std.ArrayList: add appendNTimesAssumeCapacity

1 files changed, 18 insertions, 0 deletions

diff --git a/lib/std/array_list.zig b/lib/std/array_list.zig
index 0fef070ab8..aecbc73bfe 100644
--- a/lib/std/array_list.zig
+++ b/lib/std/array_list.zig
@@ -216,6 +216,15 @@ pub fn ArrayListAligned(comptime T: type, comptime alignment: ?u29) type {
             mem.set(T, self.items[old_len..self.items.len], value);
         }
 
+        /// Append a value to the list `n` times.
+        /// Asserts the capacity is enough.
+        pub fn appendNTimesAssumeCapacity(self: *Self, value: T, n: usize) void {
+            const new_len = self.items.len + n;
+            assert(new_len <= self.capacity);
+            mem.set(T, self.items.ptr[self.items.len..new_len], value);
+            self.items.len = new_len;
+        }
+
         /// Adjust the list's length to `new_len`.
         /// Does not initialize added items if any.
         pub fn resize(self: *Self, new_len: usize) !void {
@@ -473,6 +482,15 @@ pub fn ArrayListAlignedUnmanaged(comptime T: type, comptime alignment: ?u29) typ
             mem.set(T, self.items[old_len..self.items.len], value);
         }
 
+        /// Append a value to the list `n` times.
+        /// Asserts the capacity is enough.
+        pub fn appendNTimesAssumeCapacity(self: *Self, value: T, n: usize) void {
+            const new_len = self.items.len + n;
+            assert(new_len <= self.capacity);
+            mem.set(T, self.items.ptr[self.items.len..new_len], value);
+            self.items.len = new_len;
+        }
+
         /// Adjust the list's length to `new_len`.
         /// Does not initialize added items if any.
         pub fn resize(self: *Self, allocator: *Allocator, new_len: usize) !void {