src/base/AsyncCallQueue.cc

   1 /*
   2  * Copyright (C) 1996-2021 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 /* DEBUG: section 41    Event Processing */
  10
  11 #include "squid.h"
  12 #include "base/AsyncCall.h"
  13 #include "base/AsyncCallQueue.h"
  14 #include "Debug.h"
  15
  16 AsyncCallQueue *AsyncCallQueue::TheInstance = 0;
  17
  18 AsyncCallQueue::AsyncCallQueue(): theHead(NULL), theTail(NULL)
  19 {
  20 }
  21
  22 void AsyncCallQueue::schedule(AsyncCall::Pointer &call)
  23 {
  24     assert(call != NULL);
  25     assert(!call->theNext);
  26     if (theHead != NULL) { // append
  27         assert(!theTail->theNext);
  28         theTail->theNext = call;
  29         theTail = call;
  30     } else { // create queue from cratch
  31         theHead = theTail = call;
  32     }
  33 }
  34
  35 // Fire all scheduled calls; returns true if at least one call was fired.
  36 // The calls may be added while the current call is in progress.
  37 bool
  38 AsyncCallQueue::fire()
  39 {
  40     const bool made = theHead != NULL;
  41     while (theHead) {
  42         CodeContext::Reset(theHead->codeContext);
  43         fireNext();
  44     }
  45     if (made)
  46         CodeContext::Reset();
  47     return made;
  48 }
  49
  50 void
  51 AsyncCallQueue::fireNext()
  52 {
  53     AsyncCall::Pointer call = theHead;
  54     theHead = call->theNext;
  55     call->theNext = NULL;
  56     if (theTail == call)
  57         theTail = NULL;
  58
  59     debugs(call->debugSection, call->debugLevel, "entering " << *call);
  60     call->make();
  61     debugs(call->debugSection, call->debugLevel, "leaving " << *call);
  62 }
  63
  64 AsyncCallQueue &
  65 AsyncCallQueue::Instance()
  66 {
  67     // TODO: how to remove this frequent check while supporting early calls?
  68     if (!TheInstance)
  69         TheInstance = new AsyncCallQueue();
  70
  71     return *TheInstance;
  72 }
  73