Merge branch 'LemonBoy-cprocess'

This is a partial merge of #6750. I took the Posix code paths and
dropped the Windows code paths, and then did the improvements noted in
the comments.

The Windows implementation is still TODO.

1 files changed, 13 insertions, 3 deletions

diff --git a/lib/std/array_list.zig b/lib/std/array_list.zig
index 4a8e0059e9..292e421bb1 100644
--- a/lib/std/array_list.zig
+++ b/lib/std/array_list.zig
@@ -337,11 +337,21 @@ pub fn ArrayListAligned(comptime T: type, comptime alignment: ?u29) type {
             return self.pop();
         }
 
-        // For a nicer API, `items.len` is the length, not the capacity.
-        // This requires "unsafe" slicing.
-        fn allocatedSlice(self: Self) Slice {
+        /// Returns a slice of all the items plus the extra capacity, whose memory
+        /// contents are undefined.
+        pub fn allocatedSlice(self: Self) Slice {
+            // For a nicer API, `items.len` is the length, not the capacity.
+            // This requires "unsafe" slicing.
             return self.items.ptr[0..self.capacity];
         }
+
+        /// Returns a slice of only the extra capacity after items.
+        /// This can be useful for writing directly into an `ArrayList`.
+        /// Note that such an operation must be followed up with a direct
+        /// modification of `self.items.len`.
+        pub fn unusedCapacitySlice(self: Self) Slice {
+            return self.allocatedSlice()[self.items.len..];
+        }
     };
 }