THashCache

Return to Unit Filesystem

Description

---

To be documented

Class definitions

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THashCache = class(TObject)

Note: A block cache with hash keys for faster page lookup.
constructor Create(ADriver:TFileSysDriver);
destructor Destroy; override;
private
FDriver:TFileSysDriver;
FLock:TCriticalSectionHandle;
FKeyBits:Byte;
FKeyMask:LongWord;
FKeyBuckets:Pointer;
FBuffer:Pointer;
FPageSize:LongWord;
FPageCount:LongWord;
FCacheSize:LongWord;
FCacheKeys:LongWord;
FCacheMode:TCacheMode;
FCacheState:TCacheState;
FFlushTimeout:LongWord;
FDiscardTimeout:LongWord;
FReadCached:Int64;
FReadDirect:Int64;
FWriteBack:Int64;
FWriteThrough:Int64;
FWriteDirect:Int64;
FHitCount:Int64;
FMissCount:Int64;
FFailCount:Int64;
FSuccessCount:Int64;
FFlushCount:Int64;
FDiscardCount:Int64;
FUnknownCount:Int64;
FFirstPage:TCachePage;	First Cache Page (Any State)
FLastPage:TCachePage;	Last Cache Page (Any State)
FFirstEmpty:TCachePage;	First Free Page
FLastEmpty:TCachePage;	Last Free Page
FFirstClean:TCachePage;	First Clean Page (Used with no Write pending)
FLastClean:TCachePage;	Last Clean Page (Used with no Write pending)
FFirstDirty:TCachePage;	First Dirty Page (Used with Write pending)
FLastDirty:TCachePage;	Last Dirty Page (Used with Write pending)
FTimer:THashCacheTimer;
FThread:THashCacheThread;
function AcquireLock:Boolean;
function ReleaseLock:Boolean;
function AddPage(APage:TCachePage):Boolean;
function RemovePage(APage:TCachePage):Boolean;
function AddEmpty(APage:TCachePage):Boolean;
function AddClean(APage:TCachePage):Boolean;
function AddDirty(APage:TCachePage):Boolean;
function AddUnknown(APage:TCachePage):Boolean;
function UpdateClean(APage:TCachePage):Boolean;
function UpdateDirty(APage:TCachePage):Boolean;
function RoundPageSize(APageSize:LongWord):LongWord;
function RoundCacheSize(ACacheSize,APageSize:LongWord):LongWord;
function AdjustCacheKeys(ACacheKeys:LongWord):LongWord;
function CalculatePageCount(ADevice:TDiskDevice):Word;
function CalculatePageShift(ADevice:TDiskDevice):Word;
function CalculatePageMask(ADevice:TDiskDevice):LongWord;
function KeyLink(APage:THashCachePage):Boolean;
function KeyUnlink(APage:THashCachePage):Boolean;
function KeyFirst(AKeyHash:LongWord):THashCachePage;
function LinkPage(APage:TCachePage):Boolean;
function UnlinkPage(APage:TCachePage):Boolean;
function LinkEmpty(APage:TCachePage):Boolean;
function UnlinkEmpty(APage:TCachePage):Boolean;
function LinkClean(APage:TCachePage):Boolean;
function UnlinkClean(APage:TCachePage):Boolean;
function LinkDirty(APage:TCachePage):Boolean;
function UnlinkDirty(APage:TCachePage):Boolean;
public
property PageSize:LongWord read FPageSize;
property PageCount:LongWord read FPageCount;
property CacheSize:LongWord read FCacheSize;
property CacheKeys:LongWord read FCacheKeys;
property CacheMode:TCacheMode read FCacheMode;
property CacheState:TCacheState read FCacheState;
property FlushTimeout:LongWord read FFlushTimeout;
property DiscardTimeout:LongWord read FDiscardTimeout;
property ReadCached:Int64 read FReadCached;
property ReadDirect:Int64 read FReadDirect;
property WriteBack:Int64 read FWriteBack;
property WriteThrough:Int64 read FWriteThrough;
property WriteDirect:Int64 read FWriteDirect;
property HitCount:Int64 read FHitCount;
property MissCount:Int64 read FMissCount;
property FailCount:Int64 read FFailCount;
property SuccessCount:Int64 read FSuccessCount;
property FlushCount:Int64 read FFlushCount;
property DiscardCount:Int64 read FDiscardCount;
property UnknownCount:Int64 read FUnknownCount;
function OpenCache(ACacheSize,ACacheKeys,APageSize:LongWord; ACacheMode:TCacheMode):Boolean;
function CloseCache:Boolean;
function DeviceRead(ADevice:TDiskDevice; ASector:LongWord; ACount:Word; var ABuffer):Boolean;
function DeviceWrite(ADevice:TDiskDevice; ASector:LongWord; ACount:Word; const ABuffer):Boolean;
function DeviceErase(ADevice:TDiskDevice; ASector:LongWord; ACount:Word):Boolean;
function GetDevicePage(ADevice:TDiskDevice; ASector:LongWord):TCachePage; virtual;
function GetEmptyPage:TCachePage;
function AllocDevicePage(ADevice:TDiskDevice; ASector:LongWord; AWrite:Boolean):TCachePage; virtual;
function DiscardPage(APage:TCachePage):Boolean;
function DiscardCache(AFirst,AAll:Boolean):Boolean;
function ReleaseDevicePages(ADevice:TDiskDevice):Boolean;
function FlushPage(APage:TCachePage):Boolean;
function FlushPageEx(APage:TCachePage):Boolean;
function FlushCache(AFirst,AAll:Boolean):Boolean;
function CheckTimer:Boolean;
function ProcessTimer:Boolean;
function SchedulePage(APage:TCachePage; ATimeout:LongWord):Boolean;
function UnschedulePage(APage:TCachePage):Boolean;

Function declarations

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constructor THashCache.Create(ADriver:TFileSysDriver);

Description: To be documented

Note	None documented

destructor THashCache.Destroy;

Description: To be documented

Note	None documented

function THashCache.AcquireLock:Boolean;

Description: To be documented

Note	None documented

function THashCache.ReleaseLock:Boolean;

Description: To be documented

Note	None documented

function THashCache.AddPage(APage:TCachePage):Boolean;

Description: Add a new page to the Page list and the Empty list

Note	None documented

function THashCache.RemovePage(APage:TCachePage):Boolean;

Description: Remove a Page from the Page list and any other lists then Free the Page

Note	None documented

function THashCache.AddEmpty(APage:TCachePage):Boolean;

Description: Add a Page to the Empty list, removing from other lists if needed

Note	None documented

function THashCache.AddClean(APage:TCachePage):Boolean;

Description: Add a Page to the Clean list, removing from other lists if needed

Note	None documented

function THashCache.AddDirty(APage:TCachePage):Boolean;

Description: Add a Page to the Dirty list, removing from other lists if needed

Note	None documented

function THashCache.AddUnknown(APage:TCachePage):Boolean;

Description: Make a Page Unknown by removing from any other lists if needed

Note	None documented

function THashCache.UpdateClean(APage:TCachePage):Boolean;

Description: Move a Page to the end of the Clean list

Note	None documented

function THashCache.UpdateDirty(APage:TCachePage):Boolean;

Description: Move a Page to the end of the Dirty list

Note	None documented

function THashCache.RoundPageSize(APageSize:LongWord):LongWord;

Description: Round Page Size to the power of 2 of Sector Size

Note	Caller must hold the lock

function THashCache.RoundCacheSize(ACacheSize,APageSize:LongWord):LongWord;

Description: Round Cache Size to the next multiple of Page Size

Note	Caller must hold the lock

function THashCache.AdjustCacheKeys(ACacheKeys:LongWord):LongWord;

Description: Adjust Cache Keys to be within safe limits

Note	Caller must hold the lock

function THashCache.CalculatePageCount(ADevice:TDiskDevice):Word;

Description: Calculate the power of 2 multiple of sector size which will fit within the page

Note	Caller must hold the lock

function THashCache.CalculatePageShift(ADevice:TDiskDevice):Word;

Description: Calculate the shift count for Page to Key conversion

Note	Caller must hold the lock

function THashCache.CalculatePageMask(ADevice:TDiskDevice):LongWord;

Description: Calculate the mask for Sector to Page conversion

Note	Caller must hold the lock

function THashCache.KeyLink(APage:THashCachePage):Boolean;

Description: Link APage to KeyPrev,KeyNext siblings and Adjust First

Note	Caller must hold the lock

function THashCache.KeyUnlink(APage:THashCachePage):Boolean;

Description: Unlink APage from KeyPrev,KeyNext siblings and Adjust First

Note	Caller must hold the lock

function THashCache.KeyFirst(AKeyHash:LongWord):THashCachePage;

Description: To be documented

Note	Caller must hold the lock

function THashCache.LinkPage(APage:TCachePage):Boolean;

Description: Link APage to PrevPage,NextPage siblings and Adjust FirstPage/LastPage

Note	Caller must hold the lock

function THashCache.UnlinkPage(APage:TCachePage):Boolean;

Description: Unlink APage from PrevPage,NextPage Siblings and Adjust FirstPage/LastPage

Note	Caller must hold the lock

function THashCache.LinkEmpty(APage:TCachePage):Boolean;

Description: Link APage to PrevLink,NextLink siblings and Adjust FirstEmpty/LastEmpty

Note	Caller must hold the lock

function THashCache.UnlinkEmpty(APage:TCachePage):Boolean;

Description: Unlink APage from PrevLink,NextLink Siblings and Adjust FirstEmpty/LastEmpty

Note	Caller must hold the lock

function THashCache.LinkClean(APage:TCachePage):Boolean;

Description: Link APage to PrevLink,NextLink siblings and Adjust FirstClean/LastClean

Note	Caller must hold the lock

function THashCache.UnlinkClean(APage:TCachePage):Boolean;

Description: Unlink APage from PrevLink,NextLink Siblings and Adjust FirstClean/LastClean

Note	Caller must hold the lock

function THashCache.LinkDirty(APage:TCachePage):Boolean;

Description: Link APage to PrevLink,NextLink siblings and Adjust FirstDirty/LastDirty

Note	Caller must hold the lock

function THashCache.UnlinkDirty(APage:TCachePage):Boolean;

Description: Unlink APage from PrevLink,NextLink Siblings and Adjust FirstDirty/LastDirty

Note	None documented

function THashCache.PrepareDeviceWrite(ADevice:TDiskDevice; APage:TCachePage; ASector,ACount:LongWord):Boolean;

Description: Prepare a Cache Page for Write by ensuring that required sectors are cached

Sector	Passed Sector will be the starting sector for the write to this Page
Count	Passed Count will be the write count to this Page (Calculated by caller)
Note	Only called internally by DeviceWrite Caller must hold the lock

function THashCache.CalculateDevicePage(ADevice:TDiskDevice; ASector:LongWord; var ACount:LongWord):Boolean;

Description: Calculate the number of sectors remaining in a page given the starting sector

Note	Only called internally by DeviceRead/DeviceWrite/DeviceErase Caller must hold the lock

function THashCache.OpenCache(ACacheSize,ACacheKeys,APageSize:LongWord; ACacheMode:TCacheMode):Boolean;

Description: Allocate the Memory, Create the Empty Pages and Open Cache

Note	None documented

function THashCache.CloseCache:Boolean;

Description: Flush all Dirty Pages, Release the Memory and Close the Cache

Note	None documented

function THashCache.DeviceRead(ADevice:TDiskDevice; ASector,ACount:LongWord; var ABuffer):Boolean;

Description: Read Data from the Physical Device using either Cached or Direct access

Note	AllocDevicePage does all checks for Size, Sector and Count.

function THashCache.DeviceWrite(ADevice:TDiskDevice; ASector,ACount:LongWord; const ABuffer):Boolean;

Description: Write Data to the Physical Device using either Cached or Direct access

Note	AllocDevicePage does all checks for Size, Sector and Count.

function THashCache.DeviceErase(ADevice:TDiskDevice; ASector,ACount:LongWord):Boolean;

Description: Erase Data from the Physical Device and update cached pages accordingly

Note	None documented

function THashCache.GetDevicePage(ADevice:TDiskDevice; ASector:LongWord):TCachePage;

Description: Get the Clean or Dirty Page that contains this Sector on this Device

Note	None documented

function THashCache.GetEmptyPage:TCachePage;

Description: Get the First Empty Page, Discard First Clean Page if none Empty

Note	None documented

function THashCache.AllocDevicePage(ADevice:TDiskDevice; ASector:LongWord; AWrite:Boolean):TCachePage;

Description: Allocate an Empty Page to the Device and mark as Clean or Dirty

Note	None documented

function THashCache.DiscardPage(APage:TCachePage):Boolean;

Description: Return a Clean Page to Empty

Note	None documented

function THashCache.DiscardCache(AFirst,AAll:Boolean):Boolean;

Description: Find any Clean Pages older than DiscardTimeout and Discard them

Note	None documented

function THashCache.ReleaseDevicePages(ADevice:TDiskDevice):Boolean;

Description: Return all Clean or Dirty Pages on the Device to Empty

Note	None documented

function THashCache.FlushPage(APage:TCachePage):Boolean;

Description: Return a Dirty Page to Clean

Note	None documented

function THashCache.FlushPageEx(APage:TCachePage):Boolean;

Description: Return a Dirty Page to Clean if it is older than FlushTimeout

Note	Only called by CacheThread with page scheduled from CacheTimer

function THashCache.FlushCache(AFirst,AAll:Boolean):Boolean;

Description: Find any Dirty Pages older than FlushTimeout and Flush them

Note	None documented

function THashCache.CheckTimer:Boolean;

Description: To be documented

Note	None documented

function THashCache.ProcessTimer:Boolean;

Description: To be documented

Note	None documented

function THashCache.SchedulePage(APage:TCachePage; ATimeout:LongWord):Boolean;

Description: To be documented

Note	None documented

function THashCache.UnschedulePage(APage:TCachePage):Boolean;

Description: To be documented

Note	None documented

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