Name
Reset Procedure
Syntax
procedure Reset(var F: TextFile); procedure Reset(var F: File); procedure Reset(var F: File; RecordSize: Integer);
Description
The Reset procedure opens an existing file. If the
file is a TextFile, Reset opens
the file for read-only access. If the file is a binary file, the file
is opened to allow read and write function calls, but the
FileMode variable dictates how the operating
system opens the file. Reset is not a real
procedure.
If the file is a typed binary file (e.g., file
of
something), use the
second form of Reset, that is, pass the file
variable only. If the file is an untyped binary file (just
file), you can optionally supply the second
argument to tell Delphi the record size. If you omit the record size,
Delphi uses 128
bytes.
Tips and Tricks
If the file is already open, it is closed first.
By default,
Resetopens a binary file to allow reading and writing. Set theFileModevariable to before callingResetto open a file for read-only access.To use
Resetto append to a binary file, open the file, seek to the end of the file, and then begin writing.When using an untyped file, it is usually simplest to supply a record size of 1 when calling
Reset, and then callBlockReadandBlockWriteto read and write as much data as you want. Alternatively, create a type forFileofByte, so you don’t need to set the record size inReset.
Example
// Copy a file.
procedure CopyFile(const Source, Dest: string);
const
BufferSize = 8192;
var
SourceFile, DestFile: File of Byte;
Buffer: PByte;
Count: LongInt;
begin
AssignFile(SourceFile, Source);
AssignFile(DestFile, Dest);
Buffer := nil;
try
GetMem(Buffer, BufferSize);
FileMode := 0;
Reset(SourceFile);
Rewrite(DestFile);
repeat
BlockRead(SourceFile, Buffer^, BufferSize, Count);
BlockWrite(DestFile, Buffer^, Count);
until Count = 0;
finally
CloseFile(SourceFile);
CloseFile(DestFile);
FreeMem(Buffer);
end;
end;