i am downloading a file from my server (i only get the bytes and a DateTime for the lastwritetime attribute) and after downloading the data i create a new file on my local machine and want to set the lastwritetime attribute.
For this i am using the following method:
procedure SetFileDate(const FileName: string; NewDate: TDateTime);
var
FileDate, FileHandle: Integer;
begin
try
FileDate := DateTimeToFileDate(NewDate);
FileHandle := FileOpen(FileName, fmOpenReadWrite or fmShareDenyWrite);
if FileHandle > 0 then
begin
FileSetDate(FileHandle, FileDate);
FileClose(FileHandle);
end;
except
begin
// ERROR Log
err.Msg('FileReqThrd.SetFileDate');
end;
end;
end;
For the 'NewDate' parameter i use the DateTime which i get from my server.
I tried to convert the DateTime from the server like this to get the valid lastwritetime (i am requesting the data from a WCF this is why i am converting it to UTCDateTime, the untouched data from the WCF service is TXSDateTime):
TDateTime cloudFileDateTime := StrToDateTime(DateTimeToStr(cloudDownloadResult.FileCloudData.Lastwritetime.AsUTCDateTime));
But in the end my lastwritetime attribute from files which have a lastwritetime in the wintertime period are wrong with -1h.
I hope you understand my problem and can give me an idea how to solve it.
Best regards
The easiest way to do this is to call TFile.SetLastWriteTimeUtc from the System.IOUtils unit.
TFile.SetLastWriteTimeUtc(FileName,
DateTimeUtc);
If this function is not available use the Win32 API function SetFileTime.
You'll also need DateTimeToSystemTime and then SystemTimeToFileTime in that scenario.
The answer provided by David (to use TFile.SetLastWriteTimeUtc) is correct. However, there was some discussion in the comments about bugs. As I am unable to comment (due to lack of rep), I'll add this here for anyone who comes across this problem in future.
While TFile.SetLastWriteTimeUtc works correctly, TFile.GetLastWriteTimeUtc does indeed have a bug relating to daylight saving time. There is a bug report filed with Embarcadero, and it looks like they've now fixed it in Delphi 10.3 Rio (though I haven't tried it yet).
If you are working with an older version of Delphi, you will have to work around the problem via use of the Windows API. e.g. GetFileAttributesEx:
function GetFileModTimeUtc(filePath: string): TDateTime;
var data: TWin32FindData;
var sysTime: TSystemTime;
begin
if GetFileAttributesEx(PChar(filePath), GetFileExInfoStandard, #data) and
FileTimeToSystemTime(data.ftLastWriteTime, sysTime) then begin
Result := SystemTimeToDateTime(sysTime);
end else begin
raise Exception.Create('Unable to get last file write time for ' + filePath);
end;
end;
Related
I have some problems to create an instance of the StarOffice Desktop object.
I used the standard construct below but whenever it comes to the line: StarDesktop := StarOffice.CreateInstance('com.sun.star.frame.Desktop');
My StarDesktop Variant stays unassigned. I am pretty sure that the code is ok until there but perhaps something with the OpenOffice installation is messed up.
Is there a way to check the com objects or did somebody had the same problem and could solve it...
uses
ComObj;
procedure OpenOfficeDocument;
var
StarOffice: Variant;
StarDesktop: Variant;
begin
StarOffice := CreateOleObject('com.sun.star.ServiceManager');
StarDesktop := StarOffice.CreateInstance('com.sun.star.frame.Desktop');
// StarDesktop is always "unassigned"
....
Yes, I know. I should have stated more clearly that I am too 100% sure that it would work normally in a correct environment.
But my question is what could be the cause why it doesn't work. Why the 'com.sun.star.frame.Desktop' instance is unassigned. I have no option/way to debug it...
And it is a bit unfair to vote me down, I researched for one hour without finding something to explain why it could not work.
Or how and where to check if something is wrong with the Office installation (I uninstalled and reinstalled it twice already"
Again, I know this will work for others and normally would work for me, but something is wrong at my system and I would like to know some help to point me in the direction what could be wrong in the system (and not in the code example...)
is OpenOffice installed on client?
doesn't throw any exception?
I'm using Bernard Marcelly's Delphi 7 OOo tool and as can you see his code like that;
var
OpenOffice, StarDesktop: Variant;
...
OpenOffice:= CreateOleObject('com.sun.star.ServiceManager');
if isNullEmpty(OpenOffice) then Raise Exception.Create('OpenOffice connection is impossible');
StarDesktop:= OpenOffice.createInstance('com.sun.star.frame.Desktop');
if isNullEmpty(Result) then Raise Exception.Create(Format('Impossible to create service : %s', ['com.sun.star.frame.Desktop']));
...
'some constants converted to string'
So, if StarDesktop is null, possible can not access Oo Desktop service. If OpenOffice installed properly some features may be missing, options have to set.
This works for me (in my application):
class procedure TOpenOffice.Connect;
begin
if IsConnected then
Exit;
try
FServiceManager := CreateOleObject('com.sun.star.ServiceManager');
except
FServiceManager := Null;
end;
if VarIsNull(FServiceManager) then
raise EOpenOfficeException.Create(StrConnectionFailed);
FDesktop := CreateService('com.sun.star.frame.Desktop');
FDispatchHelper := CreateService('com.sun.star.frame.DispatchHelper');
FIntrospection := CreateService('com.sun.star.beans.Introspection');
FReflection := CreateService('com.sun.star.reflection.CoreReflection');
end;
and:
class function TOpenOffice.CreateService(const ServiceName: string): Variant;
begin
Result := FServiceManager.createInstance(ServiceName);
if VarIsNull(Result) then
raise EOpenOfficeException.CreateFmt(StrCouldNotCreateService,
[ServiceName]);
end;
i am working on a little byte patching program but i encountered an error.
copying the file before modifying fails with no error, (no copied output is seen) but the file patches successfully.
Here is the Patch Code
procedure DoMyPatch();
var
i: integer;
FileName: string;
input: TFileStream;
FileByteArray, ExtractedByteArray: array of Byte;
begin
FileName := 'Cute1.res';
try
input := TFileStream.Create(FileName, fmOpenReadWrite);
except
begin
ShowMessage('Error Opening file');
Exit;
end
end;
input.Position := 0;
SetLength(FileByteArray, input.size);
input.Read(FileByteArray[0], Length(FileByteArray));
for i := 0 to Length(FileByteArray) do
begin
SetLength(ExtractedByteArray, Length(OriginalByte));
ExtractedByteArray := Copy(FileByteArray, i, Length(OriginalByte));
// function that compares my array of bytes
if CompareByteArrays(ExtractedByteArray, OriginalByte) = True then
begin
// Begin Patching
CopyFile(PChar(FileName), PChar(ChangeFileExt(FileName, '.BAK')),
true); =======>>> fails at this point, no copied output is seen.
input.Seek(i, SoFromBeginning);
input.Write(BytetoWrite[0], Length(BytetoWrite)); =====>>> patches successfully
input.Free;
ShowMessage('Patch Success');
Exit;
end;
end;
if Assigned(input) then
begin
input.Free;
end;
ShowMessage('Patch Failed');
end;
sidenote : it copies fine if i close the filestream before attempting copy.
by the way, i have tested it on Delphi 7 and XE7.
Thanks
You cannot copy the file because you locked it exclusively when you opened it for the file stream, which is why CopyFile fails.
You should close the file before attempting to call CopyFile. Which would require you to reopen the file to patch it. Or perhaps open the file with a different sharing mode.
Some other comments:
The exception handling is badly implemented. Don't catch exceptions here. Let them float up to the high level.
Lifetime management is fluffed. You can easily leak as it stands. You need to learn about try/finally.
You overrun buffers. Valid indices for a dynamic array are 0 to Length(arr)-1 inclusive. Or use low() and high().
You don't check the value returned by CopyFile. Wrap it with a call to Win32Check.
The Copy function returns a new array. So you make a spurious call to SetLength. To copy the entire array use the one parameter overload of Copy.
Showing messages in this function is probably a mistake. Better to let the caller provide user feedback.
There are loads of other oddities in the code and I've run out of energy to point them all out. I think I got the main ones.
I feel like this should be easy, but google is totally failing me at the moment. I want to open a file, or create it if it doesn't exist, and write to it.
The following
AssignFile(logFile, 'Test.txt');
Append(logFile);
throws an error on the second line when the file doesn't exist yet, which I assume is expected. But I'm really failing at finding out how to a) test if the file exists and b) create it when needed.
FYI, working in Delphi XE.
You can use the FileExists function and then use Append if exist or Rewrite if not.
AssignFile(logFile, 'Test.txt');
if FileExists('test.txt') then
Append(logFile)
else
Rewrite(logFile);
//do your stuff
CloseFile(logFile);
Any solution that uses FileExists to choose how to open the file has a race condition. If the file's existence changes between the time you test it and the time you attempt to open the file, your program will fail. Delphi doesn't provide any way to solve that problem with its native file I/O routines.
If your Delphi version is new enough to offer it, you can use the TFile.Open with the fmOpenOrCreate open mode, which does exactly what you want; it returns a TFileStream.
Otherwise, you can use the Windows API function CreateFile to open your file instead. Set the dwCreationDisposition parameter to OPEN_ALWAYS, which tells it to create the file if it doesn't already exist.
You should be using TFileStream instead. Here's a sample that will create a file if it doesn't exist, or write to it if it does:
var
FS: TFileStream;
sOut: string;
i: Integer;
Flags: Word;
begin
Flags := fmOpenReadWrite;
if not FileExists('D:\Temp\Junkfile.txt') then
Flags := Flags or fmCreate;
FS := TFileStream.Create('D:\Temp\Junkfile.txt', Flags);
try
FS.Position := FS.Size; // Will be 0 if file created, end of text if not
sOut := 'This is test line %d'#13#10;
for i := 1 to 10 do
begin
sOut := Format(sOut, [i]);
FS.Write(sOut[1], Length(sOut) * SizeOf(Char));
end;
finally
FS.Free;
end;
end;
If you are just doing something simple, the IOUtils Unit is a lot easier. It has a lot of utilities for writing to files.
e.g.
procedure WriteAllText(const Path: string; const Contents: string);
overload; static;
Creates a new file, writes the specified string to the file, and then
closes the file. If the target file already exists, it is overwritten.
You can also use the load/save feature in a TStringList to solve your problem.
This might be a bad solution, because the whole file will be loaded into memory, modified in memory and then saved to back to disk. (As opposed to your solution where you just write directly to the file). It's obviously a bad solution for multiuser situations.
But this approach is OK for smaller files, and it is easy to work with and easy understand.
const
FileName = 'test.txt';
var
strList: TStringList;
begin
strList := TStringList.Create;
try
if FileExists(FileName) then
strList.LoadFromFile(FileName);
strList.Add('My new line');
strList.SaveToFile(FileName);
finally
strList.Free;
end;
end;
I had some code before I moved to Unicode and Delphi 2009 that appended some text to a log file a line at a time:
procedure AppendToLogFile(S: string);
// this function adds our log line to our shared log file
// Doing it this way allows Wordpad to open it at the same time.
var F, C1 : dword;
begin
if LogFileName <> '' then begin
F := CreateFileA(Pchar(LogFileName), GENERIC_READ or GENERIC_WRITE, 0, nil, OPEN_ALWAYS, 0, 0);
if F <> 0 then begin
SetFilePointer(F, 0, nil, FILE_END);
S := S + #13#10;
WriteFile(F, Pchar(S)^, Length(S), C1, nil);
CloseHandle(F);
end;
end;
end;
But CreateFileA and WriteFile are binary file handlers and are not appropriate for Unicode.
I need to get something to do the equivalent under Delphi 2009 and be able to handle Unicode.
The reason why I'm opening and writing and then closing the file for each line is simply so that other programs (such as WordPad) can open the file and read it while the log is being written.
I have been experimenting with TFileStream and TextWriter but there is very little documentation on them and few examples.
Specifically, I'm not sure if they're appropriate for this constant opening and closing of the file. Also I'm not sure if they can make the file available for reading while they have it opened for writing.
Does anyone know of a how I can do this in Delphi 2009 or later?
Conclusion:
Ryan's answer was the simplest and the one that led me to my solution. With his solution, you also have to write the BOM and convert the string to UTF8 (as in my comment to his answer) and then that worked just fine.
But then I went one step further and investigated TStreamWriter. That is the equivalent of the .NET function of the same name. It understands Unicode and provides very clean code.
My final code is:
procedure AppendToLogFile(S: string);
// this function adds our log line to our shared log file
// Doing it this way allows Wordpad to open it at the same time.
var F: TStreamWriter;
begin
if LogFileName <> '' then begin
F := TStreamWriter.Create(LogFileName, true, TEncoding.UTF8);
try
F.WriteLine(S);
finally
F.Free;
end;
end;
Finally, the other aspect I discovered is if you are appending a lot of lines (e.g. 1000 or more), then the appending to the file takes longer and longer and it becomes quite inefficient.
So I ended up not recreating and freeing the LogFile each time. Instead I keep it open and then it is very fast. The only thing I can't seem to do is allow viewing of the file with notepad while it is being created.
For logging purposes why use Streams at all?
Why not use TextFiles? Here is a very simple example of one of my logging routines.
procedure LogToFile(Data:string);
var
wLogFile: TextFile;
begin
AssignFile(wLogFile, 'C:\MyTextFile.Log');
{$I-}
if FileExists('C:\MyTextFile.Log') then
Append(wLogFile)
else
ReWrite(wLogFile);
WriteLn(wLogfile, S);
CloseFile(wLogFile);
{$I+}
IOResult; //Used to clear any possible remaining I/O errors
end;
I actually have a fairly extensive logging unit that uses critical sections for thread safety, can optionally be used for internal logging via the OutputDebugString command as well as logging specified sections of code through the use of sectional identifiers.
If anyone is interested I'll gladly share the code unit here.
Char and string are Wide since D2009. Thus you should use CreateFile instead of CreateFileA!
If you werite the string you shoudl use Length( s ) * sizeof( Char ) as the byte length and not only Length( s ). because of the widechar issue. If you want to write ansi chars, you should define s as AnsiString or UTF8String and use sizeof( AnsiChar ) as a multiplier.
Why are you using the Windows API function instead of TFileStream defined in classes.pas?
Try this little function I whipped up just for you.
procedure AppendToLog(filename,line:String);
var
fs:TFileStream;
ansiline:AnsiString;
amode:Integer;
begin
if not FileExists(filename) then
amode := fmCreate
else
amode := fmOpenReadWrite;
fs := TFileStream.Create(filename,{mode}amode);
try
if (amode<>fmCreate) then
fs.Seek(fs.Size,0); {go to the end, append}
ansiline := AnsiString(line)+AnsiChar(#13)+AnsiChar(#10);
fs.WriteBuffer(PAnsiChar(ansiline)^,Length(ansiline));
finally
fs.Free;
end;
Also, try this UTF8 version:
procedure AppendToLogUTF8(filename, line: UnicodeString);
var
fs: TFileStream;
preamble:TBytes;
outpututf8: RawByteString;
amode: Integer;
begin
if not FileExists(filename) then
amode := fmCreate
else
amode := fmOpenReadWrite;
fs := TFileStream.Create(filename, { mode } amode, fmShareDenyWrite);
{ sharing mode allows read during our writes }
try
{internal Char (UTF16) codepoint, to UTF8 encoding conversion:}
outpututf8 := Utf8Encode(line); // this converts UnicodeString to WideString, sadly.
if (amode = fmCreate) then
begin
preamble := TEncoding.UTF8.GetPreamble;
fs.WriteBuffer( PAnsiChar(preamble)^, Length(preamble));
end
else
begin
fs.Seek(fs.Size, 0); { go to the end, append }
end;
outpututf8 := outpututf8 + AnsiChar(#13) + AnsiChar(#10);
fs.WriteBuffer(PAnsiChar(outpututf8)^, Length(outpututf8));
finally
fs.Free;
end;
end;
If you try to use text file or Object Pascal typed/untyped files in a multithreaded application you gonna have a bad time.
No kidding - the (Object) Pascal standard file I/O uses global variables to set file mode and sharing. If your application runs in more than one thread (or fiber if anyone still use them) using standard file operations could result in access violations and unpredictable behavior.
Since one of the main purposes of logging is debugging a multithreaded application, consider using other means of file I/O: Streams and Windows API.
(And yes, I know it is not really an answer to the original question, but I do not wish to log in - therefor I do not have the reputation score to comment on Ryan J. Mills's practically wrong answer.)
I have to make a unix compatible windows delphi routine that confirms if a file name exists in filesystem exactly in same CaSe as wanted, e.g. "John.txt" is there, not "john.txt".
If I check "FileExists('john.txt')" its always true for John.txt and JOHN.TXT due windows .
How can I create "FileExistsCaseSensitive(myfile)" function to confirm a file is really what its supposed to be.
DELPHI Sysutils.FileExists uses the following function to see if file is there, how to change it to double check file name is on file system is lowercase and exists:
function FileAge(const FileName: string): Integer;
var
Handle: THandle;
FindData: TWin32FindData;
LocalFileTime: TFileTime;
begin
Handle := FindFirstFile(PChar(FileName), FindData);
if Handle <> INVALID_HANDLE_VALUE then
begin
Windows.FindClose(Handle);
if (FindData.dwFileAttributes and FILE_ATTRIBUTE_DIRECTORY) = 0 then
begin
FileTimeToLocalFileTime(FindData.ftLastWriteTime, LocalFileTime);
if FileTimeToDosDateTime(LocalFileTime, LongRec(Result).Hi,
LongRec(Result).Lo) then Exit;
end;
end;
Result := -1;
end;
function FileExistsEx(const FileName: string): Integer;
var
Handle: THandle;
FindData: TWin32FindData;
LocalFileTime: TFileTime;
begin
Handle := FindFirstFile(PChar(FileName), FindData);
if Handle <> INVALID_HANDLE_VALUE then
begin
Windows.FindClose(Handle);
if (FindData.dwFileAttributes and FILE_ATTRIBUTE_DIRECTORY) = 0 then
begin
FileTimeToLocalFileTime(FindData.ftLastWriteTime, LocalFileTime);
if FileTimeToDosDateTime(LocalFileTime, LongRec(Result).Hi, LongRec(Result).Lo) then
if AnsiSameStr(FindData.cFileName, ExtractFileName(FileName)) then Exit;
end;
end;
Result := -1;
end;
Tom, I'm also intrigued by your use case. I tend to agree with Motti that it would be counter intuitive and might strike your users as odd.
On windows file names are not case sensitive so I don't see what you can gain from treating file names as if they were case sensitive.
In any case you can't have two files named "John.txt" and "john.txt" and failing to find "John.txt" when "john.txt" exists will probably result in very puzzled users.
Trying to enforce case sensitivity in this context is un-intuitive and I can't see a viable use-case for it (if you have one I'll be happy to hear what it is).
I dealt with this issue a while back, and even if I'm sure that there are neater solutions out there, I just ended up doing an extra check to see if the given filename was equal to the name of the found file, using the case sensitive string comparer...
I ran into a similar problem using Java. Ultimately I ended up pulling up a list of the directory's contents (which loaded the correct case of filenames for each file) and then doing string compare on the filenames of each of the files.
It's an ugly hack, but it worked.
Edit: I tried doing what Banang describes but in Java at least, if you open up file "a.txt" you'r program will stubbornly report it as "a.txt" even if the underlying file system names it "A.txt".
You can implement the approach mention by Kris using Delphi's FindFirst and FindNext routines.
See this article