DIRECTORYAlpineEnvironmentUSING[FileID, LockMode, PageCount, VolumeID],AlpineInternalUSING[FileHandle, TransHandle],FileInstance,FileMapUSING[GetFileID, GetVolumeID, GetVolumeIDAndFileID, Register],TransactionMapUSING[GetFileInstanceList, SetFileInstanceList];FileInstanceImpl: CEDAR MONITORIMPORTS FileMap, TM: TransactionMapEXPORTS AlpineInternal, FileInstance =BEGIN OPEN AE: AlpineEnvironment, AI: AlpineInternal;Handle: TYPE = REF FileInstanceObject;FileInstanceObject: PUBLIC TYPE = RECORD[trans: AI.TransHandle,fileHandle: AI.FileHandle,useCount: CARDINAL,deltaVersion: LONG INTEGER,highWaterMark: AE.PageCount,lockMode: AE.LockMode,nextForTrans: Handle];InUse: --CALLING-- ERROR = CODE;OldHandleNotFound: --CALLING-- ERROR = CODE;UseCountAlreadyZero: --CALLING-- ERROR = CODE;Register: PUBLIC ENTRY PROCEDURE [trans: AI.TransHandle, volumeID: AE.VolumeID, fileID:AE.FileID] RETURNS [handle: Handle] =BEGIN  -- errors defined in FileInstance: none.ENABLE UNWIND => NULL;firstInsHandle: Handle;TRUSTED BEGIN firstInsHandle _ TM.GetFileInstanceList[trans]; END;FOR handle _ firstInsHandle, handle.nextForTransUNTIL handle = NILDOIF FileMap.GetVolumeIDAndFileID[handle.fileHandle] = [volumeID, fileID]THEN GOTO found;REPEATfound => handle.useCount _ handle.useCount + 1;FINISHED => BEGIN handle _ NEW[FileInstanceObject _ [trans:trans, fileHandle: FileMap.Register[volumeID, fileID], useCount: 1,deltaVersion: 0, highWaterMark: LAST[AE.PageCount], lockMode: none,nextForTrans: firstInsHandle]];TRUSTED BEGIN TM.SetFileInstanceList[trans, handle]; END;END;ENDLOOP;END;Unregister: PUBLIC ENTRY PROCEDURE [handle: Handle] =BEGIN  -- errors defined in FileInstance: none.ENABLE UNWIND => NULL;IF handle.useCount = 0 THEN RETURN WITH ERROR UseCountAlreadyZero;IF (((handle.useCount _ handle.useCount - 1) = 0) AND (handle.deltaVersion = 0))THEN TRUSTED BEGINprevInsHandle: Handle _ FindHandle[handle.fileHandle,TM.GetFileInstanceList[handle.trans]];IF prevInsHandle = NILTHEN TM.SetFileInstanceList[handle.trans, handle.nextForTrans]ELSE prevInsHandle.nextForTrans _ handle.nextForTrans;END;END;FlushTransState: PUBLIC ENTRY PROCEDURE [trans: AI.TransHandle] =TRUSTED BEGIN  -- errors defined in FileInstance: none.ENABLE UNWIND => NULL;FOR insHandle: Handle _ TM.GetFileInstanceList[trans], insHandle.nextForTransUNTIL insHandle = NILDO IF ((insHandle.useCount # 0) OR (insHandle.deltaVersion = 0))THEN RETURN WITH ERROR InUse;ENDLOOP;TM.SetFileInstanceList[trans, NIL];  END;GetFileHandle: PUBLIC PROCEDURE [handle: Handle] RETURNS [fileHandle:AI.FileHandle] =BEGIN  -- errors defined in FileInstance: none.RETURN[handle.fileHandle];END;GetTransHandle: PUBLIC PROCEDURE [handle: Handle] RETURNS [trans: AI.TransHandle] =BEGIN  -- errors defined in FileInstance: none.RETURN[handle.trans];END;GetVolumeID: PUBLIC PROCEDURE [handle: Handle] RETURNS [volumeID:AE.VolumeID] =BEGIN  -- errors defined in FileInstance: none. RETURN[FileMap.GetVolumeID[handle.fileHandle]];END;GetFileID: PUBLIC PROCEDURE [handle: Handle] RETURNS [fileID: AE.FileID] =BEGIN  -- errors defined in FileInstance: none.  RETURN[FileMap.GetFileID[handle.fileHandle]];END;GetVolumeIDAndFileID: PUBLIC PROCEDURE [handle: Handle] RETURNS [volumeID:AE.VolumeID, fileID: AE.FileID] =BEGIN  -- errors defined in FileInstance: none.[volumeID, fileID] _ FileMap.GetVolumeIDAndFileID[handle.fileHandle];END;GetDeltaVersion: PUBLIC ENTRY PROCEDURE [handle: Handle] RETURNS [delta: LONGINTEGER] =BEGIN  -- errors defined in FileInstance: none.ENABLE UNWIND => NULL;RETURN[handle.deltaVersion];END;SetMaxDeltaVersion: PUBLIC ENTRY PROCEDURE [handle: Handle, increment: LONGINTEGER] =BEGIN  -- errors defined in FileInstance: none.ENABLE UNWIND => NULL;handle.deltaVersion _ MAX[handle.deltaVersion, increment];END;GetHighWaterMark: PUBLIC ENTRY PROCEDURE [handle: Handle] RETURNS[highWaterMark: AE.PageCount] =BEGIN  -- errors defined in FileInstance: none.ENABLE UNWIND => NULL;RETURN[handle.highWaterMark];END;SetHighWaterMark: PUBLIC ENTRY PROCEDURE [handle: Handle, highWaterMark:AE.PageCount] RETURNS [oldHighWaterMark: AE.PageCount] =BEGIN  -- errors defined in FileInstance: none.ENABLE UNWIND => NULL;oldHighWaterMark _ handle.highWaterMark;handle.highWaterMark _ highWaterMark;END;GetLockMode: PUBLIC ENTRY PROCEDURE [handle: Handle] RETURNS [lock: AE.LockMode] =BEGIN  -- errors defined in FileInstance: none.ENABLE UNWIND => NULL;RETURN[handle.lockMode];END;SetLockMode: PUBLIC ENTRY PROCEDURE [handle: Handle, lock: AE.LockMode] =BEGIN  -- errors defined in FileInstance: none.ENABLE UNWIND => NULL;handle.lockMode _ lock;END;GetNextHandleForTrans: PUBLIC ENTRY PROCEDURE [trans: AI.TransHandle, handle:Handle] RETURNS [nextHandle: Handle] =BEGIN  -- errors defined in FileInstance: none.ENABLE UNWIND => NULL;firstInsHandle: Handle;TRUSTED BEGIN firstInsHandle _ TM.GetFileInstanceList[trans]; END;IF handle = NIL THEN RETURN[firstInsHandle];[] _ FindHandle[handle.fileHandle, firstInsHandle];RETURN[handle.nextForTrans];END;FindHandle: INTERNAL PROCEDURE [fileHandle: AI.FileHandle, firstInsHandle: Handle]RETURNS [prevHandle: Handle] =BEGIN  -- errors defined in FileInstance: none.volumeID: AE.VolumeID;fileID: AE.FileID;[volumeID, fileID] _ FileMap.GetVolumeIDAndFileID[fileHandle];prevHandle _ NIL;FOR foundHandle: Handle _ firstInsHandle, foundHandle.nextForTransUNTIL foundHandle = NILDOIF FileMap.GetVolumeIDAndFileID[foundHandle.fileHandle] = [volumeID, fileID]THEN EXIT;prevHandle _ foundHandle;REPEAT FINISHED => ERROR OldHandleNotFound;ENDLOOP;END;END.Edit LogInitial: Kolling: October 21, 1982 2:22 pm: an impl module for FileInstance.   8  FileInstanceImpl.mesaCopyright c 1985 by Xerox Corporation.  All rights reserved.Last edited byKolling on November 2, 1983 4:09 pmerrors:Finds or creates a Handle for the supplied trans, volume, and file, and increments use count on the returned handle.  If the handle is created, it is also entered in the FileInstance list for its transaction and FileMap.Register is called.Decrements use count on handle.  If the use count becomes zero and delta version is 0 (i.e., if the file has not been updated), deletes it from the FileInstance list for its transaction.  (Updated files are taken care of by FlushTransState.)When this is called, it is a error if any handle in this transaction's FileInstance list has useCount # 0 or delta version = 0.Access to immutable attributes.Access to read/write attributes.Sets the delta version to the MAX of increment and its existing value.Returns the uncommitted highWaterMark, for this transaction.  Initialize value is LAST[PageCount].Enumeration.handle = NIL starts a new enumeration, and nextHandle = NIL is returned when theenumeration is exhausted.  The FileInstance list is assumed to not be being modified duringthis enumeration.  When handle is non-NIL, not finding it is a fatal error.main line code.Hauser, March 7, 1985 2:53:07 pm PSTNodified, added copyright.Э╩	  Ш JШ JШ ЪЬЩIcodeЪЬ
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