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package rand
Rand :: struct {
state: u64,
inc: u64,
}
@(private)
_GLOBAL_SEED_DATA := 1234567890;
@(private)
global_rand := create(u64(uintptr(&_GLOBAL_SEED_DATA)));
set_global_seed :: proc(seed: u64) {
init(&global_rand, seed);
}
create :: proc(seed: u64) -> Rand {
r: Rand;
init(&r, seed);
return r;
}
init :: proc(r: ^Rand, seed: u64) {
r.state = 0;
r.inc = (seed << 1) | 1;
_random(r);
r.state += seed;
_random(r);
}
_random :: proc(r: ^Rand) -> u32 {
r := r;
if r == nil {
// NOTE(bill, 2020-09-07): Do this so that people can
// enforce the global random state if necessary with `nil`
r = &global_rand;
}
old_state := r.state;
r.state = old_state * 6364136223846793005 + (r.inc|1);
xor_shifted := u32(((old_state>>18) ~ old_state) >> 27);
rot := u32(old_state >> 59);
return (xor_shifted >> rot) | (xor_shifted << ((-rot) & 31));
}
uint32 :: proc(r: ^Rand = nil) -> u32 { return _random(r); }
uint64 :: proc(r: ^Rand = nil) -> u64 {
a := u64(_random(r));
b := u64(_random(r));
return (a<<32) | b;
}
uint128 :: proc(r: ^Rand = nil) -> u128 {
a := u128(_random(r));
b := u128(_random(r));
c := u128(_random(r));
d := u128(_random(r));
return (a<<96) | (b<<64) | (c<<32) | d;
}
int31 :: proc(r: ^Rand = nil) -> i32 { return i32(uint32(r) << 1 >> 1); }
int63 :: proc(r: ^Rand = nil) -> i64 { return i64(uint64(r) << 1 >> 1); }
int127 :: proc(r: ^Rand = nil) -> i128 { return i128(uint128(r) << 1 >> 1); }
int31_max :: proc(n: i32, r: ^Rand = nil) -> i32 {
if n <= 0 {
panic("Invalid argument to int31_max");
}
if n&(n-1) == 0 {
return int31(r) & (n-1);
}
max := i32((1<<31) - 1 - (1<<31)&u32(n));
v := int31(r);
for v > max {
v = int31(r);
}
return v % n;
}
int63_max :: proc(n: i64, r: ^Rand = nil) -> i64 {
if n <= 0 {
panic("Invalid argument to int63_max");
}
if n&(n-1) == 0 {
return int63(r) & (n-1);
}
max := i64((1<<63) - 1 - (1<<63)&u64(n));
v := int63(r);
for v > max {
v = int63(r);
}
return v % n;
}
int127_max :: proc(n: i128, r: ^Rand = nil) -> i128 {
if n <= 0 {
panic("Invalid argument to int127_max");
}
if n&(n-1) == 0 {
return int127(r) & (n-1);
}
max := i128((1<<63) - 1 - (1<<63)&u128(n));
v := int127(r);
for v > max {
v = int127(r);
}
return v % n;
}
int_max :: proc(n: int, r: ^Rand = nil) -> int {
if n <= 0 {
panic("Invalid argument to int_max");
}
when size_of(int) == 4 {
return int(int31_max(i32(n), r));
} else {
return int(int63_max(i64(n), r));
}
}
float64 :: proc(r: ^Rand = nil) -> f64 { return f64(int63_max(1<<53, r)) / (1 << 53); }
float32 :: proc(r: ^Rand = nil) -> f32 { return f32(float64(r)); }
float64_range :: proc(lo, hi: f64, r: ^Rand = nil) -> f64 { return (hi-lo)*float64(r) + lo; }
float32_range :: proc(lo, hi: f32, r: ^Rand = nil) -> f32 { return (hi-lo)*float32(r) + lo; }
read :: proc(p: []byte, r: ^Rand = nil) -> (n: int) {
pos := i8(0);
val := i64(0);
for n = 0; n < len(p); n += 1 {
if pos == 0 {
val = int63(r);
pos = 7;
}
p[n] = byte(val);
val >>= 8;
pos -= 1;
}
return;
}
// perm returns a slice of n ints in a pseudo-random permutation of integers in the range [0, n)
perm :: proc(n: int, r: ^Rand = nil) -> []int {
m := make([]int, n);
for i := 0; i < n; i += 1 {
j := int_max(i+1, r);
m[i] = m[j];
m[j] = i;
}
return m;
}
shuffle :: proc(array: $T/[]$E, r: ^Rand = nil) {
n := i64(len(array));
if n < 2 {
return;
}
for i := i64(0); i < n; i += 1 {
j := int63_max(n, r);
array[i], array[j] = array[j], array[i];
}
}
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