1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
use bigint::{U256, Uint};
#[derive(Debug, PartialEq, Clone, Copy)]
pub struct Compact(u32);
impl From<u32> for Compact {
fn from(u: u32) -> Self {
Compact(u)
}
}
impl From<Compact> for u32 {
fn from(c: Compact) -> Self {
c.0
}
}
impl From<U256> for Compact {
fn from(u: U256) -> Self {
Compact::from_u256(u)
}
}
impl From<Compact> for U256 {
fn from(c: Compact) -> Self {
c.to_u256().unwrap_or_else(|x| x)
}
}
impl Compact {
pub fn new(u: u32) -> Self {
Compact(u)
}
pub fn max_value() -> Self {
U256::max_value().into()
}
pub fn to_u256(&self) -> Result<U256, U256> {
let size = self.0 >> 24;
let mut word = self.0 & 0x007fffff;
let result = if size <= 3 {
word >>= 8 * (3 - size as usize);
word.into()
} else {
U256::from(word) << (8 * (size as usize - 3))
};
let is_negative = word != 0 && (self.0 & 0x00800000) != 0;
let is_overflow = (word != 0 && size > 34) ||
(word > 0xff && size > 33) ||
(word > 0xffff && size > 32);
if is_negative || is_overflow {
Err(result)
} else {
Ok(result)
}
}
pub fn from_u256(val: U256) -> Self {
let mut size = (val.bits() + 7) / 8;
let mut compact = if size <= 3 {
(val.low_u64() << (8 * (3 - size))) as u32
} else {
let bn = val >> (8 * (size - 3));
bn.low_u32()
};
if (compact & 0x00800000) != 0 {
compact >>= 8;
size += 1;
}
assert!((compact & !0x007fffff) == 0);
assert!(size < 256);
Compact(compact | (size << 24) as u32)
}
pub fn to_f64(&self) -> f64 {
let mut shift = (self.0 >> 24) & 0xff;
let mut diff = f64::from(0x0000ffffu32) / f64::from(self.0 & 0x00ffffffu32);
while shift < 29 {
diff *= f64::from(256);
shift += 1;
}
while shift > 29 {
diff /= f64::from(256.0);
shift -= 1;
}
diff
}
}
#[cfg(test)]
mod tests {
use bigint::{U256, Uint};
use super::Compact;
#[test]
fn test_compact_to_u256() {
assert_eq!(Compact::new(0x01003456).to_u256(), Ok(0.into()));
assert_eq!(Compact::new(0x01123456).to_u256(), Ok(0x12.into()));
assert_eq!(Compact::new(0x02008000).to_u256(), Ok(0x80.into()));
assert_eq!(Compact::new(0x05009234).to_u256(), Ok(0x92340000u64.into()));
assert!(Compact::new(0x04923456).to_u256().is_err());
assert_eq!(Compact::new(0x04123456).to_u256(), Ok(0x12345600u64.into()));
}
#[test]
fn test_from_u256() {
let test1 = U256::from(1000u64);
assert_eq!(Compact::new(0x0203e800), Compact::from_u256(test1));
let test2 = U256::from(2).pow(U256::from(256-32)) - U256::from(1);
assert_eq!(Compact::new(0x1d00ffff), Compact::from_u256(test2));
}
#[test]
fn test_compact_to_from_u256() {
let compact = Compact::new(0x1d00ffff);
let compact2 = Compact::from_u256(compact.to_u256().unwrap());
assert_eq!(compact, compact2);
let compact = Compact::new(0x05009234);
let compact2 = Compact::from_u256(compact.to_u256().unwrap());
assert_eq!(compact, compact2);
}
#[test]
fn difficulty() {
fn compare_f64(v1: f64, v2: f64) -> bool {
(v1 - v2).abs() < 0.00001
}
assert!(compare_f64(Compact::new(0x1b0404cb).to_f64(), 16307.42094));
assert!(compare_f64(Compact::new(0x1f111111).to_f64(), 0.000001));
assert!(compare_f64(Compact::new(0x1ef88f6f).to_f64(), 0.000016));
assert!(compare_f64(Compact::new(0x1df88f6f).to_f64(), 0.004023));
assert!(compare_f64(Compact::new(0x1cf88f6f).to_f64(), 1.029916));
assert!(compare_f64(Compact::new(0x12345678).to_f64(), 5913134931067755359633408.0));
}
}