CORON

One of the most missed things when migrating from assembly language to C is a way to branch off from one point to another with ease. The intention of the coron is to provide a simple and efficient way to enable coroutine-like functions in C language. Usually, this kind of behavior is needed when developing on a constrained embedded device and dealing with some type of asynchronous communication.

Note: It uses GCC Labels as Values extension in order to achieve this.

Usage

As coron consists of only one coron.h header file providing the macros, there is straight forward way to use it any project developed in C99 that uses GCC or CLANG.

Example:

void foo(void) {
...
    PC_INIT(); /* initializes the static variable for saving the PC.
                * Next instruction called after the PC_INIT will be
                * the last saved PC, all above will always
                * execute on function call
                */
...
    PC_SAVE(); /* saves the current PC and next time
                * the function is called this line will
                * be the entry point
                */
...
    PC_RESET(); /* resets the entry back to PC_INIT (optional) */
}

Comparison between protothreads

There is an intentional similarity with Adam Dunkel's Protothreads, where the main differences are:

• no switch-case statements are used to enable the functionality and thus switch is allowed to be placed in the function body
• information about the entry and exit is declared in the function scope so there is no need to pass it as a function argument allowing the function prototype to be defined without limitations
• Only PC_INIT(); at the beginning of the function is needed to allow the function to save the PC state

Test it

A simple test is provided to demonstrate the funcionality. In order to build it run:

make

and execute: ./test_coron