scsh-0.5/scsh/select1.c

/* C support for scsh select call.
** Copyright (c) 1995 by Olin Shivers.
*/

/* To do:
** - Documentation.
** - Check Posix timeval defn.
** - What is proper include for error vals?
*/

#include "sysdep.h"

#include <sys/types.h>
#if defined(HAVE_SYS_SELECT_H)
#  include <sys/select.h>
#endif
#include <sys/time.h>

#include <errno.h>
#include <stdio.h>

#include "fdports.h"	/* Accessors for Scheme I/O port internals. */
#include "cstuff.h"

/* the traditional sleazy max non-function. */
#define max(a,b) (((a) > (b)) ? (a) : (b))

extern int errno;
extern FILE *fdes2fstar(int fd);

static void or2_fdset(fd_set *x, fd_set *y, int max_elt);
static int copyback_fdvec(scheme_value portvec, fd_set *fdset);

/* RVEC, WVEC, and EVEC are Scheme vectors of integer file descriptors
** and I/O ports. NSECS is an integer timeout value, or #f for infinite wait.
** Do the select() call. Move every element of we hit on to the front of
** its vector. The number of hits are returned in R_NUMRDY, W_NUMRDY, and
** E_NUMRDY. The principle return value is #f if we win, and a fixnum errno
** value if we error out.
*/

scheme_value scm_select(scheme_value rvec, scheme_value wvec,
			scheme_value evec, scheme_value nsecs,
			int *r_numrdy, int *w_numrdy, int *e_numrdy)
{
    struct timeval timeout, *tptr;
    fd_set rset_bufrdy, wset_bufrdy, eset_bufrdy;    /* Buffered port hits. */
    fd_set rset_try,    wset_try,    eset_try;	     /* Real select() sets. */
    int rbuf_rdy=0, wbuf_rdy=0, bufrdy;	/* Set if we find buffered I/O hits. */
    int max_fd = -1;			/* Max fdes in the sets. */
    int nelts, i;
    int nfound;

    FD_ZERO(&rset_try);		FD_ZERO(&wset_try);	FD_ZERO(&eset_try);
    FD_ZERO(&rset_bufrdy);	FD_ZERO(&wset_bufrdy);	FD_ZERO(&eset_bufrdy);
    *r_numrdy = *w_numrdy = *e_numrdy = 0;

    /* Scan the readvec elts. */
    nelts = VECTOR_LENGTH(rvec);
    for(i=nelts; --i >= 0; ) {
	scheme_value elt = VECTOR_REF(rvec,i);
	int fd;

	if( FIXNUMP(elt) ) {			    /* It's an integer fdes. */
	    fd = EXTRACT_FIXNUM(elt);
	    FD_SET(fd, &rset_try);
	    }

	else {					    /* It better be a port. */
	    FILE *f;
	    scheme_value data = *Port_PortData(elt);
	    fd = EXTRACT_FIXNUM(*PortData_Fd(data));
	    f = fdes2fstar(fd);
	    if( !f ) return ENTER_FIXNUM(errno);
	    else if( *PortData_Peek(data) != SCHFALSE /* Port has a peekchar */
		     || !ibuf_empty(f) ) { 	     /* Stdio buf has chars. */
		FD_SET(fd, &rset_bufrdy);
		rbuf_rdy = 1; /* Hit. */
		}
	    else FD_SET(fd, &rset_try);		  /* No buffered data. */
	    }

	max_fd = max(max_fd, fd);
	}

    /* Scan the writevec elts. */
    nelts = VECTOR_LENGTH(wvec);
    for(i=nelts; --i >= 0; ) {
	scheme_value elt = VECTOR_REF(wvec,i);
	int fd;

	if( FIXNUMP(elt) ) {			    /* It's an integer fdes. */
	    fd = EXTRACT_FIXNUM(elt);
	    FD_SET(fd, &wset_try);
	    }

	else {					    /* It better be a port. */
	    FILE *f;
	    fd = EXTRACT_FIXNUM(*PortFd(elt));
	    f = fdes2fstar(fd);
	    if( !f ) return ENTER_FIXNUM(errno);
	    else if( !obuf_full(f) ) {		  /* I/O buf has room. */
		FD_SET(fd, &wset_bufrdy);		
		wbuf_rdy = 1; /* Hit. */
		}
	    else FD_SET(fd, &wset_try);		  /* No room. */
	    }

	max_fd = max(max_fd, fd);
	}

    /* Scan the exception-vec elts. */
    nelts = VECTOR_LENGTH(evec);
    for(i=nelts; --i >= 0; ) {
	scheme_value elt = VECTOR_REF(evec,i);
	int fd;

	if( FIXNUMP(elt) ) {			/* It's an integer fdes. */
	    fd = EXTRACT_FIXNUM(elt);
	    FD_SET(fd, &rset_try);
	    }

	else {					/* It better be a port. */
	    fd = EXTRACT_FIXNUM(*PortFd(elt));
	    FD_SET(fd, &rset_try);
	    }

	max_fd = max(max_fd, fd);
	}

    bufrdy = rbuf_rdy || wbuf_rdy;
    if( bufrdy ) {		/* Already have some hits on buffered ports, */
	timeout.tv_sec = 0;	/* so we only poll the others.               */
	timeout.tv_usec = 0;
	tptr = &timeout;
	}
    else if ( FIXNUMP(nsecs) ) {
	timeout.tv_sec = EXTRACT_FIXNUM(nsecs);	/* Wait n seconds. */
	timeout.tv_usec = 0;
	tptr = &timeout;
	}
    else tptr = NULL;				/* #f => Infinite wait. */

    nfound = select1(max_fd+1, &rset_try, &wset_try, &eset_try, tptr);/*Do it.*/

    /* EINTR is not an error return if we have hits on buffered ports
    ** to report.
    */
    if( nfound < 0 )
	if ( errno != EINTR || !bufrdy ) return ENTER_FIXNUM(errno);
	else {	/* EINTR, but we have hits on buffered ports to report.  */
	    FD_ZERO(&rset_try);		/* This should never happen --   */
	    FD_ZERO(&wset_try);		/* EINTR on a zero-sec select()  */
	    FD_ZERO(&eset_try);		/* -- but I'm paranoid.          */
	    }

    /* OR together the buffered-io ready sets and the fd ready sets. */
    if( rbuf_rdy ) or2_fdset(&rset_try, &rset_bufrdy, max_fd);
    if( wbuf_rdy ) or2_fdset(&wset_try, &wset_bufrdy, max_fd);

    *r_numrdy = copyback_fdvec(rvec, &rset_try);
    *w_numrdy = copyback_fdvec(wvec, &wset_try);
    *e_numrdy = copyback_fdvec(evec, &eset_try);

    return SCHFALSE;
    }

/* PORTVEC is a vector of integer file descriptors and Scheme ports.
** Scan over the vector, and copy any elt whose file descriptor is in FDSET
** to the front of the vector. Return the number of elts thus copied.
*/
static int copyback_fdvec(scheme_value portvec, fd_set *fdset)
{
    int vlen = VECTOR_LENGTH(portvec);
    int i, j=0;
    for( i = -1; ++i < vlen; ) {
	scheme_value elt = VECTOR_REF(portvec, i);
	int fd = EXTRACT_FIXNUM((FIXNUMP(elt)) ? elt : *PortFd(elt));
	if( FD_ISSET(fd,fdset) ) {
	    FD_CLR(fd,fdset);	/* In case luser put elt in multiple times. */
	    VECTOR_REF(portvec, j) = elt;
	    j++;
	    }
	}
    return j;
    }


/* x = x or y */
static void or2_fdset(fd_set *x, fd_set *y, int max_elt)
{
    int i;
    for(i=max_elt+1; --i >= 0;)
	if( FD_ISSET(i,y) ) FD_SET(i,x);
    }