v/vlib/rand/util/util.v

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// Copyright (c) 2019-2021 Alexander Medvednikov. All rights reserved.
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// Use of this source code is governed by an MIT license
// that can be found in the LICENSE file.
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module util
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import time
// Commonly used constants across RNGs - some taken from "Numerical Recipes".
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pub const (
lower_mask = u64(0x00000000FFFFFFFF)
max_u32 = 0xFFFFFFFF
max_u64 = 0xFFFFFFFFFFFFFFFF
max_u32_as_f32 = f32(max_u32) + 1
max_u64_as_f64 = f64(max_u64) + 1
u31_mask = u32(0x7FFFFFFF)
u63_mask = u64(0x7FFFFFFFFFFFFFFF)
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)
// nr_next returns a next value based on the previous value `prev`.
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[inline]
fn nr_next(prev u32) u32 {
return prev * 1664525 + 1013904223
}
// time_seed_array returns the required number of u32s generated from system time.
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[inline]
pub fn time_seed_array(count int) []u32 {
ctime := time.now()
mut seed := u32(ctime.unix_time() ^ ctime.microsecond)
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mut seed_data := []u32{cap: count}
for _ in 0 .. count {
seed = nr_next(seed)
seed_data << nr_next(seed)
}
return seed_data
}
// time_seed_32 returns a 32-bit seed generated from system time.
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[inline]
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pub fn time_seed_32() u32 {
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return time_seed_array(1)[0]
}
// time_seed_64 returns a 64-bit seed generated from system time.
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[inline]
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pub fn time_seed_64() u64 {
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seed_data := time_seed_array(2)
lower := u64(seed_data[0])
upper := u64(seed_data[1])
return lower | (upper << 32)
}