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kc3-lang/libevent/evrpc.h
Niels Provos
- evrpc.h
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/* * Copyright (c) 2006 Niels Provos <provos@citi.umich.edu> * All rights reserved. * * 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 _EVRPC_H_ #define _EVRPC_H_ #ifdef __cplusplus extern "C" { #endif /** @file evrpc.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 invokved. 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. */ struct evbuffer; struct event_base; struct evrpc_req_generic; /* Encapsulates a request */ struct evrpc { TAILQ_ENTRY(evrpc) next; /* the URI at which the request handler lives */ const char* uri; /* creates a new request structure */ void *(*request_new)(void); /* frees the request structure */ void (*request_free)(void *); /* unmarshals the buffer into the proper request structure */ int (*request_unmarshal)(void *, struct evbuffer *); /* creates a new reply structure */ void *(*reply_new)(void); /* creates a new reply structure */ void (*reply_free)(void *); /* verifies that the reply is valid */ int (*reply_complete)(void *); /* marshals the reply into a buffer */ void (*reply_marshal)(struct evbuffer*, void *); /* the callback invoked for each received rpc */ void (*cb)(struct evrpc_req_generic *, void *); void *cb_arg; /* reference for further configuration */ struct evrpc_base *base; }; /** 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; /* We alias the RPC specific structs to this voided one */ struct evrpc_req_generic { /* * allows association of meta data via hooks - needs to be * synchronized with evrpc_request_wrapper */ struct evrpc_hook_meta *hook_meta; /* the unmarshaled request object */ void *request; /* the empty reply object that needs to be filled in */ void *reply; /* * the static structure for this rpc; that can be used to * automatically unmarshal and marshal the http buffers. */ struct evrpc *rpc; /* * the http request structure on which we need to answer. */ struct evhttp_request* http_req; /* * Temporary data store for marshaled data */ struct evbuffer* rpc_data; /* * callback to reply and finish answering this rpc */ void (*done)(struct evrpc_req_generic* rpc); }; /** 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; \ void (*done)(struct evrpc_status *, \ struct evrpc* rpc, void *request, void *reply); \ }; \ 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 */ struct evrpc_request_wrapper *evrpc_send_request_generic( 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); /** 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) { \ struct evrpc_status status; \ struct evrpc_request_wrapper *ctx; \ ctx = evrpc_send_request_generic(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); \ if (ctx == NULL) \ goto error; \ return (evrpc_make_request(ctx)); \ error: \ memset(&status, 0, sizeof(status)); \ status.error = EVRPC_STATUS_ERR_UNSTARTED; \ (*(cb))(&status, request, reply, cbarg); \ return (-1); \ } /** 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 /** 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); \ _req->done(_req); \ } while (0) /* Takes a request object and fills it in with the right magic */ #define EVRPC_REGISTER_OBJECT(rpc, name, request, reply) \ do { \ (rpc)->uri = strdup(#name); \ if ((rpc)->uri == NULL) { \ fprintf(stderr, "failed to register object\n"); \ exit(1); \ } \ (rpc)->request_new = (void *(*)(void))request##_new; \ (rpc)->request_free = (void (*)(void *))request##_free; \ (rpc)->request_unmarshal = (int (*)(void *, struct evbuffer *))request##_unmarshal; \ (rpc)->reply_new = (void *(*)(void))reply##_new; \ (rpc)->reply_free = (void (*)(void *))reply##_free; \ (rpc)->reply_complete = (int (*)(void *))reply##_complete; \ (rpc)->reply_marshal = (void (*)(struct evbuffer*, void *))reply##_marshal; \ } 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 * @see evrpc_free() */ 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 */ 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) \ do { \ struct evrpc* rpc = (struct evrpc *)calloc(1, sizeof(struct evrpc)); \ EVRPC_REGISTER_OBJECT(rpc, name, request, reply); \ evrpc_register_rpc(base, rpc, \ (void (*)(struct evrpc_req_generic*, void *))callback, cbarg); \ } while (0) 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) int evrpc_unregister_rpc(struct evrpc_base *base, const char *name); /* * Client-side RPC support */ struct evhttp_connection; /** * provides information about the completed RPC request. */ struct evrpc_status { #define EVRPC_STATUS_ERR_NONE 0 #define EVRPC_STATUS_ERR_TIMEOUT 1 #define EVRPC_STATUS_ERR_BADPAYLOAD 2 #define EVRPC_STATUS_ERR_UNSTARTED 3 #define EVRPC_STATUS_ERR_HOOKABORTED 4 int error; /* for looking at headers or other information */ struct evhttp_request *http_req; }; struct evrpc_request_wrapper { /* * allows association of meta data via hooks - needs to be * synchronized with evrpc_req_generic. */ struct evrpc_hook_meta *hook_meta; TAILQ_ENTRY(evrpc_request_wrapper) next; /* pool on which this rpc request is being made */ struct evrpc_pool *pool; /* connection on which the request is being sent */ struct evhttp_connection *evcon; /* the actual request */ struct evhttp_request *req; /* event for implementing request timeouts */ struct event ev_timeout; /* the name of the rpc */ char *name; /* callback */ void (*cb)(struct evrpc_status*, void *request, void *reply, void *arg); void *cb_arg; void *request; void *reply; /* unmarshals the buffer into the proper request structure */ void (*request_marshal)(struct evbuffer *, void *); /* removes all stored state in the reply */ void (*reply_clear)(void *); /* marshals the reply into a buffer */ int (*reply_unmarshal)(void *, struct evbuffer*); }; /** 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) int evrpc_make_request(struct evrpc_request_wrapper *); /** 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 * @see evrpc_pool_free() */ 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() */ void evrpc_pool_free(struct evrpc_pool *pool); /* * adds a connection over which rpc can be dispatched. the connection * object must have been newly created. */ void evrpc_pool_add_connection(struct evrpc_pool *, struct evhttp_connection *); /** * 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. */ 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 { INPUT, /**< apply the function to an input hook */ OUTPUT /**< apply the function to an output hook */ }; /** * 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() */ 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() */ 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 */ 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 requet, 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 */ 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 tothe size of the data * @return 0 on success or -1 on failure */ 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 */ struct evhttp_connection *evrpc_hook_get_connection(void *ctx); #ifdef __cplusplus } #endif #endif /* _EVRPC_H_ */