boost context

context.cpp

//          Copyright Oliver Kowalke 2009.
// Distributed under the Boost Software License, Version 1.0.
//    (See accompanying file LICENSE_1_0.txt or copy at
//          http://www.boost.org/LICENSE_1_0.txt)

#include <cstdlib>
#include <cstring>
#include <iostream>

#include <boost/assert.hpp>
#include <boost/context/all.hpp>

#ifndef BOOST_CONTEXT_SIMPLE_STACK_ALLOCATOR_H
#define BOOST_CONTEXT_SIMPLE_STACK_ALLOCATOR_H

#include <cstddef>
#include <cstdlib>
#include <stdexcept>

#include <boost/assert.hpp>
#include <boost/config.hpp>

#include <boost/context/detail/config.hpp>

#ifdef BOOST_HAS_ABI_HEADERS
#  include BOOST_ABI_PREFIX
#endif

namespace boost {
namespace context {

template< std::size_t Max, std::size_t Default, std::size_t Min >
class simple_stack_allocator
{
public:
    static std::size_t maximum_stacksize()
    { return Max; }

    static std::size_t default_stacksize()
    { return Default; }

    static std::size_t minimum_stacksize()
    { return Min; }

    void * allocate( std::size_t size) const
    {
        BOOST_ASSERT( minimum_stacksize() <= size);
        BOOST_ASSERT( maximum_stacksize() >= size);

        void * limit = std::malloc( size);
        if ( ! limit) throw std::bad_alloc();

        return static_cast< char * >( limit) + size;
    }

    void deallocate( void * vp, std::size_t size) const
    {
        BOOST_ASSERT( vp);
        BOOST_ASSERT( minimum_stacksize() <= size);
        BOOST_ASSERT( maximum_stacksize() >= size);

        void * limit = static_cast< char * >( vp) - size;
        std::free( limit);
    }
};

}}

#ifdef BOOST_HAS_ABI_HEADERS
#  include BOOST_ABI_SUFFIX
#endif

#endif // BOOST_CONTEXT_SIMPLE_STACK_ALLOCATOR_H



//          Copyright Oliver Kowalke 2009.
// Distributed under the Boost Software License, Version 1.0.
//    (See accompanying file LICENSE_1_0.txt or copy at
//          http://www.boost.org/LICENSE_1_0.txt)

namespace ctx = boost::context;

typedef ctx::simple_stack_allocator<
    8 * 1024 * 1024, // 8MB
    64 * 1024, // 64kB
    8 * 1024 // 8kB
>       stack_allocator;

ctx::fcontext_t * fc1;
ctx::fcontext_t * fc2;

ctx::fcontext_t * fc3;

void f1( intptr_t)
{
    std::cout << "f1: entered" << std::endl;
    std::cout << "f1: call jump_fcontext( fc1, fc2, 0)" << std::endl;
    ctx::jump_fcontext( fc1, fc2, 0);
    std::cout << "f1: return" << std::endl;
}

void f2( intptr_t)
{
    std::cout << "f2: entered" << std::endl;
    std::cout << "f2: call jump_fcontext( fc2, fc1, 0)" << std::endl;
    ctx::jump_fcontext( fc2, fc1, 0);
    BOOST_ASSERT( false && ! "f2: never returns");
}

int main( int argc, char * argv[])
{
    std::cout << "size: 0x" << std::hex << sizeof( ctx::fcontext_t) << std::endl;

    ctx::fcontext_t fcm;
    fc3 = &fcm;
    stack_allocator alloc;

    void * sp1 = alloc.allocate( stack_allocator::default_stacksize());
    fc1 = ctx::make_fcontext( sp1, stack_allocator::default_stacksize(), f1);

    void * sp2 = alloc.allocate( stack_allocator::default_stacksize());
    fc2 = ctx::make_fcontext( sp2, stack_allocator::default_stacksize(), f2);

    std::cout << "main: call start_fcontext( & fcm, fc1, 0)" << std::endl;
    ctx::jump_fcontext( & fcm, fc1, 0);

    std::cout << "main: done" << std::endl;

    alloc.deallocate(sp2, stack_allocator::default_stacksize());
    alloc.deallocate(sp1, stack_allocator::default_stacksize());

    return EXIT_SUCCESS;
}