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make std.HashMap.ensureCapacity round up to the nearest power of two

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Ryan Liptak 2019-05-02 00:58:26 -07:00
parent 8b7c59a414
commit 0afa2d040a
1 changed files with 8 additions and 1 deletions
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9
std/hash_map.zig
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@ -141,8 +141,15 @@ pub fn HashMap(comptime K: type, comptime V: type, comptime hash: fn (key: K) u3
if (new_capacity <= self.entries.len) {
return;
}
// make sure capacity is a power of two
var capacity = new_capacity;
const is_power_of_two = capacity & (capacity-1) == 0;
if (!is_power_of_two) {
const pow = math.log2_int_ceil(usize, capacity);
capacity = math.pow(usize, 2, pow);
}
const old_entries = self.entries;
try self.initCapacity(new_capacity);
try self.initCapacity(capacity);
if (old_entries.len > 0) {
// dump all of the old elements into the new table
for (old_entries) |*old_entry| {