ref: ff88594df5c5df6fb8f227ab8e5df3529ba6e72f
dir: /lib/std/rand.myr/
use "alloc" use "assert" use "die" use "extremum" use "mk" use "now" use "putint" use "types" pkg std = type rng const mksrng : (seed : uint32 -> rng#) const freerng : (rng : rng# -> void) generic rand : (lo : @a, hi : @a -> @a) :: numeric,integral @a generic randnum : (-> @a) :: numeric,integral @a const randbytes : (buf : byte[:] -> void) generic rngrand : (rng : rng#, lo : @a, hi : @a -> @a) ::numeric,integral @a generic rngrandnum : (rng : rng# -> @a) :: numeric,integral @a const rngrandbytes : (rng : rng#, buf : byte[:] -> void) ;; type rng = struct s0 : uint64 s1 : uint64 ;; var _rng generic rand = {lo, hi; -> rngrand(&_rng, lo, hi)} generic randnum = {; -> rngrandnum(&_rng)} const randbytes = {buf; -> rngrandbytes(&_rng, buf)} const __init__ = { _rng.s0 = (now() : uint64) _rng.s1 = (now() : uint64) } const mksrng = {seed : uint32 -> rng# -> std.mk([ .s0=(seed & 0xffff : uint64), .s1=(seed&0xffff0000>>16 : uint64) ]) } const freerng = {r std.free(r) } generic rngrand = {rng, lo, hi var span, lim, val, max span = abs(hi - lo) max = ~0 /* if ~0 is negative, we have a signed value with a different max */ if max < 0 max = (1 << (8*sizeof(@a)-1)) - 1 ;; lim = (max/span)*span val = (rngrandnum(rng) & max) while val > lim val = (rngrandnum(rng) & max) ;; -> val % span + lo } const rngrandbytes = {rng, buf var n, r : uint64 n = 0 for var i = 0; i + 8 < buf.len/8; i++ r = rngrandnum(rng) putle64(buf[n:n+8], r) n += 8 ;; r = rngrandnum(rng) for ; n != buf.len; n++ buf[n] = (r & 0xff : byte) r >>= 8 ;; } /* Generate a number using the xoroshiro algorithm, as designed by David Blackman and Sebastiano Vigna. See http://xoroshiro.di.unimi.it/ for details. */ generic rngrandnum = {rng -> @a :: numeric,integral @a var s0, s1, r s0 = rng.s0 s1 = rng.s1 r = s0 + s1 s1 ^= s0 rng.s0 = (s0 << 55 | s0 >> 9) ^ s1 ^ (s1 << 14) rng.s1 = (s1 << 36 | s1 >> 28) -> (r : @a) }