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database/apache/include/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 */