New API to wrap an initialized array with an array list (#1040)

* New API to wrap an initialized array with an array list


---------

Co-authored-by: Bret Ambrose <bambrose@amazon.com>

include/aws/common/array_list.h

@@ -59,6 +59,21 @@ void aws_array_list_init_static(
     size_t item_count,
     size_t item_size);
 
+/**
+ * Initializes an array list with a preallocated array of *already-initialized* elements. item_count is the number of
+ * elements in the array, and item_size is the size in bytes of each element.
+ *
+ * Once initialized, nothing further can be added to the list, since it will be full and cannot resize.
+ *
+ * Primary use case is to treat an already-initialized C array as an array list.
+ */
+AWS_STATIC_IMPL
+void aws_array_list_init_static_from_initialized(
+    struct aws_array_list *AWS_RESTRICT list,
+    void *raw_array,
+    size_t item_count,
+    size_t item_size);
+
 /**
  * Set of properties of a valid aws_array_list.
  */

include/aws/common/array_list.inl

@@ -81,6 +81,19 @@ void aws_array_list_init_static(
     AWS_POSTCONDITION(aws_array_list_is_valid(list));
 }
 
+AWS_STATIC_IMPL
+void aws_array_list_init_static_from_initialized(
+    struct aws_array_list *AWS_RESTRICT list,
+    void *raw_array,
+    size_t item_count,
+    size_t item_size) {
+
+    aws_array_list_init_static(list, raw_array, item_count, item_size);
+    list->length = item_count;
+
+    AWS_POSTCONDITION(aws_array_list_is_valid(list));
+}
+
 AWS_STATIC_IMPL
 bool aws_array_list_is_valid(const struct aws_array_list *AWS_RESTRICT list) {
     if (!list) {