bitcoinleveldb_rand/
random.rs

1crate::ix!();
2
3//-------------------------------------------[.cpp/bitcoin/src/leveldb/util/random.h]
4
5/**
6  | A very simple random number generator.  Not
7  | especially good at generating truly random
8  | bits, but good enough for our needs in this
9  | package.
10  */
11pub struct Random {
12    seed: u32,
13}
14
15impl Random {
16
17    pub fn new(s: u32) -> Self {
18    
19        todo!();
20        /*
21
22
23            : seed_(s & 0x7fffffffu) 
24        // Avoid bad seeds.
25        if (seed_ == 0 || seed_ == 2147483647L) {
26          seed_ = 1;
27        }
28        */
29    }
30    
31    pub fn next(&mut self) -> u32 {
32        
33        todo!();
34        /*
35            static const uint32_t M = 2147483647L;  // 2^31-1
36        static const uint64_t A = 16807;        // bits 14, 8, 7, 5, 2, 1, 0
37        // We are computing
38        //       seed_ = (seed_ * A) % M,    where M = 2^31-1
39        //
40        // seed_ must not be zero or M, or else all subsequent computed values
41        // will be zero or M respectively.  For all other values, seed_ will end
42        // up cycling through every number in [1,M-1]
43        uint64_t product = seed_ * A;
44
45        // Compute (product % M) using the fact that ((x << 31) % M) == x.
46        seed_ = static_cast<uint32_t>((product >> 31) + (product & M));
47        // The first reduction may overflow by 1 bit, so we may need to
48        // repeat.  mod == M is not possible; using > allows the faster
49        // sign-bit-based test.
50        if (seed_ > M) {
51          seed_ -= M;
52        }
53        return seed_;
54        */
55    }
56
57    /**
58      | Returns a uniformly distributed value in the
59      | range [0..n-1]
60      |
61      | REQUIRES: n > 0
62      */
63    pub fn uniform(&mut self, n: i32) -> u32 {
64        
65        todo!();
66        /*
67            return Next() % n;
68        */
69    }
70
71    /**
72      | Randomly returns true ~"1/n" of the time, and
73      | false otherwise.
74      |
75      | REQUIRES: n > 0
76      */
77    pub fn one_in(&mut self, n: i32) -> bool {
78        
79        todo!();
80        /*
81            return (Next() % n) == 0;
82        */
83    }
84
85    /**
86      | Skewed: pick "base" uniformly from range
87      | [0,max_log] and then return "base" random
88      | bits.  The effect is to pick a number in the
89      | range [0,2^max_log-1] with exponential bias
90      | towards smaller numbers.
91      */
92    pub fn skewed(&mut self, max_log: i32) -> u32 {
93        
94        todo!();
95        /*
96            return Uniform(1 << Uniform(max_log + 1));
97        */
98    }
99}
bitcoinleveldb_rand/random.rs

bitcoinleveldb_rand/
random.rs
