OSX/libsecurity_utilities/lib/globalizer.h

   1 /*
   2  * Copyright (c) 2000-2004,2011-2012,2014 Apple Inc. All Rights Reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. Please obtain a copy of the License at
  10  * http://www.opensource.apple.com/apsl/ and read it before using this
  11  * file.
  12  *
  13  * The Original Code and all software distributed under the License are
  14  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  15  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  16  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  18  * Please see the License for the specific language governing rights and
  19  * limitations under the License.
  20  *
  21  * @APPLE_LICENSE_HEADER_END@
  22  */
  23
  24
  25 /*
  26  * globalizer - multiscope globalization services
  27  */
  28 #ifndef _H_GLOBALIZER
  29 #define _H_GLOBALIZER
  30
  31 #include <security_utilities/threading.h>
  32 #include <memory>
  33 #include <set>
  34 #include <dispatch/dispatch.h>
  35 #include <libkern/OSAtomic.h>
  36 #include <os/lock.h>
  37
  38 namespace Security {
  39
  40
  41 //
  42 // GlobalNexus is the common superclass of all globality scopes.
  43 // A Nexus is an *access point* to the *single* object of a given
  44 // type in the Nexus's particular scope.
  45 //
  46 class GlobalNexus {
  47 public:
  48     class Error : public std::exception {
  49     public:
  50         virtual ~Error() _NOEXCEPT;
  51         const char * const message;
  52         Error(const char *m) : message(m) { }
  53         const char *what() const _NOEXCEPT { return message; }
  54     };
  55 };
  56
  57
  58 class ModuleNexusCommon : public GlobalNexus {
  59 private:
  60     void do_create(void *(*make)());
  61
  62 protected:
  63     void *create(void *(*make)());
  64     void lock() {os_unfair_lock_lock(&access);}
  65     void unlock() {os_unfair_lock_unlock(&access);}
  66
  67 protected:
  68     // all of these will be statically initialized to zero
  69         void *pointer;
  70     dispatch_once_t once;
  71     os_unfair_lock access;
  72 };
  73
  74 template <class Type>
  75 class ModuleNexus : public ModuleNexusCommon {
  76 public:
  77     Type &operator () ()
  78     {
  79         lock();
  80
  81         try
  82         {
  83             if (pointer == NULL)
  84             {
  85                 pointer = create(make);
  86             }
  87
  88             unlock();
  89         }
  90         catch (...)
  91         {
  92             unlock();
  93             throw;
  94         }
  95
  96                 return *reinterpret_cast<Type *>(pointer);
  97     }
  98
  99         // does the object DEFINITELY exist already?
 100         bool exists() const
 101         {
 102         bool result;
 103         lock();
 104         result = pointer != NULL;
 105         unlock();
 106         return result;
 107         }
 108
 109         // destroy the object (if any) and start over - not really thread-safe
 110     void reset()
 111     {
 112         lock();
 113         if (pointer != NULL)
 114         {
 115             delete reinterpret_cast<Type *>(pointer);
 116             pointer = NULL;
 117             once = 0;
 118         }
 119         unlock();
 120     }
 121
 122 private:
 123     static void *make() { return new Type; }
 124 };
 125
 126 template <class Type>
 127 class CleanModuleNexus : public ModuleNexus<Type> {
 128 public:
 129     ~CleanModuleNexus()
 130     {
 131         secinfo("nexus", "ModuleNexus %p destroyed object 0x%x",
 132                         this, ModuleNexus<Type>::pointer);
 133         delete reinterpret_cast<Type *>(ModuleNexus<Type>::pointer);
 134     }
 135 };
 136
 137 typedef std::set<void*> RetentionSet;
 138
 139 //
 140 // A thread-scope nexus is tied to a particular native thread AND
 141 // a particular nexus object. Its scope is all code in any one thread
 142 // that access that particular Nexus object. Any number of Nexus objects
 143 // can exist, and each implements a different scope for each thread.
 144 // NOTE: ThreadNexus is dynamically constructed. If you want static,
 145 // zero-initialization ThreadNexi, put them inside a ModuleNexus.
 146 //
 147 template <class Type>
 148 class ThreadNexus : public GlobalNexus {
 149 public:
 150     ThreadNexus() : mSlot(true) { }
 151
 152     Type &operator () ()
 153     {
 154         // no thread contention here!
 155         if (Type *p = mSlot)
 156             return *p;
 157         mSlot = new Type;
 158         return *mSlot;
 159     }
 160
 161 private:
 162     PerThreadPointer<Type> mSlot;
 163 };
 164
 165
 166 //
 167 // A ProcessNexus is global within a single process, regardless of
 168 // load module boundaries. You can have any number of ProcessNexus
 169 // scopes, each identified by a C string (compared by value, not pointer).
 170 //
 171 class ProcessNexusBase : public GlobalNexus {
 172 protected:
 173         ProcessNexusBase(const char *identifier);
 174
 175         struct Store {
 176                 void *mObject;
 177                 Mutex mLock;
 178         };
 179         Store *mStore;
 180 };
 181
 182 template <class Type>
 183 class ProcessNexus : public ProcessNexusBase {
 184 public:
 185         ProcessNexus(const char *identifier) : ProcessNexusBase(identifier) { }
 186         Type &operator () ();
 187
 188 private:
 189         Type *mObject;
 190 };
 191
 192 template <class Type>
 193 Type &ProcessNexus<Type>::operator () ()
 194 {
 195 #if !defined(PTHREAD_STRICT)
 196     // not strictly kosher POSIX, but pointers are usually atomic types
 197     if (mStore->mObject)
 198         return *reinterpret_cast<Type *>(mStore->mObject);
 199 #endif
 200     StLock<Mutex> _(mStore->mLock);
 201     if (mStore->mObject == NULL)
 202         mStore->mObject = new Type;
 203     return *reinterpret_cast<Type *>(mStore->mObject);
 204 };
 205
 206
 207 } // end namespace Security
 208
 209 #endif //_H_GLOBALIZER