从流数据获知文件类型

从流数据获知文件类型

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function StreamGetFileType(aStream:TStream):String; var Buffer:Word; begin   Result := '';   aStream.Position := 0;   if aStream.Size=0 then    exit;   aStream.ReadBuffer(Buffer,2);   case Buffer of     $4D42:Result := 'bmp';     $D8FF:Result := 'jpeg';     $4947:Result := 'gifp';     $050A:Result :='pcx';     $5089:Result :='png';     $4238:Result :='psd';     $A659:Result :='ras';     $DA01:Result :='sgi';     $4949:Result :='tiff';   end; end;