Implement A_SORT_MEM

Sorts an array of structs by a given member.

include/vm/page.h

@@ -126,6 +126,7 @@ struct page *array_popback(struct page *dst);
 struct page *array_erase(struct page *page, int i, bool *success);
 struct page *array_insert(struct page *page, int i, union vm_value v, enum ain_data_type data_type, int struct_type);
 void array_sort(struct page *page, int compare_fno);
+void array_sort_mem(struct page *page, int member_no);
 int array_find(struct page *page, int start, int end, union vm_value v, int compare_fno);
 void array_reverse(struct page *page);
 

src/page.c

@@ -542,6 +542,28 @@ void array_sort(struct page *page, int compare_fno)
 	qsort(page->values, page->nr_vars, sizeof(union vm_value), array_compare);
 }
 
+static int current_sort_member;
+
+static int array_compare_member(const void *_a, const void *_b)
+{
+	union vm_value a_slot = *((union vm_value*)_a);
+	union vm_value b_slot = *((union vm_value*)_b);
+	struct page *a = heap_get_page(a_slot.i);
+	struct page *b = heap_get_page(b_slot.i);
+	return a->values[current_sort_member].i - b->values[current_sort_member].i;
+}
+
+void array_sort_mem(struct page *page, int member_no)
+{
+	if (!page)
+		return;
+	if (page->type != ARRAY_PAGE || array_type(page->a_type) != AIN_STRUCT)
+		VM_ERROR("A_SORT_MEM called on something other than an array of structs");
+
+	current_sort_member = member_no;
+	qsort(page->values, page->nr_vars, sizeof(union vm_value), array_compare_member);
+}
+
 int array_find(struct page *page, int start, int end, union vm_value v, int compare_fno)
 {
 	if (!page)

src/vm.c

@@ -2042,6 +2042,12 @@ static enum opcode execute_instruction(enum opcode opcode)
 		stack_push(i < get_argument(1) || i >= get_argument(2));
 		break;
 	}
+	case A_SORT_MEM: {
+		int mno = stack_pop().i;
+		int array = stack_pop_var()->i;
+		array_sort_mem(heap[array].page, mno);
+		break;
+	}
 	//case DG_ADD:
 	case DG_SET: {
 		int fun = stack_pop().i;