97 lines
2.3 KiB
V
97 lines
2.3 KiB
V
// Copyright (c) 2019-2022 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 musl
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import rand.seed
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pub const seed_len = 1
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// MuslRNG ported from https://git.musl-libc.org/cgit/musl/tree/src/prng/rand_r.c
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pub struct MuslRNG {
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mut:
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state u32 = seed.time_seed_32()
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bytes_left int
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buffer u32
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}
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// seed sets the current random state based on `seed_data`.
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// seed expects `seed_data` to be only one `u32`.
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pub fn (mut rng MuslRNG) seed(seed_data []u32) {
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if seed_data.len != 1 {
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eprintln('MuslRNG needs only one unsigned 32-bit integer as a seed.')
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exit(1)
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}
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rng.state = seed_data[0]
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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 positive `byte`.
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[inline]
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pub fn (mut rng MuslRNG) byte() byte {
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if rng.bytes_left >= 1 {
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rng.bytes_left -= 1
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value := byte(rng.buffer)
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rng.buffer >>= 8
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return value
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}
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rng.buffer = rng.u32()
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rng.bytes_left = 3
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value := byte(rng.buffer)
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rng.buffer >>= 8
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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 MuslRNG) 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.u32()
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rng.buffer = ans >> 16
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rng.bytes_left = 2
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return u16(ans)
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}
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// temper returns a tempered value based on `prev` value.
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[inline]
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fn temper(prev u32) u32 {
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mut x := prev
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x ^= x >> 11
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x ^= (x << 7) & 0x9D2C5680
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x ^= (x << 15) & 0xEFC60000
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x ^= (x >> 18)
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return x
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}
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// u32 returns a pseudorandom 32-bit unsigned integer (`u32`).
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pub fn (mut rng MuslRNG) u32() u32 {
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rng.state = rng.state * 1103515245 + 12345
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// We are not dividing by 2 (or shifting right by 1)
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// because we want all 32-bits of random data
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return temper(rng.state)
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}
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// u64 returns a pseudorandom 64-bit unsigned integer (`u64`).
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[inline]
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pub fn (mut rng MuslRNG) u64() u64 {
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return u64(rng.u32()) | (u64(rng.u32()) << 32)
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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 MuslRNG) block_size() int {
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return 32
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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 MuslRNG) free() {
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unsafe { free(rng) }
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}
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