ucontext.c

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/********************************************************************************
 * Copyright (c) 2003, 2004                                                     *
 * Panagiotis E. Hadjidoukas    (peh@hpclab.ceid.upatras.gr)                    *
 * HPCLab - University of Patras. All Rights Reserved.                          *
 * Unix ucontext_t on Windows Operating System, May 2004 (revision 1)           *
 *                                                                              *
 * The author disclaims all warranties with regard to this software including   *
 * all implied warranties of merchantability and fitness for a particular       *
 * purpose. In no event shall HPCLab be liable for any special, indirect,       *
 * or consequential damages or any damages whatsoever resulting from            *
 * loss of use, data or profits, whether in action of contract negligence,      *
 * or other tortious action, arising out of or in connection with the use       *
 * or performance of this software.                                             *
 ********************************************************************************/

#include "ucontext.h"

int getcontext(ucontext_t *ucp)
{
    int ret;

    /* Retrieve the full machine context */
    ucp->uc_mcontext.ContextFlags = CONTEXT_FULL;
    ret = GetThreadContext(GetCurrentThread(), &ucp->uc_mcontext);

    return (ret == 0) ? -1: 0;
}

int setcontext(const ucontext_t *ucp)
{
    int ret;
    
    /* Restore the full machine context (already set) */
    ret = SetThreadContext(GetCurrentThread(), &ucp->uc_mcontext);

    return (ret == 0) ? -1: 0;
}

int makecontext(ucontext_t *ucp, void (*func)(), int argc, ...)
{
    int i;
    va_list ap;
    char *sp;

    /* Stack grows down */
    sp = (char *) (size_t) ucp->uc_stack.ss_sp + ucp->uc_stack.ss_size; 

    /* Reserve stack space for the arguments (maximum possible: argc*(8 bytes per argument)) */
    sp -= argc*8;

    if ( sp < (char *)ucp->uc_stack.ss_sp) {
        /* errno = ENOMEM;*/
        return -1;
    }

    /* Set the instruction and the stack pointer */
    ucp->uc_mcontext.Eip = (unsigned long) func;
    ucp->uc_mcontext.Esp = (unsigned long) sp - 4;

    /* Save/Restore the full machine context */
    ucp->uc_mcontext.ContextFlags = CONTEXT_FULL;

    /* Copy the arguments */
    va_start (ap, argc);
    for (i=0; i<argc; i++) {
        memcpy(sp, ap, 8);
        ap +=8;
        sp += 8;
    }
    va_end(ap);

    return 0;
}

int swapcontext(ucontext_t *oucp, const ucontext_t *ucp)
{
    int ret;

    if ((oucp == NULL) || (ucp == NULL)) {
        /*errno = EINVAL;*/
        return -1;
    }

    ret = getcontext(oucp);
    if (ret == 0) {
        ret = setcontext(ucp);
    }
    return ret;
}