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BDecode.pas
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BDecode.pas
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unit BDecode;
{======================================================================
BDecode.pas -- BitTorrent BDecoding Routines
Original Coding by Knowbuddy, 2003-03-19
======================================================================}
interface
uses
SysUtils, Classes, Hashes, Contnrs;
type
TISType = (tisString = 0, tisInt);
TIntString = class(TObject)
public
StringPart: String;
IntPart: Int64;
ISType: TISType;
end;
function bdecodeStream(s: TStream): TObject;
function bdecodeInt64(s: TStream): TIntString;
function bdecodeHash(s: TStream): TObjectHash;
function bdecodeString(s: TStream; i: Integer = 0): TIntString;
function bdecodeList(s: TStream): TObjectList;
function bin2hex(s: String; m: Integer = 999): String;
var
hexchars: array[0..15] of Char = '0123456789abcdef';
implementation
function bin2hex(s: String; m: Integer = 999): String;
var
i, j, k, l : Integer;
r : array of Char;
begin
l := Length(s);
if(m < l) then l := m;
SetLength(r,l * 2);
for i := 1 to l do begin
j := Ord(s[i]);
k := (i - 1) * 2;
r[k] := hexchars[j div 16];
r[k+1] := hexchars[j mod 16];
end;
bin2hex := String(r);
end;
function bdecodeStream(s: TStream): TObject;
var
r: TObject;
c: Char;
n: Integer;
begin
n := s.Read(c, 1);
if(n > 0) then begin
case c of
'd' : r:= bdecodeHash(s);
'l' : r:= bdecodeList(s);
'i' : r:= bdecodeInt64(s);
'0'..'9' : r:= bdecodeString(s,StrToInt(c));
else r := nil;
end;
end else begin
r := nil;
end;
bdecodeStream := r;
end;
function bdecodeHash(s: TStream): TObjectHash;
var
r: TObjectHash;
o: TObject;
n, st: Integer;
c: Char;
k, l: TIntString;
begin
r := TObjectHash.Create();
n := s.Read(c, 1);
while((n > 0) and (c <> 'e') and (c >= '0') and (c <= '9')) do begin
n := StrToInt(c);
k := bdecodeString(s, n);
if(k <> nil) then begin
st := s.Position;
o := bdecodeStream(s);
if((o <> nil) and (k.StringPart <> '')) then r[k.StringPart] := o;
if(k.StringPart = 'pieces') then begin
k.StringPart:='pieces';
end;
if(k.StringPart = 'info') then begin
l := TIntString.Create();
l.IntPart := st;
r['_info_start'] := l;
l := TIntString.Create();
l.IntPart := s.Position - st;
r['_info_length'] := l;
end;
end;
n := s.Read(c, 1);
end;
if ((c < '0') or (c > '9')) and (c <> 'e') then
bdecodeHash:= nil
else bdecodeHash := r;
end;
function bdecodeList(s: TStream): TObjectList;
var
r: TObjectList;
o: TObject;
n: Integer;
c: Char;
begin
r := TObjectList.Create();
n := s.Read(c, 1);
while((n > 0) and (c <> 'e')) do begin
s.Seek(-1, soFromCurrent);
o := bdecodeStream(s);
if(o <> nil) then r.Add(o);
n := s.Read(c, 1);
end;
bdecodeList := r;
end;
function bdecodeString(s: TStream; i: Integer = 0): TIntString;
var
r: TIntString;
t: String;
c: Char;
n: Integer;
begin
c := '0';
n := s.Read(c, 1);
while((n > 0) and (c >= '0') and (c <= '9')) do begin
i := (i * 10) + StrToInt(c);
n := s.Read(c, 1);
end;
SetLength(t, i);
n:=s.Read(PChar(t)^, i);
r := TIntString.Create();
r.StringPart := t;
r.ISType := tisString;
bdecodeString := r;
end;
function bdecodeInt64(s: TStream): TIntString;
var
r: TIntString;
i: Int64;
c: Char;
n: Integer;
neg: boolean;
begin
i := 0;
c := '0';
neg:= false;
repeat
if c='-' then neg:= true else i := (i * 10) + StrToInt(c);
n := s.Read(c, 1);
until not ((n > 0) and (((c >= '0')and(c <= '9'))or(c = '-')));
if neg then i:=-i;
r := TIntString.Create();
r.IntPart := i;
r.ISType := tisInt;
bdecodeInt64 := r;
end;
end.