output.c

unix环境高级编程的源代码

#include    "lprps.h"

static char    outbuf[OBSIZE];
static int    outcnt = OBSIZE;    /* #bytes remaining */
static char    *outptr = outbuf;

static void    out_buf(void);

/* Output a single character.
 * Called by main loop in send_file(). */

void
out_char(int c)
{
    if (c == EOF) {
        out_buf();        /* flag that we're all done */
        return;
    }

    if (outcnt <= 0)
        out_buf();        /* buffer is full, write it first */

    *outptr++ = c;        /* just store in buffer */
    outcnt--;
}

/* Output the buffer that out_char() has been storing into.
 * We have our own output function, so that we never block on a write
 * to the printer.  Each time we output our buffer to the printer,
 * we also see if the printer has something to send us.  If so,
 * we call proc_input_char() to process each character. */
static void
out_buf(void)
{
    char    *wptr, *rptr, ibuf[IBSIZE];
    int        wcnt, nread, nwritten;
    fd_set    rfds, wfds;

    FD_ZERO(&wfds);
    FD_ZERO(&rfds);
    set_nonblock();            /* don't want the write() to block */
    wptr = outbuf;            /* ptr to first char to output */
    wcnt = outptr - wptr;    /* #bytes to output */
    while (wcnt > 0) {
        FD_SET(psfd, &wfds);
        FD_SET(psfd, &rfds);
        if (intr_flag)
            handle_intr();
        while (select(psfd + 1, &rfds, &wfds, NULL, NULL) < 0) {
            if (errno == EINTR) {
                if (intr_flag)
                    handle_intr();        /* no return */
            } else
                log_sys("out_buf: select error");
        }
        if (FD_ISSET(psfd, &rfds)) {        /* printer is readable */
            if ( (nread = read(psfd, ibuf, IBSIZE)) < 0)
                log_sys("out_buf: read error");
            rptr = ibuf;
            while (--nread >= 0)
                proc_input_char(*rptr++);
        }
        if (FD_ISSET(psfd, &wfds)) {        /* printer is writeable */
            if ( (nwritten = write(psfd, wptr, wcnt)) < 0)
                log_sys("out_buf: write error");
            wcnt -= nwritten;
            wptr += nwritten;
        }
    }
    outptr = outbuf;    /* reset buffer pointer and count */
    outcnt = OBSIZE;
}