tty.c

unix环境高级编程的源代码

#include    "lprps.h"
#include    <fcntl.h>
#include    <termios.h>

static int        block_flag = 1;        /* default is blocking I/O */

void
set_block(void)        /* turn off nonblocking flag */
{                    /* called only by block_write() below */
    int        val;

    if (block_flag == 0) {
        if ( (val = fcntl(psfd, F_GETFL, 0)) < 0)
            log_sys("set_block: fcntl F_GETFL error");
        val &= ~O_NONBLOCK;
        if (fcntl(psfd, F_SETFL, val) < 0)
            log_sys("set_block: fcntl F_SETFL error");

        block_flag = 1;
    }
}

void
set_nonblock(void)    /* set descriptor nonblocking */
{
    int        val;

    if (block_flag) {
        if ( (val = fcntl(psfd, F_GETFL, 0)) < 0)
            log_sys("set_nonblock: fcntl F_GETFL error");
        val |= O_NONBLOCK;
        if (fcntl(psfd, F_SETFL, val) < 0)
            log_sys("set_nonblock: fcntl F_SETFL error");

        block_flag = 0;
    }
}

void
block_write(const char *buf, int n)
{
    set_block();
    if (write(psfd, buf, n) != n)
        log_sys("block_write: write error");
}

void
tty_flush(void)        /* flush (empty) tty input and output queues */
{
    if (tcflush(psfd, TCIOFLUSH) < 0)
        log_sys("tty_flush: tcflush error");
}
void
tty_open(void)
{
    struct termios    term;

    if ( (psfd = open(DEF_DEVICE, O_RDWR)) < 0)
        log_sys("tty_open: open error");

    if (tcgetattr(psfd, &term) < 0)        /* fetch attributes */
        log_sys("tty_open: tcgetattr error");
    term.c_cflag  = CS8 |            /* 8-bit data */
                    CREAD |            /* enable receiver */
                    CLOCAL;            /* ignore modem status lines */
                                    /* no parity, 1 stop bit */
    term.c_oflag &= ~OPOST;            /* turn off post processing */
    term.c_iflag  = IXON | IXOFF |    /* Xon/Xoff flow control */
                    IGNBRK |        /* ignore breaks */
                    ISTRIP |        /* strip input to 7 bits */
                    IGNCR;            /* ignore received CR */
    term.c_lflag  = 0;        /* everything off in local flag:
                               disables canonical mode, disables
                               signal generation, disables echo */
    term.c_cc[VMIN]  = 1;    /* 1 byte at a time, no timer */
    term.c_cc[VTIME] = 0;
    cfsetispeed(&term, DEF_BAUD);
    cfsetospeed(&term, DEF_BAUD);
    if (tcsetattr(psfd, TCSANOW, &term) < 0)    /* set attributes */
        log_sys("tty_open: tcsetattr error");
}