lstack: Linked list stack implementation

[ccan] / ccan / lstack / lstack.h

diff --git a/ccan/lstack/lstack.h b/ccan/lstack/lstack.h
new file mode 100644 (file)
index 0000000..41a9f05
--- /dev/null
+++ b/ccan/lstack/lstack.h
@@ -0,0 +1,155 @@
+/* Licensed under BSD-MIT - see LICENSE file for details */
+#ifndef CCAN_LSTACK_H
+#define CCAN_LSTACK_H
+
+#include <stdbool.h>
+#include <stdio.h>
+#include <assert.h>
+
+#include <ccan/container_of/container_of.h>
+
+/**
+ * struct lstack_link - a stack link
+ * @down: immedately lower entry in the stack, or NULL if this is the bottom.
+ *
+ * This is used as an entry in a stack.
+ *
+ * Example:
+ *     struct stacker {
+ *             char *name;
+ *             struct lstack_link sl;
+ *     };
+ */
+struct lstack_link {
+       struct lstack_link *down;
+};
+
+/**
+ * struct lstack - a stack
+ * @b: the top of the stack (NULL if empty)
+ */
+struct lstack {
+       struct lstack_link *top;
+};
+
+/**
+ * LSTACK - define and initialize an empty stack
+ * @name: the name of the lstack.
+ *
+ * The LSTACK macro defines an lstack and initializes it to an empty
+ * stack.  It can be prepended by "static" to define a static lstack.
+ *
+ * See also:
+ *     lstack_init()
+ *
+ * Example:
+ *     LSTACK(my_stack);
+ *
+ *     assert(lstack_empty(&my_stack));
+ */
+#define LSTACK(name) \
+       struct lstack name = { NULL, }
+
+/**
+ * lstack_init - initialize a stack
+ * @h: the lstack to set to an empty stack
+ *
+ * Example:
+ *     struct lstack *sp = malloc(sizeof(*sp));
+ *     lstack_init(sp);
+ */
+static inline void lstack_init(struct lstack *s)
+{
+       s->top = NULL;
+}
+
+/**
+ * lstack_empty - is a stack empty?
+ * @s: the stack
+ *
+ * If the stack is empty, returns true.
+ *
+ * Example:
+ *     assert(lstack_empty(sp));
+ */
+static inline bool lstack_empty(const struct lstack *s)
+{
+       return (s->top == NULL);
+}
+
+/**
+ * lstack_entry - convert an lstack_link back into the structure containing it.
+ * @e: the lstack_link
+ * @type: the type of the entry
+ * @member: the lstack_link member of the type
+ *
+ * Example:
+ *     struct stacker {
+ *             char *name;
+ *             struct lstack_link sl;
+ *     } st;
+ *     assert(lstack_entry(&st.sl, struct stacker, sl) == &st);
+ */
+#define lstack_entry(n, type, member) container_of_or_null(n, type, member)
+
+/**
+ * lstack_top - get top entry in a stack
+ * @s: the stack
+ * @type: the type of stack entries
+ * @member: the lstack_link entry
+ *
+ * If the stack is empty, returns NULL.
+ *
+ * Example:
+ *     struct stacker *t;
+ *
+ *     t = lstack_top(sp, struct stacker, sl);
+ *     assert(lstack_pop(sp, struct stacker, sl) == t);
+ */
+#define lstack_top(s, type, member) \
+       lstack_entry(lstack_top_((s)), type, member)
+static inline struct lstack_link *lstack_top_(const struct lstack *s)
+{
+       return s->top;
+}
+
+/**
+ * lstack_push - add an entry to the top of the stack
+ * @s: the stack to add the node to
+ * @e: the item to push
+ * @member: the lstack_link field of *e
+ *
+ * The lstack_link does not need to be initialized; it will be overwritten.
+ */
+#define lstack_push(s, e, member) \
+       lstack_push_((s), &((e)->member))
+static inline void lstack_push_(struct lstack *s, struct lstack_link *e)
+{
+       e->down = lstack_top_(s);
+       s->top = e;
+}
+
+/**
+ * lstack_pop - remove and return the entry from the top of the stack
+ * @s: the stack
+ * @type: the type of stack entries
+ * @member: the lstack_link field of @type
+ *
+ * Note that this leaves the returned entry's link in an undefined
+ * state; it can be added to another stack, but not deleted again.
+ */
+#define lstack_pop(s, type, member) \
+       lstack_entry(lstack_pop_((s)), type, member)
+static inline struct lstack_link *lstack_pop_(struct lstack *s)
+{
+       struct lstack_link *top;
+
+       if (lstack_empty(s))
+               return NULL;
+
+       top = lstack_top_(s);
+       s->top = top->down;
+       return top;
+}
+
+#endif /* CCAN_LSTACK_H */