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108 lines
2.5 KiB
V
108 lines
2.5 KiB
V
// Copyright (c) 2022 John Lloyd. 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 xoroshiro128pp
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import rand.seed
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import rand.buffer
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pub const seed_len = 4 // u32, that is
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fn rotl(x u64, k int) u64 {
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return (x << k) | (x >> (64 - k))
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}
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// XOROS128PPRNG ported from https://prng.di.unimi.it/xoroshiro128plusplus.c
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pub struct XOROS128PPRNG {
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buffer.PRNGBuffer
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mut:
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state0 u64 = u64(0x853c49e6748fea9b) ^ seed.time_seed_64()
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state1 u64 = u64(0xda3e39cb94b95bdb) ^ seed.time_seed_64()
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}
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// seed seeds the XOROS128PPRNG with 4 `u32` values.
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pub fn (mut rng XOROS128PPRNG) seed(seed_data []u32) {
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if seed_data.len != 4 {
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eprintln('XOROS128PPRNG needs 4 u32s to be seeded.')
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exit(1)
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}
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init_state0 := u64(seed_data[0]) | (u64(seed_data[1]) << 32)
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init_state1 := u64(seed_data[2]) | (u64(seed_data[3]) << 32)
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rng.state0 = init_state0
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rng.state1 = init_state1
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rng.u64()
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rng.u64()
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rng.bytes_left = 0
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rng.buffer = 0
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}
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// byte returns a uniformly distributed pseudorandom 8-bit unsigned `byte`.
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[inline]
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pub fn (mut rng XOROS128PPRNG) u8() u8 {
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if rng.bytes_left >= 1 {
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rng.bytes_left -= 1
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value := u8(rng.buffer)
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rng.buffer >>= 8
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return value
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}
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ans := rng.u64()
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rng.buffer = ans >> 8
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rng.bytes_left = 7
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value := u8(ans)
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return value
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}
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// u16 returns a pseudorandom 16-bit unsigned integer (`u16`).
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[inline]
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pub fn (mut rng XOROS128PPRNG) u16() u16 {
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if rng.bytes_left >= 2 {
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rng.bytes_left -= 2
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value := u16(rng.buffer)
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rng.buffer >>= 16
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return value
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}
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ans := rng.u64()
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rng.buffer = u32(ans >> 16)
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rng.bytes_left = 6
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return u16(ans)
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}
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// u32 returns a pseudorandom unsigned `u32`.
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[inline]
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pub fn (mut rng XOROS128PPRNG) u32() u32 {
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if rng.bytes_left >= 4 {
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rng.bytes_left -= 4
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value := u32(rng.buffer)
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rng.buffer >>= 32
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return value
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}
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ans := rng.u64()
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rng.buffer = ans >> 32
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rng.bytes_left = 4
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return u32(ans)
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}
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// u64 returns a pseudorandom 64-bit unsigned `u64`.
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[inline]
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pub fn (mut rng XOROS128PPRNG) u64() u64 {
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oldstate0 := rng.state0
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mut oldstate1 := rng.state1
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res := rotl(oldstate0 + oldstate1, 17) + oldstate0
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oldstate1 = oldstate1 ^ oldstate0
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rng.state0 = rotl(oldstate0, 49) ^ oldstate1 ^ (oldstate1 << 21)
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rng.state1 = rotl(oldstate1, 28)
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return res
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}
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// block_size returns the number of bits that the RNG can produce in a single iteration.
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[inline]
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pub fn (mut rng XOROS128PPRNG) block_size() int {
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return 64
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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 XOROS128PPRNG) free() {
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unsafe { free(rng) }
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}
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