cache_mngt.c

00001 /*
00002  * lib/cache_mngt.c     Cache Management
00003  *
00004  *      This library is free software; you can redistribute it and/or
00005  *      modify it under the terms of the GNU Lesser General Public
00006  *      License as published by the Free Software Foundation version 2.1
00007  *      of the License.
00008  *
00009  * Copyright (c) 2003-2008 Thomas Graf <tgraf@suug.ch>
00010  */
00011 
00012 /**
00013  * @ingroup core
00014  * @defgroup cache_mngt Caching
00015  * @{
00016  */
00017 
00018 #include <netlink-local.h>
00019 #include <netlink/netlink.h>
00020 #include <netlink/cache.h>
00021 #include <netlink/utils.h>
00022 
00023 static struct nl_cache_ops *cache_ops;
00024 
00025 /**
00026  * @name Cache Operations Sets
00027  * @{
00028  */
00029 
00030 /**
00031  * Lookup the set cache operations of a certain cache type
00032  * @arg name            name of the cache type
00033  *
00034  * @return The cache operations or NULL if no operations
00035  *         have been registered under the specified name.
00036  */
00037 struct nl_cache_ops *nl_cache_ops_lookup(const char *name)
00038 {
00039         struct nl_cache_ops *ops;
00040 
00041         for (ops = cache_ops; ops; ops = ops->co_next)
00042                 if (!strcmp(ops->co_name, name))
00043                         return ops;
00044 
00045         return NULL;
00046 }
00047 
00048 /**
00049  * Associate a message type to a set of cache operations
00050  * @arg protocol                netlink protocol
00051  * @arg msgtype                 netlink message type
00052  *
00053  * Associates the specified netlink message type with
00054  * a registered set of cache operations.
00055  *
00056  * @return The cache operations or NULL if no association
00057  *         could be made.
00058  */
00059 struct nl_cache_ops *nl_cache_ops_associate(int protocol, int msgtype)
00060 {
00061         int i;
00062         struct nl_cache_ops *ops;
00063 
00064         for (ops = cache_ops; ops; ops = ops->co_next) {
00065                 if (ops->co_protocol != protocol)
00066                         continue;
00067 
00068                 for (i = 0; ops->co_msgtypes[i].mt_id >= 0; i++)
00069                         if (ops->co_msgtypes[i].mt_id == msgtype)
00070                                 return ops;
00071         }
00072 
00073         return NULL;
00074 }
00075 
00076 /**
00077  * Lookup message type cache association
00078  * @arg ops                     cache operations
00079  * @arg msgtype                 netlink message type
00080  *
00081  * Searches for a matching message type association ing the specified
00082  * cache operations.
00083  *
00084  * @return A message type association or NULL.
00085  */
00086 struct nl_msgtype *nl_msgtype_lookup(struct nl_cache_ops *ops, int msgtype)
00087 {
00088         int i;
00089 
00090         for (i = 0; ops->co_msgtypes[i].mt_id >= 0; i++)
00091                 if (ops->co_msgtypes[i].mt_id == msgtype)
00092                         return &ops->co_msgtypes[i];
00093 
00094         return NULL;
00095 }
00096 
00097 static struct nl_cache_ops *cache_ops_lookup_for_obj(struct nl_object_ops *obj_ops)
00098 {
00099         struct nl_cache_ops *ops;
00100 
00101         for (ops = cache_ops; ops; ops = ops->co_next)
00102                 if (ops->co_obj_ops == obj_ops)
00103                         return ops;
00104 
00105         return NULL;
00106 
00107 }
00108 
00109 /**
00110  * Call a function for each registered cache operation
00111  * @arg cb              Callback function to be called
00112  * @arg arg             User specific argument.
00113  */
00114 void nl_cache_ops_foreach(void (*cb)(struct nl_cache_ops *, void *), void *arg)
00115 {
00116         struct nl_cache_ops *ops;
00117 
00118         for (ops = cache_ops; ops; ops = ops->co_next)
00119                 cb(ops, arg);
00120 }
00121 
00122 /**
00123  * Register a set of cache operations
00124  * @arg ops             cache operations
00125  *
00126  * Called by users of caches to announce the avaibility of
00127  * a certain cache type.
00128  *
00129  * @return 0 on success or a negative error code.
00130  */
00131 int nl_cache_mngt_register(struct nl_cache_ops *ops)
00132 {
00133         if (!ops->co_name || !ops->co_obj_ops)
00134                 return -NLE_INVAL;
00135 
00136         if (nl_cache_ops_lookup(ops->co_name))
00137                 return -NLE_EXIST;
00138 
00139         ops->co_next = cache_ops;
00140         cache_ops = ops;
00141 
00142         NL_DBG(1, "Registered cache operations %s\n", ops->co_name);
00143 
00144         return 0;
00145 }
00146 
00147 /**
00148  * Unregister a set of cache operations
00149  * @arg ops             cache operations
00150  *
00151  * Called by users of caches to announce a set of
00152  * cache operations is no longer available. The
00153  * specified cache operations must have been registered
00154  * previously using nl_cache_mngt_register()
00155  *
00156  * @return 0 on success or a negative error code
00157  */
00158 int nl_cache_mngt_unregister(struct nl_cache_ops *ops)
00159 {
00160         struct nl_cache_ops *t, **tp;
00161 
00162         for (tp = &cache_ops; (t=*tp) != NULL; tp = &t->co_next)
00163                 if (t == ops)
00164                         break;
00165 
00166         if (!t)
00167                 return -NLE_NOCACHE;
00168 
00169         NL_DBG(1, "Unregistered cache operations %s\n", ops->co_name);
00170 
00171         *tp = t->co_next;
00172         return 0;
00173 }
00174 
00175 /** @} */
00176 
00177 /**
00178  * @name Global Cache Provisioning/Requiring
00179  * @{
00180  */
00181 
00182 /**
00183  * Provide a cache for global use
00184  * @arg cache           cache to provide
00185  *
00186  * Offers the specified cache to be used by other modules.
00187  * Only one cache per type may be shared at a time,
00188  * a previsouly provided caches will be overwritten.
00189  */
00190 void nl_cache_mngt_provide(struct nl_cache *cache)
00191 {
00192         struct nl_cache_ops *ops;
00193 
00194         ops = cache_ops_lookup_for_obj(cache->c_ops->co_obj_ops);
00195         if (!ops)
00196                 BUG();
00197         else
00198                 ops->co_major_cache = cache;
00199 }
00200 
00201 /**
00202  * Unprovide a cache for global use
00203  * @arg cache           cache to unprovide
00204  *
00205  * Cancels the offer to use a cache globally. The
00206  * cache will no longer be returned via lookups but
00207  * may still be in use.
00208  */
00209 void nl_cache_mngt_unprovide(struct nl_cache *cache)
00210 {
00211         struct nl_cache_ops *ops;
00212 
00213         ops = cache_ops_lookup_for_obj(cache->c_ops->co_obj_ops);
00214         if (!ops)
00215                 BUG();
00216         else if (ops->co_major_cache == cache)
00217                 ops->co_major_cache = NULL;
00218 }
00219 
00220 /**
00221  * Demand the use of a global cache
00222  * @arg name            name of the required object type
00223  *
00224  * Trys to find a cache of the specified type for global
00225  * use.
00226  *
00227  * @return A cache provided by another subsystem of the
00228  *         specified type marked to be available.
00229  */
00230 struct nl_cache *nl_cache_mngt_require(const char *name)
00231 {
00232         struct nl_cache_ops *ops;
00233 
00234         ops = nl_cache_ops_lookup(name);
00235         if (!ops || !ops->co_major_cache) {
00236                 fprintf(stderr, "Application BUG: Your application must "
00237                         "call nl_cache_mngt_provide() and\nprovide a valid "
00238                         "%s cache to be used for internal lookups.\nSee the "
00239                         " API documentation for more details.\n", name);
00240 
00241                 return NULL;
00242         }
00243         
00244         return ops->co_major_cache;
00245 }
00246 
00247 /** @} */
00248 
00249 /** @} */