1// Copyright (c) 2017, 2021 Pieter Wuille
2// Copyright (c) 2021-present The Bitcoin Core developers
3// Distributed under the MIT software license, see the accompanying
4// file COPYING or http://www.opensource.org/licenses/mit-license.php.
5
6// Bech32 and Bech32m are string encoding formats used in newer
7// address types. The outputs consist of a human-readable part
8// (alphanumeric), a separator character (1), and a base32 data
9// section, the last 6 characters of which are a checksum. The
10// module is namespaced under bech32 for historical reasons.
11//
12// For more information, see BIP 173 and BIP 350.
13
14#ifndef BITCOIN_BECH32_H
15#define BITCOIN_BECH32_H
16
17#include <cstddef>
18#include <cstdint>
19#include <string>
20#include <utility>
21#include <vector>
22
23namespace bech32
24{
25
26inline constexpr size_t CHECKSUM_SIZE = 6;
27inline constexpr char SEPARATOR = '1';
28
29enum class Encoding {
30    INVALID, //!< Failed decoding
31
32    BECH32,  //!< Bech32 encoding as defined in BIP173
33    BECH32M, //!< Bech32m encoding as defined in BIP350
34};
35
36/** Character limits for Bech32(m) encoded strings. Character limits are how we provide error location guarantees.
37 *  These values should never exceed 2^31 - 1 (max value for a 32-bit int), since there are places where we may need to
38 *  convert the CharLimit::VALUE to an int. In practice, this should never happen since this CharLimit applies to an address encoding
39 *  and we would never encode an address with such a massive value */
40enum CharLimit : size_t {
41    BECH32 = 90,            //!< BIP173/350 imposed character limit for Bech32(m) encoded addresses. This guarantees finding up to 4 errors.
42};
43
44/** Encode a Bech32 or Bech32m string. If hrp contains uppercase characters, this will cause an
45 *  assertion error. Encoding must be one of BECH32 or BECH32M. */
46std::string Encode(Encoding encoding, const std::string& hrp, const std::vector<uint8_t>& values);
47
48struct DecodeResult
49{
50    Encoding encoding;         //!< What encoding was detected in the result; Encoding::INVALID if failed.
51    std::string hrp;           //!< The human readable part
52    std::vector<uint8_t> data; //!< The payload (excluding checksum)
53
54    DecodeResult() : encoding(Encoding::INVALID) {}
55    DecodeResult(Encoding enc, std::string&& h, std::vector<uint8_t>&& d) : encoding(enc), hrp(std::move(h)), data(std::move(d)) {}
56};
57
58/** Decode a Bech32 or Bech32m string. */
59DecodeResult Decode(const std::string& str, CharLimit limit = CharLimit::BECH32);
60
61/** Return the positions of errors in a Bech32 string. */
62std::pair<std::string, std::vector<int>> LocateErrors(const std::string& str, CharLimit limit = CharLimit::BECH32);
63
64} // namespace bech32
65
66#endif // BITCOIN_BECH32_H
67