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{
This file is part of the Free Component Library (FCL)
Copyright (c) 1999-2000 by Michael Van Canneyt and Florian Klaempfl
See the file COPYING.FPC, included in this distribution,
for details about the copyright.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
**********************************************************************}
{$mode objfpc}
unit iostream;
interface
uses Classes;
type
TIOSType = (iosInput,iosOutPut,iosError);
EIOStreamError = class(EStreamError);
{ TIOStream }
TIOStream = class(THandleStream)
private
FType : longint;
FPos : Int64;
zIOSType : TIOSType;
protected
procedure SetSize(const NewSize: Int64); override;
function GetPosition: Int64; override;
procedure InvalidSeek; override;
public
constructor Create(aIOSType : TiosType);
function Read(var Buffer; Count : LongInt) : Longint; override;
function Write(const Buffer; Count : LongInt) : LongInt; override;
function Seek(const Offset: int64; Origin: TSeekOrigin): int64; override;
end;
implementation
const
SReadOnlyStream = 'Cannot write to an input stream.';
SWriteOnlyStream = 'Cannot read from an output stream.';
SInvalidOperation = 'Cannot perform this operation on a IOStream.';
procedure TIOStream.SetSize(const NewSize: Int64);
begin
raise EIOStreamError.Create(SInvalidOperation);
end;
function TIOStream.GetPosition: Int64;
begin
Result:=FPos;
end;
procedure TIOStream.InvalidSeek;
begin
raise EIOStreamError.Create(SInvalidOperation);
end;
constructor TIOStream.Create(aIOSType : TIOSType);
begin
{$ifdef windows}
case aIOSType of
iosInput : FType := StdInputHandle;
iosOutput : FType := StdOutputHandle;
iosError : FType := StdErrorHandle;
end;
{$else}
FType := Ord(aIOSType);
{$endif}
inherited Create(FType);
zIOSType := aIOSType;
end;
function TIOStream.Read(var Buffer; Count : LongInt) : Longint;
begin
if (zIOSType <> iosInput) then
raise EIOStreamError.Create(SWriteOnlyStream)
else begin
result := inherited Read(Buffer,Count);
inc(FPos,result);
end;
end;
function TIOStream.Write(const Buffer; Count : LongInt) : LongInt;
begin
if (zIOSType = iosInput) then
raise EIOStreamError.Create(SReadOnlyStream)
else begin
result := inherited Write(Buffer,Count);
inc(FPos,result);
end;
end;
function TIOStream.Seek(const Offset: int64; Origin: TSeekOrigin): int64;
begin
if (Origin=soCurrent) and (Offset=0) then
Result:=FPos
else
begin
if zIOSType in [iosOutput,iosError] then
InvalidSeek;
FakeSeekForward(Offset,Origin,FPos);
Result:=FPos;
end;
end;
end.
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