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std.HashMap: add public ensureCapacity fn

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This commit is contained in:
Ryan Liptak 2019-05-01 23:38:52 -07:00
parent c00c18de6a
commit 8b7c59a414
1 changed files with 20 additions and 10 deletions
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30
std/hash_map.zig
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@ -118,7 +118,7 @@ pub fn HashMap(comptime K: type, comptime V: type, comptime hash: fn (key: K) u3
};
}
self.incrementModificationCount();
try self.ensureCapacity();
try self.autoCapacity();
const put_result = self.internalPut(key);
assert(put_result.old_kv == null);
return GetOrPutResult{
@ -135,15 +135,15 @@ pub fn HashMap(comptime K: type, comptime V: type, comptime hash: fn (key: K) u3
return res.kv;
}
fn ensureCapacity(self: *Self) !void {
if (self.entries.len == 0) {
return self.initCapacity(16);
/// Sets the capacity to the new capacity if the new
/// capacity is greater than the current capacity.
pub fn ensureCapacity(self: *Self, new_capacity: usize) !void {
if (new_capacity <= self.entries.len) {
return;
}
// if we get too full (60%), double the capacity
if (self.size * 5 >= self.entries.len * 3) {
const old_entries = self.entries;
try self.initCapacity(self.entries.len * 2);
const old_entries = self.entries;
try self.initCapacity(new_capacity);
if (old_entries.len > 0) {
// dump all of the old elements into the new table
for (old_entries) |*old_entry| {
if (old_entry.used) {
@ -157,7 +157,7 @@ pub fn HashMap(comptime K: type, comptime V: type, comptime hash: fn (key: K) u3
/// Returns the kv pair that was already there.
pub fn put(self: *Self, key: K, value: V) !?KV {
self.incrementModificationCount();
try self.ensureCapacity();
try self.autoCapacity();
const put_result = self.internalPut(key);
put_result.new_entry.kv.value = value;
@ -227,6 +227,16 @@ pub fn HashMap(comptime K: type, comptime V: type, comptime hash: fn (key: K) u3
return other;
}
fn autoCapacity(self: *Self) !void {
if (self.entries.len == 0) {
return self.ensureCapacity(16);
}
// if we get too full (60%), double the capacity
if (self.size * 5 >= self.entries.len * 3) {
return self.ensureCapacity(self.entries.len * 2);
}
}
fn initCapacity(hm: *Self, capacity: usize) !void {
hm.entries = try hm.allocator.alloc(Entry, capacity);
hm.size = 0;