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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;
/* We alias the RPC specific structs to this voided one */
struct evrpc_req_generic {
/* 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;
/*
* 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 reqstruct* request; \
struct rplystruct* reply; \
struct evrpc* rpc; \
struct evhttp_request* http_req; \
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 *);
/** 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 = (struct evrpc_request_wrapper *) \
malloc(sizeof(struct evrpc_request_wrapper)); \
if (ctx == NULL) \
goto error; \
ctx->pool = pool; \
ctx->evcon = NULL; \
ctx->name = strdup(#rpcname); \
if (ctx->name == NULL) { \
free(ctx); \
goto error; \
} \
ctx->cb = (void (*)(struct evrpc_status *, \
void *, void *, void *))cb; \
ctx->cb_arg = cbarg; \
ctx->request = (void *)request; \
ctx->reply = (void *)reply; \
ctx->request_marshal = (void (*)(struct evbuffer *, void *))reqstruct##_marshal; \
ctx->reply_clear = (void (*)(void *))rplystruct##_clear; \
ctx->reply_unmarshal = (int (*)(void *, struct evbuffer *))rplystruct##_unmarshal; \
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 evrpc_pool;
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 {
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;
/* 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 {
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
/** adds a processing hook to either an rpc base or rpc pool
*
* If a hook returns -1, the processing is aborted.
*
* 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)(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);
#ifdef __cplusplus
}
#endif
#endif /* _EVRPC_H_ */
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