Bitcoin Bech32 implementation

[Luiz Claudio]

Does anyone have a Bitcoin Bech32 implementation with address validation that they would like to share here?

I've seen examples of address validation in:

C++
C#
Java
VB.NET

However, no Delphi/Free Pascal implementation was found.

[Luiz Claudio]

Here is a Delphi code translated from F# by ChatGPT and a small change:

Code: Pascal  [Select][+][-]

1. uses
2.    Generics.Collections;
3.  
4. type
5.   TForm1 = class(TForm)
6.     Button1: TButton;
7.     procedure Button1Click(Sender: TObject);
8.   private
9.     { Private declarations }
10.   public
11.     { Public declarations }
12.   end;
13.  
14. const
15.   Charset = 'qpzry9x8gf2tvdw0s3jn54khce6mua7l';
16.   Generator: array[0..4] of UInt32 = ($3B6A57B2, $26508E6D, $1EA119FA, $3D4233DD, $2A1462B3);
17.  
18. var
19.   Form1: TForm1;
20.  
21. implementation
22.  
23. {$R *.dfm}
24.  
25. function Bech32Polymod(const values: array of UInt32): UInt32;
26. var
27.   chk, b, i, j: UInt32;
28. begin
29.   chk := 1;
30.   for i := 0 to Length(values) - 1 do
31.   begin
32.     b := chk shr 25;
33.     chk := ((chk and $1FFFFFF) shl 5) xor values[i];
34.     for j := 0 to 4 do
35.     begin
36.       if (b shr j) and 1 = 1 then
37.         chk := chk xor Generator[j];
38.     end;
39.   end;
40.   Result := chk;
41. end;
42.  
43. function HrpExpand(const hrp: string): TList<UInt32>;
44. var
45.   i: Integer;
46. begin
47.   Result := TList<UInt32>.Create;
48.   for i := 1 to Length(hrp) do
49.     Result.Add(Ord(hrp[i]) shr 5);
50.   Result.Add(0);
51.   for i := 1 to Length(hrp) do
52.     Result.Add(Ord(hrp[i]) and 31);
53. end;
54.  
55. function VerifyChecksum(const hrp: string; const data: TList<UInt32>): Boolean;
56. var
57.   lhrpExpand: TList<UInt32>;
58. begin
59.   lhrpExpand := hrpExpand(hrp);
60.   lhrpExpand.AddRange(data.ToArray);
61.   Result := Bech32Polymod(lhrpExpand.ToArray) = 1;
62. end;
63.  
64. function Decode(const str: string): TPair<string, TList<UInt32>>;
65. var
66.   lastOneIndex: Integer;
67.   hrp, data: string;
68.   dataValues: TList<UInt32>;
69.   i, v: Integer;
70. begin
71.   lastOneIndex := Pos('1', str);
72.   hrp := Copy(str, 1, lastOneIndex - 1);
73.   data := Copy(str, lastOneIndex + 1, Length(str));
74.   dataValues := TList<UInt32>.Create;
75.  
76.   for i := 1 to Length(data) do
77.   begin
78.     v := Pos(data[i], Charset);
79.     if v = 0 then
80.       raise Exception.Create('invalid bech32 address')
81.     else
82.       dataValues.Add(v - 1);
83.   end;
84.  
85.   if VerifyChecksum(hrp, dataValues) then
86.     Result := TPair<string, TList<UInt32>>.Create(hrp, dataValues)
87.   else
88.     raise Exception.Create('invalid bech32 address');
89.  
90.   ShowMessage('Valid.');
91. end;
92.  
93. procedure TForm1.Button1Click(Sender: TObject);
94. begin
95.   Decode('bc1qw508d6qejxtdg4y5r3zarvary0c5xw7kv8f3t4');
96.   Decode('abcdef1qpzry9x8gf2tvdw0s3jn54khce6mua7lmqqqxw');
97. end;
98.  

[Thaddy]

That code assumes {$mode delphi} btw. And it leaks memory like hell...
Can probably all be fixed for mode objfpc, but the memory leaks are not that easy to fix, because of the creates inside the functions. It also leaks like hell in Delphi itself...
Bad code is not finished... But except for the leaks, the results are OK.

[Luiz Claudio]

That code assumes {$mode delphi} btw. And it leaks memory like hell...
Can probably all be fixed for mode objfpc, but the memory leaks are not that easy to fix, because of the creates inside the functions. It also leaks like hell in Delphi itself...
Bad code is not finished... But except for the leaks, the results are OK.

Any suggestion to fix leaks memory will welcome.

[af0815]

Any suggestion to fix leaks memory will welcome.

(SCNR) Ask ChatGPT for a fix, because it have written leaky code

[Luiz Claudio]

Any suggestion to fix leaks memory will welcome.

(SCNR) Ask ChatGPT for a fix, because it have written leaky code

FIXED:

Code: Pascal  [Select][+][-]

1. uses
2.   Generics.Collections;
3.  
4. type
5.   TForm1 = class(TForm)
6.     Button1: TButton;
7.     procedure Button1Click(Sender: TObject);
8.   private
9.     { Private declarations }
10.   public
11.     { Public declarations }
12.   end;
13.  
14. const
15.   Charset = 'qpzry9x8gf2tvdw0s3jn54khce6mua7l';
16.   Generator: array[0..4] of UInt32 = ($3B6A57B2, $26508E6D, $1EA119FA, $3D4233DD, $2A1462B3);
17.  
18. var
19.   Form1: TForm1;
20.  
21. implementation
22.  
23. {$R *.dfm}
24.  
25. function Polymod(const Values: array of UInt32): UInt32;
26. var
27.   Chk, B, I, J: UInt32;
28. begin
29.   Chk := 1;
30.   for I := 0 to Length(Values) - 1 do
31.   begin
32.     B := Chk shr 25;
33.     Chk := ((Chk and $1FFFFFF) shl 5) xor Values[I];
34.     for J := 0 to 4 do
35.     begin
36.       if (B shr J) and 1 = 1 then
37.         Chk := Chk xor Generator[J];
38.     end;
39.   end;
40.   Result := Chk;
41. end;
42.  
43. function ExpandHrp(const Hrp: string): TList<UInt32>;
44. var
45.   I: Integer;
46. begin
47.   Result := TList<UInt32>.Create;
48.   for I := 1 to Length(Hrp) do
49.     Result.Add(Ord(Hrp[I]) shr 5);
50.   Result.Add(0);
51.   for I := 1 to Length(Hrp) do
52.     Result.Add(Ord(Hrp[I]) and 31);
53. end;
54.  
55. function VerifyChecksum(const Hrp: string; const Data: TList<UInt32>): Boolean;
56. var
57.   HrpExpand: TList<UInt32>;
58. begin
59.   HrpExpand := ExpandHrp(Hrp);
60.   try
61.     HrpExpand.AddRange(Data.ToArray);
62.     Result := Polymod(HrpExpand.ToArray) = 1;
63.   finally
64.     HrpExpand.Free;
65.   end;
66. end;
67.  
68. function IsBech32Address(const Str: string): Boolean;
69. var
70.   LastOneIndex: Integer;
71.   Hrp, Data: string;
72.   DataValues: TList<UInt32>;
73.   I, V: Integer;
74. begin
75.   LastOneIndex := Pos('1', Str);
76.   Hrp := Copy(Str, 1, LastOneIndex - 1);
77.   Data := Copy(Str, LastOneIndex + 1, Length(Str));
78.   DataValues := TList<UInt32>.Create;
79.   try
80.     for I := 1 to Length(Data) do
81.     begin
82.       V := Pos(Data[I], Charset);
83.       if V = 0 then
84.         raise Exception.Create('invalid bech32 address')
85.       else
86.         DataValues.Add(V - 1);
87.     end;
88.     if VerifyChecksum(Hrp, DataValues) then
89.       Result := True
90.     else
91.       raise Exception.Create('invalid bech32 address');
92.   finally
93.     DataValues.Free;
94.   end;
95. end;
96.  
97. procedure TForm1.Button1Click(Sender: TObject);
98. begin
99.   if IsBech32Address('bc1qw508d6qejxtdg4y5r3zarvary0c5xw7kv8f3t4') then
100.     ShowMessage('Valid.');
101. end;
102.  
103. end.
104.