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simpler range mask calculation

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a dinosaur
2024-09-01 05:11:48 +10:00
parent 1f74b79ea2
commit 64fcebf4e5
1 changed files with 2 additions and 14 deletions
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16
Sources/Voxelotl/Random/RandomRange.swift
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@ -65,21 +65,9 @@ public extension RandomProvider where Output: UnsignedInteger {
} }
mutating func nextModless(in bound: Output) -> Output { mutating func nextModless(in bound: Output) -> Output {
func pow2MaskFrom(range num: Output) -> Output { let shift = bound.leadingZeroBitCount
if num & (num - 1) == 0 { let mask = Output.max &>> shift
return num - 1
}
var result: Output = 1
for _ in 0..<Output.bitWidth {
if result >= num {
return result - 1
}
result <<= 1
}
return .max
}
let mask = pow2MaskFrom(range: bound)
var result: Output var result: Output
repeat { repeat {
result = next() & mask result = next() & mask