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 /*
  * Copyright (c) 2006-2007 Niels Provos <provos@citi.umich.edu>
  * Copyright (c) 2007-2012 Niels Provos and Nick Mathewson
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  * 3. The name of the author may not be used to endorse or promote products
  *    derived from this software without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 #ifndef EVENT2_RPC_H_INCLUDED_
 #define EVENT2_RPC_H_INCLUDED_
 
 /* For int types. */
 #include <event2/util.h>
 #include <event2/visibility.h>
 
 #ifdef __cplusplus
 extern "C" {
 #endif
 
 /** @file rpc.h
  *
  * This header files provides basic support for an RPC server and client.
  *
  * To support RPCs in a server, every supported RPC command needs to be
  * defined and registered.
  *
  * EVRPC_HEADER(SendCommand, Request, Reply);
  *
  *  SendCommand is the name of the RPC command.
  *  Request is the name of a structure generated by event_rpcgen.py.
  *    It contains all parameters relating to the SendCommand RPC.  The
  *    server needs to fill in the Reply structure.
  *  Reply is the name of a structure generated by event_rpcgen.py.  It
  *    contains the answer to the RPC.
  *
  * To register an RPC with an HTTP server, you need to first create an RPC
  * base with:
  *
  *   struct evrpc_base *base = evrpc_init(http);
  *
  * A specific RPC can then be registered with
  *
  * EVRPC_REGISTER(base, SendCommand, Request, Reply,  FunctionCB, arg);
  *
  * when the server receives an appropriately formatted RPC, the user callback
  * is invoked.   The callback needs to fill in the reply structure.
  *
  * void FunctionCB(EVRPC_STRUCT(SendCommand)* rpc, void *arg);
  *
  * To send the reply, call EVRPC_REQUEST_DONE(rpc);
  *
  * See the regression test for an example.
  */
 
 /**
    Determines if the member has been set in the message
 
    @param msg the message to inspect
    @param member the member variable to test for presences
    @return 1 if it's present or 0 otherwise.
 */
 #define EVTAG_HAS(msg, member) \
     ((msg)->member##_set == 1)
 
 #ifndef EVENT2_RPC_COMPAT_H_INCLUDED_
 
 /**
    Assigns a value to the member in the message.
 
    @param msg the message to which to assign a value
    @param member the name of the member variable
    @param value the value to assign
 */
 #define EVTAG_ASSIGN(msg, member, value) \
     (*(msg)->base->member##_assign)((msg), (value))
 /**
    Assigns a value to the member in the message.
 
    @param msg the message to which to assign a value
    @param member the name of the member variable
    @param value the value to assign
    @param len the length of the value
 */
 #define EVTAG_ASSIGN_WITH_LEN(msg, member, value, len)  \
     (*(msg)->base->member##_assign)((msg), (value), (len))
 /**
    Returns the value for a member.
 
    @param msg the message from which to get the value
    @param member the name of the member variable
    @param pvalue a pointer to the variable to hold the value
    @return 0 on success, -1 otherwise.
 */
 #define EVTAG_GET(msg, member, pvalue) \
     (*(msg)->base->member##_get)((msg), (pvalue))
 /**
    Returns the value for a member.
 
    @param msg the message from which to get the value
    @param member the name of the member variable
    @param pvalue a pointer to the variable to hold the value
    @param plen a pointer to the length of the value
    @return 0 on success, -1 otherwise.
 */
 #define EVTAG_GET_WITH_LEN(msg, member, pvalue, plen)   \
     (*(msg)->base->member##_get)((msg), (pvalue), (plen))
 
 #endif  /* EVENT2_RPC_COMPAT_H_INCLUDED_ */
 
 /**
    Adds a value to an array.
 */
 #define EVTAG_ARRAY_ADD_VALUE(msg, member, value) \
     (*(msg)->base->member##_add)((msg), (value))
 /**
    Allocates a new entry in the array and returns it.
 */
 #define EVTAG_ARRAY_ADD(msg, member) \
     (*(msg)->base->member##_add)(msg)
 /**
    Gets a variable at the specified offset from the array.
 */
 #define EVTAG_ARRAY_GET(msg, member, offset, pvalue)    \
     (*(msg)->base->member##_get)((msg), (offset), (pvalue))
 /**
    Returns the number of entries in the array.
 */
 #define EVTAG_ARRAY_LEN(msg, member) ((msg)->member##_length)
 
 
 struct evbuffer;
 struct event_base;
 struct evrpc_req_generic;
 struct evrpc_request_wrapper;
 struct evrpc;
 
 /** The type of a specific RPC Message
  *
  * @param rpcname the name of the RPC message
  */
 #define EVRPC_STRUCT(rpcname) struct evrpc_req__##rpcname
 
 struct evhttp_request;
 struct evrpc_status;
 struct evrpc_hook_meta;
 
 /** Creates the definitions and prototypes for an RPC
  *
  * You need to use EVRPC_HEADER to create structures and function prototypes
  * needed by the server and client implementation.  The structures have to be
  * defined in an .rpc file and converted to source code via event_rpcgen.py
  *
  * @param rpcname the name of the RPC
  * @param reqstruct the name of the RPC request structure
  * @param replystruct the name of the RPC reply structure
  * @see EVRPC_GENERATE()
  */
 #define EVRPC_HEADER(rpcname, reqstruct, rplystruct) \
 EVRPC_STRUCT(rpcname) { \
     struct evrpc_hook_meta *hook_meta; \
     struct reqstruct* request; \
     struct rplystruct* reply; \
     struct evrpc* rpc; \
     struct evhttp_request* http_req; \
     struct evbuffer* rpc_data; \
 };                                   \
 EVENT2_EXPORT_SYMBOL \
 int evrpc_send_request_##rpcname(struct evrpc_pool *, \
     struct reqstruct *, struct rplystruct *, \
     void (*)(struct evrpc_status *, \
     struct reqstruct *, struct rplystruct *, void *cbarg),  \
     void *);
 
 struct evrpc_pool;
 
 /** use EVRPC_GENERATE instead */
 EVENT2_EXPORT_SYMBOL
 struct evrpc_request_wrapper *evrpc_make_request_ctx(
     struct evrpc_pool *pool, void *request, void *reply,
     const char *rpcname,
     void (*req_marshal)(struct evbuffer*, void *),
     void (*rpl_clear)(void *),
     int (*rpl_unmarshal)(void *, struct evbuffer *),
     void (*cb)(struct evrpc_status *, void *, void *, void *),
     void *cbarg);
 
 /** Creates a context structure that contains rpc specific information.
  *
  * EVRPC_MAKE_CTX is used to populate a RPC specific context that
  * contains information about marshaling the RPC data types.
  *
  * @param rpcname the name of the RPC
  * @param reqstruct the name of the RPC request structure
  * @param replystruct the name of the RPC reply structure
  * @param pool the evrpc_pool over which to make the request
  * @param request a pointer to the RPC request structure object
  * @param reply a pointer to the RPC reply structure object
  * @param cb the callback function to call when the RPC has completed
  * @param cbarg the argument to supply to the callback
  */
 #define EVRPC_MAKE_CTX(rpcname, reqstruct, rplystruct, \
     pool, request, reply, cb, cbarg)                    \
     evrpc_make_request_ctx(pool, request, reply,            \
         #rpcname,                           \
         (void (*)(struct evbuffer *, void *))reqstruct##_marshal,   \
         (void (*)(void *))rplystruct##_clear,           \
         (int (*)(void *, struct evbuffer *))rplystruct##_unmarshal, \
         (void (*)(struct evrpc_status *, void *, void *, void *))cb, \
         cbarg)
 
 /** Generates the code for receiving and sending an RPC message
  *
  * EVRPC_GENERATE is used to create the code corresponding to sending
  * and receiving a particular RPC message
  *
  * @param rpcname the name of the RPC
  * @param reqstruct the name of the RPC request structure
  * @param replystruct the name of the RPC reply structure
  * @see EVRPC_HEADER()
  */
 #define EVRPC_GENERATE(rpcname, reqstruct, rplystruct)          \
     int evrpc_send_request_##rpcname(struct evrpc_pool *pool,   \
         struct reqstruct *request, struct rplystruct *reply,    \
         void (*cb)(struct evrpc_status *,               \
         struct reqstruct *, struct rplystruct *, void *cbarg),  \
         void *cbarg) {                      \
     return evrpc_send_request_generic(pool, request, reply, \
         (void (*)(struct evrpc_status *, void *, void *, void *))cb, \
         cbarg,                          \
         #rpcname,                           \
         (void (*)(struct evbuffer *, void *))reqstruct##_marshal,   \
         (void (*)(void *))rplystruct##_clear,           \
         (int (*)(void *, struct evbuffer *))rplystruct##_unmarshal); \
 }
 
 /** Provides access to the HTTP request object underlying an RPC
  *
  * Access to the underlying http object; can be used to look at headers or
  * for getting the remote ip address
  *
  * @param rpc_req the rpc request structure provided to the server callback
  * @return an struct evhttp_request object that can be inspected for
  * HTTP headers or sender information.
  */
 #define EVRPC_REQUEST_HTTP(rpc_req) (rpc_req)->http_req
 
 /** completes the server response to an rpc request */
 EVENT2_EXPORT_SYMBOL
 void evrpc_request_done(struct evrpc_req_generic *req);
 
 /** accessors for request and reply */
 EVENT2_EXPORT_SYMBOL
 void *evrpc_get_request(struct evrpc_req_generic *req);
 EVENT2_EXPORT_SYMBOL
 void *evrpc_get_reply(struct evrpc_req_generic *req);
 
 /** Creates the reply to an RPC request
  *
  * EVRPC_REQUEST_DONE is used to answer a request; the reply is expected
  * to have been filled in.  The request and reply pointers become invalid
  * after this call has finished.
  *
  * @param rpc_req the rpc request structure provided to the server callback
  */
 #define EVRPC_REQUEST_DONE(rpc_req) do { \
   struct evrpc_req_generic *req_ = (struct evrpc_req_generic *)(rpc_req); \
   evrpc_request_done(req_);                 \
 } while (0)
 
 
 struct evrpc_base;
 struct evhttp;
 
 /* functions to start up the rpc system */
 
 /** Creates a new rpc base from which RPC requests can be received
  *
  * @param server a pointer to an existing HTTP server
  * @return a newly allocated evrpc_base struct or NULL if an error occurred
  * @see evrpc_free()
  */
 EVENT2_EXPORT_SYMBOL
 struct evrpc_base *evrpc_init(struct evhttp *server);
 
 /**
  * Frees the evrpc base
  *
  * For now, you are responsible for making sure that no rpcs are ongoing.
  *
  * @param base the evrpc_base object to be freed
  * @see evrpc_init
  */
 EVENT2_EXPORT_SYMBOL
 void evrpc_free(struct evrpc_base *base);
 
 /** register RPCs with the HTTP Server
  *
  * registers a new RPC with the HTTP server, each RPC needs to have
  * a unique name under which it can be identified.
  *
  * @param base the evrpc_base structure in which the RPC should be
  *   registered.
  * @param name the name of the RPC
  * @param request the name of the RPC request structure
  * @param reply the name of the RPC reply structure
  * @param callback the callback that should be invoked when the RPC
  * is received.  The callback has the following prototype
  *   void (*callback)(EVRPC_STRUCT(Message)* rpc, void *arg)
  * @param cbarg an additional parameter that can be passed to the callback.
  *   The parameter can be used to carry around state.
  */
 #define EVRPC_REGISTER(base, name, request, reply, callback, cbarg) \
     evrpc_register_generic(base, #name,             \
         (void (*)(struct evrpc_req_generic *, void *))callback, cbarg, \
         (void *(*)(void *))request##_new_with_arg, NULL,        \
         (void (*)(void *))request##_free,               \
         (int (*)(void *, struct evbuffer *))request##_unmarshal,    \
         (void *(*)(void *))reply##_new_with_arg, NULL,      \
         (void (*)(void *))reply##_free, \
         (int (*)(void *))reply##_complete, \
         (void (*)(struct evbuffer *, void *))reply##_marshal)
 
 /**
    Low level function for registering an RPC with a server.
 
    Use EVRPC_REGISTER() instead.
 
    @see EVRPC_REGISTER()
 */
 EVENT2_EXPORT_SYMBOL
 int evrpc_register_rpc(struct evrpc_base *, struct evrpc *,
     void (*)(struct evrpc_req_generic*, void *), void *);
 
 /**
  * Unregisters an already registered RPC
  *
  * @param base the evrpc_base object from which to unregister an RPC
  * @param name the name of the rpc to unregister
  * @return -1 on error or 0 when successful.
  * @see EVRPC_REGISTER()
  */
 #define EVRPC_UNREGISTER(base, name) evrpc_unregister_rpc((base), #name)
 
 EVENT2_EXPORT_SYMBOL
 int evrpc_unregister_rpc(struct evrpc_base *base, const char *name);
 
 /*
  * Client-side RPC support
  */
 
 struct evhttp_connection;
 struct evrpc_status;
 
 /** launches an RPC and sends it to the server
  *
  * EVRPC_MAKE_REQUEST() is used by the client to send an RPC to the server.
  *
  * @param name the name of the RPC
  * @param pool the evrpc_pool that contains the connection objects over which
  *   the request should be sent.
  * @param request a pointer to the RPC request structure - it contains the
  *   data to be sent to the server.
  * @param reply a pointer to the RPC reply structure.  It is going to be filled
  *   if the request was answered successfully
  * @param cb the callback to invoke when the RPC request has been answered
  * @param cbarg an additional argument to be passed to the client
  * @return 0 on success, -1 on failure
  */
 #define EVRPC_MAKE_REQUEST(name, pool, request, reply, cb, cbarg)   \
     evrpc_send_request_##name((pool), (request), (reply), (cb), (cbarg))
 
 /**
    Makes an RPC request based on the provided context.
 
    This is a low-level function and should not be used directly
    unless a custom context object is provided.  Use EVRPC_MAKE_REQUEST()
    instead.
 
    @param ctx a context from EVRPC_MAKE_CTX()
    @returns 0 on success, -1 otherwise.
    @see EVRPC_MAKE_REQUEST(), EVRPC_MAKE_CTX()
 */
 EVENT2_EXPORT_SYMBOL
 int evrpc_make_request(struct evrpc_request_wrapper *ctx);
 
 /** creates an rpc connection pool
  *
  * a pool has a number of connections associated with it.
  * rpc requests are always made via a pool.
  *
  * @param base a pointer to an struct event_based object; can be left NULL
  *   in singled-threaded applications
  * @return a newly allocated struct evrpc_pool object or NULL if an error
  *   occurred
  * @see evrpc_pool_free()
  */
 EVENT2_EXPORT_SYMBOL
 struct evrpc_pool *evrpc_pool_new(struct event_base *base);
 /** frees an rpc connection pool
  *
  * @param pool a pointer to an evrpc_pool allocated via evrpc_pool_new()
  * @see evrpc_pool_new()
  */
 EVENT2_EXPORT_SYMBOL
 void evrpc_pool_free(struct evrpc_pool *pool);
 
 /**
  * Adds a connection over which rpc can be dispatched to the pool.
  *
  * The connection object must have been newly created.
  *
  * @param pool the pool to which to add the connection
  * @param evcon the connection to add to the pool.
  */
 EVENT2_EXPORT_SYMBOL
 void evrpc_pool_add_connection(struct evrpc_pool *pool,
     struct evhttp_connection *evcon);
 
 /**
  * Removes a connection from the pool.
  *
  * The connection object must have been newly created.
  *
  * @param pool the pool from which to remove the connection
  * @param evcon the connection to remove from the pool.
  */
 EVENT2_EXPORT_SYMBOL
 void evrpc_pool_remove_connection(struct evrpc_pool *pool,
     struct evhttp_connection *evcon);
 
 /**
  * Sets the timeout in secs after which a request has to complete.  The
  * RPC is completely aborted if it does not complete by then.  Setting
  * the timeout to 0 means that it never timeouts and can be used to
  * implement callback type RPCs.
  *
  * Any connection already in the pool will be updated with the new
  * timeout.  Connections added to the pool after set_timeout has be
  * called receive the pool timeout only if no timeout has been set
  * for the connection itself.
  *
  * @param pool a pointer to a struct evrpc_pool object
  * @param timeout_in_secs the number of seconds after which a request should
  *   timeout and a failure be returned to the callback.
  */
 EVENT2_EXPORT_SYMBOL
 void evrpc_pool_set_timeout(struct evrpc_pool *pool, int timeout_in_secs);
 
 /**
  * Hooks for changing the input and output of RPCs; this can be used to
  * implement compression, authentication, encryption, ...
  */
 
 enum EVRPC_HOOK_TYPE {
     EVRPC_INPUT,        /**< apply the function to an input hook */
     EVRPC_OUTPUT        /**< apply the function to an output hook */
 };
 
 #ifndef _WIN32
 /** Deprecated alias for EVRPC_INPUT.  Not available on windows, where it
  * conflicts with platform headers. */
 #define INPUT EVRPC_INPUT
 /** Deprecated alias for EVRPC_OUTPUT.  Not available on windows, where it
  * conflicts with platform headers. */
 #define OUTPUT EVRPC_OUTPUT
 #endif
 
 /**
  * Return value from hook processing functions
  */
 
 enum EVRPC_HOOK_RESULT {
     EVRPC_TERMINATE = -1,   /**< indicates the rpc should be terminated */
     EVRPC_CONTINUE = 0, /**< continue processing the rpc */
     EVRPC_PAUSE = 1     /**< pause processing request until resumed */
 };
 
 /** adds a processing hook to either an rpc base or rpc pool
  *
  * If a hook returns TERMINATE, the processing is aborted. On CONTINUE,
  * the request is immediately processed after the hook returns.  If the
  * hook returns PAUSE, request processing stops until evrpc_resume_request()
  * has been called.
  *
  * The add functions return handles that can be used for removing hooks.
  *
  * @param vbase a pointer to either struct evrpc_base or struct evrpc_pool
  * @param hook_type either INPUT or OUTPUT
  * @param cb the callback to call when the hook is activated
  * @param cb_arg an additional argument for the callback
  * @return a handle to the hook so it can be removed later
  * @see evrpc_remove_hook()
  */
 EVENT2_EXPORT_SYMBOL
 void *evrpc_add_hook(void *vbase,
     enum EVRPC_HOOK_TYPE hook_type,
     int (*cb)(void *, struct evhttp_request *, struct evbuffer *, void *),
     void *cb_arg);
 
 /** removes a previously added hook
  *
  * @param vbase a pointer to either struct evrpc_base or struct evrpc_pool
  * @param hook_type either INPUT or OUTPUT
  * @param handle a handle returned by evrpc_add_hook()
  * @return 1 on success or 0 on failure
  * @see evrpc_add_hook()
  */
 EVENT2_EXPORT_SYMBOL
 int evrpc_remove_hook(void *vbase,
     enum EVRPC_HOOK_TYPE hook_type,
     void *handle);
 
 /** resume a paused request
  *
  * @param vbase a pointer to either struct evrpc_base or struct evrpc_pool
  * @param ctx the context pointer provided to the original hook call
  */
 EVENT2_EXPORT_SYMBOL
 int evrpc_resume_request(void *vbase, void *ctx, enum EVRPC_HOOK_RESULT res);
 
 /** adds meta data to request
  *
  * evrpc_hook_add_meta() allows hooks to add meta data to a request. for
  * a client request, the meta data can be inserted by an outgoing request hook
  * and retrieved by the incoming request hook.
  *
  * @param ctx the context provided to the hook call
  * @param key a NUL-terminated c-string
  * @param data the data to be associated with the key
  * @param data_size the size of the data
  */
 EVENT2_EXPORT_SYMBOL
 void evrpc_hook_add_meta(void *ctx, const char *key,
     const void *data, size_t data_size);
 
 /** retrieves meta data previously associated
  *
  * evrpc_hook_find_meta() can be used to retrieve meta data associated to a
  * request by a previous hook.
  * @param ctx the context provided to the hook call
  * @param key a NUL-terminated c-string
  * @param data pointer to a data pointer that will contain the retrieved data
  * @param data_size pointer to the size of the data
  * @return 0 on success or -1 on failure
  */
 EVENT2_EXPORT_SYMBOL
 int evrpc_hook_find_meta(void *ctx, const char *key,
     void **data, size_t *data_size);
 
 /**
  * returns the connection object associated with the request
  *
  * @param ctx the context provided to the hook call
  * @return a pointer to the evhttp_connection object or NULL if an error
  *   occurred
  */
 EVENT2_EXPORT_SYMBOL
 struct evhttp_connection *evrpc_hook_get_connection(void *ctx);
 
 /**
    Function for sending a generic RPC request.
 
    Do not call this function directly, use EVRPC_MAKE_REQUEST() instead.
 
    @see EVRPC_MAKE_REQUEST()
  */
 EVENT2_EXPORT_SYMBOL
 int evrpc_send_request_generic(struct evrpc_pool *pool,
     void *request, void *reply,
     void (*cb)(struct evrpc_status *, void *, void *, void *),
     void *cb_arg,
     const char *rpcname,
     void (*req_marshal)(struct evbuffer *, void *),
     void (*rpl_clear)(void *),
     int (*rpl_unmarshal)(void *, struct evbuffer *));
 
 /**
    Function for registering a generic RPC with the RPC base.
 
    Do not call this function directly, use EVRPC_REGISTER() instead.
 
    @see EVRPC_REGISTER()
  */
 EVENT2_EXPORT_SYMBOL
 int evrpc_register_generic(struct evrpc_base *base, const char *name,
     void (*callback)(struct evrpc_req_generic *, void *), void *cbarg,
     void *(*req_new)(void *), void *req_new_arg, void (*req_free)(void *),
     int (*req_unmarshal)(void *, struct evbuffer *),
     void *(*rpl_new)(void *), void *rpl_new_arg, void (*rpl_free)(void *),
     int (*rpl_complete)(void *),
     void (*rpl_marshal)(struct evbuffer *, void *));
 
 /** accessors for obscure and undocumented functionality */
 EVENT2_EXPORT_SYMBOL
 struct evrpc_pool* evrpc_request_get_pool(struct evrpc_request_wrapper *ctx);
 EVENT2_EXPORT_SYMBOL
 void evrpc_request_set_pool(struct evrpc_request_wrapper *ctx,
     struct evrpc_pool *pool);
 EVENT2_EXPORT_SYMBOL
 void evrpc_request_set_cb(struct evrpc_request_wrapper *ctx,
     void (*cb)(struct evrpc_status*, void *request, void *reply, void *arg),
     void *cb_arg);
 
 #ifdef __cplusplus
 }
 #endif
 
 #endif /* EVENT2_RPC_H_INCLUDED_ */

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