qpkg: towards "struct id" without jrb reference - change iteration and lookup

- id.h, id.c (first_id, next_id): removed
- qpkg.c (list_all_packages): use jrb_first/jrb_next instead of
  first_id/next_id
- id.h, id.c (find_id): return the RB tree node instead of the ID
- qpkg.c (list_one_package, find_prereq): adapted for above change
- id.h: explain the role of key and value

qpkg/id.c

@@ -67,32 +67,12 @@ struct id *make_id(struct tree *tree, const char *s, size_t len)
 }
 
 
-const struct id *find_id(const struct tree *tree, const char *s, size_t len)
+const struct jrb *find_id(const struct tree *tree, const char *s, size_t len)
 {
 	struct id id = {
 		.s = s,
 		.len = len
 	};
-	struct jrb *node;
 
-	node = jrb_find(tree->root, &id, tree->comp);
-	return node ? node->key : NULL;
-}
-
-
-const struct id *first_id(const struct tree *tree)
-{
-	struct jrb *node;
-
-	node = jrb_first(tree->root);
-	return node ? node->key : NULL;
-}
-
-
-const struct id *next_id(const struct id *id)
-{
-	struct jrb *next;
-
-	next = jrb_next(id->jrb);
-	return next ? next->key : NULL;
+	return jrb_find(tree->root, &id, tree->comp);
 }

qpkg/id.h

@@ -18,6 +18,33 @@
 #include "jrb.h"
 
 
+/*
+ * The role of key and value in jrb nodes:
+ *
+ * - the key points to a "struct id". This "struct id" is unique for the
+ *   identifier in question and its location can be used to check for equality
+ *   with a simple pointer comparison.
+ *
+ *   A caller to find_id may therefore be interested in a pointer to the key,
+ *   even if the content of the key is known.
+ *
+ * - for the value, we have to distinguish between packages and versions:
+ *
+ *   - package: pointer to the first package definition. If there are multiple
+ *     packages with the same name, the rest is linked via pkg->more.
+ *
+ *     The value can be NULL if a reference to the package has been
+ *     encountered, but
+ *
+ *     - the package definition has not been parsed yet,
+ *     - no corresponding package definition exist (which would be an error),
+ *     - the reference is an item listed in Provides: (this will change once
+ *       we handle Provides: properly)
+ *
+ *   - version: the value is not used
+ */
+
+
 struct id;
 
 struct tree {
@@ -36,8 +63,6 @@ int comp_id(const void *a, const void *b);
 
 struct tree *make_tree(int (*comp)(const void *a, const void *b));
 struct id *make_id(struct tree *tree, const char *s, size_t len);
-const struct id *find_id(const struct tree *tree, const char *s, size_t len);
-const struct id *first_id(const struct tree *tree);
-const struct id *next_id(const struct id *id);
+const struct jrb *find_id(const struct tree *tree, const char *s, size_t len);
 
 #endif /* !ID_H */

qpkg/qpkg.c

@@ -15,6 +15,7 @@
 #include <stdio.h>
 #include <string.h>
 
+#include "jrb.h"
 #include "id.h"
 #include "prereq.h"
 #include "gobble.h"
@@ -27,10 +28,11 @@ struct tree *versions = NULL;
 
 static void list_all_packages(void)
 {
-	const struct id *id;
+	const struct jrb *n;
 
-	for (id = first_id(packages); id; id = next_id(id)) {
-		struct pkg *pkg = id->jrb->val;
+	for (n = jrb_first(packages->root); n; n = jrb_next(n)) {
+		const struct id *id = n->key;
+		struct pkg *pkg = n->val;
 
 		printf("%.*s", (int) id->len, id->s);
 		if (!pkg)
@@ -49,40 +51,40 @@ static void list_all_packages(void)
 
 static void list_one_package(const char *name)
 {
-	const struct id *id = find_id(packages, name, strlen(name));
+	const struct jrb *n = find_id(packages, name, strlen(name));
 	const struct pkg *pkg;
 
-	if (!id) {
+	if (!n) {
 		fprintf(stderr, "no such package \"%s\"\n", name);
 		exit(1);
 	}
-	for (pkg = id->jrb->val; pkg; pkg = pkg->more)
+	for (pkg = n->val; pkg; pkg = pkg->more)
 		printf("%.*s\n", (int) pkg->version->len, pkg->version->s);
 }
 
 
 static void find_prereq(const char *name, const char *version)
 {
-	const struct id *id = find_id(packages, name, strlen(name));
+	const struct jrb *n = find_id(packages, name, strlen(name));
 	struct pkg *pkg;
 	struct pkg **pkgs;
 
-	if (!id) {
+	if (!n) {
 		fprintf(stderr, "no such package \"%s\"\n", name);
 		exit(1);
 	}
-	pkg = id->jrb->val;
+	pkg = n->val;
 	if (!pkg) {
 		fprintf(stderr, "package %s is a ghost\n", name);
 		exit(1);
 	}
 	if (version) {
-		id = find_id(versions, version, strlen(version));
-		if (!id) {
+		n = find_id(versions, version, strlen(version));
+		if (!n) {
 			fprintf(stderr, "no such version\"%s\"\n", version);
 			exit(1);
 		}
-		while (pkg && pkg->version != id)
+		while (pkg && pkg->version != n->key)
 			pkg = pkg->more;
 		if (pkg) {
 			fprintf(stderr, "no %s version\"%s\" found\n",