Bitcoin Core  0.20.99
P2P Digital Currency
base58.cpp
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1 // Copyright (c) 2014-2019 The Bitcoin Core developers
2 // Distributed under the MIT software license, see the accompanying
3 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
4 
5 #include <base58.h>
6 
7 #include <hash.h>
8 #include <uint256.h>
9 #include <util/strencodings.h>
10 #include <util/string.h>
11 
12 #include <assert.h>
13 #include <string.h>
14 
15 #include <limits>
16 
18 static const char* pszBase58 = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz";
19 static const int8_t mapBase58[256] = {
20  -1,-1,-1,-1,-1,-1,-1,-1, -1,-1,-1,-1,-1,-1,-1,-1,
21  -1,-1,-1,-1,-1,-1,-1,-1, -1,-1,-1,-1,-1,-1,-1,-1,
22  -1,-1,-1,-1,-1,-1,-1,-1, -1,-1,-1,-1,-1,-1,-1,-1,
23  -1, 0, 1, 2, 3, 4, 5, 6, 7, 8,-1,-1,-1,-1,-1,-1,
24  -1, 9,10,11,12,13,14,15, 16,-1,17,18,19,20,21,-1,
25  22,23,24,25,26,27,28,29, 30,31,32,-1,-1,-1,-1,-1,
26  -1,33,34,35,36,37,38,39, 40,41,42,43,-1,44,45,46,
27  47,48,49,50,51,52,53,54, 55,56,57,-1,-1,-1,-1,-1,
28  -1,-1,-1,-1,-1,-1,-1,-1, -1,-1,-1,-1,-1,-1,-1,-1,
29  -1,-1,-1,-1,-1,-1,-1,-1, -1,-1,-1,-1,-1,-1,-1,-1,
30  -1,-1,-1,-1,-1,-1,-1,-1, -1,-1,-1,-1,-1,-1,-1,-1,
31  -1,-1,-1,-1,-1,-1,-1,-1, -1,-1,-1,-1,-1,-1,-1,-1,
32  -1,-1,-1,-1,-1,-1,-1,-1, -1,-1,-1,-1,-1,-1,-1,-1,
33  -1,-1,-1,-1,-1,-1,-1,-1, -1,-1,-1,-1,-1,-1,-1,-1,
34  -1,-1,-1,-1,-1,-1,-1,-1, -1,-1,-1,-1,-1,-1,-1,-1,
35  -1,-1,-1,-1,-1,-1,-1,-1, -1,-1,-1,-1,-1,-1,-1,-1,
36 };
37 
38 NODISCARD static bool DecodeBase58(const char* psz, std::vector<unsigned char>& vch, int max_ret_len)
39 {
40  // Skip leading spaces.
41  while (*psz && IsSpace(*psz))
42  psz++;
43  // Skip and count leading '1's.
44  int zeroes = 0;
45  int length = 0;
46  while (*psz == '1') {
47  zeroes++;
48  if (zeroes > max_ret_len) return false;
49  psz++;
50  }
51  // Allocate enough space in big-endian base256 representation.
52  int size = strlen(psz) * 733 /1000 + 1; // log(58) / log(256), rounded up.
53  std::vector<unsigned char> b256(size);
54  // Process the characters.
55  static_assert(sizeof(mapBase58)/sizeof(mapBase58[0]) == 256, "mapBase58.size() should be 256"); // guarantee not out of range
56  while (*psz && !IsSpace(*psz)) {
57  // Decode base58 character
58  int carry = mapBase58[(uint8_t)*psz];
59  if (carry == -1) // Invalid b58 character
60  return false;
61  int i = 0;
62  for (std::vector<unsigned char>::reverse_iterator it = b256.rbegin(); (carry != 0 || i < length) && (it != b256.rend()); ++it, ++i) {
63  carry += 58 * (*it);
64  *it = carry % 256;
65  carry /= 256;
66  }
67  assert(carry == 0);
68  length = i;
69  if (length + zeroes > max_ret_len) return false;
70  psz++;
71  }
72  // Skip trailing spaces.
73  while (IsSpace(*psz))
74  psz++;
75  if (*psz != 0)
76  return false;
77  // Skip leading zeroes in b256.
78  std::vector<unsigned char>::iterator it = b256.begin() + (size - length);
79  // Copy result into output vector.
80  vch.reserve(zeroes + (b256.end() - it));
81  vch.assign(zeroes, 0x00);
82  while (it != b256.end())
83  vch.push_back(*(it++));
84  return true;
85 }
86 
88 {
89  // Skip & count leading zeroes.
90  int zeroes = 0;
91  int length = 0;
92  while (input.size() > 0 && input[0] == 0) {
93  input = input.subspan(1);
94  zeroes++;
95  }
96  // Allocate enough space in big-endian base58 representation.
97  int size = input.size() * 138 / 100 + 1; // log(256) / log(58), rounded up.
98  std::vector<unsigned char> b58(size);
99  // Process the bytes.
100  while (input.size() > 0) {
101  int carry = input[0];
102  int i = 0;
103  // Apply "b58 = b58 * 256 + ch".
104  for (std::vector<unsigned char>::reverse_iterator it = b58.rbegin(); (carry != 0 || i < length) && (it != b58.rend()); it++, i++) {
105  carry += 256 * (*it);
106  *it = carry % 58;
107  carry /= 58;
108  }
109 
110  assert(carry == 0);
111  length = i;
112  input = input.subspan(1);
113  }
114  // Skip leading zeroes in base58 result.
115  std::vector<unsigned char>::iterator it = b58.begin() + (size - length);
116  while (it != b58.end() && *it == 0)
117  it++;
118  // Translate the result into a string.
119  std::string str;
120  str.reserve(zeroes + (b58.end() - it));
121  str.assign(zeroes, '1');
122  while (it != b58.end())
123  str += pszBase58[*(it++)];
124  return str;
125 }
126 
127 bool DecodeBase58(const std::string& str, std::vector<unsigned char>& vchRet, int max_ret_len)
128 {
129  if (!ValidAsCString(str)) {
130  return false;
131  }
132  return DecodeBase58(str.c_str(), vchRet, max_ret_len);
133 }
134 
136 {
137  // add 4-byte hash check to the end
138  std::vector<unsigned char> vch(input.begin(), input.end());
139  uint256 hash = Hash(vch);
140  vch.insert(vch.end(), (unsigned char*)&hash, (unsigned char*)&hash + 4);
141  return EncodeBase58(vch);
142 }
143 
144 NODISCARD static bool DecodeBase58Check(const char* psz, std::vector<unsigned char>& vchRet, int max_ret_len)
145 {
146  if (!DecodeBase58(psz, vchRet, max_ret_len > std::numeric_limits<int>::max() - 4 ? std::numeric_limits<int>::max() : max_ret_len + 4) ||
147  (vchRet.size() < 4)) {
148  vchRet.clear();
149  return false;
150  }
151  // re-calculate the checksum, ensure it matches the included 4-byte checksum
152  uint256 hash = Hash(MakeSpan(vchRet).first(vchRet.size() - 4));
153  if (memcmp(&hash, &vchRet[vchRet.size() - 4], 4) != 0) {
154  vchRet.clear();
155  return false;
156  }
157  vchRet.resize(vchRet.size() - 4);
158  return true;
159 }
160 
161 bool DecodeBase58Check(const std::string& str, std::vector<unsigned char>& vchRet, int max_ret)
162 {
163  if (!ValidAsCString(str)) {
164  return false;
165  }
166  return DecodeBase58Check(str.c_str(), vchRet, max_ret);
167 }
CONSTEXPR_IF_NOT_DEBUG Span< C > subspan(std::size_t offset) const noexcept
Definition: span.h:160
std::deque< CInv >::iterator it
constexpr C * end() const noexcept
Definition: span.h:142
NODISCARD bool ValidAsCString(const std::string &str) noexcept
Check if a string does not contain any embedded NUL (\0) characters.
Definition: string.h:62
constexpr std::size_t size() const noexcept
Definition: span.h:153
std::string EncodeBase58(Span< const unsigned char > input)
Why base-58 instead of standard base-64 encoding?
Definition: base58.cpp:87
#define NODISCARD
Definition: attributes.h:18
static const char * pszBase58
All alphanumeric characters except for "0", "I", "O", and "l".
Definition: base58.cpp:18
std::string EncodeBase58Check(Span< const unsigned char > input)
Encode a byte span into a base58-encoded string, including checksum.
Definition: base58.cpp:135
constexpr C * begin() const noexcept
Definition: span.h:141
static NODISCARD bool DecodeBase58Check(const char *psz, std::vector< unsigned char > &vchRet, int max_ret_len)
Definition: base58.cpp:144
256-bit opaque blob.
Definition: uint256.h:124
static NODISCARD bool DecodeBase58(const char *psz, std::vector< unsigned char > &vch, int max_ret_len)
Definition: base58.cpp:38
constexpr bool IsSpace(char c) noexcept
Tests if the given character is a whitespace character.
Definition: strencodings.h:95
A Span is an object that can refer to a contiguous sequence of objects.
Definition: span.h:82
uint256 Hash(const T &in1)
Compute the 256-bit hash of an object.
Definition: hash.h:75
static const int8_t mapBase58[256]
Definition: base58.cpp:19
Span< A > constexpr MakeSpan(A(&a)[N])
MakeSpan for arrays:
Definition: span.h:193