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apr_hooks.h
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/* 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. */ #ifndef APR_HOOKS_H #define APR_HOOKS_H #include "apu.h" /* For apr_array_header_t */ #include "apr_tables.h" /** * @file apr_hooks.h * @brief Apache hook functions */ #ifdef __cplusplus extern "C" { #endif /** * @defgroup APR_Util_Hook Hook Functions * @ingroup APR_Util * @{ */ /** * @defgroup apr_hook_probes Hook probe capability * APR hooks provide a trace probe capability for capturing * the flow of control and return values with hooks. * * In order to use this facility, the application must define * the symbol APR_HOOK_PROBES_ENABLED and the four APR_HOOK_PROBE_ * macros described below before including apr_hooks.h in files * that use the APR_IMPLEMENT_EXTERNAL_HOOK_* macros. * * This probe facility is not provided for APR optional hooks. * @{ */ #ifdef APR_HOOK_PROBES_ENABLED #define APR_HOOK_INT_DCL_UD void *ud = NULL #else /** internal implementation detail to avoid the ud declaration when * hook probes are not used */ #define APR_HOOK_INT_DCL_UD /** * User-defined hook probe macro that is invoked when the hook * is run, before calling any hook functions. * @param ud A void * user data field that should be filled in by * this macro, and will be provided to the other hook probe macros. * @param ns The namespace prefix of the hook functions * @param name The name of the hook * @param args The argument list to the hook functions, with enclosing * parens. */ #define APR_HOOK_PROBE_ENTRY(ud,ns,name,args) /** * User-defined hook probe macro that is invoked after the hook * has run. * @param ud A void * user data field that was filled in by the user- * provided APR_HOOK_PROBE_ENTRY(). * @param ns The namespace prefix of the hook functions * @param name The name of the hook * @param rv The return value of the hook, or 0 if the hook is void. * @param args The argument list to the hook functions, with enclosing * parens. */ #define APR_HOOK_PROBE_RETURN(ud,ns,name,rv,args) /** * User-defined hook probe macro that is invoked before calling a * hook function. * @param ud A void * user data field that was filled in by the user- * provided APR_HOOK_PROBE_ENTRY(). * @param ns The namespace prefix of the hook functions * @param name The name of the hook * @param src The value of apr_hook_debug_current at the time the function * was hooked (usually the source file implementing the hook function). * @param args The argument list to the hook functions, with enclosing * parens. */ #define APR_HOOK_PROBE_INVOKE(ud,ns,name,src,args) /** * User-defined hook probe macro that is invoked after calling a * hook function. * @param ud A void * user data field that was filled in by the user- * provided APR_HOOK_PROBE_ENTRY(). * @param ns The namespace prefix of the hook functions * @param name The name of the hook * @param src The value of apr_hook_debug_current at the time the function * was hooked (usually the source file implementing the hook function). * @param rv The return value of the hook function, or 0 if the hook is void. * @param args The argument list to the hook functions, with enclosing * parens. */ #define APR_HOOK_PROBE_COMPLETE(ud,ns,name,src,rv,args) #endif /** @} */ /** macro to return the prototype of the hook function */ #define APR_IMPLEMENT_HOOK_GET_PROTO(ns,link,name) \ link##_DECLARE(apr_array_header_t *) ns##_hook_get_##name(void) /** macro to declare the hook correctly */ #define APR_DECLARE_EXTERNAL_HOOK(ns,link,ret,name,args) \ typedef ret ns##_HOOK_##name##_t args; \ link##_DECLARE(void) ns##_hook_##name(ns##_HOOK_##name##_t *pf, \ const char * const *aszPre, \ const char * const *aszSucc, int nOrder); \ link##_DECLARE(ret) ns##_run_##name args; \ APR_IMPLEMENT_HOOK_GET_PROTO(ns,link,name); \ typedef struct ns##_LINK_##name##_t \ { \ ns##_HOOK_##name##_t *pFunc; \ const char *szName; \ const char * const *aszPredecessors; \ const char * const *aszSuccessors; \ int nOrder; \ } ns##_LINK_##name##_t; /** macro to declare the hook structure */ #define APR_HOOK_STRUCT(members) \ static struct { members } _hooks; /** macro to link the hook structure */ #define APR_HOOK_LINK(name) \ apr_array_header_t *link_##name; /** macro to implement the hook */ #define APR_IMPLEMENT_EXTERNAL_HOOK_BASE(ns,link,name) \ link##_DECLARE(void) ns##_hook_##name(ns##_HOOK_##name##_t *pf,const char * const *aszPre, \ const char * const *aszSucc,int nOrder) \ { \ ns##_LINK_##name##_t *pHook; \ if(!_hooks.link_##name) \ { \ _hooks.link_##name=apr_array_make(apr_hook_global_pool,1,sizeof(ns##_LINK_##name##_t)); \ apr_hook_sort_register(#name,&_hooks.link_##name); \ } \ pHook=apr_array_push(_hooks.link_##name); \ pHook->pFunc=pf; \ pHook->aszPredecessors=aszPre; \ pHook->aszSuccessors=aszSucc; \ pHook->nOrder=nOrder; \ pHook->szName=apr_hook_debug_current; \ if(apr_hook_debug_enabled) \ apr_hook_debug_show(#name,aszPre,aszSucc); \ } \ APR_IMPLEMENT_HOOK_GET_PROTO(ns,link,name) \ { \ return _hooks.link_##name; \ } /** * Implement a hook that has no return code, and therefore runs all of the * registered functions * @param ns The namespace prefix of the hook functions * @param link The linkage declaration prefix of the hook * @param name The name of the hook * @param args_decl The declaration of the arguments for the hook * @param args_use The names for the arguments for the hook * @note The link prefix FOO corresponds to FOO_DECLARE() macros, which * provide export linkage from the module that IMPLEMENTs the hook, and * import linkage from external modules that link to the hook's module. */ #define APR_IMPLEMENT_EXTERNAL_HOOK_VOID(ns,link,name,args_decl,args_use) \ APR_IMPLEMENT_EXTERNAL_HOOK_BASE(ns,link,name) \ link##_DECLARE(void) ns##_run_##name args_decl \ { \ ns##_LINK_##name##_t *pHook; \ int n; \ APR_HOOK_INT_DCL_UD; \ \ APR_HOOK_PROBE_ENTRY(ud, ns, name, args_use); \ \ if(_hooks.link_##name) \ { \ pHook=(ns##_LINK_##name##_t *)_hooks.link_##name->elts; \ for(n=0 ; n < _hooks.link_##name->nelts ; ++n) \ { \ APR_HOOK_PROBE_INVOKE(ud, ns, name, (char *)pHook[n].szName, args_use); \ pHook[n].pFunc args_use; \ APR_HOOK_PROBE_COMPLETE(ud, ns, name, (char *)pHook[n].szName, 0, args_use); \ } \ } \ \ APR_HOOK_PROBE_RETURN(ud, ns, name, 0, args_use); \ \ } /* FIXME: note that this returns ok when nothing is run. I suspect it should really return decline, but that breaks Apache currently - Ben */ /** * Implement a hook that runs until one of the functions returns something * other than OK or DECLINE * @param ns The namespace prefix of the hook functions * @param link The linkage declaration prefix of the hook * @param ret Type to return * @param name The name of the hook * @param args_decl The declaration of the arguments for the hook * @param args_use The names for the arguments for the hook * @param ok Success value * @param decline Decline value * @note The link prefix FOO corresponds to FOO_DECLARE() macros, which * provide export linkage from the module that IMPLEMENTs the hook, and * import linkage from external modules that link to the hook's module. */ #define APR_IMPLEMENT_EXTERNAL_HOOK_RUN_ALL(ns,link,ret,name,args_decl,args_use,ok,decline) \ APR_IMPLEMENT_EXTERNAL_HOOK_BASE(ns,link,name) \ link##_DECLARE(ret) ns##_run_##name args_decl \ { \ ns##_LINK_##name##_t *pHook; \ int n; \ ret rv = ok; \ APR_HOOK_INT_DCL_UD; \ \ APR_HOOK_PROBE_ENTRY(ud, ns, name, args_use); \ \ if(_hooks.link_##name) \ { \ pHook=(ns##_LINK_##name##_t *)_hooks.link_##name->elts; \ for(n=0 ; n < _hooks.link_##name->nelts ; ++n) \ { \ APR_HOOK_PROBE_INVOKE(ud, ns, name, (char *)pHook[n].szName, args_use); \ rv=pHook[n].pFunc args_use; \ APR_HOOK_PROBE_COMPLETE(ud, ns, name, (char *)pHook[n].szName, rv, args_use); \ if(rv != ok && rv != decline) \ break; \ rv = ok; \ } \ } \ \ APR_HOOK_PROBE_RETURN(ud, ns, name, rv, args_use); \ \ return rv; \ } /** * Implement a hook that runs until the first function returns something * other than the value of decline * @param ns The namespace prefix of the hook functions * @param link The linkage declaration prefix of the hook * @param name The name of the hook * @param ret Type to return * @param args_decl The declaration of the arguments for the hook * @param args_use The names for the arguments for the hook * @param decline Decline value * @note The link prefix FOO corresponds to FOO_DECLARE() macros, which * provide export linkage from the module that IMPLEMENTs the hook, and * import linkage from external modules that link to the hook's module. */ #define APR_IMPLEMENT_EXTERNAL_HOOK_RUN_FIRST(ns,link,ret,name,args_decl,args_use,decline) \ APR_IMPLEMENT_EXTERNAL_HOOK_BASE(ns,link,name) \ link##_DECLARE(ret) ns##_run_##name args_decl \ { \ ns##_LINK_##name##_t *pHook; \ int n; \ ret rv = decline; \ APR_HOOK_INT_DCL_UD; \ \ APR_HOOK_PROBE_ENTRY(ud, ns, name, args_use); \ \ if(_hooks.link_##name) \ { \ pHook=(ns##_LINK_##name##_t *)_hooks.link_##name->elts; \ for(n=0 ; n < _hooks.link_##name->nelts ; ++n) \ { \ APR_HOOK_PROBE_INVOKE(ud, ns, name, (char *)pHook[n].szName, args_use); \ rv=pHook[n].pFunc args_use; \ APR_HOOK_PROBE_COMPLETE(ud, ns, name, (char *)pHook[n].szName, rv, args_use); \ \ if(rv != decline) \ break; \ } \ } \ \ APR_HOOK_PROBE_RETURN(ud, ns, name, rv, args_use); \ \ return rv; \ } /* Hook orderings */ /** run this hook first, before ANYTHING */ #define APR_HOOK_REALLY_FIRST (-10) /** run this hook first */ #define APR_HOOK_FIRST 0 /** run this hook somewhere */ #define APR_HOOK_MIDDLE 10 /** run this hook after every other hook which is defined*/ #define APR_HOOK_LAST 20 /** run this hook last, after EVERYTHING */ #define APR_HOOK_REALLY_LAST 30 /** * The global pool used to allocate any memory needed by the hooks. */ APU_DECLARE_DATA extern apr_pool_t *apr_hook_global_pool; /** * A global variable to determine if debugging information about the * hooks functions should be printed. */ APU_DECLARE_DATA extern int apr_hook_debug_enabled; /** * The name of the module that is currently registering a function. */ APU_DECLARE_DATA extern const char *apr_hook_debug_current; /** * Register a hook function to be sorted. * @param szHookName The name of the Hook the function is registered for * @param aHooks The array which stores all of the functions for this hook */ APU_DECLARE(void) apr_hook_sort_register(const char *szHookName, apr_array_header_t **aHooks); /** * Sort all of the registered functions for a given hook. */ APU_DECLARE(void) apr_hook_sort_all(void); /** * Print all of the information about the current hook. This is used for * debugging purposes. * @param szName The name of the hook * @param aszPre All of the functions in the predecessor array * @param aszSucc All of the functions in the successor array */ APU_DECLARE(void) apr_hook_debug_show(const char *szName, const char * const *aszPre, const char * const *aszSucc); /** * Remove all currently registered functions. */ APU_DECLARE(void) apr_hook_deregister_all(void); /** @} */ #ifdef __cplusplus } #endif #endif /* APR_HOOKS_H */
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