TCache

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Description

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To be documented

Class definitions

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TCache = class(TObject)

Note: A simple block cache with Read Only/Read Write modes and Free/Clean/Dirty page tracking. (No longer used)
constructor Create(ADriver:TFileSysDriver);
destructor Destroy; override;
private
FDriver:TFileSysDriver;
FLock:TCriticalSectionHandle;
FBuffer:Pointer;
FPageSize:LongWord;
FPageCount:LongWord;
FCacheSize:LongWord;
FCacheMode:TCacheMode;
FCacheState:TCacheState;
FCacheTimeout: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:TCacheTimer;
FThread:TCacheThread;
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 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 CacheMode:TCacheMode read FCacheMode;
property CacheState:TCacheState read FCacheState;
property CacheTimeout:LongWord read FCacheTimeout;
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,APageSize:LongWord; ACacheMode:TCacheMode):Boolean;
function CloseCache:Boolean;
function DeviceRead(ADevice:TDiskDevice; ASector:LongWord; ACount:Word; var 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 TCache.Create(ADriver:TFileSysDriver);

Description: To be documented

Note	None documented

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destructor TCache.Destroy;

Description: To be documented

Note	None documented

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function TCache.AcquireLock:Boolean;

Description: To be documented

Note	None documented

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function TCache.ReleaseLock:Boolean;

Description: To be documented

Note	None documented

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

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

Note	None documented

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

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

Note	None documented

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

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

Note	None documented

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

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

Note	None documented

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

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

Note	None documented

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

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

Note	None documented

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

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

Note	None documented

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

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

Note	None documented

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

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

Note	Caller must hold the lock

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

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

Note	Caller must hold the lock

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

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

Note	Caller must hold the lock

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

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

Note	Caller must hold the lock

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

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

Note	Caller must hold the lock

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

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

Note	Caller must hold the lock

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

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

Note	Caller must hold the lock

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

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

Note	Caller must hold the lock

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

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

Note	Caller must hold the lock

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

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

Note	None documented

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function TCache.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

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function TCache.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

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

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

Note	None documented

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function TCache.CloseCache:Boolean;

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

Note	None documented

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function TCache.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.

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function TCache.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.

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

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

Note	None documented

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

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

Note	None documented

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function TCache.GetEmptyPage:TCachePage;

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

Note	None documented

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function TCache.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

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

Description: Return a Clean Page to Empty

Note	None documented

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

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

Note	None documented

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

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

Note	None documented

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

Description: Return a Dirty Page to Clean

Note	None documented

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

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

Note	Only called by CacheThread with page scheduled from CacheTimer

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

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

Note	None documented

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function TCache.CheckTimer:Boolean;

Description: To be documented

Note	None documented

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function TCache.ProcessTimer:Boolean;

Description: To be documented

Note	None documented

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

Description: To be documented

Note	None documented

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

Description: To be documented

Note	None documented

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