src/base/AsyncCallList.h

   1 /*
   2  * Copyright (C) 1996-2023 The Squid Software Foundation and contributors
   3  *
   4  * Squid software is distributed under GPLv2+ license and includes
   5  * contributions from numerous individuals and organizations.
   6  * Please see the COPYING and CONTRIBUTORS files for details.
   7  */
   8
   9 #ifndef SQUID_BASE_ASYNCCALLLIST_H
  10 #define SQUID_BASE_ASYNCCALLLIST_H
  11
  12 #include "base/forward.h"
  13 #include "base/RefCount.h"
  14
  15 /// An efficient (but intrusive) AsyncCall storage preserving FIFO order.
  16 /// A given AsyncCall object may reside in at most one such storage.
  17 class AsyncCallList
  18 {
  19 public:
  20     AsyncCallList() = default;
  21     // prohibit copying: no AsyncCall should be present in two lists
  22     AsyncCallList(const AsyncCallList &) = delete;
  23     AsyncCallList &operator=(const AsyncCallList &) = delete;
  24
  25     /// stores the given async call
  26     void add(const AsyncCallPointer &);
  27
  28     /// removes the earliest add()-ed call that is still stored (if any)
  29     /// \returns the removed call (or nil)
  30     /// \retval nil means the list stored no calls at extract() time
  31     AsyncCallPointer extract();
  32
  33     /// the number of currently stored calls
  34     size_t size() const { return length; }
  35
  36 private:
  37     AsyncCallPointer head; ///< the earliest still-stored call (or nil)
  38     AsyncCallPointer tail; ///< the latest still-stored call (or nil)
  39     size_t length = 0; ///< \copydoc size()
  40 };
  41
  42 #endif /* SQUID_BASE_ASYNCCALLLIST_H */
  43