addons update

git-svn-id: https://svn.code.sf.net/p/kolmck/code@67 91bb2d04-0c0c-4d2d-88a5-bbb6f4c1fa07

Addons/UBitTreeDecoder.pas

@@ -0,0 +1,74 @@
+unit UBitTreeDecoder;
+
+{$IFDEF FPC}
+{$MODE Delphi}
+{$ENDIF}
+
+interface
+
+uses KOL, URangeDecoder;
+
+type PBitTreeDecoder = ^TBitTreeDecoder;
+     TBitTreeDecoder=object(TObj)
+       public
+         Models: array of smallint;
+         NumBitLevels:integer;
+         constructor Create(const AnumBitLevels:integer);
+         procedure _Init;
+         function Decode(const ArangeDecoder:PRangeDecoder):integer;
+         function ReverseDecode(const ArangeDecoder:PRangeDecoder):integer;overload;
+       end;
+
+function ReverseDecode(var AModels: array of smallint; const AstartIndex:integer;const ArangeDecoder:PRangeDecoder; const ANumBitLevels:integer):integer;overload;
+
+implementation
+
+constructor TBitTreeDecoder.Create(const AnumBitLevels:integer);
+begin
+self.NumBitLevels := AnumBitLevels;
+setlength(Models,1 shl AnumBitLevels);
+end;
+
+procedure TBitTreeDecoder._Init;
+begin
+urangedecoder.InitBitModels(Models);
+end;
+
+function TBitTreeDecoder.Decode(const ArangeDecoder:PRangeDecoder):integer;
+var m,bitIndex:integer;
+begin
+m:=1;
+for bitIndex := NumBitLevels downto 1 do begin
+    m:=m shl 1 + ArangeDecoder.DecodeBit(Models, m);
+    end;
+result:=m - (1 shl NumBitLevels);
+end;
+
+function TBitTreeDecoder.ReverseDecode(const ArangeDecoder:PRangeDecoder):integer;
+var m,symbol,bitindex,bit:integer;
+begin
+m:=1;
+symbol:=0;
+for bitindex:=0 to numbitlevels-1 do begin
+    bit:=ArangeDecoder.DecodeBit(Models, m);
+    m:=(m shl 1) + bit;
+    symbol:=symbol or (bit shl bitIndex);
+    end;
+result:=symbol;
+end;
+
+function ReverseDecode(var AModels: array of smallint;const AstartIndex:integer;
+            const ArangeDecoder:PRangeDecoder;const ANumBitLevels:integer):integer;
+var m,symbol,bitindex,bit:integer;
+begin
+m:=1;
+symbol:=0;
+for bitindex:=0 to ANumBitLevels -1 do begin
+    bit := ArangeDecoder.DecodeBit(AModels, AstartIndex + m);
+    m := (m shl 1) + bit;
+    symbol := symbol or bit shl bitindex;
+    end;
+result:=symbol;
+end;
+
+end.