Decompress compressed string with Huffman algorithm - delphi

Question

I am trying to use Huffman algorithm from http://www.explainth.at/downloads/huff.zip
There are two function in the unit :
function Compress(ASource:TMemoryStream):TMemoryStream;
function DeCompress(ASource:TMemoryStream):TMemoryStream;
I've successfully compressed each lines from a file onto an another file.
function StreamToString(const stream: TStream) : string;
var
Size: Integer;
begin
result:='';
Size := Stream.Size - Stream.Position;
SetString(result, nil, Size);
Stream.Read(Pointer(result)^, Size);
end;
procedure TMaster.Button1Click(Sender: TObject);
var
list,list_:TStringlist;
AStream:TMemoryStream;
BStream:TMemoryStream;
s:string;
i,j:integer;
begin
list := TStringList.Create;
list_:= TStringList.Create;
list.LoadFromFile('d:\input.txt');
for j := 0 to List.Count - 1 do
begin
s:=list[j];
if (Length(s) = 0) then exit;
{i:=Pos(#13#10,s);
while (i > 0) do
begin
Delete(s,i,2);
i:=Pos(#13#10,s);
end;}
AStream:=TMemoryStream.Create;
with AStream do WriteBuffer(s[1],Length(s));
with THuffman.Create do
try
BStream:=Compress(AStream);
finally
Free;
AStream.Free;
end;
with THuffman.Create do
try
AStream:=ProcessToDecrypt (BStream);
list_.Add(StreamToString(BStream));
finally
BStream.Free;
end
end; //for j := 0 to List.Count - 1 do
list_.SaveToFile('d:\output.txt');
list_.free;
list.free;
end;
function THuffman.ProcessToDecrypt(ASource:TMemoryStream):TMemoryStream;
var ASize:Integer;
begin
ASize:=ReBuildTree(ASource);
exit;
end;
I also want to decompress each compressed line from a file to string.
Here's what I done to decompress the string
procedure TMaster.Button2Click(Sender: TObject);
var i:Integer;
AText:String;
AStream:TMemoryStream;
BStream:TMemoryStream;
begin
AText:='È1ëz-';
BStream:=TMemoryStream.Create;
with BStream do WriteBuffer(AText[1],Length(AText));
with THuffman.Create do
try
AStream:=ProcessToDecrypt (BStream);
AStream:=Decompress(BStream);
memoOut.Lines.add.StreamToString(BStream);
finally
BStream.Free;
end;
end;
Button2Click procedure doesn't work. The short question is how do I decompress the compressed string?
The parameter of DeCompress is TMemoryStream, How do I use a string as the parameter?
How to make the output of DeCompress as string?

Answer 1

In addition to my comments above, just looking at your code, the value in AText is likely not a correct representation of the compressed string. The following very simple program (based on yours) works:
uses Huffman;
procedure TForm1.UncompressButtonClick(Sender: TObject);
var
AStream:TMemoryStream;
BStream:TMemoryStream;
begin
BStream:=TMemoryStream.Create;
with BStream do LoadFromFile('c:\temp\in.txt');
with THuffman.Create do
try
AStream:=Decompress(BStream);
AStream.SaveToFile('c:\temp\out.txt');
finally
BStream.Free;
end;
end;
procedure TForm1.CompressButtonClick(Sender: TObject);
var
AText:String;
AStream:TMemoryStream;
BStream:TMemoryStream;
begin
AText := Edit1.Text;
BStream:=TMemoryStream.Create;
with BStream do WriteBuffer(AText[1],Length(AText));
with THuffman.Create do
try
AStream:=Compress(BStream);
AStream.SaveToFile('c:\temp\in.txt');
finally
BStream.Free;
end;
end;