Security/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
  37 namespace Security {
  38
  39
  40 //
  41 // GlobalNexus is the common superclass of all globality scopes.
  42 // A Nexus is an *access point* to the *single* object of a given
  43 // type in the Nexus's particular scope.
  44 //
  45 class GlobalNexus {
  46 public:
  47     class Error : public std::exception {
  48     public:
  49         virtual ~Error() throw();
  50         const char * const message;
  51         Error(const char *m) : message(m) { }
  52         const char *what() const throw() { return message; }
  53     };
  54 };
  55
  56
  57 class ModuleNexusCommon : public GlobalNexus {
  58 private:
  59     void do_create(void *(*make)());
  60
  61 protected:
  62     void *create(void *(*make)());
  63     void lock() {OSSpinLockLock(&access);}
  64     void unlock() {OSSpinLockUnlock(&access);}
  65
  66 protected:
  67     // all of these will be statically initialized to zero
  68         void *pointer;
  69     dispatch_once_t once;
  70     OSSpinLock access;
  71 };
  72
  73 template <class Type>
  74 class ModuleNexus : public ModuleNexusCommon {
  75 public:
  76     Type &operator () ()
  77     {
  78         lock();
  79
  80         try
  81         {
  82             if (pointer == NULL)
  83             {
  84                 pointer = create(make);
  85             }
  86
  87             unlock();
  88         }
  89         catch (...)
  90         {
  91             unlock();
  92             throw;
  93         }
  94
  95                 return *reinterpret_cast<Type *>(pointer);
  96     }
  97
  98         // does the object DEFINITELY exist already?
  99         bool exists() const
 100         {
 101         bool result;
 102         lock();
 103         result = pointer != NULL;
 104         unlock();
 105         return result;
 106         }
 107
 108         // destroy the object (if any) and start over - not really thread-safe
 109     void reset()
 110     {
 111         lock();
 112         if (pointer != NULL)
 113         {
 114             delete reinterpret_cast<Type *>(pointer);
 115             pointer = NULL;
 116             once = 0;
 117         }
 118         unlock();
 119     }
 120
 121 private:
 122     static void *make() { return new Type; }
 123 };
 124
 125 template <class Type>
 126 class CleanModuleNexus : public ModuleNexus<Type> {
 127 public:
 128     ~CleanModuleNexus()
 129     {
 130         secdebug("nexus", "ModuleNexus %p destroyed object 0x%x",
 131                         this, ModuleNexus<Type>::pointer);
 132         delete reinterpret_cast<Type *>(ModuleNexus<Type>::pointer);
 133     }
 134 };
 135
 136 typedef std::set<void*> RetentionSet;
 137
 138 //
 139 // A thread-scope nexus is tied to a particular native thread AND
 140 // a particular nexus object. Its scope is all code in any one thread
 141 // that access that particular Nexus object. Any number of Nexus objects
 142 // can exist, and each implements a different scope for each thread.
 143 // NOTE: ThreadNexus is dynamically constructed. If you want static,
 144 // zero-initialization ThreadNexi, put them inside a ModuleNexus.
 145 //
 146 template <class Type>
 147 class ThreadNexus : public GlobalNexus {
 148 public:
 149     ThreadNexus() : mSlot(true) { }
 150
 151     Type &operator () ()
 152     {
 153         // no thread contention here!
 154         if (Type *p = mSlot)
 155             return *p;
 156         mSlot = new Type;
 157         return *mSlot;
 158     }
 159
 160 private:
 161     PerThreadPointer<Type> mSlot;
 162 };
 163
 164
 165 //
 166 // A ProcessNexus is global within a single process, regardless of
 167 // load module boundaries. You can have any number of ProcessNexus
 168 // scopes, each identified by a C string (compared by value, not pointer).
 169 //
 170 class ProcessNexusBase : public GlobalNexus {
 171 protected:
 172         ProcessNexusBase(const char *identifier);
 173
 174         struct Store {
 175                 void *mObject;
 176                 Mutex mLock;
 177         };
 178         Store *mStore;
 179 };
 180
 181 template <class Type>
 182 class ProcessNexus : public ProcessNexusBase {
 183 public:
 184         ProcessNexus(const char *identifier) : ProcessNexusBase(identifier) { }
 185         Type &operator () ();
 186
 187 private:
 188         Type *mObject;
 189 };
 190
 191 template <class Type>
 192 Type &ProcessNexus<Type>::operator () ()
 193 {
 194 #if !defined(PTHREAD_STRICT)
 195     // not strictly kosher POSIX, but pointers are usually atomic types
 196     if (mStore->mObject)
 197         return *reinterpret_cast<Type *>(mStore->mObject);
 198 #endif
 199     StLock<Mutex> _(mStore->mLock);
 200     if (mStore->mObject == NULL)
 201         mStore->mObject = new Type;
 202     return *reinterpret_cast<Type *>(mStore->mObject);
 203 };
 204
 205
 206 } // end namespace Security
 207
 208 #endif //_H_GLOBALIZER