270 lines
9.8 KiB
C
270 lines
9.8 KiB
C
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/*++
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Copyright (C) 2000-2001 Microsoft Corporation
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Module Name:
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VarObjHeap.H
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Abstract:
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Implements the storage of variable length objects over the top of of a fixed
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length page system. It keeps a set of admin pages for holding the pages active
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by this subsystem, along with how much space is used on each. When a page becomes
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empty it frees up the page to the page system. It also deals with blocks that span
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multiple pages
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History:
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paulall 02-Feb-2001 Created
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--*/
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#include <unk.h>
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#include <arrtempl.h>
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class CPageFile;
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class CPageSource;
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#define VAROBJ_VERSION 1
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//**************************************************************************************
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//VarObjAdminPageEntry - This is a structure that is stored within the
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//m_aAdminPages cache. It has an entry for each of the admin pages
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//that we cache. It stores the PageId (0 for the first one!),
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//pointer to the actual page, and a flag to determine if we need to
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//flush it next time around.
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//**************************************************************************************
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typedef struct _VarObjAdminPageEntry
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{
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DWORD dwPageId;
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BYTE *pbPage;
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bool bDirty;
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} VarObjAdminPageEntry;
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//**************************************************************************************
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//VarObjObjOffsetEntry: There is an array of these objects stored at the
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//start of the object page to point out where each object is stored.
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//If this is a continuation block we do not have one of these, however
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//continuation blocks have consecutive pageIds so it should be fairly easy
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//to conclude
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//**************************************************************************************
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typedef struct _VarObjObjOffsetEntry
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{
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DWORD dwOffsetId;
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DWORD dwPhysicalStartOffset;
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DWORD dwBlockLength;
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DWORD dwCRC;
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} VarObjObjOffsetEntry;
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//**************************************************************************************
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//VarObjHeapAdminPage - This is the header of each of the admin pages
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//that are stored in the object file. The version is only relevant
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//in the first page (page 0). The last entry is a buffer to make
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//it 4-DWORD structure rather than 3. May use it at a later date.
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//Should always set it to 0 for now.
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//**************************************************************************************
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typedef struct _VarObjHeapAdminPage
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{
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DWORD dwVersion;
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DWORD dwNextAdminPage;
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DWORD dwNumberEntriesOnPage;
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//VarObjHeapFreeList aFreeListEntries[dwNumberEntriesOnPage];
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} VarObjHeapAdminPage;
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//**************************************************************************************
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//VarObjHeapFreeList - This structure follows the admin page header
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//and there is an entry for each page we use to store objects. The
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//page may not be full, so we do not shuffle items on a second page
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//to this page when we delete an entry.
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//**************************************************************************************
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typedef struct _VarObjHeapFreeList
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{
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DWORD dwPageId;
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DWORD dwFreeSpace;
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DWORD dwCRC32;
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DWORD dwReserved;
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} VarObjHeapFreeList;
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//**************************************************************************************
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//CVarObjHeap - This is the implementation of the variable sized object store
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//over the top of the transacted fixed page manager. It tracks the admin pages
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//that hold all pages we use to store objects in (it caches these pages), and
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//also manages cases when an object is too big to fit on a single page.
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//**************************************************************************************
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class CVarObjHeap
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{
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private:
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//Current status of admin page
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enum
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{
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NoError = 0,
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AdminPageReadFailure = 1,
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RootAdminPageCreationFailure = 2,
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AdminPagesNeedReading = 3
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} m_dwStatus;
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//Pointer to the transacted file for the object storage
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CPageFile *m_pObjectFile;
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//Page size used within the object storage file.
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DWORD m_dwPageSize;
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//Admin page structure
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CLockableFlexArray m_aAdminPages;
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protected:
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//Adds an allocation to the end of the existing allocations
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DWORD AllocateFromPage(/* in */ DWORD dwPageId,
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/* in */ BYTE *pbPage,
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/* in */ ULONG ulBlockSize,
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/* in */ const BYTE *pBlock,
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/* out*/ ULONG *pdwNewOffset);
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//Allocates a multi-page entry in the object file. This requires
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//different algorithms to work things out so is a special case
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DWORD AllocateMultiPageBuffer(/* in */ ULONG ulBlockSize,
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/* in */ const BYTE *pBlock,
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/* out */ ULONG *pulPageId,
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/* out */ ULONG *pulOffsetId);
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//Given and offsetId and a page, calculate the physical pointer to the object and also
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//return the size of the block
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DWORD OffsetToPointer(/* in */ ULONG ulOffsetId,
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/* in */ BYTE *pbPage,
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/* out*/ BYTE **pOffsetPointer,
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/* out*/ ULONG *pdwBlockSize,
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/* out*/ DWORD *pdwCRC32);
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//Reads the admin pages into memory and marks them as clean (no changes)
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//setting bReReadPages to false has an affect of clearing the pages out
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DWORD ReadAdminPages(CPageSource *pTransactionManager, bool bReReadPages);
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//Writes each of the changed admin pages back to the object file
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DWORD FlushAdminPages();
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//Find a page form the admin pages that can accomodate a particular buffer size
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DWORD FindPageWithSpace(/* in */ DWORD dwRequiredSize,
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/* out*/ DWORD *pdwPageId);
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//Allocate a new page for use with objects. A buffer for the new page is passed
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//in, however the PageId of this page is passed out
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DWORD AllocateNewPage(/* in */ DWORD ulBlockSize,
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/* out*/ DWORD *dwPageId,
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/* in */ BYTE *pbNewObjectPage);
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//Deletes a page, and updates the admin pages as appropriage
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DWORD DeletePage(/* in */ DWORD ulPageId);
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//DeleteFromPage - removes an object from a specific object page
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DWORD RemoveFromPage(/* in */ ULONG ulPageId,
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/* in */ ULONG ulOffsetId,
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/* in */ BYTE *pbPage,
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/* out*/ DWORD *pdwSize);
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//MultiPageObject - returns true if the provided page is the first page
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//of a multi-page object
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bool MultiPageObject(/* in */ BYTE *pbPage) { return ((VarObjObjOffsetEntry*) pbPage)->dwBlockLength > (m_dwPageSize - (sizeof(VarObjObjOffsetEntry) * 2)); }
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//DeleteMultiPageBuffer - handles the deletion of an object when it spans
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//multiple pages
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DWORD DeleteMultiPageBuffer(/* in */ ULONG ulPageId,
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/* in */ ULONG ulOffsetId,
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/* in */ BYTE *pbPage);
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//UpdateAdminPageForAllocate - Updates the admin page to decrement the amount
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//of free space on a page by this amount ( + sizeof(VarObjObjOffsetEntry))
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DWORD UpdateAdminPageForAllocate(/* in */ ULONG ulPageId,
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/* in */ ULONG ulBlockSize,
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/* in */ DWORD dwCRC32);
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//UpdateAdminPageForDelete - Updates the admin page for giving space back. If
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//the page is totally empty we should delete the page altogether
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DWORD UpdateAdminPageForDelete(/* in */ ULONG ulPageId,
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/* in */ ULONG ulBlockSize,
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/* in */ DWORD dwCRC32,
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/* out */ bool *pbPageDeleted);
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//Removes an object page entry from an admin page, removing the
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//admin page if it is no longer needed
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DWORD RemoveEntryFromAdminPage(/* in */ DWORD dwAdminPageIndex,
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/* in */ DWORD dwAdminPageEntry);
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//Returns a CRC based on a given block of memory
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#define FINALIZE_CRC32(x) (x=~x)
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DWORD CreateCRC32(/* in */ const BYTE *pBlock,
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/* in */ DWORD dwSize,
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/* in */ DWORD dwPreviousCRC = (DWORD) -1); // Must be 0xFFFFFFFF if no previous CRC
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#ifdef DBG
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//Given a page we validate that there is in fact enough space
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//for this block. If there is not it asserts. This implies
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//that the admin page is not in sync with the actual pages.
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DWORD ValidatePageFreeSpace(/* in */ const BYTE *pbPage,
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/* in */ DWORD ulBlockSize);
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//Given a page and a page ID, it validates the amount of free space
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//on the page is equal to the amount the admin page thinks is on
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//there.
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DWORD ValidatePageFreeSpaceWithAdminPage(/* in */ const BYTE *pbPage,
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/* in */ DWORD ulPageId);
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//Dumps the offset table of a page to the debugger
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DWORD DumpPageOffsetTable(/* in */ DWORD dwPageId,
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/* in */ const BYTE *pbPage);
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//Checks the CRCs of all objects on a page (cannot do this
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//for a multi-page object though as we only have the first
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//page!)
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DWORD ValidateAllCRC32OnPage(/* in */ const BYTE *pbPage);
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//Validates the page check-sum with the admin page
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DWORD ValidatePageCRCWithAdminPage(/* in */ const BYTE *pbPage,
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/* in */ DWORD dwPageId);
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#endif /* DBG */
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public:
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CVarObjHeap();
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~CVarObjHeap();
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DWORD Initialize(CPageSource *pPageManager);
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DWORD Shutdown(DWORD dwShutdownType);
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//Re-read admin pages
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DWORD InvalidateCache();
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//Discard admin pages
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DWORD FlushCaches();
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//ReadBuffer pages the virtual page and offset of the block and returns a new[]-ed block
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DWORD ReadBuffer(/* in */ ULONG ulPageId,
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/* in */ ULONG ulOffsetId,
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/* out */ BYTE **ppReturnedBlock,
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/* out */ DWORD *pdwBlockSize);
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//WriteNewBuffer will write a new page based on size of BYTE *, and return the
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//new virtual pageId and offsetId of the block.
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DWORD WriteNewBuffer(/* in */ ULONG ulBlockSize,
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/* in */ const BYTE *pBlock,
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/* out */ ULONG *pulPageId,
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/* out */ ULONG *pulOffsetId);
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//WriteExistingBuffer will update an existing block with new data. The old virtual page
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//and offset are passed in, and new ones are returned. They may or may not be the same
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//depending on if it still fits in the page or not.
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DWORD WriteExistingBuffer(/* in */ ULONG ulBlockSize,
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/* in */ const BYTE *pBlock,
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/* in */ ULONG ulOldPageId,
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/* in */ ULONG ulOldOffsetId,
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/* out */ ULONG *pulNewPageId,
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/* out */ ULONG *pulNewOffsetId);
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//DeleteBuffer is called to delete the item in the store given the virtual pageId and
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//offsetId.
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DWORD DeleteBuffer(/* in */ ULONG ulPageId,
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/* in */ ULONG ulOffsetId);
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};
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