src/ipc/RequestId.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_SRC_IPC_REQUESTID_H
  10 #define SQUID_SRC_IPC_REQUESTID_H
  11
  12 #include "ipc/forward.h"
  13 #include "ipc/QuestionerId.h"
  14
  15 #include <iosfwd>
  16
  17 namespace Ipc
  18 {
  19
  20 /// uniquely identifies an IPC request among same-type concurrent IPC requests
  21 /// submitted by a single Squid instance
  22 class RequestId
  23 {
  24 public:
  25     /// A simple ID for correlating IPC responses with pending requests.
  26     /// Value 0 has a special meaning of "unset/unknown", but otherwise opaque.
  27     typedef unsigned int Index;
  28
  29     /// Request sender's constructor.
  30     /// For performance and clarity sake, default constructor is preferred to 0 index.
  31     explicit RequestId(Index);
  32
  33     /// request recipient's constructor
  34     RequestId() = default;
  35
  36     /// Make the ID unset/unknown.
  37     /// Optimization: leaves the questioner field alone.
  38     void reset() { index_ = 0; }
  39
  40     /// Make the ID set/known with the given (by the questioner) index.
  41     /// For performance and clarity sake, reset(void) is preferred to reset(0).
  42     void reset(const Index anIndex) { *this = RequestId(anIndex); }
  43
  44     QuestionerId questioner() const { return qid_; }
  45     Index index() const { return index_; }
  46
  47     // these conversion operators allow our users to treat us as an Index
  48     operator Index() const { return index_; }
  49     RequestId &operator =(const Index anIndex) { anIndex ? reset(anIndex) : reset(); return *this; }
  50
  51 private:
  52     /// the sender of the request
  53     QuestionerId qid_;
  54
  55     /// request ID; unique within pending same-qid_ questions of the same kind
  56     Index index_ = 0;
  57 };
  58
  59 std::ostream &operator <<(std::ostream &, const RequestId &);
  60
  61 } // namespace Ipc;
  62
  63 #endif /* SQUID_SRC_IPC_REQUESTID_H */
  64