frontend: add a line editor for shell input

frontend/line-ed/hook.c

@@ -0,0 +1,37 @@
+#include "hook.h"
+
+#include "line-ed.h"
+
+void line_ed_add_hook(struct line_ed *ed, struct line_ed_hook *hook)
+{
+	b_queue_push_back(&ed->l_hooks, &hook->hook_entry);
+}
+
+void line_ed_remove_hook(struct line_ed *ed, struct line_ed_hook *hook)
+{
+	b_queue_delete(&ed->l_hooks, &hook->hook_entry);
+}
+
+void hook_keypress(struct line_ed *ed, s_keycode key)
+{
+	b_queue_iterator it;
+	b_queue_foreach (&it, &ed->l_hooks) {
+		struct line_ed_hook *hook
+			= b_unbox(struct line_ed_hook, it.entry, hook_entry);
+		if (hook->hook_keypress) {
+			hook->hook_keypress(ed, hook, key);
+		}
+	}
+}
+
+void hook_buffer_modified(struct line_ed *ed)
+{
+	b_queue_iterator it;
+	b_queue_foreach (&it, &ed->l_hooks) {
+		struct line_ed_hook *hook
+			= b_unbox(struct line_ed_hook, it.entry, hook_entry);
+		if (hook->hook_buffer_modified) {
+			hook->hook_buffer_modified(ed, hook);
+		}
+	}
+}