astobj2: Avoid using temporary objects + ao2_find() with OBJ_POINTER.

There is a fairly common pattern making its way through the code base where we
put a temporary object on the stack so we can call ao2_find() with OBJ_POINTER.
The purpose is so that it can be passed into the object hash function.
However, this really seems like a hack and potentially error prone.  This patch
is a first stab at approach to avoid having to do that.

It adds a new flag, OBJ_KEY, which can be used instead of OBJ_POINTER in these
situations.  Then, the hash function can know whether it was given an object or
some custom data to hash.

The patch also changes some uses of ao2_find() for iax2_user and iax2_peer
objects to reflect how OBJ_KEY would be used.

So long, and thanks for all the fish.

Review: https://reviewboard.asterisk.org/r/1184/


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@330273 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/chan_iax2.c

@@ -1726,8 +1726,9 @@ static int iax2_data_add_codecs(struct ast_data *root, const char *node_name, ia
 static int peer_hash_cb(const void *obj, const int flags)
 {
 	const struct iax2_peer *peer = obj;
+	const char *name = obj;
 
-	return ast_str_hash(peer->name);
+	return ast_str_hash(flags & OBJ_KEY ? name : peer->name);
 }
 
 /*!
@@ -1736,8 +1737,10 @@ static int peer_hash_cb(const void *obj, const int flags)
 static int peer_cmp_cb(void *obj, void *arg, int flags)
 {
 	struct iax2_peer *peer = obj, *peer2 = arg;
+	const char *name = arg;
 
-	return !strcmp(peer->name, peer2->name) ? CMP_MATCH | CMP_STOP : 0;
+	return !strcmp(peer->name, flags & OBJ_KEY ? name : peer2->name) ?
+			CMP_MATCH | CMP_STOP : 0;
 }
 
 /*!
@@ -1746,8 +1749,9 @@ static int peer_cmp_cb(void *obj, void *arg, int flags)
 static int user_hash_cb(const void *obj, const int flags)
 {
 	const struct iax2_user *user = obj;
+	const char *name = obj;
 
-	return ast_str_hash(user->name);
+	return ast_str_hash(flags & OBJ_KEY ? name : user->name);
 }
 
 /*!
@@ -1756,8 +1760,10 @@ static int user_hash_cb(const void *obj, const int flags)
 static int user_cmp_cb(void *obj, void *arg, int flags)
 {
 	struct iax2_user *user = obj, *user2 = arg;
+	const char *name = arg;
 
-	return !strcmp(user->name, user2->name) ? CMP_MATCH | CMP_STOP : 0;
+	return !strcmp(user->name, flags & OBJ_KEY ? name : user2->name) ?
+			CMP_MATCH | CMP_STOP : 0;
 }
 
 /*!
@@ -1767,11 +1773,8 @@ static int user_cmp_cb(void *obj, void *arg, int flags)
 static struct iax2_peer *find_peer(const char *name, int realtime) 
 {
 	struct iax2_peer *peer = NULL;
-	struct iax2_peer tmp_peer = {
-		.name = name,
-	};
 
-	peer = ao2_find(peers, &tmp_peer, OBJ_POINTER);
+	peer = ao2_find(peers, name, OBJ_KEY);
 
 	/* Now go for realtime if applicable */
 	if(!peer && realtime)
@@ -1794,11 +1797,7 @@ static inline struct iax2_peer *peer_unref(struct iax2_peer *peer)
 
 static struct iax2_user *find_user(const char *name)
 {
-	struct iax2_user tmp_user = {
-		.name = name,
-	};
-
-	return ao2_find(users, &tmp_user, OBJ_POINTER);
+	return ao2_find(users, name, OBJ_KEY);
 }
 static inline struct iax2_user *user_ref(struct iax2_user *user)
 {
@@ -1854,11 +1853,8 @@ static void iax2_destroy_helper(struct chan_iax2_pvt *pvt)
 	/* Decrement AUTHREQ count if needed */
 	if (ast_test_flag64(pvt, IAX_MAXAUTHREQ)) {
 		struct iax2_user *user;
-		struct iax2_user tmp_user = {
-			.name = pvt->username,
-		};
 
-		user = ao2_find(users, &tmp_user, OBJ_POINTER);
+		user = ao2_find(users, pvt->username, OBJ_KEY);
 		if (user) {
 			ast_atomic_fetchadd_int(&user->curauthreq, -1);
 			user_unref(user);
@@ -6943,12 +6939,9 @@ static char *handle_cli_iax2_unregister(struct ast_cli_entry *e, int cmd, struct
 	p = find_peer(a->argv[2], 1);
 	if (p) {
 		if (p->expire > 0) {
-			struct iax2_peer tmp_peer = {
-				.name = a->argv[2],
-			};
 			struct iax2_peer *peer;
 
-			peer = ao2_find(peers, &tmp_peer, OBJ_POINTER);
+			peer = ao2_find(peers, a->argv[2], OBJ_KEY);
 			if (peer) {
 				expire_registry(peer_ref(peer)); /* will release its own reference when done */
 				peer_unref(peer); /* ref from ao2_find() */
@@ -7887,11 +7880,9 @@ static int authenticate_request(int call_num)
 
 	/* If an AUTHREQ restriction is in place, make sure we can send an AUTHREQ back */
 	if (ast_test_flag64(p, IAX_MAXAUTHREQ)) {
-		struct iax2_user *user, tmp_user = {
-			.name = p->username,	
-		};
+		struct iax2_user *user;
 
-		user = ao2_find(users, &tmp_user, OBJ_POINTER);
+		user = ao2_find(users, p->username, OBJ_KEY);
 		if (user) {
 			if (user->curauthreq == user->maxauthreq)
 				authreq_restrict = 1;
@@ -7937,14 +7928,12 @@ static int authenticate_verify(struct chan_iax2_pvt *p, struct iax_ies *ies)
 	char rsasecret[256] = "";
 	int res = -1; 
 	int x;
-	struct iax2_user *user, tmp_user = {
-		.name = p->username,	
-	};
+	struct iax2_user *user;
 
 	if (p->authrej) {
 		return res;
 	}
-	user = ao2_find(users, &tmp_user, OBJ_POINTER);
+	user = ao2_find(users, p->username, OBJ_KEY);
 	if (user) {
 		if (ast_test_flag64(p, IAX_MAXAUTHREQ)) {
 			ast_atomic_fetchadd_int(&user->curauthreq, -1);
@@ -12400,12 +12389,9 @@ static struct iax2_peer *build_peer(const char *name, struct ast_variable *v, st
 	int maskfound = 0;
 	int found = 0;
 	int firstpass = 1;
-	struct iax2_peer tmp_peer = {
-		.name = name,
-	};
 
 	if (!temponly) {
-		peer = ao2_find(peers, &tmp_peer, OBJ_POINTER);
+		peer = ao2_find(peers, name, OBJ_KEY);
 		if (peer && !ast_test_flag64(peer, IAX_DELME))
 			firstpass = 0;
 	}
@@ -12697,12 +12683,9 @@ static struct iax2_user *build_user(const char *name, struct ast_variable *v, st
 	int oldcurauthreq = 0;
 	char *varname = NULL, *varval = NULL;
 	struct ast_variable *tmpvar = NULL;
-	struct iax2_user tmp_user = {
-		.name = name,
-	};
 
 	if (!temponly) {
-		user = ao2_find(users, &tmp_user, OBJ_POINTER);
+		user = ao2_find(users, name, OBJ_KEY);
 		if (user && !ast_test_flag64(user, IAX_DELME))
 			firstpass = 0;
 	}

include/asterisk/astobj2.h

@@ -680,6 +680,16 @@ enum search_flags {
 	 * by another mechanism other that the internal ao2_lock.
 	 */
 	OBJ_NOLOCK     = (1 << 5),
+	/*!
+	 * \brief The data is hashable, but is not an object.
+	 *
+	 * This can be used when you want to be able to pass custom data
+	 * to a hash function that is not a full object, but perhaps just
+	 * a string.
+	 *
+	 * \note OBJ_KEY and OBJ_POINTER are mutually exclusive options.
+	 */
+	OBJ_KEY        = (1 << 6),
 };
 
 /*!
@@ -964,9 +974,9 @@ void *__ao2_callback_data(struct ao2_container *c, enum search_flags flags,
 
 #endif
 
-void *__ao2_find_debug(struct ao2_container *c, void *arg, enum search_flags flags, char *tag,
+void *__ao2_find_debug(struct ao2_container *c, const void *arg, enum search_flags flags, char *tag,
 		       char *file, int line, const char *funcname);
-void *__ao2_find(struct ao2_container *c, void *arg, enum search_flags flags);
+void *__ao2_find(struct ao2_container *c, const void *arg, enum search_flags flags);
 
 /*! \brief
  *

main/astobj2.c

@@ -648,8 +648,8 @@ static void *internal_ao2_callback(struct ao2_container *c,
 	 * run the hash function. Otherwise, scan the whole container
 	 * (this only for the time being. We need to optimize this.)
 	 */
-	if ((flags & OBJ_POINTER))	/* we know hash can handle this case */
-		start = i = c->hash_fn(arg, flags & OBJ_POINTER) % c->n_buckets;
+	if ((flags & (OBJ_POINTER | OBJ_KEY)))	/* we know hash can handle this case */
+		start = i = c->hash_fn(arg, flags & (OBJ_POINTER | OBJ_KEY)) % c->n_buckets;
 	else			/* don't know, let's scan all buckets */
 		start = i = -1;		/* XXX this must be fixed later. */
 
@@ -801,14 +801,14 @@ void *__ao2_callback_data(struct ao2_container *c, const enum search_flags flags
 /*!
  * the find function just invokes the default callback with some reasonable flags.
  */
-void *__ao2_find_debug(struct ao2_container *c, void *arg, enum search_flags flags, char *tag, char *file, int line, const char *funcname)
+void *__ao2_find_debug(struct ao2_container *c, const void *arg, enum search_flags flags, char *tag, char *file, int line, const char *funcname)
 {
-	return __ao2_callback_debug(c, flags, c->cmp_fn, arg, tag, file, line, funcname);
+	return __ao2_callback_debug(c, flags, c->cmp_fn, (void *) arg, tag, file, line, funcname);
 }
 
-void *__ao2_find(struct ao2_container *c, void *arg, enum search_flags flags)
+void *__ao2_find(struct ao2_container *c, const void *arg, enum search_flags flags)
 {
-	return __ao2_callback(c, flags, c->cmp_fn, arg);
+	return __ao2_callback(c, flags, c->cmp_fn, (void *) arg);
 }
 
 /*!

tests/test_astobj2.c

@@ -38,7 +38,6 @@ ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
 #include "asterisk/astobj2.h"
 
 struct test_obj {
-	char c[20];
 	int i;
 	int *destructor_count;
 };
@@ -75,20 +74,35 @@ static int multiple_cb(void *obj, void *arg, int flag)
 static int test_cmp_cb(void *obj, void *arg, int flags)
 {
 	struct test_obj *cmp_obj = (struct test_obj *) obj;
-	struct test_obj *test_obj = (struct test_obj *) arg;
+
 	if (!arg) {
 		return 0;
 	}
-	return (cmp_obj->i == test_obj->i) ? CMP_MATCH | CMP_STOP : 0;
+
+	if (flags & OBJ_KEY) {
+		int *i = (int *) arg;
+		return (cmp_obj->i == *i) ? CMP_MATCH | CMP_STOP : 0;
+	} else {
+		struct test_obj *test_obj = (struct test_obj *) arg;
+		return (cmp_obj->i == test_obj->i) ? CMP_MATCH | CMP_STOP : 0;
+	}
 }
 
 static int test_hash_cb(const void *obj, const int flags)
 {
-	struct test_obj *test_obj = (struct test_obj *) obj;
-	if (!test_obj || ast_strlen_zero(test_obj->c)) {
+	if (!obj) {
 		return 0;
 	}
-	return ast_str_hash(test_obj->c);
+
+	if (flags & OBJ_KEY) {
+		const int *i = obj;
+
+		return *i;
+	} else {
+		const struct test_obj *test_obj = obj;
+
+		return test_obj->i;
+	}
 }
 
 static int astobj2_test_helper(int use_hash, int use_cmp, unsigned int lim, struct ast_test *test)
@@ -128,7 +142,6 @@ static int astobj2_test_helper(int use_hash, int use_cmp, unsigned int lim, stru
 			res = AST_TEST_FAIL;
 			goto cleanup;
 		}
-		snprintf(obj->c, sizeof(obj->c), "zombie #%d", num);
 		obj->destructor_count = &destructor_count;
 		obj->i = num;
 		ao2_link(c1, obj);
@@ -163,7 +176,6 @@ static int astobj2_test_helper(int use_hash, int use_cmp, unsigned int lim, stru
 	num = 75;
 	for (; num; num--) {
 		int i = (ast_random() % ((lim / 2)) + 1); /* find a random object */
-		snprintf(tmp_obj.c, sizeof(tmp_obj.c), "zombie #%d", i);
 		tmp_obj.i = i;
 		if (!(obj = ao2_find(c1, &tmp_obj, OBJ_POINTER))) {
 			res = AST_TEST_FAIL;
@@ -178,6 +190,23 @@ static int astobj2_test_helper(int use_hash, int use_cmp, unsigned int lim, stru
 		}
 	}
 
+	/* Testing ao2_find with OBJ_KEY */
+	num = 75;
+	for (; num; num--) {
+		int i = (ast_random() % ((lim / 2)) + 1); /* find a random object */
+		if (!(obj = ao2_find(c1, &i, OBJ_KEY))) {
+			res = AST_TEST_FAIL;
+			ast_test_status_update(test, "COULD NOT FIND:%d, ao2_find() with OBJ_KEY flag failed.\n", i);
+		} else {
+			/* a correct match will only take place when the custom cmp function is used */
+			if (use_cmp && obj->i != i) {
+				ast_test_status_update(test, "object %d does not match object %d\n", obj->i, tmp_obj.i);
+				res = AST_TEST_FAIL;
+			}
+			ao2_t_ref(obj, -1, "test");
+		}
+	}
+
 	/* Testing ao2_find with OBJ_POINTER | OBJ_UNLINK | OBJ_CONTINUE.
 	 * In this test items are unlinked from c1 and placed in c2.  Then
 	 * unlinked from c2 and placed back into c1.
@@ -374,7 +403,7 @@ AST_TEST_DEFINE(astobj2_test_2)
 	int num;
 	static const int NUM_OBJS = 5;
 	int destructor_count = NUM_OBJS;
-	struct test_obj tmp_obj = { "", };
+	struct test_obj tmp_obj = { 0, };
 
 	switch (cmd) {
 	case TEST_INIT: