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std: Add ArrayList.insertAssumeCapacity()

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Also test and document that inserting at list.items.len is allowed.
This commit is contained in:
Isaac Freund 2023-03-11 14:52:38 +01:00
parent 4ea2f441df
commit a097779b61
1 changed files with 26 additions and 7 deletions
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33
lib/std/array_list.zig
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@ -141,11 +141,21 @@ pub fn ArrayListAligned(comptime T: type, comptime alignment: ?u29) type {
return cloned;
}
/// Insert `item` at index `n` by moving `list[n .. list.len]` to make room.
/// Insert `item` at index `n`. Moves `list[n .. list.len]` to higher indices to make room.
/// If `n` is equal to the length of the list this operation is equivalent to append.
/// This operation is O(N).
/// Invalidates pointers if additional memory is needed.
pub fn insert(self: *Self, n: usize, item: T) Allocator.Error!void {
try self.ensureUnusedCapacity(1);
self.insertAssumeCapacity(n, item);
}
/// Insert `item` at index `n`. Moves `list[n .. list.len]` to higher indices to make room.
/// If `n` is equal to the length of the list this operation is equivalent to append.
/// This operation is O(N).
/// Asserts that there is enough capacity for the new item.
pub fn insertAssumeCapacity(self: *Self, n: usize, item: T) void {
assert(self.items.len < self.capacity);
self.items.len += 1;
mem.copyBackwards(T, self.items[n + 1 .. self.items.len], self.items[n .. self.items.len - 1]);
@ -609,12 +619,21 @@ pub fn ArrayListAlignedUnmanaged(comptime T: type, comptime alignment: ?u29) typ
return cloned;
}
/// Insert `item` at index `n`. Moves `list[n .. list.len]`
/// to higher indices to make room.
/// Insert `item` at index `n`. Moves `list[n .. list.len]` to higher indices to make room.
/// If `n` is equal to the length of the list this operation is equivalent to append.
/// This operation is O(N).
/// Invalidates pointers if additional memory is needed.
pub fn insert(self: *Self, allocator: Allocator, n: usize, item: T) Allocator.Error!void {
try self.ensureUnusedCapacity(allocator, 1);
self.insertAssumeCapacity(n, item);
}
/// Insert `item` at index `n`. Moves `list[n .. list.len]` to higher indices to make room.
/// If `n` is equal to the length of the list this operation is equivalent to append.
/// This operation is O(N).
/// Asserts that there is enough capacity for the new item.
pub fn insertAssumeCapacity(self: *Self, n: usize, item: T) void {
assert(self.items.len < self.capacity);
self.items.len += 1;
mem.copyBackwards(T, self.items[n + 1 .. self.items.len], self.items[n .. self.items.len - 1]);
@ -1309,9 +1328,9 @@ test "std.ArrayList/ArrayListUnmanaged.insert" {
var list = ArrayList(i32).init(a);
defer list.deinit();
try list.append(1);
try list.insert(0, 1);
try list.append(2);
try list.append(3);
try list.insert(2, 3);
try list.insert(0, 5);
try testing.expect(list.items[0] == 5);
try testing.expect(list.items[1] == 1);
@ -1322,9 +1341,9 @@ test "std.ArrayList/ArrayListUnmanaged.insert" {
var list = ArrayListUnmanaged(i32){};
defer list.deinit(a);
try list.append(a, 1);
try list.insert(a, 0, 1);
try list.append(a, 2);
try list.append(a, 3);
try list.insert(a, 2, 3);
try list.insert(a, 0, 5);
try testing.expect(list.items[0] == 5);
try testing.expect(list.items[1] == 1);