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package runtime
import "base:intrinsics"
@(require_results)
random_generator_read_bytes :: proc(rg: Random_Generator, p: []byte) -> bool {
if rg.procedure != nil {
rg.procedure(rg.data, .Read, p)
return true
}
return false
}
@(require_results)
random_generator_read_ptr :: proc(rg: Random_Generator, p: rawptr, len: uint) -> bool {
if rg.procedure != nil {
rg.procedure(rg.data, .Read, ([^]byte)(p)[:len])
return true
}
return false
}
@(require_results)
random_generator_query_info :: proc(rg: Random_Generator) -> (info: Random_Generator_Query_Info) {
if rg.procedure != nil {
rg.procedure(rg.data, .Query_Info, ([^]byte)(&info)[:size_of(info)])
}
return
}
random_generator_reset_bytes :: proc(rg: Random_Generator, p: []byte) {
if rg.procedure != nil {
rg.procedure(rg.data, .Reset, p)
}
}
random_generator_reset_u64 :: proc(rg: Random_Generator, p: u64) {
if rg.procedure != nil {
p := p
rg.procedure(rg.data, .Reset, ([^]byte)(&p)[:size_of(p)])
}
}
Default_Random_State :: struct {
state: u64,
inc: u64,
}
default_random_generator_proc :: proc(data: rawptr, mode: Random_Generator_Mode, p: []byte) {
@(require_results)
read_u64 :: proc "contextless" (r: ^Default_Random_State) -> u64 {
old_state := r.state
r.state = old_state * 6364136223846793005 + (r.inc|1)
xor_shifted := (((old_state >> 59) + 5) ~ old_state) * 12605985483714917081
rot := (old_state >> 59)
return (xor_shifted >> rot) | (xor_shifted << ((-rot) & 63))
}
@(thread_local)
global_rand_seed: Default_Random_State
init :: proc "contextless" (r: ^Default_Random_State, seed: u64) {
seed := seed
if seed == 0 {
seed = u64(intrinsics.read_cycle_counter())
}
r.state = 0
r.inc = (seed << 1) | 1
_ = read_u64(r)
r.state += seed
_ = read_u64(r)
}
r: ^Default_Random_State = ---
if data == nil {
r = &global_rand_seed
} else {
r = cast(^Default_Random_State)data
}
switch mode {
case .Read:
if r.state == 0 && r.inc == 0 {
init(r, 0)
}
switch len(p) {
case size_of(u64):
// Fast path for a 64-bit destination.
intrinsics.unaligned_store((^u64)(raw_data(p)), read_u64(r))
case:
// All other cases.
pos := i8(0)
val := u64(0)
for &v in p {
if pos == 0 {
val = read_u64(r)
pos = 7
}
v = byte(val)
val >>= 8
pos -= 1
}
}
case .Reset:
seed: u64
mem_copy_non_overlapping(&seed, raw_data(p), min(size_of(seed), len(p)))
init(r, seed)
case .Query_Info:
if len(p) != size_of(Random_Generator_Query_Info) {
return
}
info := (^Random_Generator_Query_Info)(raw_data(p))
info^ += {.Uniform, .Resettable}
}
}
@(require_results)
default_random_generator :: proc "contextless" (state: ^Default_Random_State = nil) -> Random_Generator {
return {
procedure = default_random_generator_proc,
data = state,
}
}
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