1
0
mirror of https://github.com/vlang/v.git synced 2023-08-10 21:13:21 +03:00
v/vlib/rand/wyrand/wyrand.v

103 lines
2.3 KiB
V
Raw Normal View History

2022-01-04 12:21:08 +03:00
// Copyright (c) 2019-2022 Alexander Medvednikov. All rights reserved.
2020-06-01 22:13:56 +03:00
// Use of this source code is governed by an MIT license
// that can be found in the LICENSE file.
2020-06-09 16:06:07 +03:00
module wyrand
2020-06-01 22:13:56 +03:00
import hash
import rand.buffer
import rand.seed
2020-06-01 22:13:56 +03:00
// Redefinition of some constants that we will need for pseudorandom number generation.
2020-06-01 22:13:56 +03:00
const (
wyp0 = u64(0xa0761d6478bd642f)
wyp1 = u64(0xe7037ed1a0b428db)
)
pub const seed_len = 2
// WyRandRNG is a RNG based on the WyHash hashing algorithm.
2020-06-01 22:13:56 +03:00
pub struct WyRandRNG {
buffer.PRNGBuffer
2020-06-01 22:13:56 +03:00
mut:
state u64 = seed.time_seed_64()
bytes_left int
buffer u64
2020-06-01 22:13:56 +03:00
}
// seed sets the seed, needs only two `u32`s in little-endian format as [lower, higher].
2020-06-01 22:13:56 +03:00
pub fn (mut rng WyRandRNG) seed(seed_data []u32) {
if seed_data.len != 2 {
eprintln('WyRandRNG needs 2 32-bit unsigned integers as the seed.')
exit(1)
}
rng.state = seed_data[0] | (u64(seed_data[1]) << 32)
rng.bytes_left = 0
rng.buffer = 0
2020-06-01 22:13:56 +03:00
}
// byte returns a uniformly distributed pseudorandom 8-bit unsigned positive `byte`.
[inline]
2022-04-15 18:25:45 +03:00
pub fn (mut rng WyRandRNG) u8() u8 {
// Can we extract a value from the buffer?
if rng.bytes_left >= 1 {
rng.bytes_left -= 1
2022-04-15 14:45:52 +03:00
value := u8(rng.buffer)
rng.buffer >>= 8
return value
}
// Add a new value to the buffer
rng.buffer = rng.u64()
rng.bytes_left = 7
2022-04-15 14:45:52 +03:00
value := u8(rng.buffer)
rng.buffer >>= 8
return value
}
// u16 returns a pseudorandom 16bit int in range `[0, 2¹⁶)`.
[inline]
pub fn (mut rng WyRandRNG) u16() u16 {
if rng.bytes_left >= 2 {
rng.bytes_left -= 2
value := u16(rng.buffer)
rng.buffer >>= 16
return value
}
ans := rng.u64()
rng.buffer = ans >> 16
rng.bytes_left = 6
return u16(ans)
}
// u32 returns a pseudorandom 32bit int in range `[0, 2³²)`.
2020-06-01 22:13:56 +03:00
[inline]
pub fn (mut rng WyRandRNG) u32() u32 {
if rng.bytes_left >= 4 {
rng.bytes_left -= 4
value := u32(rng.buffer)
rng.buffer >>= 32
return value
2020-06-01 22:13:56 +03:00
}
ans := rng.u64()
rng.buffer = ans >> 32
rng.bytes_left = 4
return u32(ans)
2020-06-01 22:13:56 +03:00
}
// u64 returns a pseudorandom 64bit int in range `[0, 2⁶⁴)`.
2020-06-01 22:13:56 +03:00
[inline]
pub fn (mut rng WyRandRNG) u64() u64 {
unsafe {
mut seed1 := rng.state
seed1 += wyrand.wyp0
2020-06-01 22:13:56 +03:00
rng.state = seed1
return hash.wymum(seed1 ^ wyrand.wyp1, seed1)
2020-06-01 22:13:56 +03:00
}
return 0
}
// block_size returns the number of bits that the RNG can produce in a single iteration.
[inline]
pub fn (mut rng WyRandRNG) block_size() int {
return 64
}