context.hpp

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#pragma once
#include <fc/thread/thread.hpp>
#include <fc/exception/exception.hpp>
#include <vector>
 
#include <boost/version.hpp>
 
#define BOOST_COROUTINES_NO_DEPRECATION_WARNING // Boost 1.61
#define BOOST_COROUTINE_NO_DEPRECATION_WARNING // Boost 1.62
 
#if BOOST_VERSION >= 106800
#include <boost/context/continuation_fcontext.hpp>
#else
#include <boost/context/all.hpp>
#endif
 
#if BOOST_VERSION >= 106100
  #include <boost/coroutine/stack_allocator.hpp>
  namespace bc  = boost::context::detail;
  namespace bco = boost::coroutines;
  typedef bco::stack_allocator stack_allocator;
#else
# include <boost/coroutine/stack_context.hpp>
  namespace bc  = boost::context;
  namespace bco = boost::coroutines;
# if !defined(NDEBUG)
#  include <boost/assert.hpp>
#  include <boost/coroutine/protected_stack_allocator.hpp>
  typedef bco::protected_stack_allocator stack_allocator;
# else
#  include <boost/coroutine/stack_allocator.hpp>
  typedef bco::stack_allocator stack_allocator;
# endif
 
#endif // BOOST_VERSION >= 106100
 
namespace fc {
  class thread;
  class promise_base;
  class task_base;
 
  struct context  {
    typedef fc::context* ptr;
    bco::stack_context stack_ctx;
 
#if BOOST_VERSION >= 106100
    using context_fn = void (*)(bc::transfer_t);
#else
    using context_fn = void(*)(intptr_t);
#endif
 
    context( context_fn sf, stack_allocator& alloc, fc::thread* t )
    : caller_context(0),
      stack_alloc(&alloc),
      next_blocked(0), 
      next_blocked_mutex(0), 
      next(0), 
      ctx_thread(t),
      canceled(false),
#ifndef NDEBUG
      cancellation_reason(nullptr),
#endif
      complete(false),
      cur_task(0),
      context_posted_num(0)
    {
     size_t stack_size = FC_CONTEXT_STACK_SIZE;
     alloc.allocate(stack_ctx, stack_size);
     my_context = bc::make_fcontext( stack_ctx.sp, stack_ctx.size, sf); 
    }
 
    context( fc::thread* t) :
     my_context(nullptr),
     caller_context(0),
     stack_alloc(0),
     next_blocked(0), 
     next_blocked_mutex(0), 
     next(0), 
     ctx_thread(t),
     canceled(false),
#ifndef NDEBUG
     cancellation_reason(nullptr),
#endif
     complete(false),
     cur_task(0),
     context_posted_num(0)
    {}
 
    ~context() {
      if(stack_alloc)
        stack_alloc->deallocate( stack_ctx );
    }
 
    void reinitialize()
    {
      canceled = false;
#ifndef NDEBUG
      cancellation_reason = nullptr;
#endif
      blocking_prom.clear();
      caller_context = nullptr;
      resume_time = fc::time_point();
      next_blocked = nullptr;
      next_blocked_mutex = nullptr;
      next = nullptr;
      complete = false;
    }
 
    struct blocked_promise {
      blocked_promise( promise_base* p=0, bool r=true )
      :prom(p),required(r){}
 
      promise_base* prom;
      bool          required;
    };
    
    void add_blocking_promise( promise_base* p, bool req = true ) {
      for( auto i = blocking_prom.begin(); i != blocking_prom.end(); ++i ) {
        if( i->prom == p ) {
          i->required = req;
          return;
        }
      }
      blocking_prom.push_back( blocked_promise(p,req) );
    }
    bool try_unblock( promise_base* p ) {
      if( blocking_prom.size() == 0 )  {
        return true;
     }
      bool req = false;
      for( uint32_t i = 0; i < blocking_prom.size(); ++i ) {
        if( blocking_prom[i].prom == p ) {
           blocking_prom[i].required = false;
           return true;
        }
        req = req || blocking_prom[i].required;
      }
      return !req;
    }
 
    void remove_blocking_promise( promise_base* p ) {
      for( auto i = blocking_prom.begin(); i != blocking_prom.end(); ++i ) {
        if( i->prom == p ) {
          blocking_prom.erase(i);
          return;
        }
      }
    }
 
    void timeout_blocking_promises() {
      for( auto i = blocking_prom.begin(); i != blocking_prom.end(); ++i ) {
        i->prom->set_exception( std::make_shared<timeout_exception>() );
      }
    }
    void set_exception_on_blocking_promises( const exception_ptr& e ) {
      for( auto i = blocking_prom.begin(); i != blocking_prom.end(); ++i ) {
        i->prom->set_exception( e );
      }
    }
    void clear_blocking_promises() {
      blocking_prom.clear();
    }
 
    bool is_complete()const { return complete; }
 
    bc::fcontext_t               my_context;
    fc::context*                caller_context;
    stack_allocator*            stack_alloc;
    priority                     prio;
    //promise_base*              prom; 
    std::vector<blocked_promise> blocking_prom;
    time_point                   resume_time;
   // time_point                   ready_time; // time that this context was put on ready queue
    fc::context*                next_blocked;
    fc::context*                next_blocked_mutex;
    fc::context*                next;
    fc::thread*                 ctx_thread;
    bool                         canceled;
#ifndef NDEBUG
    const char*                  cancellation_reason;
#endif
    bool                         complete;
    task_base*                   cur_task;
    uint64_t                     context_posted_num; // serial number set each tiem the context is added to the ready list
  };
 
} // naemspace fc