context_util.h

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/*
 *  This file is part of SST/macroscale:
 *               The macroscale architecture simulator from the SST suite.
 *  Copyright (c) 2009 Sandia Corporation.
 *  This software is distributed under the BSD License.
 *  Under the terms of Contract DE-AC04-94AL85000 with Sandia Corporation,
 *  the U.S. Government retains certain rights in this software.
 *  For more information, see the LICENSE file in the top
 *  SST/macroscale directory.
 */

#ifndef SSTMAC_SOFTWARE_THREADING_CONTEXT_UTIL_H_INCLUDED
#define SSTMAC_SOFTWARE_THREADING_CONTEXT_UTIL_H_INCLUDED

#include <sstmac/common/sstmac_config.h>
#include <sprockit/errors.h>
#include <assert.h>

namespace sstmac {
namespace sw {

/**
 * A set of utilities to deal with the odd arguments to makecontext.
 */

// We assume that we can always fit a pointer (void* or void (*ptr)(void*))
// into two integers.  This should ideally be tested by autoconf.
struct intpair {
  int a;
  int b;
};

/// Pack a void* argument into a pair of integers.
union  voidptr {
  intpair  vpair;
  void    *vpointer;
  voidptr() {
    vpair.a = 0;
    vpair.b = 0;
    vpointer = 0;
  }
  voidptr(void *ptr) {
    assert(sizeof(void*) <= (2*sizeof(int)));
    vpair.a = 0;
    vpair.b = 0;
    vpointer = ptr;
  }
  voidptr(int a, int b) {
    vpointer = 0;
    vpair.a = a;
    vpair.b = b;
  }
};

/// Pack a function pointer of the form void(*)(void*) as a pair of integers.
union funcptr {
  intpair fpair;
  void (*fpointer)(void*);
  funcptr() {
    fpair.a  = 0;
    fpair.b  = 0;
    fpointer = 0;
  }
  funcptr(void (*ptr)(void*)) {
    assert(sizeof(void(*)(void*)) <= (2*sizeof(int)));
    fpair.a  = 0;
    fpair.b  = 0;
    fpointer = ptr;
  }
  funcptr(int a, int b) {
    fpointer = 0;
    fpair.a  = a;
    fpair.b  = b;
  }
  void call(const voidptr &arg) {
    if(fpointer == 0) {
      spkt_throw(sprockit::null_error,
        "union functpr::call(const voidptr&): NULL function pointer");
    }
    (*fpointer)(arg.vpointer);
  }
};

/// Springboard routine to wrap a makecontext call.
/// We have to be able to take a pointer to this function
/// (so no inline).
void context_springboard(int func_ptr_a, int func_ptr_b,
                         int arg_ptr_a,  int arg_ptr_b);

}
} // end of namespace sstmac

#endif