TFileStream

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A TFileStream is a descendant of TStream that reads or writes data to a file on disk.

Constant	Decimal	Description
fmCreate	65280	Creates a new file or overwrites an existing file.
fmOpenRead	0	Opens a file for reading only.
fmOpenWrite	1	Opens a file for writing.
fmOpenReadWrite	2	Opens a file for reading and writing (Modify Data).
fmShareDenyWrite	32	Prevent other processes from writing to the file while it is open.
fmShareDenyRead	16	Prevent other processes from reading the file while it is open.
fmShareDenyNone	64	Allows other processes to read and write the file without restrictions.

Read entire file fnam into a string

function readstream(fnam: string): string;
var
  strm: TFileStream;
  n: longint;
  txt: string;
begin
  txt := '';
  strm := TFileStream.Create(fnam, fmOpenRead or fmShareDenyWrite);
  try
    n := strm.Size;
    SetLength(txt, n);
    strm.Read(txt[1], n);
  finally
    strm.Free;
  end;
  result := txt;
end;

Read 8 bytes of fnam into a byte array

..
type
    TByte8Array = array [0..7] of byte;
..
function readstream(fnam: string; position= integer): TByte8Array;
var
  strm : TFileStream;
begin
  strm := TFileStream.Create(fnam, fmOpenRead or fmShareDenyWrite);
  try
    strm.Position:=position;
    strm.Read (Result[0],8);
  finally
    strm.Free;
  end;
end;

Write a string txt to the file fnam

procedure writestream(fnam: string; txt: string);
var
  strm: TFileStream;
  n: longint;
begin
  strm := TFileStream.Create(fnam, fmCreate);
  n := Length(txt);
  try
    strm.Position := 0;
    strm.Write(txt[1], n);
  finally
    strm.Free;
  end;
end;

See also

• File types
• TFileStream doc
• TStream doc