* Fix 19851 19852 19855 (modified patch by Chad B)

git-svn-id: trunk@18193 -

packages/fcl-base/src/iostream.pp

@@ -22,17 +22,22 @@ 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;
-    procedure SetSize(NewSize: Longint); override;
-    function Seek(Offset: Longint; Origin: Word): Longint; override;
+    function Seek(const Offset: int64; Origin: TSeekOrigin): int64; override;
     end;
 
 implementation
@@ -42,9 +47,24 @@ const
   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
-{$ifdef win32}
+{$ifdef windows}
   case aIOSType of
     iosInput : FType := StdInputHandle;
     iosOutput : FType := StdOutputHandle;
@@ -77,32 +97,18 @@ begin
   end;
 end;
 
-procedure TIOStream.SetSize(NewSize: Longint);
-begin
-  raise EIOStreamError.Create(SInvalidOperation);
-end;
 
-function TIOStream.Seek(Offset: Longint; Origin: Word): Longint;
-const
-  BufSize = 1024;
-var
-  Buf : array[1..BufSize] of Byte;
+function TIOStream.Seek(const Offset: int64; Origin: TSeekOrigin): int64;
 begin
-  If (Origin=soFromCurrent) and (Offset=0) then
-     result:=FPos;
-  { Try to fake seek by reading and discarding }
-  if (zIOSType = iosOutput) or
-     Not((Origin=soFromCurrent) and (Offset>=0) or
-         ((Origin=soFrombeginning) and (OffSet>=FPos))) then
-     Raise EIOStreamError.Create(SInvalidOperation);
-  if Origin=soFromBeginning then
-    Dec(Offset,FPos);
-  While ((Offset Div BufSize)>0)
-        and (Read(Buf,SizeOf(Buf))=BufSize) do
-     Dec(Offset,BufSize);
-  If (Offset>0) then
-    Read(Buf,BufSize);
-  Result:=FPos;
+  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.