WSSetYieldFunction (C Function)

int WSSetYieldFunction(WSLINK link,WSYieldFunctionObject yf)

installs the yield function yf for the link referenced by link.


  • Some WSTP API calls will block until data is available to read or space is available for writing. If an application needs to perform other useful processing during that blocking time, the application can install a yield function for the link and WSTP will automatically make calls to the yield function while it blocks.
  • To back out of a blocked read or write, the yield function should return a nonzero value.
  • WSSetYieldFunction() will return 0 in the event of an error, and a nonzero value if the function succeeds.
  • On Windows the WSYieldFunctionObject uses the WINAPI calling convention.
  • Use WSError() to retrieve the error code if WSSetYieldFunction() fails.
  • WSSetYieldFunction() is declared in the WSTP header file wstp.h.


Basic Examples  (1)

#include "wstp.h"


int CALLING_CONVENTION AppYieldFunction(WSLINK lp, WSYieldParameters yp)
    /* ... */
    return 0;

int main(int argc, char **argv)
    WSENV env;
    WSLINK link;
    int error;

    env = WSInitialize((WSEnvironmentParameter)0);
    if(env == (WSENV)0)
        { /* unable to initialize WSTP environment */ }

    link = WSOpenArgcArgv(env, argv, argv + argc, &error);
    if(link == (WSLINK)0 || error != WSEOK)
        { /* unable to create the link */ }

    if(! WSSetYieldFunction(link, AppYieldFunction))
        { /* unable to set the yield function for link */ }

    /* ... */

    return 0;