From a812c5c8c9aabf6e0fd934bd55ec553c6dbb60c2 Mon Sep 17 00:00:00 2001 From: Tavian Barnes Date: Wed, 12 Apr 2023 10:32:06 -0400 Subject: list: New SLIST_INSERT() macro --- src/list.h | 71 ++++++++++++++++++++++++++++++++++++-------------------------- 1 file changed, 41 insertions(+), 30 deletions(-) diff --git a/src/list.h b/src/list.h index 55242a3..87e2bf2 100644 --- a/src/list.h +++ b/src/list.h @@ -105,12 +105,14 @@ #define LIST_BLOCK_(block) do { block } while (0) /** - * Add an item to the tail of a singly-linked list. + * Insert an item into a singly-linked list. * * @param list - * The list to modify. + * The list to remove from. + * @param cursor + * A pointer to the item to insert after, e.g. &list->head or list->tail. * @param item - * The item to append. + * The item to insert. * @param node (optional) * If specified, use item->node.next rather than item->next. * @@ -118,27 +120,29 @@ * * We play some tricks with variadic macros to handle the optional parameter: * - * SLIST_APPEND(list, item) => { - * *list->tail = item; - * list->tail = &item->next; + * SLIST_INSERT(list, cursor, item) => { + * item->next = *cursor; + * *cursor = item; + * list->tail = item->next ? list->tail : &item->next; * } * - * SLIST_APPEND(list, item, node) => { - * *list->tail = item; - * list->tail = &item->node.next; + * SLIST_INSERT(list, cursor, item, node) => { + * item->node.next = *cursor; + * *cursor = item; + * list->tail = item->node.next ? list->tail : &item->node.next; * } * * The first trick is that * - * #define SLIST_APPEND(list, item, ...) + * #define SLIST_INSERT(list, item, cursor, ...) * * won't work because both commas are required (until C23; see N3033). As a * workaround, we dispatch to another macro and add a trailing comma. * - * SLIST_APPEND(list, item) => SLIST_APPEND_(list, item, ) - * SLIST_APPEND(list, item, node) => SLIST_APPEND_(list, item, node, ) + * SLIST_INSERT(list, cursor, item) => SLIST_INSERT_(list, cursor, item, ) + * SLIST_INSERT(list, cursor, item, node) => SLIST_INSERT_(list, cursor, item, node, ) */ -#define SLIST_APPEND(list, ...) SLIST_APPEND_(list, __VA_ARGS__, ) +#define SLIST_INSERT(list, cursor, ...) SLIST_INSERT_(list, cursor, __VA_ARGS__, ) /** * Now we need a way to generate either ->next or ->node.next depending on @@ -178,18 +182,31 @@ #define LIST_NODE__(dir, node, ignored, dot, ...) node dot dir /** - * SLIST_APPEND_() uses LIST_NEXT_() to generate the right name for the list + * SLIST_INSERT_() uses LIST_NEXT_() to generate the right name for the list * node, and finally delegates to the actual implementation. + */ +#define SLIST_INSERT_(list, cursor, item, ...) \ + LIST_BLOCK_(SLIST_INSERT__((list), (cursor), (item), LIST_NEXT_(__VA_ARGS__))) + +#define SLIST_INSERT__(list, cursor, item, next) \ + item->next = *cursor; \ + *cursor = item; \ + list->tail = item->next ? list->tail : &item->next; + +/** + * Add an item to the tail of a singly-linked list. * - * SLIST_APPEND_(list, item, ) => SLIST_APPEND__((list), (item), next) - * SLIST_APPEND_(list, item, node, ) => SLIST_APPEND__((list), (item), node.next) + * @param list + * The list to modify. + * @param item + * The item to append. + * @param node (optional) + * If specified, use item->node.next rather than item->next. */ -#define SLIST_APPEND_(list, item, ...) \ - LIST_BLOCK_(SLIST_APPEND__((list), (item), LIST_NEXT_(__VA_ARGS__))) +#define SLIST_APPEND(list, ...) SLIST_APPEND_(list, __VA_ARGS__, ) -#define SLIST_APPEND__(list, item, next) \ - *list->tail = item; \ - list->tail = &item->next; +#define SLIST_APPEND_(list, item, ...) \ + SLIST_INSERT_(list, (list)->tail, item, __VA_ARGS__) /** * Add an item to the head of a singly-linked list. @@ -204,12 +221,7 @@ #define SLIST_PREPEND(list, ...) SLIST_PREPEND_(list, __VA_ARGS__, ) #define SLIST_PREPEND_(list, item, ...) \ - LIST_BLOCK_(SLIST_PREPEND__((list), (item), LIST_NEXT_(__VA_ARGS__))) - -#define SLIST_PREPEND__(list, item, next) \ - list->tail = list->head ? list->tail : &item->next; \ - item->next = list->head; \ - list->head = item; + SLIST_INSERT_(list, &(list)->head, item, __VA_ARGS__) /** * Add an entire singly-linked list to the tail of another. @@ -260,9 +272,8 @@ */ #define SLIST_POP(...) SLIST_POP_(__VA_ARGS__, ) -#define SLIST_POP_(list, ...) SLIST_POP__((list), LIST_NEXT_(__VA_ARGS__)) - -#define SLIST_POP__(list, next) SLIST_REMOVE__(list, (&list->head), next) +#define SLIST_POP_(list, ...) \ + SLIST_REMOVE_(list, &(list)->head, __VA_ARGS__) /** * Initialize a doubly-linked list. -- cgit v1.2.3