[PATCH 2/6] socketeutils: allow to pass a user data to the callback function of receive_responses()

[Masatake YAMATO]

Now I'm working on decoding the communication on Netlink GENERIC
protocol.  For the task, many lines of receive_responses can be reused
with two minor modifications. This is the second one.

* socketutils.c (receive_responses): change the data type
of parameter `proto_name' to `void *' from `const char *'
to allow callee passing arbitrary data to the call backward
function `parser'. In addition the parameter name is
changed to `user_data'. To follow common convention, the
parameter is passed to `parser' as its last argument.
(unix_get, inet_get, netlink_get): Cast statically given
the protocol name to `void *' to pass it to the call
back function.
(inet_parse_response,unix_parse_response,netlink_parse_response):
Introduce a local variable `proto_name' to convert the data type
of argument from `void *' to `const char*'.

Signed-off-by: Masatake YAMATO <yamato at redhat.com>
---
 socketutils.c | 33 +++++++++++++++++++--------------
 1 file changed, 19 insertions(+), 14 deletions(-)

diff --git a/socketutils.c b/socketutils.c
index 3292c2e..0016942 100644
--- a/socketutils.c
+++ b/socketutils.c
@@ -134,9 +134,10 @@ inet_send_query(const int fd, const int family, const int proto)
 }
 
 static int
-inet_parse_response(const char *const proto_name, const void *const data,
-		    const int data_len, const unsigned long inode)
+inet_parse_response(const void *const data,
+		    const int data_len, const unsigned long inode, void *user_data)
 {
+	const char *const proto_name = user_data;
 	const struct inet_diag_msg *const diag_msg = data;
 	static const char zero_addr[sizeof(struct in6_addr)];
 	socklen_t addr_size, text_size;
@@ -190,9 +191,9 @@ inet_parse_response(const char *const proto_name, const void *const data,
 static bool
 receive_responses(const int fd, const unsigned long inode,
 		  unsigned long expected_msg_type,
-		  const char *proto_name,
-		  int (* parser) (const char *, const void *,
-				  int, unsigned long))
+		  void *user_data,
+		  int (* parser) (const void *,
+				  int, unsigned long, void *))
 {
 	static union {
 		struct nlmsghdr hdr;
@@ -229,8 +230,8 @@ receive_responses(const int fd, const unsigned long inode,
 		for (; NLMSG_OK(h, ret); h = NLMSG_NEXT(h, ret)) {
 			if (h->nlmsg_type != expected_msg_type)
 				return false;
-			const int rc = parser(proto_name, NLMSG_DATA(h),
-					      h->nlmsg_len, inode);
+			const int rc = parser(NLMSG_DATA(h),
+					      h->nlmsg_len, inode, user_data);
 			if (rc > 0)
 				return true;
 			if (rc < 0)
@@ -263,9 +264,11 @@ unix_send_query(const int fd, const unsigned long inode)
 }
 
 static int
-unix_parse_response(const char *proto_name, const void *data,
-		    const int data_len, const unsigned long inode)
+unix_parse_response(const void *data,
+		    const int data_len, const unsigned long inode,
+		    void *user_data)
 {
+	const char *proto_name = user_data;
 	const struct unix_diag_msg *diag_msg = data;
 	struct rtattr *attr;
 	int rta_len = data_len - NLMSG_LENGTH(sizeof(*diag_msg));
@@ -361,9 +364,11 @@ netlink_send_query(const int fd, const unsigned long inode)
 }
 
 static int
-netlink_parse_response(const char *proto_name, const void *data,
-		    const int data_len, const unsigned long inode)
+netlink_parse_response(const void *data,
+		    const int data_len, const unsigned long inode,
+		    void *user_data)
 {
+	const char *proto_name = user_data;
 	const struct netlink_diag_msg *const diag_msg = data;
 	const char *netlink_proto;
 	char *details;
@@ -397,7 +402,7 @@ static const char *
 unix_get(const int fd, const unsigned long inode)
 {
 	return unix_send_query(fd, inode)
-		&& receive_responses(fd, inode, SOCK_DIAG_BY_FAMILY, "UNIX", unix_parse_response)
+		&& receive_responses(fd, inode, SOCK_DIAG_BY_FAMILY, (void *)"UNIX", unix_parse_response)
 		? get_sockaddr_by_inode_cached(inode) : NULL;
 }
 
@@ -406,7 +411,7 @@ inet_get(const int fd, const int family, const int protocol,
 	 const unsigned long inode, const char *proto_name)
 {
 	return inet_send_query(fd, family, protocol)
-		&& receive_responses(fd, inode, SOCK_DIAG_BY_FAMILY, proto_name, inet_parse_response)
+		&& receive_responses(fd, inode, SOCK_DIAG_BY_FAMILY, (void *)proto_name, inet_parse_response)
 		? get_sockaddr_by_inode_cached(inode) : NULL;
 }
 
@@ -438,7 +443,7 @@ static const char *
 netlink_get(const int fd, const unsigned long inode)
 {
 	return netlink_send_query(fd, inode)
-		&& receive_responses(fd, inode, SOCK_DIAG_BY_FAMILY, "NETLINK",
+		&& receive_responses(fd, inode, SOCK_DIAG_BY_FAMILY, (void *)"NETLINK",
 				     netlink_parse_response)
 		? get_sockaddr_by_inode_cached(inode) : NULL;
 }
-- 
2.9.4