Add checks for derived socket type

1. Use a single instance of the vtable for each object. This saves some
memory at the expense of an extra pointer dereference per method
invocation.

2. Compare the class vtable pointer in sub-class methods to determine if
the object type is correct.

Signed-off-by: Michael Steinert <mike.steinert@gmail.com>

4 files changed, 58 insertions, 29 deletions

diff --git a/librabbitmq/amqp-openssl.c b/librabbitmq/amqp-openssl.c
index 16d81e0..4678a4a 100644
--- a/librabbitmq/amqp-openssl.c
+++ b/librabbitmq/amqp-openssl.c
@@ -55,7 +55,7 @@ static pthread_mutex_t *amqp_openssl_lockarray = NULL;
 #endif /* ENABLE_THREAD_SAFETY */
 
 struct amqp_ssl_socket_t {
-	amqp_socket_t base;
+	const struct amqp_socket_class_t *klass;
 	BIO *bio;
 	SSL_CTX *ctx;
 	char *buffer;
@@ -269,6 +269,16 @@ amqp_ssl_socket_get_sockfd(void *base)
 	return BIO_get_fd(self->bio, NULL);
 }
 
+static const struct amqp_socket_class_t amqp_ssl_socket_class = {
+	amqp_ssl_socket_writev, /* writev */
+	amqp_ssl_socket_send, /* send */
+	amqp_ssl_socket_recv, /* recv */
+	amqp_ssl_socket_open, /* open */
+	amqp_ssl_socket_close, /* close */
+	amqp_ssl_socket_error, /* error */
+	amqp_ssl_socket_get_sockfd /* get_sockfd */
+};
+
 amqp_socket_t *
 amqp_ssl_socket_new(void)
 {
@@ -285,13 +295,7 @@ amqp_ssl_socket_new(void)
 	if (!self->ctx) {
 		goto error;
 	}
-	self->base.writev = amqp_ssl_socket_writev;
-	self->base.send = amqp_ssl_socket_send;
-	self->base.recv = amqp_ssl_socket_recv;
-	self->base.open = amqp_ssl_socket_open;
-	self->base.close = amqp_ssl_socket_close;
-	self->base.error = amqp_ssl_socket_error;
-	self->base.get_sockfd = amqp_ssl_socket_get_sockfd;
+	self->klass = &amqp_ssl_socket_class;
 	self->verify = 1;
 	return (amqp_socket_t *)self;
 error:
@@ -303,8 +307,13 @@ int
 amqp_ssl_socket_set_cacert(amqp_socket_t *base,
 			   const char *cacert)
 {
-	struct amqp_ssl_socket_t *self = (struct amqp_ssl_socket_t *)base;
-	int status = SSL_CTX_load_verify_locations(self->ctx, cacert, NULL);
+	int status;
+	struct amqp_ssl_socket_t *self;
+	if (base->klass != &amqp_ssl_socket_class) {
+		amqp_abort("<%p> is not of type amqp_ssl_socket_t", base);
+	}
+	self = (struct amqp_ssl_socket_t *)base;
+	status = SSL_CTX_load_verify_locations(self->ctx, cacert, NULL);
 	if (1 != status) {
 		return -1;
 	}
@@ -316,7 +325,11 @@ amqp_ssl_socket_set_key(amqp_socket_t *base,
 			const char *key,
 			const char *cert)
 {
-	struct amqp_ssl_socket_t *self = (struct amqp_ssl_socket_t *)base;
+	struct amqp_ssl_socket_t *self;
+	if (base->klass != &amqp_ssl_socket_class) {
+		amqp_abort("<%p> is not of type amqp_ssl_socket_t", base);
+	}
+	self = (struct amqp_ssl_socket_t *)base;
 	if (key && cert) {
 		int status = SSL_CTX_use_PrivateKey_file(self->ctx, key,
 							 SSL_FILETYPE_PEM);
@@ -336,7 +349,11 @@ void
 amqp_ssl_socket_set_verify(amqp_socket_t *base,
 			   amqp_boolean_t verify)
 {
-	struct amqp_ssl_socket_t *self = (struct amqp_ssl_socket_t *)base;
+	struct amqp_ssl_socket_t *self;
+	if (base->klass != &amqp_ssl_socket_class) {
+		amqp_abort("<%p> is not of type amqp_ssl_socket_t", base);
+	}
+	self = (struct amqp_ssl_socket_t *)base;
 	self->verify = verify;
 }
 
diff --git a/librabbitmq/amqp-socket.h b/librabbitmq/amqp-socket.h
index 1c21da0..a40d13e 100644
--- a/librabbitmq/amqp-socket.h
+++ b/librabbitmq/amqp-socket.h
@@ -37,7 +37,7 @@ typedef int (*amqp_socket_close_fn)(void *);
 typedef int (*amqp_socket_error_fn)(void *);
 typedef int (*amqp_socket_get_sockfd_fn)(void *);
 
-struct amqp_socket_t_ {
+struct amqp_socket_class_t {
 	amqp_socket_writev_fn writev;
 	amqp_socket_send_fn send;
 	amqp_socket_recv_fn recv;
@@ -47,6 +47,10 @@ struct amqp_socket_t_ {
 	amqp_socket_get_sockfd_fn get_sockfd;
 };
 
+struct amqp_socket_t_ {
+	const struct amqp_socket_class_t *klass;
+};
+
 ssize_t
 amqp_socket_writev(amqp_socket_t *self, const struct iovec *iov, int iovcnt);
 
diff --git a/librabbitmq/amqp-tcp-socket.c b/librabbitmq/amqp-tcp-socket.c
index 10430a9..2307c5c 100644
--- a/librabbitmq/amqp-tcp-socket.c
+++ b/librabbitmq/amqp-tcp-socket.c
@@ -29,7 +29,7 @@
 #include <stdlib.h>
 
 struct amqp_tcp_socket_t {
-	amqp_socket_t base;
+	const struct amqp_socket_class_t *klass;
 	int sockfd;
 };
 
@@ -117,6 +117,16 @@ amqp_tcp_socket_get_sockfd(void *base)
 	return self->sockfd;
 }
 
+static const struct amqp_socket_class_t amqp_tcp_socket_class = {
+	amqp_tcp_socket_writev, /* writev */
+	amqp_tcp_socket_send, /* send */
+	amqp_tcp_socket_recv, /* recv */
+	amqp_tcp_socket_open, /* open */
+	amqp_tcp_socket_close, /* close */
+	amqp_tcp_socket_error, /* error */
+	amqp_tcp_socket_get_sockfd /* get_sockfd */
+};
+
 amqp_socket_t *
 amqp_tcp_socket_new(void)
 {
@@ -124,13 +134,7 @@ amqp_tcp_socket_new(void)
 	if (!self) {
 		return NULL;
 	}
-	self->base.writev = amqp_tcp_socket_writev;
-	self->base.send = amqp_tcp_socket_send;
-	self->base.recv = amqp_tcp_socket_recv;
-	self->base.open = amqp_tcp_socket_open;
-	self->base.close = amqp_tcp_socket_close;
-	self->base.error = amqp_tcp_socket_error;
-	self->base.get_sockfd = amqp_tcp_socket_get_sockfd;
+	self->klass = &amqp_tcp_socket_class;
 	self->sockfd = -1;
 	return (amqp_socket_t *)self;
 }
@@ -138,6 +142,10 @@ amqp_tcp_socket_new(void)
 void
 amqp_tcp_socket_set_sockfd(amqp_socket_t *base, int sockfd)
 {
-	struct amqp_tcp_socket_t *self = (struct amqp_tcp_socket_t *)base;
+	struct amqp_tcp_socket_t *self;
+	if (base->klass != &amqp_tcp_socket_class) {
+		amqp_abort("<%p> is not of type amqp_tcp_socket_t", base);
+	}
+	self = (struct amqp_tcp_socket_t *)base;
 	self->sockfd = sockfd;
 }
diff --git a/librabbitmq/amqp_socket.c b/librabbitmq/amqp_socket.c
index d7be798..4ce2093 100644
--- a/librabbitmq/amqp_socket.c
+++ b/librabbitmq/amqp_socket.c
@@ -52,32 +52,32 @@
 ssize_t
 amqp_socket_writev(amqp_socket_t *self, const struct iovec *iov, int iovcnt)
 {
-  return self->writev(self, iov, iovcnt);
+  return self->klass->writev(self, iov, iovcnt);
 }
 
 ssize_t
 amqp_socket_send(amqp_socket_t *self, const void *buf, size_t len, int flags)
 {
-  return self->send(self, buf, len, flags);
+  return self->klass->send(self, buf, len, flags);
 }
 
 ssize_t
 amqp_socket_recv(amqp_socket_t *self, void *buf, size_t len, int flags)
 {
-  return self->recv(self, buf, len, flags);
+  return self->klass->recv(self, buf, len, flags);
 }
 
 int
 amqp_socket_open(amqp_socket_t *self, const char *host, int port)
 {
-  return self->open(self, host, port);
+  return self->klass->open(self, host, port);
 }
 
 int
 amqp_socket_close(amqp_socket_t *self)
 {
   if (self) {
-    return self->close(self);
+    return self->klass->close(self);
   }
   return 0;
 }
@@ -85,13 +85,13 @@ amqp_socket_close(amqp_socket_t *self)
 int
 amqp_socket_error(amqp_socket_t *self)
 {
-  return self->error(self);
+  return self->klass->error(self);
 }
 
 int
 amqp_socket_get_sockfd(amqp_socket_t *self)
 {
-  return self->get_sockfd(self);
+  return self->klass->get_sockfd(self);
 }
 
 int amqp_open_socket(char const *hostname,