+++ /dev/null
-// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
-// vim: ts=8 sw=2 smarttab
-/*
- * Ceph - scalable distributed file system
- *
- * Copyright (C) 2014 Red Hat
- *
- * This is free software; you can redistribute it and/or
- * modify it under the terms of the GNU Lesser General Public
- * License version 2.1, as published by the Free Software
- * Foundation. See file COPYING.
- *
- */
-
-#include "include/Context.h"
-
-/**
- * The Continuation interface is designed to help easily create multi-step
- * operations that share data without having to pass it around or create
- * custom Context classes for each step. To write a Continuation:
- * 1) create a child class with a function for each stage.
- * 2) Put all your shared data members into the class.
- * 3) In the constructor, register each function stage with set_callback().
- * 4) Whenever you need to provide a Context callback that activates the next
- * stage, call get_callback(stage_number). If you need to proceed to another
- * stage immediately, call immediate(stage, retcode) and return its result.
- *
- * To use a class:
- * 1) Construct the child class on the heap.
- * 2) Call begin().
- * 3) The destructor will be called once one of your functions returns true to
- * indicate it is done.
- *
- * Please note that while you can skip stages and get multiple Callback
- * objects at once, you *cannot* have any stage report that the Continuation
- * is completed while any other stage Callbacks are outstanding. It's best to
- * be serial unless you want to maintain your own metadata about which stages
- * are still pending.
- *
- * In fact, there are only two situations in which a stage should return
- * true while others are running:
- * 1) A Callback was issued and completed in the same thread,
- * 2) you called immediate(stage) and it is returning true.
- */
-
-class Continuation {
- std::set<int> stages_in_flight;
- std::set<int> stages_processing;
- int rval;
- Context *on_finish;
- bool reported_done;
-
- class Callback : public Context {
- Continuation *continuation;
- int stage_to_activate;
- public:
- Callback(Continuation *c, int stage) :
- continuation(c),
- stage_to_activate(stage) {}
- void finish(int r) override {
- continuation->continue_function(r, stage_to_activate);
- }
- };
-
-protected:
- typedef bool (Continuation::*stagePtr)(int r);
- /**
- * Continue immediately to the given stage. It will be executed
- * immediately, in the given thread.
- * @pre You are in a callback function.
- * @param stage The stage to execute
- * @param r The return code that will be provided to the next stage
- */
- bool immediate(int stage, int r) {
- assert(!stages_in_flight.count(stage));
- assert(!stages_processing.count(stage));
- stages_in_flight.insert(stage);
- stages_processing.insert(stage);
- return _continue_function(r, stage);
- }
-
- /**
- * Obtain a Context * that when complete()ed calls back into the given stage.
- * @pre You are in a callback function.
- * @param stage The stage this Context should activate
- */
- Context *get_callback(int stage) {
- stages_in_flight.insert(stage);
- return new Callback(this, stage);
- }
-
- /**
- * Set the return code that is passed to the finally-activated Context.
- * @param new_rval The return code to use.
- */
- void set_rval(int new_rval) { rval = new_rval; }
- int get_rval() { return rval; }
-
- /**
- * Register member functions as associated with a given stage. Start
- * your stage IDs at 0 and make that one the setup phase.
- * @pre There are no other functions associated with the stage.
- * @param stage The stage to associate this function with
- * @param func The function to use
- */
- void set_callback(int stage, stagePtr func) {
- assert(callbacks.find(stage) == callbacks.end());
- callbacks[stage] = func;
- }
-
- /**
- * Called when the Continuation is done, as determined by a stage returning
- * true and us having finished all the currently-processing ones.
- */
- virtual void _done() {
- on_finish->complete(rval);
- on_finish = NULL;
- return;
- }
-
-private:
- std::map<int, Continuation::stagePtr> callbacks;
-
- bool _continue_function(int r, int n) {
- set<int>::iterator stage_iter = stages_in_flight.find(n);
- assert(stage_iter != stages_in_flight.end());
- assert(callbacks.count(n));
- stagePtr p = callbacks[n];
-
- pair<set<int>::iterator,bool> insert_r = stages_processing.insert(n);
-
- bool done = (this->*p)(r);
- if (done)
- reported_done = true;
-
- stages_processing.erase(insert_r.first);
- stages_in_flight.erase(stage_iter);
- return done;
- }
-
- void continue_function(int r, int stage) {
- bool done = _continue_function(r, stage);
-
- assert (!done ||
- stages_in_flight.size() == stages_processing.size());
-
- if (done ||
- (reported_done && stages_processing.empty())) {
- _done();
- delete this;
- }
- }
-
-
-
-public:
- /**
- * Construct a new Continuation object. Call this from your child class,
- * obviously.
- *
- * @Param c The Context which should be complete()ed when this Continuation
- * is done.
- */
- Continuation(Context *c) :
- rval(0), on_finish(c), reported_done(false) {}
- /**
- * Clean up.
- */
- virtual ~Continuation() { assert(on_finish == NULL); }
- /**
- * Begin running the Continuation.
- */
- void begin() { stages_in_flight.insert(0); continue_function(0, 0); }
-};
Code Review / stor4nfv.git / blobdiff