arc4.g in prng function sometimes returns NaN #74
Description
arc4.g in prng function sometimes (rare) returns NaN.
Software used: Scripting interface of Adobe After Effects 2020
For folks having the same issue:
I did this (ugly) quickfix which works:
// This function returns a random double in [0, 1) that contains
// randomness in every bit of the mantissa of the IEEE 754 value.
var prng = function() {
var n = arc4.g(chunks); // Start with a numerator n < 2 ^ 48
while (isNaN(n)) { // [KGH] Quickfix
n = arc4.g(chunks); // [KGH] Quickfix
} // [KGH] Quickfix
var d = startdenom, // and denominator d = 2 ^ 48.
x = 0; // and no 'extra last byte'.
while (n < significance) { // Fill up all significant digits by
n = (n + x) * width; // shifting numerator and
d *= width; // denominator and generating a
x = arc4.g(1); // new least-significant-byte.
while (isNaN(x)) { // [KGH] Quickfix
x = arc4.g(1); // [KGH] Quickfix
} // [KGH] Quickfix
}
while (n >= overflow) { // To avoid rounding up, before adding
n /= 2; // last byte, shift everything
d /= 2; // right using integer math until
x >>>= 1; // we have exactly the desired bits.
}
return (n + x) / d; // Form the number within [0, 1).
};