This program raises an I/O 104 error on EoF when first entering the while loop.
The purpose of the program is to look up if a username is already taken. The existing usernames are stored in a text file.
procedure TForm1.btnRegisterClick(Sender: TObject);
begin
sCUser := edtUserName.Text;
AssignFile(tNames, 'Names.txt');
begin
try
Reset(tNames);
except
ShowMessage('File not found');
Exit;
end;
end;
rewrite(tNames);
while not EoF(tNames) do // I get a I/O 104 Error here `
begin
Readln(tNames, sLine);
iPosComme := Pos(',', sLine);
sUser := Copy(sLine, 1, iPosComme - 1);
Delete(sLine, 1, iPosComme - 1);
if sCUser = sUser then begin
ShowMessage('Username taken');
end
else
begin
rewrite(tNames);
Writeln(tNames, sCUser + ',' + '0');
CloseFile(tNames);
end;
end;
end;
Remove the call to Rewrite()before Eof(). Even if you were not getting an IO error, your code would still fail because Rewrite() closes the file you opened with Reset() and then it creates a new bank file, so Eof() would always be True.
Update: error 104 is file not open for input, which means Reset() is not opening the file but is not raising an exception (which sounds like an RTL bug if Eof() is raising an exception, indicating that {I+} is active).
In any case, using AssignFile() and related routines is the old way to do file I/O. You should use newer techniques, like FileOpen() with FileRead(), TFileStream with TStreamReader, TStringList, etc...
Update: your loop logic is wrong. You are comparing only the first line. If it does not match the user, you are wiping out the file, writing the user to a new file, closing the file, and then continuing the loop. EoF() will then fail at that point. You need to rewrite your loop to the following:
procedure TForm1.btnRegisterClick(Sender: TObject
var
SCUser, sUser: String;
tNames: TextFile;
iPosComme: Integer;
Found: Boolean;
begin
sCUser := edtUserName.Text;
AssignFile(tNames,'Names.txt');
try
Reset(tNames);
except
ShowMessage('File not found');
Exit;
end;
try
Found := False;
while not EoF(tNames) do
begin
Readln(tNames,sLine);
iPosComme := Pos(',', sLine);
sUser := Copy(sLine ,1,iPosComme -1);
if sCUser = sUser then
begin
ShowMessage('Username taken') ;
Found := True;
Break;
end;
end;
if not Found then
Writeln(tNames,sCUser + ',0');
finally
CloseFile(tNames);
end;
end;
For the sake of completeness, this Version works for me, but it is hard to guess what the code is intended to do. Especially the while loop seems a bit displaced, since the file will contain exactly one line after the rewrite-case has ben hit once.
program wtf;
{$APPTYPE CONSOLE}
{$I+}
uses
SysUtils;
procedure Sample( sCUser : string);
var sUser, sLine : string;
iPosComme : Integer;
tnames : textfile;
begin
AssignFile(tNames,'Names.txt');
try
Reset(tNames);
except
Writeln('File not found');
Exit;
end;
while not EoF(tNames) do
begin
Readln(tNames,sLine);
iPosComme := Pos(',', sLine);
sUser := Copy(sLine ,1,iPosComme -1);
Delete( sLine,1, iPosComme -1);
if sCuser = sUser then begin
Writeln('Username taken') ;
end
else begin
Rewrite(tNames);
Writeln(tNames,sCUser + ',' + '0');
CloseFile(tNames);
Break; // file has been overwritten and closed
end;
end;
end;
begin
try
Sample('foobar');
except
on E: Exception do Writeln(E.ClassName, ': ', E.Message);
end;
end.
I wrote a version of this method that uses the newer TStreamReader and TStreamWriter classes.
This won't work with Delphi 7 of course, it's just to show how this could be done in newer versions of Delphi.
The code was heavily inspired by Remys answer.
procedure TForm1.btnRegisterClick(Sender: TObject);
var
Stream: TStream;
Reader: TStreamReader;
Writer: TStreamWriter;
Columns: TStringList;
UserName: string;
Found: Boolean;
FileName: string;
Encoding: TEncoding;
begin
FileName := ExpandFileName('Names.txt'); // An absolute path would be even better
UserName := edtUsername.Text;
Found := False;
Encoding := TEncoding.Default; // or another encoding, e.g. TEncoding.Unicode for Unicode
Stream := TFileStream.Create(FileName, fmOpenRead or fmShareDenyWrite);
try
Reader := TStreamReader.Create(Stream, Encoding);
try
Columns := TStringList.Create;
try
Columns.Delimiter := ',';
Columns.StrictDelimiter := True; // or False, depending on the file format
while not Reader.EndOfStream do
begin
Columns.DelimitedText := Reader.ReadLine;
if Columns.Count > 0 then
begin
if AnsiSameStr(Columns[0], UserName) then // or AnsiSameText if UserName is not case-sensitive
begin
ShowMessage('Username taken') ;
Found := True;
Break;
end;
end;
end;
finally
Columns.Free;
end;
finally
Reader.Free;
end;
finally
Stream.Free;
end;
if not Found then
begin
Writer := TStreamWriter.Create(FileName, True, Encoding);
try
// Warning: This will cause problems when the file does not end with a new line
Writer.WriteLine(UserName + ',0');
finally
Writer.Free;
end;
end;
end;
If performance and memory usage are not a concern:
procedure TForm1.btnRegisterClick(Sender: TObject);
var
Rows: TStringList;
Columns: TStringList;
UserName: string;
Found: Boolean;
FileName: string;
Encoding: TEncoding;
Row: string;
begin
FileName := ExpandFileName('Names.txt'); // An absolute path would be even better
UserName := edtUsername.Text;
Found := False;
Encoding := TEncoding.Default; // or another encoding, e.g. TEncoding.Unicode for Unicode
Rows := TStringList.Create;
try
Rows.LoadFromFile(FileName, Encoding);
Columns := TStringList.Create;
try
Columns.Delimiter := ',';
Columns.StrictDelimiter := True; // or False, depending on the file format
for Row in Rows do
begin
Columns.DelimitedText := Row;
if Columns.Count > 0 then
begin
if AnsiSameStr(Columns[0], UserName) then // or AnsiSameText if UserName is not case-sensitive
begin
ShowMessage('Username taken') ;
Found := True;
Break;
end;
end;
end;
finally
Columns.Free;
end;
if not Found then
begin
Rows.Add(UserName + ',0');
Rows.SaveToFile(FileName, Encoding);
end;
finally
Rows.Free;
end;
end;
This solution can be adapted to Delphi 7 by removing the Encoding variable.
If it's part of a bigger database it should be stored in a real database management system rather than a text file.
Related
In Delphi 10.4, I try to save a valid TPicture base64-encoded to an INI file:
procedure TForm1.SavePictureToIniFile(const APicture: TPicture);
var
LInput: TMemoryStream;
LOutput: TMemoryStream;
MyIni: TIniFile;
ThisFile: string;
begin
if FileSaveDialog1.Execute then
ThisFile := FileSaveDialog1.FileName
else EXIT;
LInput := TMemoryStream.Create;
LOutput := TMemoryStream.Create;
try
APicture.SaveToStream(LInput);
LInput.Position := 0;
TNetEncoding.Base64.Encode(LInput, LOutput);
LOutput.Position := 0;
MyIni := TIniFile.Create(ThisFile);
try
MyIni.WriteBinaryStream('Custom', 'IMG', LOutput); // Exception# 234
finally
MyIni.Free;
end;
finally
LInput.Free;
LOutput.Free;
end;
end;
WriteBinaryStream creates an exception:
ERROR_MORE_DATA 234 (0xEA) More data is available.
Why? What does this mean? How can this problem be solved?
EDIT: Taking into consideration what #Uwe Raabe and #Andreas Rejbrand said, this code (which does not use base64-encoding) now works:
procedure TForm1.SavePictureToIniFile(const APicture: TPicture);
var
LInput: TMemoryStream;
MyIni: System.IniFiles.TMemIniFile;
ThisFile: string;
begin
if FileSaveDialog1.Execute then
ThisFile := FileSaveDialog1.FileName
else EXIT;
LInput := TMemoryStream.Create;
try
APicture.SaveToStream(LInput);
LInput.Position := 0;
MyIni := TMemIniFile.Create(ThisFile);
try
MyIni.WriteBinaryStream('Custom', 'IMG', LInput);
MyIni.UpdateFile;
finally
MyIni.Free;
end;
finally
LInput.Free;
end;
end;
I believe this is a limitation in the operating system's functions for handling INI files; the string is too long for it.
If you instead use the Delphi INI file implementation, TMemIniFile, it works just fine. Just don't forget to call MyIni.UpdateFile at the end.
Yes, this is indeed a limitation in the Windows API, as demonstrated by the following minimal example:
var
wini: TIniFile;
dini: TMemIniFile;
begin
wini := TIniFile.Create('C:\Users\Andreas Rejbrand\Desktop\winini.ini');
try
wini.WriteString('General', 'Text', StringOfChar('W', 10*1024*1024));
finally
wini.Free;
end;
dini := TMemIniFile.Create('C:\Users\Andreas Rejbrand\Desktop\pasini.ini');
try
dini.WriteString('General', 'Text', StringOfChar('D', 10*1024*1024));
dini.UpdateFile;
finally
dini.Free;
end;
(Recall that INI files were initially used to store small amounts of configuration data in the 16-bit Windows era.)
Also, Uwe Raabe is right: you should save the Base64 string as text.
All,
I am working on a new datasnap project based on the example project located in C:\Users\Public\Documents\Embarcadero\Studio\18.0\Samples\Object Pascal\DataSnap\FireDAC_DBX.
I am trying to transfer a large stream (1,606,408 bytes) from datasnap server to client. I am running into what appears to be a common issue and that is that the entire stream does not make it to the client.
Here is my server code:
//Returns Customer Info
function TServerMethods.GetBPInfo(CardCode : String): TStringStream;
begin
Result := TStringStream.Create;
try
qBPInfo.Close;
if CardCode.Trim = '' then
qBPInfo.ParamByName('ParmCardCode').AsString := '%%'
else
qBPInfo.ParamByName('ParmCardCode').AsString := '%' + CardCode + '%';
qBPInfo.Open;
FDSchemaAdapterBPInfo.SaveToStream(Result, TFDStorageFormat.sfBinary);
Result.Position := 0;
// Result.SaveToFile('output.adb');
except
raise;
end;
end;
Here is my client code:
procedure TdmDataSnap.GetBPInfo(CardCode : String);
var
LStringStream : TStringStream;
begin
dmDataSnap.FDStoredProcBPInfo.ParamByName('CardCode').AsString := CardCode;
FDStoredProcBPInfo.ExecProc;
LStringStream := TStringStream.Create(FDStoredProcBPInfo.ParamByName('ReturnValue').asBlob);
//LStringStream.Clear;
//LStringStream.LoadFromFile('Output.adb');
try
if LStringStream <> nil then
begin
LStringStream.Position := 0;
try
DataModuleFDClient.FDSchemaAdapterBP.LoadFromStream(LStringStream, TFDStorageFormat.sfBinary);
except
on E : Exception do
showmessage(e.Message);
end;
end;
finally
LStringStream.Free;
end;
end;
You will see the stream save and load code; that is how I determined that the server was getting the entire result set into the stream, and that the client could handle the entire result set and display it properly.
So smaller streams transfer just fine, but this big one, when examined in the ide debugger, does not start with the 65,66,68,83 characters and the load fails with the error, '[FireDAC][Stan]-710. Invalid binary storage format'.
I know from extended Googling that there are work-arounds for this, but I do not understand how to apply the workarounds to my case, with the use of Tfdstoredproc and TfdSchemaAdaptor components. I'm trying to stay with this coding scheme.
How do I adapt this code to correctly receive large streams?
Update 1:
Ok, I tried strings and Base64 encoding. It didn't work.
Client Code:
procedure TdmDataSnap.GetBPInfo(CardCode : String);
var
LStringStream : TStringStream;
TempStream : TStringStream;
begin
dmDataSnap.FDStoredProcBPInfo.ParamByName('CardCode').AsString := CardCode;
FDStoredProcBPInfo.ExecProc;
try
TempStream := TStringStream.Create;
TIdDecoderMIME.DecodeStream(FDStoredProcBPInfo.ParamByName('ReturnValue').asString,TempStream);
if TempStream <> nil then
begin
TempStream.Position := 0;
try
DataModuleFDClient.FDSchemaAdapterBP.LoadFromStream(TempStream, TFDStorageFormat.sfBinary);
except
on E : Exception do
showmessage(e.Message);
end;
end;
finally
TempStream.Free;
end;
end;
Here is my server code:
//Returns Customer Info
function TServerMethods.GetBPInfo(CardCode : String): String;
var
TempStream : TMemoryStream;
OutputStr : String;
begin
Result := '';
TempStream := TMemoryStream.Create;
try
try
qBPInfo.Close;
if CardCode.Trim = '' then
qBPInfo.ParamByName('ParmCardCode').AsString := '%%'
else
qBPInfo.ParamByName('ParmCardCode').AsString := '%' + CardCode + '%';
qBPInfo.Open;
FDSchemaAdapterBPInfo.SaveToStream(TempStream, TFDStorageFormat.sfBinary);
TempStream.Position := 0;
OutputStr := IdEncoderMIMEBPInfo.EncodeStream(TempStream);
Result := OutputStr
except
raise;
end;
finally
TempStream.Free;
end;
end;
The result is the same.
I have a puzzling result that I'm struggling to understand.
I've been attempting to improve the speed of this routine
function TStringRecord.GetWord: String;
begin
// return the next word in Input
Result := '';
while (PC^ <> #$00) and not PC^.IsLetter do begin
inc(FPC);
end;
while (PC^ <> #$00) and PC^.IsLetter do begin
Result := Result + PC^;
inc(FPC);
end;
end;
by replacing the Result := Result + PC^ by a pointer-based operation. This
is my attempt:
function TStringRecord.GetWord2: String;
var
Len : Integer;
StartPC,
DestPC : PChar;
begin
// return the next word in Input
Result := '';
while (PC^ <> #$00) and not PC^.IsLetter do begin
inc(FPC);
end;
Len := Length(Input);
SetLength(Result, Len);
StartPC := PChar(Result);
DestPC := PChar(Result);
while (PC^ <> #$00) and PC^.IsLetter do begin
WStrPLCopy(DestPC, PC, 1);
inc(FPC);
inc(DestPC);
end;
SetLength(Result, DestPC - StartPC);
end;
According to my line profiler, WStrPLCopy(DestPC, PC, 1) takes 50 times longer
than Result := Result + PC^. As far as I can tell, this is because on entry
to WStrPLCopy there is a call to _WStrFromPWChar which seems to copy many more
characters than the one necessary. How can I avoid this, or can someone suggest
an alternative PChar-based method?
The remainder of my code is below:
TStringRecord = record
private
FPC: PChar;
FInput: String;
procedure SetInput(const Value: String);
public
function NextWord : String;
function NextWord2 : String;
property Input : String read FInput write SetInput;
property PC : PChar read FPC;
end;
procedure TStringRecord.SetInput(const Value: String);
begin
FInput := Value;
FPC := PChar(Input);
end;
This is how I would write it:
function TStringRecord.GetWord: String;
var beg: PChar;
begin
// return the next word in Input
while (FPC^ <> #0) and not FPC^.IsLetter do
inc(FPC);
beg := FPC;
while (FPC^ <> #0) and FPC^.IsLetter do
inc(FPC);
SetString(result, beg, FPC-beg);
end;
With this, code is very readable, and you have a single memory allocation, and I guess you could not write anything faster (but by inlining PC^.IsLetter, which is the only call to an external piece of code).
I am trying to find and replace text in a text file. I have been able to do this in the past with methods like:
procedure SmallFileFindAndReplace(FileName, Find, ReplaceWith: string);
begin
with TStringList.Create do
begin
LoadFromFile(FileName);
Text := StringReplace(Text, Find, ReplaceWith, [rfReplaceAll, rfIgnoreCase]);
SaveToFile(FileName);
Free;
end;
end;
The above works fine when a file is relatively small, however; when the the file size is something like 170 Mb the above code will cause the following error:
EOutOfMemory with message 'Out of memory'
I have tried the following with success, however it takes a long time to run:
procedure Tfrm_Main.button_MakeReplacementClick(Sender: TObject);
var
fs : TFileStream;
s : AnsiString;
//s : string;
begin
fs := TFileStream.Create(edit_SQLFile.Text, fmOpenread or fmShareDenyNone);
try
SetLength(S, fs.Size);
fs.ReadBuffer(S[1], fs.Size);
finally
fs.Free;
end;
s := StringReplace(s, edit_Find.Text, edit_Replace.Text, [rfReplaceAll, rfIgnoreCase]);
fs := TFileStream.Create(edit_SQLFile.Text, fmCreate);
try
fs.WriteBuffer(S[1], Length(S));
finally
fs.Free;
end;
end;
I am new to "Streams" and working with buffers.
Is there a better way to do this?
Thank You.
You have two mistakes in first code example and three - in second example:
Do not load whole large file in memory, especially in 32bit application. If file size more than ~1 Gb, you always get "Out of memory"
StringReplace slows with large strings, because of repeated memory reallocation
In second code you don`t use text encoding in file, so (for Windows) your code "think" that file has UCS2 encoding (two bytes per character). But what you get, if file encoding is Ansi (one byte per character) or UTF8 (variable size of char)?
Thus, for correct find&replace you must use file encoding and read/write parts of file, as LU RD said:
interface
uses
System.Classes,
System.SysUtils;
type
TFileSearchReplace = class(TObject)
private
FSourceFile: TFileStream;
FtmpFile: TFileStream;
FEncoding: TEncoding;
public
constructor Create(const AFileName: string);
destructor Destroy; override;
procedure Replace(const AFrom, ATo: string; ReplaceFlags: TReplaceFlags);
end;
implementation
uses
System.IOUtils,
System.StrUtils;
function Max(const A, B: Integer): Integer;
begin
if A > B then
Result := A
else
Result := B;
end;
{ TFileSearchReplace }
constructor TFileSearchReplace.Create(const AFileName: string);
begin
inherited Create;
FSourceFile := TFileStream.Create(AFileName, fmOpenReadWrite);
FtmpFile := TFileStream.Create(ChangeFileExt(AFileName, '.tmp'), fmCreate);
end;
destructor TFileSearchReplace.Destroy;
var
tmpFileName: string;
begin
if Assigned(FtmpFile) then
tmpFileName := FtmpFile.FileName;
FreeAndNil(FtmpFile);
FreeAndNil(FSourceFile);
TFile.Delete(tmpFileName);
inherited;
end;
procedure TFileSearchReplace.Replace(const AFrom, ATo: string;
ReplaceFlags: TReplaceFlags);
procedure CopyPreamble;
var
PreambleSize: Integer;
PreambleBuf: TBytes;
begin
// Copy Encoding preamble
SetLength(PreambleBuf, 100);
FSourceFile.Read(PreambleBuf, Length(PreambleBuf));
FSourceFile.Seek(0, soBeginning);
PreambleSize := TEncoding.GetBufferEncoding(PreambleBuf, FEncoding);
if PreambleSize <> 0 then
FtmpFile.CopyFrom(FSourceFile, PreambleSize);
end;
function GetLastIndex(const Str, SubStr: string): Integer;
var
i: Integer;
tmpSubStr, tmpStr: string;
begin
if not(rfIgnoreCase in ReplaceFlags) then
begin
i := Pos(SubStr, Str);
Result := i;
while i > 0 do
begin
i := PosEx(SubStr, Str, i + 1);
if i > 0 then
Result := i;
end;
if Result > 0 then
Inc(Result, Length(SubStr) - 1);
end
else
begin
tmpStr := UpperCase(Str);
tmpSubStr := UpperCase(SubStr);
i := Pos(tmpSubStr, tmpStr);
Result := i;
while i > 0 do
begin
i := PosEx(tmpSubStr, tmpStr, i + 1);
if i > 0 then
Result := i;
end;
if Result > 0 then
Inc(Result, Length(tmpSubStr) - 1);
end;
end;
var
SourceSize: int64;
procedure ParseBuffer(Buf: TBytes; var IsReplaced: Boolean);
var
i: Integer;
ReadedBufLen: Integer;
BufStr: string;
DestBytes: TBytes;
LastIndex: Integer;
begin
if IsReplaced and (not(rfReplaceAll in ReplaceFlags)) then
begin
FtmpFile.Write(Buf, Length(Buf));
Exit;
end;
// 1. Get chars from buffer
ReadedBufLen := 0;
for i := Length(Buf) downto 0 do
if FEncoding.GetCharCount(Buf, 0, i) <> 0 then
begin
ReadedBufLen := i;
Break;
end;
if ReadedBufLen = 0 then
raise EEncodingError.Create('Cant convert bytes to str');
FSourceFile.Seek(ReadedBufLen - Length(Buf), soCurrent);
BufStr := FEncoding.GetString(Buf, 0, ReadedBufLen);
if rfIgnoreCase in ReplaceFlags then
IsReplaced := ContainsText(BufStr, AFrom)
else
IsReplaced := ContainsStr(BufStr, AFrom);
if IsReplaced then
begin
LastIndex := GetLastIndex(BufStr, AFrom);
LastIndex := Max(LastIndex, Length(BufStr) - Length(AFrom) + 1);
end
else
LastIndex := Length(BufStr);
SetLength(BufStr, LastIndex);
FSourceFile.Seek(FEncoding.GetByteCount(BufStr) - ReadedBufLen, soCurrent);
BufStr := StringReplace(BufStr, AFrom, ATo, ReplaceFlags);
DestBytes := FEncoding.GetBytes(BufStr);
FtmpFile.Write(DestBytes, Length(DestBytes));
end;
var
Buf: TBytes;
BufLen: Integer;
bReplaced: Boolean;
begin
FSourceFile.Seek(0, soBeginning);
FtmpFile.Size := 0;
CopyPreamble;
SourceSize := FSourceFile.Size;
BufLen := Max(FEncoding.GetByteCount(AFrom) * 5, 2048);
BufLen := Max(FEncoding.GetByteCount(ATo) * 5, BufLen);
SetLength(Buf, BufLen);
bReplaced := False;
while FSourceFile.Position < SourceSize do
begin
BufLen := FSourceFile.Read(Buf, Length(Buf));
SetLength(Buf, BufLen);
ParseBuffer(Buf, bReplaced);
end;
FSourceFile.Size := 0;
FSourceFile.CopyFrom(FtmpFile, 0);
end;
how to use:
procedure TForm2.btn1Click(Sender: TObject);
var
Replacer: TFileSearchReplace;
StartTime: TDateTime;
begin
StartTime:=Now;
Replacer:=TFileSearchReplace.Create('c:\Temp\123.txt');
try
Replacer.Replace('some текст', 'some', [rfReplaceAll, rfIgnoreCase]);
finally
Replacer.Free;
end;
Caption:=FormatDateTime('nn:ss.zzz', Now - StartTime);
end;
Your first try creates several copies of the file in memory:
it loads the whole file into memory (TStringList)
it creates a copy of this memory when accessing the .Text property
it creates yet another copy of this memory when passing that string to StringReplace (The copy is the result which is built in StringReplace.)
You could try to solve the out of memory problem by getting rid of one or more of these copies:
e.g. read the file into a simple string variable rather than a TStringList
or keep the string list but run the StringReplace on each line separately and write the result to the file line by line.
That would increase the maximum file size your code can handle, but you will still run out of memory for huge files. If you want to handle files of any size, your second approach is the way to go.
No - I don't think there's a faster way that the 2nd option (if you want a completely generic search'n'replace function for any file of any size). It may be possible to make a faster version if you code it specifically according to your requirements, but as a general-purpose search'n'replace function, I don't believe you can go faster...
For instance, are you sure you need case-insensitive replacement? I would expect that this would be a large part of the time spent in the replace function. Try (just for kicks) to remove that requirement and see if it doesn't speed up the execution quite a bit on large files (this depends on how the internal coding of the StringReplace function is made - if it has a specific optimization for case-sensitive searches)
I believe refinement of Kami's code is needed to account for the string not being found, but the start of a new instance of the string might occur at the end of the buffer. The else clause is different:
if IsReplaced then begin
LastIndex := GetLastIndex(BufStr, AFrom);
LastIndex := Max(LastIndex, Length(BufStr) - Length(AFrom) + 1);
end else
LastIndex :=Length(BufStr) - Length(AFrom) + 1;
Correct fix is this one:
if IsReplaced then
begin
LastIndex := GetLastIndex(BufStr, AFrom);
LastIndex := Max(LastIndex, Length(BufStr) - Length(AFrom) + 1);
end
else
if FSourceFile.Position < SourceSize then
LastIndex := Length(BufStr) - Length(AFrom) + 1
else
LastIndex := Length(BufStr);
How is it possible to write to Delphi files, oem encoding?
How do you set the encoding? as string encoding is set by
setCodePage(RawBytes;Word;boolean);
You need the Windows API function CharToOemBuff().
EDIT
Inspired by #Free Consulting, the above API is what you would use in an older non-Unicode Delphi.
As #Free Consulting correctly points out, the new versions of Delphi offer extensive code page translation services. As a more modern variant of the old-style Pascal I/O, you could use a TStringList saved with a specified encoding.
Encoding := TEncoding.GetEncoding(GetOEMCP);
Try
StringList.SaveToFile('test.txt', Encoding);
Finally
Encoding.Free;
End;
I have a wrote a function that does that. It is no pretty, but it works.
function SetFileContent(aFileName: string; aFileContent: string; out aErrorMsg: string; aEncoding: TEncoding = nil; aRecreateFile: Boolean = True): Boolean;
var
vStream: TFileStream;
vCurEncoding: TEncoding;
vPreamble, vContent: TBytes;
vOffSet: Integer;
procedure _SetFileContent(aNewFile: Boolean);
begin
if aNewFile then begin
vStream := TFileStream.Create(aFileName, fmCreate);
try
vPreamble := aEncoding.GetPreamble;
If Length(vPreamble) > 0 then begin
vStream.WriteBuffer(Pointer(vPreamble)^, Length(vPreamble));
end;
vStream.WriteBuffer(Pointer(vContent)^, Length(vContent));
finally
vStream.Free;
End;
end
else begin
vStream := TFileStream.Create(aFileName, fmOpenWrite);
try
vStream.Position := vStream.Size;
vStream.WriteBuffer(Pointer(vContent)^, Length(vContent));
finally
vStream.Free;
end;
end;
end;
begin
Result := True;
try
vContent := BytesOf(aFileContent);
vCurEncoding := nil;
if aEncoding = nil then begin
aEncoding := TEncoding.Default;
end;
vOffSet := TEncoding.GetBufferEncoding(vContent, vCurEncoding);
if (vCurEncoding <> aEncoding) and aRecreateFile then begin
vContent := TEncoding.Convert(vCurEncoding, aEncoding, vContent, vOffSet, Length(vContent) - vOffSet);
end;
if FileExists(aFileName) then begin
if aRecreateFile then begin
_SetFileContent(True);
end
else begin
_SetFileContent(False);
end;
end
else begin
_SetFileContent(True);
end;
except
on E: Exception do begin
Result := False;
aErrorMsg := 'There was an error while trying to write the string ' + aFileContent + ' in the file ' + aFileName + '. Error: ' + E.Message;
end;
end;
end;
TStringList.SaveToFile() has a TEncoding parameter, you can use TEncoding.GetEncoding() to get an encoding object for any installed codepage, so you can specify the return value of GetOEMCP() for that. Or use TFileStream or FileWrite() to write to a file manually, and then use TEncoding.GetBytes() to encode String values during your writing.
With ease. It depends on file I/O method to be used. Example of one:
procedure TForm11.FormCreate(Sender: TObject);
var
S: string;
begin
DefaultSystemCodePage := GetOEMCP();
S := 'Если используешь мой код, то ты должен мне почку';
AssignFile(Output, 'license.txt');
Rewrite(Output);
Write(Output, S); // converts to single byte here
CloseFile(Output);
Application.Terminate;
end;
NO bum rap about Pascal I/O, please :-P