[list] Add list_is_first_entry() and list_is_last_entry()

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/include/ipxe/list.h

 					 member );		\
 	( ( &prev->member == (head) ) ? NULL : prev ); } )
 
+/**
+ * Test if entry is first in a list
+ *
+ * @v entry		List entry
+ * @v head		List head
+ * @v member		Name of list field within iterator's type
+ * @ret is_first	Entry is first in the list
+ */
+#define list_is_first_entry( entry, head, member )		\
+	( (head)->next == &(entry)->member )
+
+/**
+ * Test if entry is last in a list
+ *
+ * @v entry		List entry
+ * @v head		List head
+ * @v member		Name of list field within iterator's type
+ * @ret is_last		Entry is last in the list
+ */
+#define list_is_last_entry( entry, head, member )		\
+	( (head)->prev == &(entry)->member )
+
 /**
  * Iterate over a list
  *

src/tests/list_test.c

 	ok ( list_prev_entry ( &list_tests[1], list, list ) == &list_tests[5] );
 	ok ( list_next_entry ( &list_tests[1], list, list ) == NULL );
 
+	/* Test list_is_first_entry() and list_is_last_entry() */
+	INIT_LIST_HEAD ( list );
+	list_add_tail ( &list_tests[4].list, list );
+	list_add_tail ( &list_tests[8].list, list );
+	list_add_tail ( &list_tests[3].list, list );
+	list_add_tail ( &list_tests[6].list, list );
+	ok ( list_is_first_entry ( &list_tests[4], list, list ) );
+	ok ( ! list_is_first_entry ( &list_tests[8], list, list ) );
+	ok ( ! list_is_first_entry ( &list_tests[3], list, list ) );
+	ok ( ! list_is_first_entry ( &list_tests[6], list, list ) );
+	ok ( ! list_is_last_entry ( &list_tests[4], list, list ) );
+	ok ( ! list_is_last_entry ( &list_tests[8], list, list ) );
+	ok ( ! list_is_last_entry ( &list_tests[3], list, list ) );
+	ok ( list_is_last_entry ( &list_tests[6], list, list ) );
+	list_del ( &list_tests[4].list );
+	ok ( list_is_first_entry ( &list_tests[8], list, list ) );
+	list_del ( &list_tests[8].list );
+	list_del ( &list_tests[6].list );
+	ok ( list_is_first_entry ( &list_tests[3], list, list ) );
+	ok ( list_is_last_entry ( &list_tests[3], list, list ) );
+
 	/* Test list_for_each() */
 	INIT_LIST_HEAD ( list );
 	list_add_tail ( &list_tests[6].list, list );