opend.c

#include "opend.h"
#include "apue.h"
#include <fcntl.h>

int buf_args(char *buf, int (*optfunc)(int, char **));
int cli_args(int argc, char **argv);

char errmsg[MAXLINE];
int oflag;
char *pathname;

void handle_request(char *buf, int nread, int fd);

int main(void)
{
    int nread;
    char buf[MAXLINE];

    for ( ; ; ) { /* read arg buffer from client, process request */
        if ((nread = read(STDIN_FILENO, buf, MAXLINE)) < 0)
            err_sys("read error on stream pipe");
        else if (nread == 0)
            break; /* client has closed the stream pipe */
        handle_request(buf, nread, STDOUT_FILENO);
    }
    exit(0);
}

void handle_request(char *buf, int nread, int fd)
{
    int newfd;

    if (buf[nread-1] != 0) {
        snprintf(errmsg, MAXLINE-1, "request not null terminated: %*.*s\n", nread, nread, buf);
        send_err(fd, -1, errmsg);
        return;
    }
    if (buf_args(buf, cli_args) < 0) { /* parse args & set options */
        send_err(fd, -1, errmsg);
        return;
    }
    if ((newfd = open(pathname, oflag)) < 0) {
        snprintf(errmsg, MAXLINE-1, "can't open %s: %s\n", pathname, strerror(errno));
        send_err(fd, -1, errmsg);
    }
    if (send_fd(fd, newfd) < 0) /* send the descriptor */
        err_sys("send_fd error");
    close(newfd); /* we're done with descriptor */
}

#define MAXARGC 50 /* max number of arguments in buf */
#define WHITE " \t\n" /* white space for tokenizing arguments */

/*
 * buf[] contains white-space-separated arguments. We convert it to an
 * argv-style array of pointers, and call the user's function (optfunc)
 * to process the array. We return -1 if there's a problem parsing buf,
 * else we return whatever optfunc() returns. Note that user's buf[],
 * array is modified (nulls placed after each token).
 */

int buf_args(char *buf, int (*optfunc)(int, char **))
{
    char *ptr, *argv[MAXARGC];
    int argc;

    if (strtok(buf, WHITE) == NULL) /* an argv[0] is required */
        return (-1);
    argv[argc = 0] = buf;
    while ((ptr = strtok(NULL, WHITE)) != NULL) {
        if (++argc >= MAXARGC-1) /* -1 for room for NULL at end */
            return (-1);
        argv[argc] = ptr;
    }
    argv[++argc] = NULL;
    /*
     * Since argv[] pointers point into the user's buf[], user's function
     * can just copy the pointers, even though argv[] array will disappear
     * on return.
     */
    return ((*optfunc)(argc, argv));
}

/*
 * This function is called by buf_args(), which is called by handle_request().
 * buf_args() has broken up the client's buffer into an argv[]-style array, which
 * we now process.
 */
int cli_args(int argc, char **argv)
{
    if (argc != 3 || strcmp(argv[0], CL_OPEN) != 0) {
        strcpy(errmsg, "usage: open <pathname> <oflag>\n");
        return (-1);
    }
    pathname = argv[1]; /* save ptr to pathname to open */
    oflag = atoi(argv[2]);
    return (0);
}