Data commit

Task/Variable-length-quantity/Delphi/variable-length-quantity.delphi

@@ -0,0 +1,91 @@
+function NumberToVLQ(Num: int64): string;
+{Convert Num to Variable-Length Quantity VLQ Octets (bytes)}
+{Octet = 7-bit data and MSB indicating the last data item = 0 }
+{Note: String are being used as byte-array because they are easy}
+var I: integer;
+var T: byte;
+var BA: string;
+begin
+Result:='';
+BA:='';
+{Get array of octets}
+while Num>0 do
+	begin
+	BA:=BA+char($7F and Num);
+	Num:=Num shr 7;
+	end;
+{Reverse data and flag more data is coming}
+Result:='';
+for I:=Length(BA) downto 1 do
+	begin
+	T:=Byte(BA[I]);
+	if I<>1 then T:=T or $80;
+	Result:=Result+char(T);
+	end;
+end;
+
+
+function VLQToNumber(VLQ: string): int64;
+{Convert Variable-Length Quantity VLQ Octets (bytes) to numbers}
+{Octet = 7-bit data and MSB indicating the last data item = 0 }
+{Note: String are being used as byte-array because they are easy}
+var I: integer;
+var T: byte;
+var BA: string;
+begin
+Result:=0;
+for I:=1 to Length(VLQ) do
+Result:=(Result shl 7) or (Byte(VLQ[I]) and $7F);
+end;
+
+
+
+function VLQToString(VLQ: string): string;
+{Convert VLQ to string of hex numbers}
+var I: integer;
+begin
+Result:='(';
+for I:=1 to Length(VLQ) do
+	begin
+	if I>1 then Result:=Result+', ';
+	Result:=Result+IntToHex(byte(VLQ[I]),2);
+	end;
+Result:=Result+')';
+end;
+
+
+
+procedure ShowVLQ(Memo: TMemo; Num: int64);
+var VLQ: string;
+var I: int64;
+var S: string;
+begin
+VLQ:=NumberToVLQ(Num);
+S:=VLQToString(VLQ);
+I:=VLQToNumber(VLQ);
+Memo.Lines.Add('Original Number:  '+Format('%x',[Num]));
+Memo.Lines.Add('Converted to VLQ: '+Format('%s',[S]));
+Memo.Lines.Add('Back to Original: '+Format('%x',[I]));
+Memo.Lines.Add('');
+end;
+
+const Num1 = $0;
+const Num2 = $7F;
+const Num3 = $4000;
+const Num4 = $1FFFFF;
+const Num5 = $200000;
+const Num6 = $3FFFFE;
+const Num7 = $3311A1234DF31413;
+
+
+
+procedure VariableLengthOctets(Memo: TMemo);
+begin
+ShowVLQ(Memo, Num1);
+ShowVLQ(Memo, Num2);
+ShowVLQ(Memo, Num3);
+ShowVLQ(Memo, Num4);
+ShowVLQ(Memo, Num5);
+ShowVLQ(Memo, Num6);
+ShowVLQ(Memo, Num7);
+end;