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v/vlib/rand/xoroshiro128pp/xoros128pp.v

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// Copyright (c) 2022 John Lloyd. All rights reserved.
// Use of this source code is governed by an MIT license
// that can be found in the LICENSE file.
module xoroshiro128pp
import rand.seed
import rand.buffer
pub const seed_len = 4 // u32, that is
fn rotl(x u64, k int) u64 {
return (x << k) | (x >> (64 - k))
}
// XOROS128PPRNG ported from https://prng.di.unimi.it/xoroshiro128plusplus.c
pub struct XOROS128PPRNG {
buffer.PRNGBuffer
mut:
state0 u64 = u64(0x853c49e6748fea9b) ^ seed.time_seed_64()
state1 u64 = u64(0xda3e39cb94b95bdb) ^ seed.time_seed_64()
}
// seed seeds the XOROS128PPRNG with 4 `u32` values.
pub fn (mut rng XOROS128PPRNG) seed(seed_data []u32) {
if seed_data.len != 4 {
eprintln('XOROS128PPRNG needs 4 u32s to be seeded.')
exit(1)
}
init_state0 := u64(seed_data[0]) | (u64(seed_data[1]) << 32)
init_state1 := u64(seed_data[2]) | (u64(seed_data[3]) << 32)
rng.state0 = init_state0
rng.state1 = init_state1
rng.u64()
rng.u64()
rng.bytes_left = 0
rng.buffer = 0
}
// byte returns a uniformly distributed pseudorandom 8-bit unsigned `byte`.
[inline]
pub fn (mut rng XOROS128PPRNG) u8() u8 {
if rng.bytes_left >= 1 {
rng.bytes_left -= 1
value := u8(rng.buffer)
rng.buffer >>= 8
return value
}
ans := rng.u64()
rng.buffer = ans >> 8
rng.bytes_left = 7
value := u8(ans)
return value
}
// u16 returns a pseudorandom 16-bit unsigned integer (`u16`).
[inline]
pub fn (mut rng XOROS128PPRNG) 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 = u32(ans >> 16)
rng.bytes_left = 6
return u16(ans)
}
// u32 returns a pseudorandom unsigned `u32`.
[inline]
pub fn (mut rng XOROS128PPRNG) u32() u32 {
if rng.bytes_left >= 4 {
rng.bytes_left -= 4
value := u32(rng.buffer)
rng.buffer >>= 32
return value
}
ans := rng.u64()
rng.buffer = ans >> 32
rng.bytes_left = 4
return u32(ans)
}
// u64 returns a pseudorandom 64-bit unsigned `u64`.
[inline]
pub fn (mut rng XOROS128PPRNG) u64() u64 {
oldstate0 := rng.state0
mut oldstate1 := rng.state1
res := rotl(oldstate0 + oldstate1, 17) + oldstate0
oldstate1 = oldstate1 ^ oldstate0
rng.state0 = rotl(oldstate0, 49) ^ oldstate1 ^ (oldstate1 << 21)
rng.state1 = rotl(oldstate1, 28)
return res
}
// block_size returns the number of bits that the RNG can produce in a single iteration.
[inline]
pub fn (mut rng XOROS128PPRNG) block_size() int {
return 64
}
// free should be called when the generator is no longer needed
[unsafe]
pub fn (mut rng XOROS128PPRNG) free() {
unsafe { free(rng) }
}