/* Licensed to the Apache Software Foundation (ASF) under one or more

 * contributor license agreements.  See the NOTICE file distributed with

 * this work for additional information regarding copyright ownership.

 * The ASF licenses this file to You under the Apache License, Version 2.0

 * (the "License"); you may not use this file except in compliance with

 * the License.  You may obtain a copy of the License at

 *

 *     http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

/**

 * @file ap_socache.h

 * @brief Small object cache provider interface.

 *

 * @defgroup AP_SOCACHE ap_socache

 * @ingroup  APACHE_MODS

 * @{

 */

#ifndef AP_SOCACHE_H

#define AP_SOCACHE_H

#include "httpd.h"

#include "ap_provider.h"

#include "apr_pools.h"

#include "apr_time.h"

#ifdef __cplusplus

extern "C" {

#endif

/** If this flag is set, the store/retrieve/remove/status interfaces

 * of the provider are NOT safe to be called concurrently from

 * multiple processes or threads, and an external global mutex must be

 * used to serialize access to the provider.

 */

/* XXX: Even if store/retrieve/remove is atomic, isn't it useful to note

 * independently that status and iterate may or may not be?

 */

#define AP_SOCACHE_FLAG_NOTMPSAFE (0x0001)

/** A cache instance. */

typedef struct ap_socache_instance_t ap_socache_instance_t;

/** Hints which may be passed to the init function; providers may

 * ignore some or all of these hints. */

struct ap_socache_hints {

    /** Approximate average length of IDs: */

    apr_size_t avg_id_len;

    /** Approximate average size of objects: */

    apr_size_t avg_obj_size;

    /** Suggested interval between expiry cleanup runs; */

    apr_interval_time_t expiry_interval;

};

/**

 * Iterator callback prototype for the ap_socache_provider_t->iterate() method

 * @param instance The cache instance

 * @param s Associated server context (for logging)

 * @param userctx User defined pointer passed from the iterator call

 * @param id Unique ID for the object (binary blob)

 * with a trailing null char for convenience

 * @param idlen Length of id blob

 * @param data Output buffer to place retrieved data (binary blob)

 * with a trailing null char for convenience

 * @param datalen Length of data buffer

 * @param pool Pool for temporary allocations

 * @return APR status value; return APR_SUCCESS or the iteration will halt;

 * this value is returned to the ap_socache_provider_t->iterate() caller

 */

typedef apr_status_t (ap_socache_iterator_t)(ap_socache_instance_t *instance,

                                             server_rec *s,

                                             void *userctx,

                                             const unsigned char *id,

                                             unsigned int idlen,

                                             const unsigned char *data,

                                             unsigned int datalen,

                                             apr_pool_t *pool);

/** A socache provider structure.  socache providers are registered

 * with the ap_provider.h interface using the AP_SOCACHE_PROVIDER_*

 * constants. */

typedef struct ap_socache_provider_t {

    /** Canonical provider name. */

    const char *name;

    /** Bitmask of AP_SOCACHE_FLAG_* flags. */

    unsigned int flags;

    /**

     * Create a session cache based on the given configuration string.

     * The instance pointer returned in the instance parameter will be

     * passed as the first argument to subsequent invocations.

     *

     * @param instance Output parameter to which instance object is written.

     * @param arg User-specified configuration string.  May be NULL to

     *        force use of defaults.

     * @param tmp Pool to be used for any temporary allocations

     * @param p Pool to be use for any allocations lasting as long as

     * the created instance

     * @return NULL on success, or an error string on failure.

     */

    const char *(*create)(ap_socache_instance_t **instance, const char *arg,

                          apr_pool_t *tmp, apr_pool_t *p);

    /**

     * Initialize the cache.  The cname must be of maximum length 16

     * characters, and uniquely identifies the consumer of the cache

     * within the server; using the module name is recommended, e.g.

     * "mod_ssl-sess".  This string may be used within a filesystem

     * path so use of only alphanumeric [a-z0-9_-] characters is

     * recommended.  If hints is non-NULL, it gives a set of hints for

     * the provider.  Returns APR error code.

     *

     * @param instance The cache instance

     * @param cname A unique string identifying the consumer of this API

     * @param hints Optional hints argument describing expected cache use

     * @param s Server structure to which the cache is associated

     * @param pool Pool for long-lived allocations

     * @return APR status value indicating success.

     */

    apr_status_t (*init)(ap_socache_instance_t *instance, const char *cname,

                         const struct ap_socache_hints *hints,

                         server_rec *s, apr_pool_t *pool);

    /**

     * Destroy a given cache instance object.

     * @param instance The cache instance to destroy.

     * @param s Associated server structure (for logging purposes)

     */

    void (*destroy)(ap_socache_instance_t *instance, server_rec *s);

    /**

     * Store an object in a cache instance.

     * @param instance The cache instance

     * @param s Associated server structure (for logging purposes)

     * @param id Unique ID for the object; binary blob

     * @param idlen Length of id blob

     * @param expiry Absolute time at which the object expires

     * @param data Data to store; binary blob

     * @param datalen Length of data blob

     * @param pool Pool for temporary allocations.

     * @return APR status value.

     */

    apr_status_t (*store)(ap_socache_instance_t *instance, server_rec *s,

                          const unsigned char *id, unsigned int idlen,

                          apr_time_t expiry,

                          unsigned char *data, unsigned int datalen,

                          apr_pool_t *pool);

    /**

     * Retrieve a cached object.

     * 

     * @param instance The cache instance

     * @param s Associated server structure (for logging purposes)

     * @param id Unique ID for the object; binary blob

     * @param idlen Length of id blob

     * @param data Output buffer to place retrievd data (binary blob)

     * @param datalen On entry, length of data buffer; on exit, the

     * number of bytes written to the data buffer.

     * @param pool Pool for temporary allocations.

     * @return APR status value; APR_NOTFOUND if the object was not

     * found

     */

    apr_status_t (*retrieve)(ap_socache_instance_t *instance, server_rec *s,

                             const unsigned char *id, unsigned int idlen,

                             unsigned char *data, unsigned int *datalen,

                             apr_pool_t *pool);

    /**

     * Remove an object from the cache

     *

     * @param instance The cache instance

     * @param s Associated server structure (for logging purposes)

     * @param id Unique ID for the object; binary blob

     * @param idlen Length of id blob

     * @param pool Pool for temporary allocations.

     */

    apr_status_t (*remove)(ap_socache_instance_t *instance, server_rec *s,

                           const unsigned char *id, unsigned int idlen,

                           apr_pool_t *pool);

    /** 

     * Dump the status of a cache instance for mod_status.  Will use

     * the ap_r* interfaces to produce appropriate status output.

     * XXX: ap_r* are deprecated, bad dogfood

     *

     * @param instance The cache instance

     * @param r The request structure

     * @param flags The AP_STATUS_* constants used (see mod_status.h)

     */

    void (*status)(ap_socache_instance_t *instance, request_rec *r, int flags);

    /**

     * Dump all cached objects through an iterator callback.

     * @param instance The cache instance

     * @param s Associated server context (for processing and logging)

     * @param userctx User defined pointer passed through to the iterator

     * @param iterator The user provided callback function which will receive

     * individual calls for each unexpired id/data pair

     * @param pool Pool for temporary allocations.

     * @return APR status value; APR_NOTFOUND if the object was not

     * found

     */

    apr_status_t (*iterate)(ap_socache_instance_t *instance, server_rec *s,

                            void *userctx, ap_socache_iterator_t *iterator,

                            apr_pool_t *pool);

} ap_socache_provider_t;

/** The provider group used to register socache providers. */

#define AP_SOCACHE_PROVIDER_GROUP "socache"

/** The provider version used to register socache providers. */

#define AP_SOCACHE_PROVIDER_VERSION "0"

/** Default provider name. */

#define AP_SOCACHE_DEFAULT_PROVIDER "default"

#ifdef __cplusplus

}

#endif

#endif /* AP_SOCACHE_H */

/** @} */