stx::CBTreeDB< _Key, _Compare, _BTreePageSize, _AppVersionId >::PageCache Class Reference
PageCache and PageCacheImpl implement a LRU-strategy cache of B-tree pages used by CBTreeDB reader objects. More...
#include <stx-cbtreedb.h>
Public Member Functions | |
| PageCache (unsigned int maxpages) | |
| Create a new page cache containg maxsize pages. | |
| PageCache (const PageCache &pc) | |
| Copy Constructor: increment reference counter on base object. | |
| ~PageCache () | |
| Destructor: decrement reference counter on buffer and possibly deallocate it. | |
| PageCache & | operator= (const PageCache &pc) |
| Assignment Operator: increment reference counter on base object. | |
| void | Clear () |
| Remove all pages from the cache and reset status. | |
| void | Store (void *btreeid, uint32_t pageid, const BTreePage &page) |
| Store a page object in a cache cell identified by (btreeid,pageid). | |
| bool | Retrieve (void *btreeid, uint32_t pageid, BTreePage &outpage) |
| Retrieve a cached page identified by (btreeid,pageid). | |
| void | SetMaxSize (unsigned int maxsize) |
| Change maximum number of pages in cache, note that this does not immediately have effect. | |
| std::vector< std::pair< void *, uint32_t > > | GetPagelist () const |
| Return a vector listing all currently contained (btreeid,pageid) pairs in LRU order. | |
| bool | Verify () const |
| Verify the integrity of the LRU list and hash table. | |
Protected Attributes | |
| PageCacheImpl * | m_impl |
| pointer to implementation class. | |
Detailed Description
template<typename _Key = uint32_t, typename _Compare = std::less<_Key>, unsigned int _BTreePageSize = 1024, uint32_t _AppVersionId = 0>
class stx::CBTreeDB< _Key, _Compare, _BTreePageSize, _AppVersionId >::PageCache
PageCache and PageCacheImpl implement a LRU-strategy cache of B-tree pages used by CBTreeDB reader objects.
One cache object can be shared between multiple readers. However, this page cache is not thread safe. You may have to wrap some mutex libraries if needed.
The cached pages are put into a hash table for quick lookup by (btreeid,pageid). Simultaneously the HashCells are linked into a doubly chained "LRU"-list with the most recently used page at the head. This allows O(1) algorithms for both Store() and Retrieve() functions. When the maximum number of pages is exceeded, the tail pages of the LRU-list are removed. The drawing below illustrates the data structure used by the class.
Structure of PageCache's arrays and nodes
Definition at line 1328 of file stx-cbtreedb.h.
Constructor & Destructor Documentation
| stx::CBTreeDB< _Key, _Compare, _BTreePageSize, _AppVersionId >::PageCache::PageCache | ( | unsigned int | maxpages | ) | [inline, explicit] |
Create a new page cache containg maxsize pages.
Definition at line 1337 of file stx-cbtreedb.h.
| stx::CBTreeDB< _Key, _Compare, _BTreePageSize, _AppVersionId >::PageCache::PageCache | ( | const PageCache & | pc | ) | [inline] |
Copy Constructor: increment reference counter on base object.
Definition at line 1344 of file stx-cbtreedb.h.
| stx::CBTreeDB< _Key, _Compare, _BTreePageSize, _AppVersionId >::PageCache::~PageCache | ( | ) | [inline] |
Destructor: decrement reference counter on buffer and possibly deallocate it.
Definition at line 1352 of file stx-cbtreedb.h.
Member Function Documentation
| void stx::CBTreeDB< _Key, _Compare, _BTreePageSize, _AppVersionId >::PageCache::Clear | ( | ) | [inline] |
Remove all pages from the cache and reset status.
Definition at line 1374 of file stx-cbtreedb.h.
| std::vector< std::pair<void*, uint32_t> > stx::CBTreeDB< _Key, _Compare, _BTreePageSize, _AppVersionId >::PageCache::GetPagelist | ( | ) | const [inline] |
Return a vector listing all currently contained (btreeid,pageid) pairs in LRU order.
Used by the test cases for verification.
Definition at line 1401 of file stx-cbtreedb.h.
| PageCache& stx::CBTreeDB< _Key, _Compare, _BTreePageSize, _AppVersionId >::PageCache::operator= | ( | const PageCache & | pc | ) | [inline] |
Assignment Operator: increment reference counter on base object.
Definition at line 1359 of file stx-cbtreedb.h.
| bool stx::CBTreeDB< _Key, _Compare, _BTreePageSize, _AppVersionId >::PageCache::Retrieve | ( | void * | btreeid, | |
| uint32_t | pageid, | |||
| BTreePage & | outpage | |||
| ) | [inline] |
Retrieve a cached page identified by (btreeid,pageid).
Returns true if the page was found.
Definition at line 1387 of file stx-cbtreedb.h.
| void stx::CBTreeDB< _Key, _Compare, _BTreePageSize, _AppVersionId >::PageCache::SetMaxSize | ( | unsigned int | maxsize | ) | [inline] |
Change maximum number of pages in cache, note that this does not immediately have effect.
Definition at line 1394 of file stx-cbtreedb.h.
| void stx::CBTreeDB< _Key, _Compare, _BTreePageSize, _AppVersionId >::PageCache::Store | ( | void * | btreeid, | |
| uint32_t | pageid, | |||
| const BTreePage & | page | |||
| ) | [inline] |
Store a page object in a cache cell identified by (btreeid,pageid).
Definition at line 1380 of file stx-cbtreedb.h.
| bool stx::CBTreeDB< _Key, _Compare, _BTreePageSize, _AppVersionId >::PageCache::Verify | ( | ) | const [inline] |
Verify the integrity of the LRU list and hash table.
Definition at line 1407 of file stx-cbtreedb.h.
Member Data Documentation
PageCacheImpl* stx::CBTreeDB< _Key, _Compare, _BTreePageSize, _AppVersionId >::PageCache::m_impl [protected] |
pointer to implementation class.
Definition at line 1333 of file stx-cbtreedb.h.
The documentation for this class was generated from the following file:
- include/stx-cbtreedb.h
