odin-js-fundamentals-part-5/node_modules/pure-rand/lib/esm/distribution/UnsafeUniformBigIntDistribu...

25 lines
844 B
JavaScript

var SBigInt = typeof BigInt !== 'undefined' ? BigInt : undefined;
export function unsafeUniformBigIntDistribution(from, to, rng) {
var diff = to - from + SBigInt(1);
var MinRng = SBigInt(-0x80000000);
var NumValues = SBigInt(0x100000000);
var FinalNumValues = NumValues;
var NumIterations = 1;
while (FinalNumValues < diff) {
FinalNumValues *= NumValues;
++NumIterations;
}
var MaxAcceptedRandom = FinalNumValues - (FinalNumValues % diff);
while (true) {
var value = SBigInt(0);
for (var num = 0; num !== NumIterations; ++num) {
var out = rng.unsafeNext();
value = NumValues * value + (SBigInt(out) - MinRng);
}
if (value < MaxAcceptedRandom) {
var inDiff = value % diff;
return inDiff + from;
}
}
}