mark.c

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/* mark.c - markinit, mark */

#include <xinu.h>

int32   *marks[MAXMARK];        /* Pointers to marked locations */
int32   nmarks;             /* Number of marked locations   */
sid32   mkmutex;            /* Mutual exclusion semaphore   */

/*------------------------------------------------------------------------
 *  markinit  -  Called once at system startup
 *------------------------------------------------------------------------
 */
void    markinit(void)
{
    nmarks = 0;
    mkmutex = semcreate(1);
}


/*------------------------------------------------------------------------
 *  mark  -  Mark a specified memory location
 *------------------------------------------------------------------------
 */
status  mark(
      int32 *loc            /* Location to mark     */
    )
{

    /* If location is already marked, do nothing */

    if ( (*loc>=0) && (*loc<nmarks) && (marks[*loc]==loc) ) {
        return OK;
    }

    /* If no more memory marks are available, indicate an error */

    if (nmarks >= MAXMARK) {
        return SYSERR;
    }

    /* Obtain exclusive access and mark the specified location */

    wait(mkmutex);
    marks[ (*loc) = nmarks++ ] = loc;
    signal(mkmutex);
    return OK;
}