lib: add const-ness to appropriate parameters in addr, attr, data

This patch changes the signatures of some functions to allow const pointers in
places where a const qualified pointer is enough access for what the function
does (e.g. nla_get_u8). It also changes some functions that take a pointer
parameter and return a pointer derived from it to use the strchr idiom.

This is not exhaustive in terms of places where const can be added, but it's
a decent chunk that should not make the external api any more restrictive.

http://lists.infradead.org/pipermail/libnl/2015-February/001826.html

Signed-off-by: Rohan Joyce <rojoyce.github@gmail.com>
Signed-off-by: Thomas Haller <thaller@redhat.com>

3 files changed, 47 insertions, 41 deletions

diff --git a/include/netlink/addr.h b/include/netlink/addr.h
index db3e4c2..9d0d24a 100644
--- a/include/netlink/addr.h
+++ b/include/netlink/addr.h
@@ -22,42 +22,45 @@ struct nl_addr;
 
 /* Creation */
 extern struct nl_addr *	nl_addr_alloc(size_t);
-extern struct nl_addr *	nl_addr_alloc_attr(struct nlattr *, int);
-extern struct nl_addr *	nl_addr_build(int, void *, size_t);
+extern struct nl_addr *	nl_addr_alloc_attr(const struct nlattr *, int);
+extern struct nl_addr *	nl_addr_build(int, const void *, size_t);
 extern int		nl_addr_parse(const char *, int, struct nl_addr **);
-extern struct nl_addr *	nl_addr_clone(struct nl_addr *);
+extern struct nl_addr *	nl_addr_clone(const struct nl_addr *);
 
 /* Usage Management */
 extern struct nl_addr *	nl_addr_get(struct nl_addr *);
 extern void		nl_addr_put(struct nl_addr *);
-extern int		nl_addr_shared(struct nl_addr *);
+extern int		nl_addr_shared(const struct nl_addr *);
 
-extern int		nl_addr_cmp(struct nl_addr *, struct nl_addr *);
-extern int		nl_addr_cmp_prefix(struct nl_addr *, struct nl_addr *);
-extern int		nl_addr_iszero(struct nl_addr *);
-extern int		nl_addr_valid(char *, int);
-extern int      	nl_addr_guess_family(struct nl_addr *);
-extern int		nl_addr_fill_sockaddr(struct nl_addr *,
+extern int		nl_addr_cmp(const struct nl_addr *,
+				    const struct nl_addr *);
+extern int		nl_addr_cmp_prefix(const struct nl_addr *,
+					   const struct nl_addr *);
+extern int		nl_addr_iszero(const struct nl_addr *);
+extern int		nl_addr_valid(const char *, int);
+extern int      	nl_addr_guess_family(const struct nl_addr *);
+extern int		nl_addr_fill_sockaddr(const struct nl_addr *,
 					      struct sockaddr *, socklen_t *);
-extern int		nl_addr_info(struct nl_addr *, struct addrinfo **);
-extern int		nl_addr_resolve(struct nl_addr *, char *, size_t);
+extern int		nl_addr_info(const struct nl_addr *,
+				     struct addrinfo **);
+extern int		nl_addr_resolve(const struct nl_addr *, char *, size_t);
 
 /* Access Functions */
 extern void		nl_addr_set_family(struct nl_addr *, int);
-extern int		nl_addr_get_family(struct nl_addr *);
-extern int		nl_addr_set_binary_addr(struct nl_addr *, void *,
+extern int		nl_addr_get_family(const struct nl_addr *);
+extern int		nl_addr_set_binary_addr(struct nl_addr *, const void *,
 						size_t);
-extern void *		nl_addr_get_binary_addr(struct nl_addr *);
-extern unsigned int	nl_addr_get_len(struct nl_addr *);
+extern void *		nl_addr_get_binary_addr(const struct nl_addr *);
+extern unsigned int	nl_addr_get_len(const struct nl_addr *);
 extern void		nl_addr_set_prefixlen(struct nl_addr *, int);
-extern unsigned int	nl_addr_get_prefixlen(struct nl_addr *);
+extern unsigned int	nl_addr_get_prefixlen(const struct nl_addr *);
 
 /* Address Family Translations */
 extern char *		nl_af2str(int, char *, size_t);
 extern int		nl_str2af(const char *);
 
 /* Translations to Strings */
-extern char *		nl_addr2str(struct nl_addr *, char *, size_t);
+extern char *		nl_addr2str(const struct nl_addr *, char *, size_t);
 
 #ifdef __cplusplus
 }
diff --git a/include/netlink/attr.h b/include/netlink/attr.h
index 82e4c38..b84b62e 100644
--- a/include/netlink/attr.h
+++ b/include/netlink/attr.h
@@ -81,12 +81,12 @@ extern int		nla_ok(const struct nlattr *, int);
 extern struct nlattr *	nla_next(const struct nlattr *, int *);
 extern int		nla_parse(struct nlattr **, int, struct nlattr *,
 				  int, struct nla_policy *);
-extern int		nla_validate(struct nlattr *, int, int,
-				     struct nla_policy *);
-extern struct nlattr *	nla_find(struct nlattr *, int, int);
+extern int		nla_validate(const struct nlattr *, int, int,
+				     const struct nla_policy *);
+extern struct nlattr *	nla_find(const struct nlattr *, int, int);
 
 /* Helper Functions */
-extern int		nla_memcpy(void *, struct nlattr *, int);
+extern int		nla_memcpy(void *, const struct nlattr *, int);
 extern size_t		nla_strlcpy(char *, const struct nlattr *, size_t);
 extern int		nla_memcmp(const struct nlattr *, const void *, size_t);
 extern int		nla_strcmp(const struct nlattr *, const char *);
@@ -94,40 +94,42 @@ extern int		nla_strcmp(const struct nlattr *, const char *);
 /* Unspecific attribute */
 extern struct nlattr *	nla_reserve(struct nl_msg *, int, int);
 extern int		nla_put(struct nl_msg *, int, int, const void *);
-extern int		nla_put_data(struct nl_msg *, int, struct nl_data *);
+extern int		nla_put_data(struct nl_msg *, int,
+				     const struct nl_data *);
 extern int		nla_put_addr(struct nl_msg *, int, struct nl_addr *);
 
 /* Integer attribute */
-extern uint8_t		nla_get_u8(struct nlattr *);
+extern uint8_t		nla_get_u8(const struct nlattr *);
 extern int		nla_put_u8(struct nl_msg *, int, uint8_t);
-extern uint16_t		nla_get_u16(struct nlattr *);
+extern uint16_t		nla_get_u16(const struct nlattr *);
 extern int		nla_put_u16(struct nl_msg *, int, uint16_t);
-extern uint32_t		nla_get_u32(struct nlattr *);
+extern uint32_t		nla_get_u32(const struct nlattr *);
 extern int		nla_put_u32(struct nl_msg *, int, uint32_t);
-extern uint64_t		nla_get_u64(struct nlattr *);
+extern uint64_t		nla_get_u64(const struct nlattr *);
 extern int		nla_put_u64(struct nl_msg *, int, uint64_t);
 
 /* String attribute */
-extern char *		nla_get_string(struct nlattr *);
-extern char *		nla_strdup(struct nlattr *);
+extern char *		nla_get_string(const struct nlattr *);
+extern char *		nla_strdup(const struct nlattr *);
 extern int		nla_put_string(struct nl_msg *, int, const char *);
 
 /* Flag attribute */
-extern int		nla_get_flag(struct nlattr *);
+extern int		nla_get_flag(const struct nlattr *);
 extern int		nla_put_flag(struct nl_msg *, int);
 
 /* Msec attribute */
-extern unsigned long	nla_get_msecs(struct nlattr *);
+extern unsigned long	nla_get_msecs(const struct nlattr *);
 extern int		nla_put_msecs(struct nl_msg *, int, unsigned long);
 
 /* Attribute nesting */
-extern int		nla_put_nested(struct nl_msg *, int, struct nl_msg *);
+extern int		nla_put_nested(struct nl_msg *, int,
+				       const struct nl_msg *);
 extern struct nlattr *	nla_nest_start(struct nl_msg *, int);
 extern int		nla_nest_end(struct nl_msg *, struct nlattr *);
-extern void		nla_nest_cancel(struct nl_msg *, struct nlattr *);
+extern void		nla_nest_cancel(struct nl_msg *, const struct nlattr *);
 extern int		nla_parse_nested(struct nlattr **, int, struct nlattr *,
 					 struct nla_policy *);
-extern int		nla_is_nested(struct nlattr *);
+extern int		nla_is_nested(const struct nlattr *);
 
 /**
  * @name Attribute Construction (Exception Based)
diff --git a/include/netlink/data.h b/include/netlink/data.h
index 071159e..b091c4b 100644
--- a/include/netlink/data.h
+++ b/include/netlink/data.h
@@ -21,18 +21,19 @@ extern "C" {
 struct nl_data;
 
 /* General */
-extern struct nl_data *	nl_data_alloc(void *, size_t);
-extern struct nl_data * nl_data_alloc_attr(struct nlattr *);
-extern struct nl_data *	nl_data_clone(struct nl_data *);
-extern int		nl_data_append(struct nl_data *, void *, size_t);
+extern struct nl_data *	nl_data_alloc(const void *, size_t);
+extern struct nl_data * nl_data_alloc_attr(const struct nlattr *);
+extern struct nl_data *	nl_data_clone(const struct nl_data *);
+extern int		nl_data_append(struct nl_data *, const void *, size_t);
 extern void		nl_data_free(struct nl_data *);
 
 /* Access Functions */
-extern void *		nl_data_get(struct nl_data *);
-extern size_t		nl_data_get_size(struct nl_data *);
+extern void *		nl_data_get(const struct nl_data *);
+extern size_t		nl_data_get_size(const struct nl_data *);
 
 /* Misc */
-extern int		nl_data_cmp(struct nl_data *, struct nl_data *);
+extern int		nl_data_cmp(const struct nl_data *,
+				    const struct nl_data *);
 
 #ifdef __cplusplus
 }