src/base/Lock.h

   1 #ifndef SQUID_SRC_BASE_LOCK_H
   2 #define SQUID_SRC_BASE_LOCK_H
   3
   4 /**
   5  * This class provides a tracking counter and presents
   6  * lock(), unlock() and LockCount() accessors.
   7  *
   8  * All locks must be cleared with unlock() before this object
   9  * is destroyed.
  10  *
  11  * Accessors provided by this interface are not private,
  12  * to allow class hierarchies.
  13  *
  14  * Build with -DLOCKCOUNT_DEBUG flag to enable lock debugging.
  15  * It is disabled by default due to the cost of debug output.
  16  */
  17 class Lock
  18 {
  19 public:
  20     Lock():count_(0) {}
  21
  22     virtual ~Lock() { assert(count_ == 0); }
  23
  24     /// Register one lock / reference against this object.
  25     /// All locks must be cleared before it may be destroyed.
  26     void lock() const {
  27 #if defined(LOCKCOUNT_DEBUG)
  28         old_debug(0,1)("Incrementing this %p from count %u\n",this,count_);
  29 #endif
  30         ++count_;
  31     }
  32
  33     /// Clear one lock / reference against this object.
  34     /// All locks must be cleared before it may be destroyed.
  35     unsigned unlock() const {
  36 #if defined(LOCKCOUNT_DEBUG)
  37         old_debug(0,1)("Decrementing this %p from count %u\n",this,count_);
  38 #endif
  39         assert(count_ > 0);
  40         return --count_;
  41     }
  42
  43     /// Inspect the current count of references.
  44     unsigned LockCount() const { return count_; }
  45
  46 private:
  47     mutable unsigned count_; ///< number of references currently being tracked
  48 };
  49
  50 // For clarity we provide some aliases for the tracking mechanisms
  51 // using Lock so that we can easily see what type of smart pointers
  52 // are to be used for the child object.
  53 // NP: CbcPointer<> and RefCount<> pointers should be used consistently
  54 //     for any given child class type
  55
  56 /// The locking interface for use on Reference-Counted classes
  57 #define RefCountable virtual Lock
  58
  59 #endif /* SQUID_SRC_BASE_LOCK_H */