scriptnum10.h raw
1 // Copyright (c) 2009-2010 Satoshi Nakamoto
2 // Copyright (c) 2009-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 #ifndef BITCOIN_TEST_SCRIPTNUM10_H
7 #define BITCOIN_TEST_SCRIPTNUM10_H
8
9 #include <cassert>
10 #include <cstdint>
11 #include <limits>
12 #include <stdexcept>
13 #include <string>
14 #include <vector>
15
16 class scriptnum10_error : public std::runtime_error
17 {
18 public:
19 explicit scriptnum10_error(const std::string& str) : std::runtime_error(str) {}
20 };
21
22 class CScriptNum10
23 {
24 /**
25 * The ScriptNum implementation from Bitcoin Core 0.10.0, for cross-comparison.
26 */
27 public:
28
29 explicit CScriptNum10(const int64_t& n)
30 {
31 m_value = n;
32 }
33
34 static const size_t nDefaultMaxNumSize = 4;
35
36 explicit CScriptNum10(const std::vector<unsigned char>& vch, bool fRequireMinimal,
37 const size_t nMaxNumSize = nDefaultMaxNumSize)
38 {
39 if (vch.size() > nMaxNumSize) {
40 throw scriptnum10_error("script number overflow");
41 }
42 if (fRequireMinimal && vch.size() > 0) {
43 // Check that the number is encoded with the minimum possible
44 // number of bytes.
45 //
46 // If the most-significant-byte - excluding the sign bit - is zero
47 // then we're not minimal. Note how this test also rejects the
48 // negative-zero encoding, 0x80.
49 if ((vch.back() & 0x7f) == 0) {
50 // One exception: if there's more than one byte and the most
51 // significant bit of the second-most-significant-byte is set
52 // it would conflict with the sign bit. An example of this case
53 // is +-255, which encode to 0xff00 and 0xff80 respectively.
54 // (big-endian).
55 if (vch.size() <= 1 || (vch[vch.size() - 2] & 0x80) == 0) {
56 throw scriptnum10_error("non-minimally encoded script number");
57 }
58 }
59 }
60 m_value = set_vch(vch);
61 }
62
63 inline bool operator==(const int64_t& rhs) const { return m_value == rhs; }
64 inline auto operator<=>(const int64_t& rhs) const { return m_value <=> rhs; }
65
66 inline bool operator==(const CScriptNum10& rhs) const { return operator==(rhs.m_value); }
67 inline auto operator<=>(const CScriptNum10& rhs) const { return operator<=>(rhs.m_value); }
68
69 inline CScriptNum10 operator+( const int64_t& rhs) const { return CScriptNum10(m_value + rhs);}
70 inline CScriptNum10 operator-( const int64_t& rhs) const { return CScriptNum10(m_value - rhs);}
71 inline CScriptNum10 operator+( const CScriptNum10& rhs) const { return operator+(rhs.m_value); }
72 inline CScriptNum10 operator-( const CScriptNum10& rhs) const { return operator-(rhs.m_value); }
73
74 inline CScriptNum10& operator+=( const CScriptNum10& rhs) { return operator+=(rhs.m_value); }
75 inline CScriptNum10& operator-=( const CScriptNum10& rhs) { return operator-=(rhs.m_value); }
76
77 inline CScriptNum10 operator-() const
78 {
79 assert(m_value != std::numeric_limits<int64_t>::min());
80 return CScriptNum10(-m_value);
81 }
82
83 inline CScriptNum10& operator=( const int64_t& rhs)
84 {
85 m_value = rhs;
86 return *this;
87 }
88
89 inline CScriptNum10& operator+=( const int64_t& rhs)
90 {
91 assert(rhs == 0 || (rhs > 0 && m_value <= std::numeric_limits<int64_t>::max() - rhs) ||
92 (rhs < 0 && m_value >= std::numeric_limits<int64_t>::min() - rhs));
93 m_value += rhs;
94 return *this;
95 }
96
97 inline CScriptNum10& operator-=( const int64_t& rhs)
98 {
99 assert(rhs == 0 || (rhs > 0 && m_value >= std::numeric_limits<int64_t>::min() + rhs) ||
100 (rhs < 0 && m_value <= std::numeric_limits<int64_t>::max() + rhs));
101 m_value -= rhs;
102 return *this;
103 }
104
105 int getint() const
106 {
107 if (m_value > std::numeric_limits<int>::max())
108 return std::numeric_limits<int>::max();
109 else if (m_value < std::numeric_limits<int>::min())
110 return std::numeric_limits<int>::min();
111 return m_value;
112 }
113
114 std::vector<unsigned char> getvch() const
115 {
116 return serialize(m_value);
117 }
118
119 static std::vector<unsigned char> serialize(const int64_t& value)
120 {
121 if(value == 0)
122 return std::vector<unsigned char>();
123
124 std::vector<unsigned char> result;
125 const bool neg = value < 0;
126 uint64_t absvalue = neg ? -value : value;
127
128 while(absvalue)
129 {
130 result.push_back(absvalue & 0xff);
131 absvalue >>= 8;
132 }
133
134 // - If the most significant byte is >= 0x80 and the value is positive, push a
135 // new zero-byte to make the significant byte < 0x80 again.
136
137 // - If the most significant byte is >= 0x80 and the value is negative, push a
138 // new 0x80 byte that will be popped off when converting to an integral.
139
140 // - If the most significant byte is < 0x80 and the value is negative, add
141 // 0x80 to it, since it will be subtracted and interpreted as a negative when
142 // converting to an integral.
143
144 if (result.back() & 0x80)
145 result.push_back(neg ? 0x80 : 0);
146 else if (neg)
147 result.back() |= 0x80;
148
149 return result;
150 }
151
152 private:
153 static int64_t set_vch(const std::vector<unsigned char>& vch)
154 {
155 if (vch.empty())
156 return 0;
157
158 int64_t result = 0;
159 for (size_t i = 0; i != vch.size(); ++i)
160 result |= static_cast<int64_t>(vch[i]) << 8*i;
161
162 // If the input vector's most significant byte is 0x80, remove it from
163 // the result's msb and return a negative.
164 if (vch.back() & 0x80)
165 return -((int64_t)(result & ~(0x80ULL << (8 * (vch.size() - 1)))));
166
167 return result;
168 }
169
170 int64_t m_value;
171 };
172
173
174 #endif // BITCOIN_TEST_SCRIPTNUM10_H
175