Continuations / Coroutines / Generators in C ++ / gcc / linux

Question

Background: I'm trying to figure out how to implement continuations / coroutines / generators (regardless of what is called below) by putting this toy. The environment is C ++ 11 on gcc 4.6 and linux 3.0 x86_64. Not portable, but using an external library (boost.coroutine, COROUTINE, etc.) is not allowed. I think that longjmp(3)both makecontext(2)friends can help, but are not sure.

Description:

The next toy parser should analyze sequences of as and bs of equal length. i.e

((a+)(b+))+

so the length of the second bracket is the third.

When he finds a work (e.g. aaabbb), he gives out the number ahe finds (e.g. 3).

The code:

#include <stdlib.h>
#include <iostream>
using namespace std;

const char* s;

void yield()
{
        // TODO: no data, return from produce
        abort();
}

void advance()
{
        s++;
        if (*s == 0)
                yield();
}

void consume()
{
        while (true)
        {
                int i = 0;

                while (*s == 'a')
                {
                        i++;
                        advance();
                }

                cout << i << " ";

                while (i-- > 0)
                {
                    if (*s != 'b')
                        abort();
                    advance();
                }
        }
}

void produce(const char* s_)
{
        s = s_;

        // TODO: data available, continue into consume()
        consume();
}

int main()
{
        produce("aaab");
        produce("bba");
        produce("baa");
        produce("aabbb");
        produce("b");

        // should print: 3 1 4

        return 0;
}

Problem:

, consume yield, produce. produce , consume , yield. , produce consume yield, .

(, , , .)

, , , mankontext man: http://www.kernel.org/doc/man-pages/online/pages/man3/makecontext.3.html, , . ( )

:

( )

#include <stdlib.h>
#include <iostream>
#include <ucontext.h>
using namespace std;

const char* s;
ucontext_t main_context, consume_context;

void yield()
{
    swapcontext(&consume_context, &main_context);
}

void advance()
{
    s++;
    if (*s == 0)
            yield();
}

void consume()
{
    while (true)
    {
            int i = 0;

            while (*s == 'a')
            {
                    i++;
                    advance();
            }

            cout << i << " ";

            while (i-- > 0)
            {
                    advance();
            }
    }
}

void produce(const char* s_)
{
    s = s_;

    swapcontext(&main_context, &consume_context);
}

int main()
{
    char consume_stack[4096];

    getcontext(&consume_context);
    consume_context.uc_stack.ss_sp = consume_stack;
    consume_context.uc_stack.ss_size = sizeof(consume_stack);
    makecontext(&consume_context, consume, 0);

    produce("aaab");
    produce("bba");
    produce("baa");
    produce("aabbb");
    produce("b");

    // should print: 3 1 4

    return 0;
}

Answer 1

makecontext/swapcontext - makecontext coroutine swapcontext . consume, main .

main getcontext + makecontext , :

getcontext(&consume_ctxt);
// set up stack in consume_context
makecontext(&consume_ctxt, consume, 0);

produce consume:

void produce(const char* s_)
{
    s = s_; 
    swapcontext(&main_ctxt, &consume_ctxt);
}

, , yield swapcontext(&consume_ctxt, &main_ctxt);, ( produce ).

, consume , , , ( )