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| author | Clark Gaebel <cg.wowus.cg@gmail.com> | 2014-03-26 21:58:08 -0400 |
|---|---|---|
| committer | Clark Gaebel <cg.wowus.cg@gmail.com> | 2014-04-18 20:15:41 -0400 |
| commit | 9f45484db5cc4570b4e489e82646efc5c628b6ea (patch) | |
| tree | 54102b238bcabee223a61d96c754e23d0360fde2 /src/libstd/num/mod.rs | |
| parent | b75683cadf6c4c55360202cd6a0106be80532451 (diff) | |
| download | rust-9f45484db5cc4570b4e489e82646efc5c628b6ea.tar.gz rust-9f45484db5cc4570b4e489e82646efc5c628b6ea.zip | |
Reduce HashMap allocations.
Diffstat (limited to 'src/libstd/num/mod.rs')
| -rw-r--r-- | src/libstd/num/mod.rs | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/src/libstd/num/mod.rs b/src/libstd/num/mod.rs index 12befed743a..b21a80cfd23 100644 --- a/src/libstd/num/mod.rs +++ b/src/libstd/num/mod.rs @@ -311,6 +311,12 @@ pub fn next_power_of_two<T: Unsigned + Int>(n: T) -> T { tmp + one() } +// Returns `true` iff `n == 2^k` for some k. +#[inline] +pub fn is_power_of_two<T: Unsigned + Int>(n: T) -> bool { + (n - one()) & n == zero() +} + /// Returns the smallest power of 2 greater than or equal to `n`. If the next /// power of two is greater than the type's maximum value, `None` is returned, /// otherwise the power of 2 is wrapped in `Some`. |