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rand: simplify rand.PRNG, move to optional types for error handling (#13570)

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This commit is contained in:
Subhomoy Haldar
2022-02-23 16:06:14 +05:30
committed by GitHub
parent 5c0b7b0d05
commit 114a341f5f
49 changed files with 609 additions and 1586 deletions
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199
vlib/rand/sys/system_rng.c.v
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@@ -5,7 +5,6 @@ module sys
import math.bits
import rand.seed
import rand.constants
// Implementation note:
// ====================
@@ -76,204 +75,6 @@ pub fn (r SysRNG) u64() u64 {
return result
}
// r.u32n(max) returns a pseudorandom u32 value that is guaranteed to be less than max
[inline]
pub fn (r SysRNG) u32n(max u32) u32 {
if max == 0 {
eprintln('max must be positive integer')
exit(1)
}
// Owing to the pigeon-hole principle, we can't simply do
// val := rng.u32() % max.
// It'll wreck the properties of the distribution unless
// max evenly divides 2^32. So we divide evenly to
// the closest power of two. Then we loop until we find
// an int in the required range
bit_len := bits.len_32(max)
if bit_len == 32 {
for {
value := r.u32()
if value < max {
return value
}
}
} else {
mask := (u32(1) << (bit_len + 1)) - 1
for {
value := r.u32() & mask
if value < max {
return value
}
}
}
return u32(0)
}
// r.u64n(max) returns a pseudorandom u64 value that is guaranteed to be less than max
[inline]
pub fn (r SysRNG) u64n(max u64) u64 {
if max == 0 {
eprintln('max must be positive integer')
exit(1)
}
// Similar procedure for u64s
bit_len := bits.len_64(max)
if bit_len == 64 {
for {
value := r.u64()
if value < max {
return value
}
}
} else {
mask := (u64(1) << (bit_len + 1)) - 1
for {
value := r.u64() & mask
if value < max {
return value
}
}
}
return u64(0)
}
// r.u32n(min, max) returns a pseudorandom u32 value that is guaranteed to be in [min, max)
[inline]
pub fn (r SysRNG) u32_in_range(min u32, max u32) u32 {
if max <= min {
eprintln('max must be greater than min')
exit(1)
}
return min + r.u32n(max - min)
}
// r.u64n(min, max) returns a pseudorandom u64 value that is guaranteed to be in [min, max)
[inline]
pub fn (r SysRNG) u64_in_range(min u64, max u64) u64 {
if max <= min {
eprintln('max must be greater than min')
exit(1)
}
return min + r.u64n(max - min)
}
// r.int() returns a pseudorandom 32-bit int (which may be negative)
[inline]
pub fn (r SysRNG) int() int {
return int(r.u32())
}
// r.i64() returns a pseudorandom 64-bit i64 (which may be negative)
[inline]
pub fn (r SysRNG) i64() i64 {
return i64(r.u64())
}
// r.int31() returns a pseudorandom 31-bit int which is non-negative
[inline]
pub fn (r SysRNG) int31() int {
return int(r.u32() & constants.u31_mask) // Set the 32nd bit to 0.
}
// r.int63() returns a pseudorandom 63-bit int which is non-negative
[inline]
pub fn (r SysRNG) int63() i64 {
return i64(r.u64() & constants.u63_mask) // Set the 64th bit to 0.
}
// r.intn(max) returns a pseudorandom int that lies in [0, max)
[inline]
pub fn (r SysRNG) intn(max int) int {
if max <= 0 {
eprintln('max has to be positive.')
exit(1)
}
return int(r.u32n(u32(max)))
}
// r.i64n(max) returns a pseudorandom i64 that lies in [0, max)
[inline]
pub fn (r SysRNG) i64n(max i64) i64 {
if max <= 0 {
eprintln('max has to be positive.')
exit(1)
}
return i64(r.u64n(u64(max)))
}
// r.int_in_range(min, max) returns a pseudorandom int that lies in [min, max)
[inline]
pub fn (r SysRNG) int_in_range(min int, max int) int {
if max <= min {
eprintln('max must be greater than min')
exit(1)
}
// This supports negative ranges like [-10, -5) because the difference is positive
return min + r.intn(max - min)
}
// r.i64_in_range(min, max) returns a pseudorandom i64 that lies in [min, max)
[inline]
pub fn (r SysRNG) i64_in_range(min i64, max i64) i64 {
if max <= min {
eprintln('max must be greater than min')
exit(1)
}
return min + r.i64n(max - min)
}
// r.f32() returns a pseudorandom f32 value between 0.0 (inclusive) and 1.0 (exclusive) i.e [0, 1)
[inline]
pub fn (r SysRNG) f32() f32 {
return f32(r.u32()) / constants.max_u32_as_f32
}
// r.f64() returns a pseudorandom f64 value between 0.0 (inclusive) and 1.0 (exclusive) i.e [0, 1)
[inline]
pub fn (r SysRNG) f64() f64 {
return f64(r.u64()) / constants.max_u64_as_f64
}
// r.f32n() returns a pseudorandom f32 value in [0, max)
[inline]
pub fn (r SysRNG) f32n(max f32) f32 {
if max <= 0 {
eprintln('max has to be positive.')
exit(1)
}
return r.f32() * max
}
// r.f64n() returns a pseudorandom f64 value in [0, max)
[inline]
pub fn (r SysRNG) f64n(max f64) f64 {
if max <= 0 {
eprintln('max has to be positive.')
exit(1)
}
return r.f64() * max
}
// r.f32_in_range(min, max) returns a pseudorandom f32 that lies in [min, max)
[inline]
pub fn (r SysRNG) f32_in_range(min f32, max f32) f32 {
if max <= min {
eprintln('max must be greater than min')
exit(1)
}
return min + r.f32n(max - min)
}
// r.i64_in_range(min, max) returns a pseudorandom i64 that lies in [min, max)
[inline]
pub fn (r SysRNG) f64_in_range(min f64, max f64) f64 {
if max <= min {
eprintln('max must be greater than min')
exit(1)
}
return min + r.f64n(max - min)
}
// free should be called when the generator is no longer needed
[unsafe]
pub fn (mut rng SysRNG) free() {