cache: add high-level cache API

Makefile.in

@@ -11,7 +11,7 @@ pkgconfigdir		= @PKGCONFIGDIR@
 
 CC			= @CC@
 PROG			= pkgconf@EXEEXT@
-SRCS			= main.c pkg.c bsdstubs.c getopt_long.c fragment.c argvsplit.c fileio.c tuple.c dependency.c queue.c
+SRCS			= main.c cache.c pkg.c bsdstubs.c getopt_long.c fragment.c argvsplit.c fileio.c tuple.c dependency.c queue.c
 OBJS			= ${SRCS:.c=.o}
 GCOV_OBJS		= ${SRCS:.c=.og}
 CFLAGS			= @CFLAGS@

cache.c

@@ -0,0 +1,78 @@
+/*
+ * cache.c
+ * package object cache
+ *
+ * Copyright (c) 2013 pkgconf authors (see AUTHORS).
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * This software is provided 'as is' and without any warranty, express or
+ * implied.  In no event shall the authors be liable for any damages arising
+ * from the use of this software.
+ */
+
+#include "pkg.h"
+
+static pkg_t *pkg_cache = NULL;
+
+/*
+ * pkg_cache_lookup(id)
+ *
+ * looks up a package in the cache given an 'id' atom,
+ * such as 'gtk+-3.0' and returns the already loaded version
+ * if present.
+ */
+pkg_t *
+pkg_cache_lookup(const char *id)
+{
+	pkg_t *pkg;
+
+	PKG_FOREACH_LIST_ENTRY(pkg_cache, pkg)
+	{
+		if (!strcmp(pkg->id, id))
+			return pkg;
+	}
+
+	return NULL;
+}
+
+/*
+ * pkg_cache_add(pkg)
+ *
+ * adds an entry for the package to the package cache.
+ * the cache entry must be removed if the package is freed.
+ */
+void
+pkg_cache_add(pkg_t *pkg)
+{
+	pkg->next = pkg_cache;
+	pkg_cache = pkg;
+
+	if (pkg->next != NULL)
+		pkg->next->prev = pkg;
+}
+
+/*
+ * pkg_cache_delete
+ *
+ * deletes a package from the cache entry.
+ */
+void
+pkg_cache_delete(pkg_t *pkg)
+{
+	if (pkg->prev != NULL)
+		pkg->prev->next = pkg->next;
+
+	if (pkg->next != NULL)
+		pkg->next->prev = pkg->prev;
+
+	if (pkg == pkg_cache)
+	{
+		if (pkg->prev != NULL)
+			pkg_cache = pkg->prev;
+		else
+			pkg_cache = pkg->next;
+	}
+}

pkg.h

@@ -187,4 +187,9 @@ void pkg_queue_free(pkg_queue_t *head);
 bool pkg_queue_apply(pkg_queue_t *head, pkg_queue_apply_func_t func, int maxdepth, unsigned int flags, void *data);
 bool pkg_queue_validate(pkg_queue_t *head, int maxdepth, unsigned int flags);
 
+/* cache.c */
+pkg_t *pkg_cache_lookup(const char *id);
+void pkg_cache_add(pkg_t *pkg);
+void pkg_cache_remove(pkg_t *pkg);
+
 #endif