Coroutines in C

Macros
#define	CORO_CONTEXT(name)   co_t co_##name
	Define the coroutine context (a pointer to label). More...
#define	CORO_CONTEXT_INIT(name)
#define	CORO_LOCAL   static
	Declare the local variable that preserves a value across a coroutine switching.
#define	CORO_DEFINE(name)   int coro_##name( co_t *co_p )
	Define the coroutine. More...
#define	CORO_BEGIN(initial)
	The coroutine beginning. More...
#define	CORO_END(final)
	The coroutine end. More...
#define	CORO_YIELD(final)
	Switching to the next coroutine. More...
#define	CORO_WAIT(cond, ...)
	Waiting for the condition is true. More...
#define	CORO_RESTART(final)
	Restart the coroutine. More...
#define	CORO_QUIT(final)   CORO_END( final )
	Quit the coroutine. More...
#define	CORO_CALL(name)   coro_##name( &co_##name )
	Call the coroutine. More...
#define	CORO_ALIVE(coro)   (( coro ) < CO_END )
	Checking the coroutine is not completed. More...
#define	CORO_WAIT_CORO(coro, ...)   CORO_WAIT( !CORO_ALIVE( coro ), ## __VA_ARGS__ )
	Start and waiting for the child coroutine is completed. More...
#define	SEMAPHORE_INIT(name, val)
	Initialize the semaphore. More...
#define	SEMAPHORE_ACQUIRE(name, ...)
	Waiting and acquire the semaphore. More...
#define	SEMAPHORE_RELEASE(name)
	Release the semaphore. More...

Typedefs
typedef void *	co_t
typedef unsigned int	semaphore_t

Enumerations
enum	{   CO_READY, CO_WAIT, CO_YIELD, CO_END,   CO_SKIP }

Detailed Description

Coroutine mechanics, implemented using the C language extensions "Labels as Values", "Statements and Declarations in Expressions" and "Locally Declared Labels". Based on Simon Tatham "Coroutines in C".

CORO_CONTEXT( A );
CORO_CONTEXT( B );

CORO_DEFINE( A )
{
    CORO_BEGIN();
    for ( ; ; ) {
        // ...
        CORO_YIELD();
    }
    CORO_END();
}

CORO_DEFINE( B )
{
    CORO_LOCAL int b;

    CORO_BEGIN();
    for ( ; ; ) {
        // ...
        CORO_WAIT( cond );
    }
    CORO_END();
}

int main( void )
{
    for ( ; ; ) {
        CORO_CALL( A );
        CORO_CALL( B );
    }
    return 0;
}

Any local variables which need to be persistent across a coroutine switching must be declared static (CORO_LOCAL).

Macro Definition Documentation

#define CORO_ALIVE

(

coro

)

(( coro ) < CO_END )

Checking the coroutine is not completed.

Parameters

coro	Result of the coroutine call.

Returns

Alive flag.

#define CORO_BEGIN

(

initial

)

Value:

({ \
    initial; \
    if ( *co_p ) goto **co_p; \
})

The coroutine beginning.

Parameters

initial

The initial operation, executed whenever enter in the coroutine.

Examples:

drive.c, and remote.c.

#define CORO_CALL

(

name

)

coro_##name( &co_##name )

Call the coroutine.

Parameters

name	Coroutine name.

Examples:

drive.c, and remote.c.

#define CORO_CONTEXT

(

name

)

co_t co_##name

Define the coroutine context (a pointer to label).

Parameters

name	Coroutine name.

Examples:

drive.c, and remote.c.

#define CORO_CONTEXT_INIT

(

name

)

Value:

({ \
    co_##name = NULL; \
})

#define CORO_DEFINE

(

name

)

int coro_##name( co_t *co_p )

Define the coroutine.

Parameters

name	Coroutine name.

Examples:

drive.c, and remote.c.

#define CORO_END

(

final

)

The coroutine end.

Parameters

final

The final operation, executed whenever exit from the coroutine.

Examples:

drive.c, and remote.c.

#define CORO_QUIT

(

final

)

CORO_END( final )

Quit the coroutine.

Parameters

final

Final operation.

Examples:

drive.c, and remote.c.

#define CORO_RESTART

(

final

)

Value:

({ \
    *co_p = NULL; \
    final; \
    return CO_YIELD; \
})

Restart the coroutine.

Parameters

final

Final operation.

#define CORO_WAIT	(		cond,
			...
	)

Value:

({ \
    __label__ L; \
    *co_p = &&L; \
L: \
    if (!( cond )) { \
        __VA_ARGS__;  /* final */ \
        return CO_WAIT; \
    } \
})

Waiting for the condition is true.

Parameters

cond	Condition.
...	Final operation.

Examples:

drive.c, and remote.c.

#define CORO_WAIT_CORO	(		coro,
			...
	)		CORO_WAIT( !CORO_ALIVE( coro ), ## __VA_ARGS__ )

Start and waiting for the child coroutine is completed.

Parameters

coro	Child coroutine.
...	Final operation.

#define CORO_YIELD

(

final

)

Value:

({ \
    __label__ L; \
    *co_p = &&L; \
    final; \
    return CO_YIELD; \
L:; \
})

Switching to the next coroutine.

Parameters

final

Final operation.

Examples:

drive.c, and remote.c.

#define SEMAPHORE_ACQUIRE	(		name,
			...
	)

Value:

({ \
	CORO_WAIT(( name > 0 ), ## __VA_ARGS__ ); \
    --name; \
})

Waiting and acquire the semaphore.

Parameters

name	Semaphore name.
...	Final operation.

#define SEMAPHORE_INIT	(		name,
			val
	)

Value:

({ \
    name = val; \
})

Initialize the semaphore.

Parameters

name	Semaphore name.
val	Semaphore capacity.

#define SEMAPHORE_RELEASE

(

name

)

Value:

({ \
    ++name; \
})

Release the semaphore.

Parameters

name	Semaphore name.