361 lines
11 KiB
Plaintext
361 lines
11 KiB
Plaintext
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unit IdTransactedFileStream;
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interface
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{$I IdCompilerDefines.inc}
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{
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Original author: Grahame Grieve
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His notes are:
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If you want transactional file handling, with commit and rollback,
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then this is the unit for you. It provides transactional safety on
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Vista, win7, and windows server 2008, and just falls through to
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normal file handling on earlier versions of windows.
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There's a couple of issues with the wrapper classes TKernelTransaction
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and TIdTransactedFileStream:
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- you can specify how you want file reading to work with a transactional
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isolation. I don't surface this.
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- you can elevate the transactions to coordinate with DTC. They don't
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do this (for instance, you could put your file handling in the same
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transaction as an SQLServer transaction). I haven't done this - but if
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you do this, I'd love a copy ;-)
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you use it like this:
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procedure StringToFile(const AStr, AFilename: String);
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var
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oFileStream: TIdTransactedFileStream;
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oTransaction : TKernelTransaction;
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begin
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oTransaction := TIdKernelTransaction.Create('Save Content to file '+aFilename, false);
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Try
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Try
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oFileStream := TIdTransactedFileStream.Create(AFilename, fmCreate);
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try
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if Length(AStr) > 0 then
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WriteStringToStream(LFileStream, AStr, IndyTextEncoding_8Bit);
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finally
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LFileStream.Free;
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end;
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oTransaction.Commit;
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Except
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oTransaction.Rollback;
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raise;
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End;
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Finally
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oTransaction.Free;
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End;
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end;
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anyway - maybe useful in temporary file handling with file and email? I've
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been burnt with temporary files and server crashes before.
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}
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uses
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{$IFDEF WIN32_OR_WIN64}
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Windows,
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Consts,
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{$ENDIF}
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Classes, SysUtils, IdGlobal;
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{$IFDEF WIN32_OR_WIN64}
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const
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TRANSACTION_DO_NOT_PROMOTE = 1;
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TXFS_MINIVERSION_COMMITTED_VIEW : Word = $0000; // The view of the file as of its last commit.
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TXFS_MINIVERSION_DIRTY_VIEW : Word = $FFFE; // The view of the file as it is being modified by the transaction.
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TXFS_MINIVERSION_DEFAULT_VIEW : Word = $FFFF; // Either the committed or dirty view of the file, depending on the context.
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// A transaction that is modifying the file gets the dirty view, while a transaction
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// that is not modifying the file gets the committed view.
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// remember to close the transaction handle. Use the CloseTransaction function here to avoid problems if the transactions are not available
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type
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TktmCreateTransaction = function (lpSecurityAttributes: PSecurityAttributes;
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pUow : Pointer;
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CreateOptions, IsolationLevel, IsolationFlags, Timeout : DWORD;
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Description : PWideChar) : THandle; stdcall;
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TktmCreateFileTransacted = function (lpFileName: PChar;
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dwDesiredAccess, dwShareMode: DWORD;
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lpSecurityAttributes: PSecurityAttributes;
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dwCreationDisposition, dwFlagsAndAttributes: DWORD;
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hTemplateFile: THandle;
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hTransaction : THandle;
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MiniVersion : Word;
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pExtendedParameter : Pointer): THandle; stdcall;
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TktmCommitTransaction = function (hTransaction : THandle) : Boolean; stdcall;
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TktmRollbackTransaction = function (hTransaction : THandle) :
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Boolean; stdcall;
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TktmCloseTransaction = function (hTransaction : THandle) : Boolean; stdcall;
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var
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CreateTransaction : TktmCreateTransaction;
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CreateFileTransacted : TktmCreateFileTransacted;
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CommitTransaction : TktmCommitTransaction;
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RollbackTransaction : TktmRollbackTransaction;
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CloseTransaction : TktmCloseTransaction;
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{$ENDIF}
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Function IsTransactionsWorking : Boolean;
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type
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TIdKernelTransaction = class (TObject)
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protected
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FHandle : THandle;
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public
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constructor Create(Const sDescription : String; bCanPromote : Boolean = false);
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destructor Destroy; override;
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function IsTransactional : Boolean;
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procedure Commit;
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procedure RollBack;
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end;
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TIdTransactedFileStream = class(THandleStream)
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{$IFNDEF WIN32_OR_WIN64}
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protected
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FFileStream : TFileStream;
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{$ENDIF}
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public
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constructor Create(const FileName: string; Mode: Word; oTransaction : TIdKernelTransaction);
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destructor Destroy; override;
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end;
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implementation
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uses RTLConsts;
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{$IFDEF WIN32_OR_WIN64}
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var
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GHandleKtm : HModule;
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GHandleKernel : HModule;
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function DummyCreateTransaction(lpSecurityAttributes: PSecurityAttributes;
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pUow : Pointer; CreateOptions, IsolationLevel,
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IsolationFlags, Timeout : DWORD;
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Description : PWideChar) : THandle; stdcall;
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begin
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result := 1;
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end;
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function DummyCreateFileTransacted(lpFileName: PChar;
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dwDesiredAccess, dwShareMode: DWORD;
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lpSecurityAttributes: PSecurityAttributes;
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dwCreationDisposition, dwFlagsAndAttributes: DWORD;
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hTemplateFile: THandle;
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hTransaction : THandle;
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MiniVersion : Word;
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pExtendedParameter : Pointer): THandle; stdcall;
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begin
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result := CreateFile(lpFilename, dwDesiredAccess, dwShareMode,
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lpSecurityAttributes, dwCreationDisposition, dwFlagsAndAttributes,
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hTemplateFile);
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end;
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function DummyCommitTransaction(hTransaction : THandle) : Boolean; stdcall;
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begin
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assert(hTransaction = 1);
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result := true;
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end;
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function DummyRollbackTransaction(hTransaction : THandle) : Boolean; stdcall;
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begin
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assert(hTransaction = 1);
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result := true;
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end;
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function DummyCloseTransaction(hTransaction : THandle) : Boolean; stdcall;
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begin
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assert(hTransaction = 1);
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result := true;
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end;
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procedure LoadDll;
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begin
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GHandleKtm := LoadLibrary('ktmw32.dll');
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if GHandleKtm <> 0 Then begin
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GHandleKernel := GetModuleHandle('Kernel32.dll'); //LoadLibrary('kernel32.dll');
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@CreateTransaction := GetProcAddress(GHandleKtm, 'CreateTransaction');
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@CommitTransaction := GetProcAddress(GHandleKtm, 'CommitTransaction');
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@RollbackTransaction := GetProcAddress(GHandleKtm, 'RollbackTransaction');
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@CloseTransaction := GetProcAddress(GHandleKernel, 'CloseHandle');
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{$IFDEF UNICODE}
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@CreateFileTransacted := GetProcAddress(GHandleKernel, 'CreateFileTransactedW');
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{$ELSE}
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@CreateFileTransacted := GetProcAddress(GHandleKernel, 'CreateFileTransactedA');
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{$ENDIF}
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end else begin
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@CreateTransaction := @DummyCreateTransaction;
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@CommitTransaction := @DummyCommitTransaction;
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@RollbackTransaction := @DummyRollbackTransaction;
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@CloseTransaction := @DummyCloseTransaction;
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@CreateFileTransacted := @DummyCreateFileTransacted;
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end;
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end;
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procedure UnloadDll;
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begin
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if GHandleKtm <> 0 then begin
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freelibrary(GHandleKtm);
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// freelibrary(GHandleKernel);
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end
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end;
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function IsTransactionsWorking : Boolean;
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{$IFDEF USE_INLINE} inline; {$ENDIF}
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begin
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result := GHandleKtm <> 0;
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end;
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{$ELSE}
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function IsTransactionsWorking : Boolean;
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{$IFDEF USE_INLINE} inline; {$ENDIF}
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begin
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result := False;
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end;
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{$ENDIF}
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{ TIdKernelTransaction }
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constructor TIdKernelTransaction.Create(const sDescription: String; bCanPromote : Boolean);
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var
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pDesc : PWideChar;
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begin
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inherited Create;
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{$IFDEF UNICODE}
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GetMem(pDesc, length(sDescription) + 2);
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try
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StringToWideChar(sDescription, pDesc, length(sDescription) + 2);
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{$ELSE}
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GetMem(pDesc, length(sDescription) * 2 + 4);
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try
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StringToWideChar(sDescription, pDesc, length(sDescription) * 2 + 4);
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{$ENDIF}
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{$IFDEF WIN32_OR_WIN64}
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if bCanPromote Then begin
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FHandle := CreateTransaction(nil, nil, 0, 0, 0, 0, pDesc);
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end else begin
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FHandle := CreateTransaction(nil, nil, TRANSACTION_DO_NOT_PROMOTE, 0, 0, 0, pDesc);
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end;
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{$ENDIF}
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finally
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FreeMem(pDesc);
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end;
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end;
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destructor TIdKernelTransaction.Destroy;
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begin
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{$IFDEF WIN32_OR_WIN64}
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CloseTransaction(FHandle);
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{$ENDIF}
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inherited Destroy;
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end;
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procedure TIdKernelTransaction.Commit;
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begin
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{$IFDEF WIN32_OR_WIN64}
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if not CommitTransaction(FHandle) then begin
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IndyRaiseLastError;
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end;
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{$ENDIF}
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end;
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function TIdKernelTransaction.IsTransactional: Boolean;
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begin
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result := IsTransactionsWorking;
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end;
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procedure TIdKernelTransaction.RollBack;
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begin
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{$IFDEF WIN32_OR_WIN64}
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if not RollbackTransaction(FHandle) then begin
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IndyRaiseLastError;
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end;
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{$ENDIF}
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end;
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{$IFDEF WIN32_OR_WIN64}
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function FileCreateTransacted(const FileName: string; hTransaction : THandle): THandle;
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begin
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Result := THandle(CreateFileTransacted(PChar(FileName), GENERIC_READ or GENERIC_WRITE,
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0, nil, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, 0, hTransaction, 0, nil));
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if result = INVALID_HANDLE_VALUE Then begin
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IndyRaiseLastError;
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end;
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end;
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function FileOpenTransacted(const FileName: string; Mode: LongWord; hTransaction : THandle): THandle;
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const
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AccessMode: array[0..2] of LongWord = (
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GENERIC_READ,
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GENERIC_WRITE,
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GENERIC_READ or GENERIC_WRITE);
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ShareMode: array[0..4] of LongWord = (
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0,
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0,
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FILE_SHARE_READ,
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FILE_SHARE_WRITE,
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FILE_SHARE_READ or FILE_SHARE_WRITE);
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begin
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Result := THandle(CreateFileTransacted(PChar(FileName),AccessMode[Mode and 3],
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ShareMode[(Mode and $F0) shr 4], nil, OPEN_EXISTING,
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FILE_ATTRIBUTE_NORMAL, 0, hTransaction,TXFS_MINIVERSION_DEFAULT_VIEW, nil));
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end;
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{$ENDIF}
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{ TIdTransactedFileStream }
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{$IFDEF WIN32_OR_WIN64}
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constructor TIdTransactedFileStream.Create(const FileName: string; Mode: Word; oTransaction: TIdKernelTransaction);
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var
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aHandle : THandle;
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begin
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if Mode = fmCreate then begin
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aHandle := FileCreateTransacted(FileName, oTransaction.FHandle);
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if aHandle = INVALID_HANDLE_VALUE then begin
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raise EFCreateError.CreateResFmt(@SFCreateError, [FileName]);
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end;
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end else begin
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aHandle := FileOpenTransacted(FileName, Mode, oTransaction.FHandle);
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if aHandle = INVALID_HANDLE_VALUE then begin
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raise EFOpenError.CreateResFmt(@SFOpenError, [FileName]);
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end;
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end;
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inherited Create(ahandle);
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end;
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{$ELSE}
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constructor TIdTransactedFileStream.Create(const FileName: string; Mode: Word; oTransaction: TIdKernelTransaction);
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var LStream : TFileStream;
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begin
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LStream := FFileStream.Create(FileName,Mode);
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inherited Create ( LStream.Handle);
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FFileStream := LStream;
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end;
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{$ENDIF}
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destructor TIdTransactedFileStream.Destroy ;
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begin
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{$IFDEF WIN32_OR_WIN64}
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if Handle = INVALID_HANDLE_VALUE then begin
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FileClose(Handle);
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end;
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inherited Destroy;
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{$ELSE}
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//we have to deference our copy of the THandle so we don't free it twice.
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FHandle := INVALID_HANDLE_VALUE;
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FreeAndNil( FFileStream );
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inherited Destroy;
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{$ENDIF}
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end;
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{$IFDEF WIN32_OR_WIN64}
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initialization
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LoadDLL;
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finalization
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UnloadDLL;
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{$ENDIF}
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End.
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