259 lines
5.9 KiB
V
259 lines
5.9 KiB
V
// Copyright (c) 2019-2021 Alexander Medvednikov. All rights reserved.
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// Use of this source code is governed by an MIT license
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// that can be found in the LICENSE file.
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module wyrand
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import math.bits
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import rand.seed
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import rand.constants
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import hash
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// Redefinition of some constants that we will need for pseudorandom number generation.
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const (
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wyp0 = u64(0xa0761d6478bd642f)
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wyp1 = u64(0xe7037ed1a0b428db)
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)
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// WyRandRNG is a RNG based on the WyHash hashing algorithm.
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pub struct WyRandRNG {
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mut:
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state u64 = seed.time_seed_64()
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has_extra bool
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extra u32
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}
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// free should be called when the generator is no longer needed
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[unsafe]
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pub fn (mut rng WyRandRNG) free() {
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unsafe { free(rng) }
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}
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// seed sets the seed, needs only two `u32`s in little-endian format as [lower, higher].
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pub fn (mut rng WyRandRNG) seed(seed_data []u32) {
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if seed_data.len != 2 {
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eprintln('WyRandRNG needs 2 32-bit unsigned integers as the seed.')
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exit(1)
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}
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rng.state = seed_data[0] | (u64(seed_data[1]) << 32)
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rng.has_extra = false
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}
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// u32 updates the PRNG state and returns the next pseudorandom `u32`.
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[inline]
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pub fn (mut rng WyRandRNG) u32() u32 {
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if rng.has_extra {
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rng.has_extra = false
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return rng.extra
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}
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full_value := rng.u64()
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lower := u32(full_value & constants.lower_mask)
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upper := u32(full_value >> 32)
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rng.extra = upper
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rng.has_extra = true
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return lower
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}
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// u64 updates the PRNG state and returns the next pseudorandom `u64`.
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[inline]
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pub fn (mut rng WyRandRNG) u64() u64 {
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unsafe {
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mut seed1 := rng.state
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seed1 += wyrand.wyp0
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rng.state = seed1
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return hash.wymum(seed1 ^ wyrand.wyp1, seed1)
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}
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return 0
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}
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// u32n returns a pseudorandom `u32` less than `max`.
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[inline]
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pub fn (mut rng WyRandRNG) u32n(max u32) u32 {
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if max == 0 {
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eprintln('max must be positive integer')
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exit(1)
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}
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// Check SysRNG in system_rng.c.v for explanation
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bit_len := bits.len_32(max)
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if bit_len == 32 {
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for {
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value := rng.u32()
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if value < max {
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return value
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}
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}
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} else {
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mask := (u32(1) << (bit_len + 1)) - 1
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for {
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value := rng.u32() & mask
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if value < max {
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return value
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}
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}
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}
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return u32(0)
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}
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// u64n returns a pseudorandom `u64` less than `max`.
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[inline]
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pub fn (mut rng WyRandRNG) u64n(max u64) u64 {
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if max == 0 {
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eprintln('max must be positive integer')
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exit(1)
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}
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bit_len := bits.len_64(max)
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if bit_len == 64 {
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for {
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value := rng.u64()
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if value < max {
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return value
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}
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}
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} else {
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mask := (u64(1) << (bit_len + 1)) - 1
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for {
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value := rng.u64() & mask
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if value < max {
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return value
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}
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}
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}
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return u64(0)
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}
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// u32n returns a pseudorandom `u32` value that is guaranteed to be in range `[min, max)`.
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[inline]
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pub fn (mut rng WyRandRNG) u32_in_range(min u32, max u32) u32 {
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if max <= min {
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eprintln('max must be greater than min')
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exit(1)
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}
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return min + rng.u32n(max - min)
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}
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// u64n returns a pseudorandom `u64` value that is guaranteed to be in range `[min, max)`.
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[inline]
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pub fn (mut rng WyRandRNG) u64_in_range(min u64, max u64) u64 {
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if max <= min {
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eprintln('max must be greater than min')
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exit(1)
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}
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return min + rng.u64n(max - min)
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}
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// int returns a (possibly negative) pseudorandom 32-bit `int`.
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[inline]
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pub fn (mut rng WyRandRNG) int() int {
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return int(rng.u32())
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}
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// i64 returns a (possibly negative) pseudorandom 64-bit `i64`.
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[inline]
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pub fn (mut rng WyRandRNG) i64() i64 {
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return i64(rng.u64())
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}
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// int31 returns a positive pseudorandom 31-bit `int`.
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[inline]
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pub fn (mut rng WyRandRNG) int31() int {
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return int(rng.u32() & constants.u31_mask) // Set the 32nd bit to 0.
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}
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// int63 returns a positive pseudorandom 63-bit `i64`.
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[inline]
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pub fn (mut rng WyRandRNG) int63() i64 {
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return i64(rng.u64() & constants.u63_mask) // Set the 64th bit to 0.
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}
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// intn returns a pseudorandom `int` in range `[0, max)`.
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[inline]
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pub fn (mut rng WyRandRNG) intn(max int) int {
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if max <= 0 {
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eprintln('max has to be positive.')
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exit(1)
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}
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return int(rng.u32n(u32(max)))
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}
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// i64n returns a pseudorandom int that lies in `[0, max)`.
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[inline]
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pub fn (mut rng WyRandRNG) i64n(max i64) i64 {
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if max <= 0 {
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eprintln('max has to be positive.')
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exit(1)
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}
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return i64(rng.u64n(u64(max)))
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}
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// int_in_range returns a pseudorandom `int` in range `[min, max)`.
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[inline]
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pub fn (mut rng WyRandRNG) int_in_range(min int, max int) int {
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if max <= min {
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eprintln('max must be greater than min')
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exit(1)
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}
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// This supports negative ranges like [-10, -5) because the difference is positive
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return min + rng.intn(max - min)
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}
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// i64_in_range returns a pseudorandom `i64` in range `[min, max)`.
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[inline]
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pub fn (mut rng WyRandRNG) i64_in_range(min i64, max i64) i64 {
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if max <= min {
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eprintln('max must be greater than min')
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exit(1)
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}
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return min + rng.i64n(max - min)
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}
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// f32 returns a pseudorandom `f32` value in range `[0, 1)`.
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[inline]
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pub fn (mut rng WyRandRNG) f32() f32 {
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return f32(rng.u32()) / constants.max_u32_as_f32
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}
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// f64 returns a pseudorandom `f64` value in range `[0, 1)`.
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[inline]
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pub fn (mut rng WyRandRNG) f64() f64 {
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return f64(rng.u64()) / constants.max_u64_as_f64
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}
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// f32n returns a pseudorandom `f32` value in range `[0, max)`.
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[inline]
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pub fn (mut rng WyRandRNG) f32n(max f32) f32 {
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if max <= 0 {
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eprintln('max has to be positive.')
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exit(1)
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}
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return rng.f32() * max
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}
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// f64n returns a pseudorandom `f64` value in range `[0, max)`.
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[inline]
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pub fn (mut rng WyRandRNG) f64n(max f64) f64 {
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if max <= 0 {
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eprintln('max has to be positive.')
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exit(1)
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}
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return rng.f64() * max
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}
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// f32_in_range returns a pseudorandom `f32` in range `[min, max)`.
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[inline]
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pub fn (mut rng WyRandRNG) f32_in_range(min f32, max f32) f32 {
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if max <= min {
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eprintln('max must be greater than min')
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exit(1)
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}
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return min + rng.f32n(max - min)
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}
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// i64_in_range returns a pseudorandom `i64` in range `[min, max)`.
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[inline]
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pub fn (mut rng WyRandRNG) f64_in_range(min f64, max f64) f64 {
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if max <= min {
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eprintln('max must be greater than min')
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exit(1)
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}
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return min + rng.f64n(max - min)
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}
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