Coroutines in C (2000)

Post by s-macke » Thu, Feb 07, 2019, 9:34 PM UTC

tangent128 wrote: post #34

s-macke wrote: post #27

I guess one of the applications of Coroutines could be WebAssembly. When you run WebAssembly on a website which needs 100% of the CPU for more than a few ms, you have to use the "setTimeout(fn, 0)" trick to prevent the "this website stopped responding" message. That means you have to store the current state at some point and continue in the function fn (after waiting 0 ms). Languages which support coroutines out of t…

Aren't Web Workers (which can run WASM) supposed to fill that role?

Post by davidgrenier » Thu, Feb 07, 2019, 10:04 PM UTC

loeg wrote: post #39

sandov wrote: post #26

Earlier quoted context omitted.

The only issue of these websites is the width: using the full width of the screen is just too much for reading. If you add {max-width: 60em; margin: auto;} to the body tag it looks much better.

Not too wide for my browser windows, which are a bit under 50% of screen width.

Post by plaguuuuuu » Thu, Feb 07, 2019, 10:55 PM UTC

Post by wahern » Fri, Feb 08, 2019, 12:10 AM UTC

plaguuuuuu wrote: post #46

As an OOP dev this kind of horrifies me, even though it works okay (though it's surely not thread-safe?) Nevertheless, even in C, I'd find it conceptually simpler to understand if the functions were written as pure functions, returning a tuple with (c, state) and passing the state back into the caller. Using non-idiomatic tricks and macros in this way is harder to read and understand.

  static int
  u_getopt_r(int argc, char *const argv[], const char *shortopts, struct u_getopt_r *K)
  {
    K->optarg = NULL;
    K->optopt = 0;
  
    GETOPT_ENTER;
  
    while (K->optind cp = argv[K->optind];
  
      if (!K->cp || *(K->cp) != '-' || !strcmp(K->cp, "-")) {
        break;
      } else if (!strcmp(K->cp, "--")) {
        K->optind++;
        break;
      }
  
      for (;;) {
        char *shortopt;
  
        if (!(K->optopt = *++K->cp)) {
          K->optind++;
          break;
        } else if (!(shortopt = strchr(shortopts, K->optopt))) {
          getopt_err(argc, argv, shortopts, K, "illegal option -- %c\n", K->optopt);
          GETOPT_YIELD('?');
        } else if (shortopt[1] != ':') {
          GETOPT_YIELD(K->optopt);
        } else if (K->cp[1]) {
          K->optarg = &K->cp[1];
          K->optind++;
          GETOPT_YIELD(K->optopt);
          break;
        } else if (K->optind + 1 optarg = argv[K->optind + 1];
          K->optind += 2;
          GETOPT_YIELD(K->optopt);
          break;
        } else {
          getopt_err(argc, argv, shortopts, K, "option requires an argument -- %c\n", K->optopt);
          K->optind++;
          GETOPT_YIELD((*shortopts == ':')? ':' : '?');
          break;
        }
      }
    }
  
    GETOPT_LEAVE;
  
    return -1;
  }
  

  #define GETOPT_ENTER \
    do { \
    static const int pc0 = __LINE__; \
    switch (pc0 + K->pc) { \
    case __LINE__: (void)0
  
  #define GETOPT_SAVE_AND_DO(do_statement) \
    do { \
      K->pc = __LINE__ - pc0; \
      do_statement; \
      case __LINE__: (void)0; \
    } while (0)
  
  #define GETOPT_YIELD(rv) \
    GETOPT_SAVE_AND_DO(return (rv))
  
  #define GETOPT_LEAVE \
    GETOPT_SAVE_AND_DO(break); \
    } \
    } while (0)

Post by convolvatron » Fri, Feb 08, 2019, 1:51 AM UTC

nraynaud wrote: post #31

evancox100 wrote: post #28

Has anyone used these to write interrupt service routines? Seems like there's an opportunity here. You can take your existing synchronous code and not have to rewrite it into something like continuation-passing style. This is a source of a lot of bugs.

I have, it's not pretty either: https://github.com/nraynaud/webgcode/blob/gh-pages/interpola...