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std.MultiArrayList: add clear methods

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Andrew Kelley 2024-10-13 23:43:07 -07:00
parent 3bf89f55c2
commit 9fd61f7460
1 changed files with 20 additions and 5 deletions
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25
lib/std/multi_array_list.zig
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@ -346,11 +346,8 @@ pub fn MultiArrayList(comptime T: type) type {
/// If `new_len` is greater than zero, this may fail to reduce the capacity, /// If `new_len` is greater than zero, this may fail to reduce the capacity,
/// but the data remains intact and the length is updated to new_len. /// but the data remains intact and the length is updated to new_len.
pub fn shrinkAndFree(self: *Self, gpa: Allocator, new_len: usize) void { pub fn shrinkAndFree(self: *Self, gpa: Allocator, new_len: usize) void {
if (new_len == 0) { if (new_len == 0) return clearAndFree(self, gpa);
gpa.free(self.allocatedBytes());
self.* = .{};
return;
}
assert(new_len <= self.capacity); assert(new_len <= self.capacity);
assert(new_len <= self.len); assert(new_len <= self.len);
@ -391,6 +388,11 @@ pub fn MultiArrayList(comptime T: type) type {
self.* = other; self.* = other;
} }
pub fn clearAndFree(self: *Self, gpa: Allocator) void {
gpa.free(self.allocatedBytes());
self.* = .{};
}
/// Reduce length to `new_len`. /// Reduce length to `new_len`.
/// Invalidates pointers to elements `items[new_len..]`. /// Invalidates pointers to elements `items[new_len..]`.
/// Keeps capacity the same. /// Keeps capacity the same.
@ -398,6 +400,11 @@ pub fn MultiArrayList(comptime T: type) type {
self.len = new_len; self.len = new_len;
} }
/// Invalidates all element pointers.
pub fn clearRetainingCapacity(self: *Self) void {
self.len = 0;
}
/// Modify the array so that it can hold at least `new_capacity` items. /// Modify the array so that it can hold at least `new_capacity` items.
/// Implements super-linear growth to achieve amortized O(1) append operations. /// Implements super-linear growth to achieve amortized O(1) append operations.
/// Invalidates pointers if additional memory is needed. /// Invalidates pointers if additional memory is needed.
@ -677,6 +684,14 @@ test "basic usage" {
try testing.expectEqual(@as(u32, 2), list.pop().a); try testing.expectEqual(@as(u32, 2), list.pop().a);
try testing.expectEqual(@as(u8, 'a'), list.pop().c); try testing.expectEqual(@as(u8, 'a'), list.pop().c);
try testing.expectEqual(@as(?Foo, null), list.popOrNull()); try testing.expectEqual(@as(?Foo, null), list.popOrNull());
list.clearRetainingCapacity();
try testing.expectEqual(0, list.len);
try testing.expect(list.capacity > 0);
list.clearAndFree(ally);
try testing.expectEqual(0, list.len);
try testing.expectEqual(0, list.capacity);
} }
// This was observed to fail on aarch64 with LLVM 11, when the capacityInBytes // This was observed to fail on aarch64 with LLVM 11, when the capacityInBytes