ACE/examples/APG/Threads/Guards.cpp

   1 #include "ace/config-lite.h"
   2 #if defined (ACE_HAS_THREADS)
   3
   4 #include "ace/OS_main.h"
   5 #include "ace/OS_Memory.h"
   6 #include "ace/Guard_T.h"
   7 #include "ace/Log_Msg.h"
   8 #include "ace/Thread_Mutex.h"
   9
  10 // This file exists primarily to get code into the book to show different
  11 // ways to do the same thing. For complete context and explanation, please
  12 // see APG chapter 12.
  13
  14 class HA_Device_Repository {
  15 public:
  16   int update_device (int device_id);
  17
  18 private:
  19   ACE_Thread_Mutex  mutex_;
  20 };
  21
  22 class Object {
  23 };
  24 static Object *object;
  25
  26 #if 0
  27 // This is less-desired way to do this...
  28
  29 // Listing 1 code/ch12
  30 int
  31 HA_Device_Repository::update_device (int device_id)
  32 {
  33   this->mutex_.acquire ();
  34   ACE_DEBUG ((LM_DEBUG, ACE_TEXT ("(%t) Updating device %d\n"),
  35               device_id));
  36
  37   // Allocate a new object.
  38   ACE_NEW_RETURN (object, Object, -1);
  39   // ...
  40   // Use the object
  41
  42   this->mutex_.release ();
  43 }
  44 // Listing 1
  45 // Listing 2 code/ch12
  46 int
  47 HA_Device_Repository::update_device (int device_id)
  48 {
  49   // Construct a guard specifying the type of the mutex as
  50   // a template parameter and passing in the mutex to hold
  51   // as a parameter.
  52   // FUZZ: disable check_for_ACE_Guard
  53   ACE_Guard<ACE_Thread_Mutex> guard (this->mutex_);
  54   // FUZZ: enable check_for_ACE_Guard
  55
  56   // This can throw an exception that is not caught here.
  57   ACE_NEW_RETURN (object, Object, -1);
  58   // ..
  59   // Use the object.
  60   // ..
  61   // Guard is destroyed, automatically releasing the lock.
  62 }
  63 // Listing 2
  64 #endif /* 0 */
  65
  66 // Listing 3 code/ch12
  67 int
  68 HA_Device_Repository::update_device (int /* device_id */)
  69 {
  70   ACE_GUARD_RETURN (ACE_Thread_Mutex, mon, mutex_, -1);
  71
  72   ACE_NEW_RETURN (object, Object, -1);
  73   // Use the object.
  74   // ...
  75   return 0;
  76 }
  77 // Listing 3
  78
  79 int ACE_TMAIN (int, ACE_TCHAR *[])
  80 {
  81   HA_Device_Repository rep;
  82   rep.update_device (42);
  83   return 0;
  84 }
  85
  86 #else
  87 #include "ace/OS_main.h"
  88 #include "ace/OS_NS_stdio.h"
  89
  90 int ACE_TMAIN (int, ACE_TCHAR *[])
  91 {
  92   ACE_OS::puts (ACE_TEXT ("This example requires threads."));
  93   return 0;
  94 }
  95
  96 #endif /* ACE_HAS_THREADS */