Difference between revisions of "TCache"
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Latest revision as of 04:36, 17 May 2018
Return to Unit Filesystem
Description
To be documented
Class definitions
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);
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destructor Destroy; override;
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private
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FDriver:TFileSysDriver;
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FLock:TCriticalSectionHandle;
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FBuffer:Pointer;
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FPageSize:LongWord;
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FPageCount:LongWord;
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FCacheSize:LongWord;
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FCacheMode:TCacheMode;
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FCacheState:TCacheState;
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FCacheTimeout:LongWord;
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FReadCached:Int64;
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FReadDirect:Int64;
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FWriteBack:Int64;
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FWriteThrough:Int64;
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FWriteDirect:Int64;
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FHitCount:Int64;
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FMissCount:Int64;
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FFailCount:Int64;
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FSuccessCount:Int64;
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FFlushCount:Int64;
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FDiscardCount:Int64;
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FUnknownCount:Int64;
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FFirstPage:TCachePage;
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First Cache Page (Any State) |
FLastPage:TCachePage;
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Last Cache Page (Any State) |
FFirstEmpty:TCachePage;
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First Free Page |
FLastEmpty:TCachePage;
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Last Free Page |
FFirstClean:TCachePage;
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First Clean Page (Used with no Write pending) |
FLastClean:TCachePage;
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Last Clean Page (Used with no Write pending) |
FFirstDirty:TCachePage;
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First Dirty Page (Used with Write pending) |
FLastDirty:TCachePage;
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Last Dirty Page (Used with Write pending) |
FTimer:TCacheTimer;
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FThread:TCacheThread;
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function AcquireLock:Boolean;
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function ReleaseLock:Boolean;
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function AddPage(APage:TCachePage):Boolean;
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function RemovePage(APage:TCachePage):Boolean;
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function AddEmpty(APage:TCachePage):Boolean;
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function AddClean(APage:TCachePage):Boolean;
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function AddDirty(APage:TCachePage):Boolean;
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function AddUnknown(APage:TCachePage):Boolean;
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function UpdateClean(APage:TCachePage):Boolean;
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function UpdateDirty(APage:TCachePage):Boolean;
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function RoundPageSize(APageSize:LongWord):LongWord;
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function RoundCacheSize(ACacheSize,APageSize:LongWord):LongWord;
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function LinkPage(APage:TCachePage):Boolean;
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function UnlinkPage(APage:TCachePage):Boolean;
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function LinkEmpty(APage:TCachePage):Boolean;
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function UnlinkEmpty(APage:TCachePage):Boolean;
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function LinkClean(APage:TCachePage):Boolean;
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function UnlinkClean(APage:TCachePage):Boolean;
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function LinkDirty(APage:TCachePage):Boolean;
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function UnlinkDirty(APage:TCachePage):Boolean;
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public
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property PageSize:LongWord read FPageSize;
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property PageCount:LongWord read FPageCount;
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property CacheSize:LongWord read FCacheSize;
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property CacheMode:TCacheMode read FCacheMode;
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property CacheState:TCacheState read FCacheState;
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property CacheTimeout:LongWord read FCacheTimeout;
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property ReadCached:Int64 read FReadCached;
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property ReadDirect:Int64 read FReadDirect;
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property WriteBack:Int64 read FWriteBack;
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property WriteThrough:Int64 read FWriteThrough;
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property WriteDirect:Int64 read FWriteDirect;
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property HitCount:Int64 read FHitCount;
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property MissCount:Int64 read FMissCount;
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property FailCount:Int64 read FFailCount;
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property SuccessCount:Int64 read FSuccessCount;
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property FlushCount:Int64 read FFlushCount;
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property DiscardCount:Int64 read FDiscardCount;
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property UnknownCount:Int64 read FUnknownCount;
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function OpenCache(ACacheSize,APageSize:LongWord; ACacheMode:TCacheMode):Boolean;
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function CloseCache:Boolean;
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function DeviceRead(ADevice:TDiskDevice; ASector:LongWord; ACount:Word; var ABuffer):Boolean;
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function DeviceErase(ADevice:TDiskDevice; ASector:LongWord; ACount:Word):Boolean;
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function GetDevicePage(ADevice:TDiskDevice; ASector:LongWord):TCachePage; virtual;
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function GetEmptyPage:TCachePage;
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function AllocDevicePage(ADevice:TDiskDevice; ASector:LongWord; AWrite:Boolean):TCachePage; virtual;
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function DiscardPage(APage:TCachePage):Boolean;
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function DiscardCache(AFirst,AAll:Boolean):Boolean;
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function ReleaseDevicePages(ADevice:TDiskDevice):Boolean;
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function FlushPage(APage:TCachePage):Boolean;
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function FlushPageEx(APage:TCachePage):Boolean;
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function FlushCache(AFirst,AAll:Boolean):Boolean;
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function CheckTimer:Boolean;
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function ProcessTimer:Boolean;
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function SchedulePage(APage:TCachePage; ATimeout:LongWord):Boolean;
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function UnschedulePage(APage:TCachePage):Boolean;
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Function declarations
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 |
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| 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 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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