common/CSyncHashtableIter.h"
namespace gpos
{
/---------------------------------------------------------------------------
/ @class:
/ CSyncHashtableAccessByIter<T, K, S>
/
/ @doc:
/ Accessor class to provide access to the element pointed to by a
/ hash table iterator
/
/---------------------------------------------------------------------------
template <class T, class K>
class CSyncHashtableAccessByIter : public CSyncHashtableAccessorBase<T, K>
{
/ iterator class is a friend
friend class CSyncHashtableIter<T, K>;
private:
/ shorthand for base class
using Base = class CSyncHashtableAccessorBase<T, K>;
/ target iterator
CSyncHashtableIter<T, K> &m_iter;
/ returns the first valid element starting from the given element
T *
FirstValid(T *value) const
{
GPOS_ASSERT(nullptr != value);
T *curr = value;
while (nullptr != curr &&
!Base::GetHashTable().IsValid(Base::GetHashTable().Key(curr)))
{
curr = Base::Next(curr);
}
return curr;
}
public:
CSyncHashtableAccessByIter<T, K>(const CSyncHashtableAccessByIter<T, K> &) =
delete;
/ ctor
explicit CSyncHashtableAccessByIter<T, K>(CSyncHashtableIter<T, K> &iter)
: Base(iter.m_ht, iter.m_bucket_idx), m_iter(iter)
{
}
/ returns the element pointed to by iterator
T *
Value() const
{
GPOS_ASSERT(m_iter.m_invalid_elem_inserted &&
"Iterator's advance is not called");
/ advance in the current bucket until finding a valid element;
/ this is needed because the next valid element pointed to by
/ iterator might have been deleted by another client just before
/ using the accessor
return FirstValid(m_iter.m_invalid_elem);
}
}; / class CSyncHashtableAccessByIter
} / namespace gpos
#endif / !GPOS_CSyncHashtableAccessByIter_H
/ EOF