lstack: Linked list stack implementation

This new module provides a simple stack implementation as a singly
linked list.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

Makefile-ccan

@@ -69,6 +69,7 @@ MODS_WITH_SRC := antithread \
 	likely \
 	list \
 	lqueue \
+	lstack \
 	md4 \
 	memmem \
 	net \

ccan/lstack/LICENSE

@@ -0,0 +1 @@
+../../licenses/BSD-MIT

ccan/lstack/_info

@@ -0,0 +1,57 @@
+#include "config.h"
+#include <stdio.h>
+#include <string.h>
+
+/**
+ * lstack - Simple, singly-linked-list stack implementation
+ *
+ * This code provides a simple implementation of the Stack abstract
+ * data type in terms of a singly linked list.
+ *
+ * License: BSD-MIT
+ * Author: David Gibson <david@gibson.dropbear.id.au>
+ *
+ * Example:
+ *	#include <ccan/lstack/lstack.h>
+ *
+ *	struct arg {
+ *		const char *arg;
+ *		struct lstack_link sl;
+ *	};
+ *
+ *	int main(int argc, char *argv[])
+ *	{
+ *		int i;
+ *		struct arg *a;
+ *		LSTACK(argstack);
+ *
+ *		for (i = 0; i < argc; i++) {
+ *			a = malloc(sizeof(*a));
+ *			a->arg = argv[i];
+ *			lstack_push(&argstack, a, sl);
+ *		}
+ *
+ *		printf("Command line arguments in reverse:\n");
+ *
+ *		while (!lstack_empty(&argstack)) {
+ *			a = lstack_pop(&argstack, struct arg, sl);
+ *			printf("Argument: %s\n", a->arg);
+ *			free(a);
+ *		}
+ *
+ *		return 0;
+ *	}
+ */
+int main(int argc, char *argv[])
+{
+	/* Expect exactly one argument */
+	if (argc != 2)
+		return 1;
+
+	if (strcmp(argv[1], "depends") == 0) {
+		printf("ccan/container_of\n");
+		return 0;
+	}
+
+	return 1;
+}

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 */

ccan/lstack/test/run.c

@@ -0,0 +1,62 @@
+#include "config.h"
+
+#include <ccan/lstack/lstack.h>
+#include <ccan/tap/tap.h>
+
+struct stacker {
+	const char *name;
+	struct lstack_link sl;
+};
+
+int main(void)
+{
+	LSTACK(s);
+	struct stacker a = { "Alice" };
+	struct stacker b = { "Bob" };
+	struct stacker c = { "Carol" };
+	struct stacker *stacker;
+
+	/* This is how many tests you plan to run */
+	plan_tests(18);
+
+	ok1(lstack_empty(&s));
+	ok1(lstack_top(&s, struct stacker, sl) == NULL);
+
+	lstack_push(&s, &a, sl);
+
+	ok1(!lstack_empty(&s));
+	ok1(lstack_top(&s, struct stacker, sl) == &a);
+
+	lstack_push(&s, &b, sl);
+
+	ok1(!lstack_empty(&s));
+	ok1(lstack_top(&s, struct stacker, sl) == &b);
+
+	lstack_push(&s, &c, sl);
+
+	ok1(!lstack_empty(&s));
+	ok1(lstack_top(&s, struct stacker, sl) == &c);
+
+	stacker = lstack_pop(&s, struct stacker, sl);
+	ok1(stacker == &c);
+
+	ok1(!lstack_empty(&s));
+	ok1(lstack_top(&s, struct stacker, sl) == &b);
+
+	stacker = lstack_pop(&s, struct stacker, sl);
+	ok1(stacker == &b);
+
+	ok1(!lstack_empty(&s));
+	ok1(lstack_top(&s, struct stacker, sl) == &a);
+
+	stacker = lstack_pop(&s, struct stacker, sl);
+	ok1(stacker == &a);
+
+	ok1(lstack_empty(&s));
+	ok1(lstack_top(&s, struct stacker, sl) == NULL);
+
+	ok1(lstack_pop(&s, struct stacker, sl) == NULL);
+
+	/* This exits depending on whether all tests passed */
+	return exit_status();
+}