src/Pipeline.h

   1 /*
   2  * Copyright (C) 1996-2017 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_PIPELINE_H
  10 #define SQUID_SRC_PIPELINE_H
  11
  12 #include "base/RefCount.h"
  13 #include "http/forward.h"
  14
  15 #include <list>
  16
  17 /**
  18  * A queue of transactions awaiting completion.
  19  *
  20  * Transactions in the queue may be fully processed, but not yet delivered,
  21  * or only partially processed.
  22  *
  23  * - HTTP/1 pipelined requests can be processed out of order but
  24  *   responses MUST be written to the client in-order.
  25  *   The front() context is for the response writing transaction.
  26  *   The back context may still be reading a request payload/body.
  27  *   Other contexts are in deferred I/O state, but may be accumulating
  28  *   payload/body data to be written later.
  29  *
  30  * - HTTP/2 multiplexed streams can be processed and delivered in any order.
  31  *
  32  * For consistency we treat the pipeline as a FIFO queue in both cases.
  33  */
  34 class Pipeline
  35 {
  36     Pipeline(const Pipeline &) = delete;
  37     Pipeline & operator =(const Pipeline &) = delete;
  38
  39 public:
  40     Pipeline() : nrequests(0) {}
  41     ~Pipeline() = default;
  42
  43     /// register a new request context to the pipeline
  44     void add(const Http::StreamPointer &);
  45
  46     /// get the first request context in the pipeline
  47     Http::StreamPointer front() const;
  48
  49     /// get the last request context in the pipeline
  50     Http::StreamPointer back() const;
  51
  52     /// how many requests are currently pipelined
  53     size_t count() const {return requests.size();}
  54
  55     /// whether there are none or any requests currently pipelined
  56     bool empty() const {return requests.empty();}
  57
  58     /// tell everybody about the err, and abort all waiting requests
  59     void terminateAll(const int xerrno);
  60
  61     /// deregister the front request from the pipeline
  62     void popMe(const Http::StreamPointer &);
  63
  64     /// Number of requests seen in this pipeline (so far).
  65     /// Includes incomplete transactions.
  66     uint32_t nrequests;
  67
  68 private:
  69     /// requests parsed from the connection but not yet completed.
  70     std::list<Http::StreamPointer> requests;
  71 };
  72
  73 #endif /* SQUID_SRC_PIPELINE_H */
  74