csapp.c

/*
 * csapp.c - Functions for the CS:APP3e book
 *
 * Updated 10/2016 reb:
 *   - Fixed bug in sio_ltoa that didn't cover negative numbers
 *
 * Updated 2/2016 droh:
 *   - Updated open_clientfd and open_listenfd to fail more gracefully
 *
 * Updated 8/2014 droh:
 *   - New versions of open_clientfd and open_listenfd are reentrant and
 *     protocol independent.
 *
 *   - Added protocol-independent inet_ntop and inet_pton functions. The
 *     inet_ntoa and inet_aton functions are obsolete.
 *
 * Updated 7/2014 droh:
 *   - Aded reentrant sio (signal-safe I/O) routines
 *
 * Updated 4/2013 droh:
 *   - rio_readlineb: fixed edge case bug
 *   - rio_readnb: removed redundant EINTR check
 */
/* $begin csapp.c */
#include "csapp.h"

/**************************
 * Error-handling functions
 **************************/
/* $begin errorfuns */
/* $begin unixerror */
void unix_error(char *msg) /* Unix-style error */
{
    fprintf(stderr, "%s: %s\n", msg, strerror(errno));
    exit(0);
}
/* $end unixerror */

/********************************
 * Client/server helper functions
 ********************************/
/*
 * open_clientfd - Open connection to server at <hostname, port> and
 *     return a socket descriptor ready for reading and writing. This
 *     function is reentrant and protocol-independent.
 *
 *     On error, returns:
 *       -2 for getaddrinfo error
 *       -1 with errno set for other errors.
 */
/* $begin open_clientfd */
int open_clientfd(char *hostname, char *port) {
    int clientfd, rc;
    struct addrinfo hints, *listp, *p;

    /* Get a list of potential server addresses */
    memset(&hints, 0, sizeof(struct addrinfo));
    hints.ai_socktype = SOCK_STREAM;  /* Open a connection */
    hints.ai_flags = AI_NUMERICSERV;  /* ... using a numeric port arg. */
    hints.ai_flags |= AI_ADDRCONFIG;  /* Recommended for connections */
    if ((rc = getaddrinfo(hostname, port, &hints, &listp)) != 0) {
        fprintf(stderr, "getaddrinfo failed (%s:%s): %s\n", hostname, port, gai_strerror(rc));
        return -2;
    }

    /* Walk the list for one that we can successfully connect to */
    for (p = listp; p; p = p->ai_next) {
        /* Create a socket descriptor */
        if ((clientfd = socket(p->ai_family, p->ai_socktype, p->ai_protocol)) < 0)
            continue; /* Socket failed, try the next */

        /* Connect to the server */
        if (connect(clientfd, p->ai_addr, p->ai_addrlen) != -1)
            break; /* Success */
        if (close(clientfd) < 0) { /* Connect failed, try another */  //line:netp:openclientfd:closefd
            fprintf(stderr, "open_clientfd: close failed: %s\n", strerror(errno));
            return -1;
        }
    }

    /* Clean up */
    freeaddrinfo(listp);
    if (!p) /* All connects failed */
        return -1;
    else    /* The last connect succeeded */
        return clientfd;
}
/* $end open_clientfd */

/*
 * open_listenfd - Open and return a listening socket on port. This
 *     function is reentrant and protocol-independent.
 *
 *     On error, returns:
 *       -2 for getaddrinfo error
 *       -1 with errno set for other errors.
 */
/* $begin open_listenfd */
int open_listenfd(char *port)
{
    struct addrinfo hints, *listp, *p;
    int listenfd, rc, optval=1;

    /* Get a list of potential server addresses */
    memset(&hints, 0, sizeof(struct addrinfo));
    hints.ai_socktype = SOCK_STREAM;             /* Accept connections */
    hints.ai_flags = AI_PASSIVE | AI_ADDRCONFIG; /* ... on any IP address */
    hints.ai_flags |= AI_NUMERICSERV;            /* ... using port number */
    if ((rc = getaddrinfo(NULL, port, &hints, &listp)) != 0) {
        fprintf(stderr, "getaddrinfo failed (port %s): %s\n", port, gai_strerror(rc));
        return -2;
    }

    /* Walk the list for one that we can bind to */
    for (p = listp; p; p = p->ai_next) {
        /* Create a socket descriptor */
        if ((listenfd = socket(p->ai_family, p->ai_socktype, p->ai_protocol)) < 0)
            continue;  /* Socket failed, try the next */

        /* Eliminates "Address already in use" error from bind */
        setsockopt(listenfd, SOL_SOCKET, SO_REUSEADDR,    //line:netp:csapp:setsockopt
                   (const void *)&optval , sizeof(int));

        /* Bind the descriptor to the address */
        if (bind(listenfd, p->ai_addr, p->ai_addrlen) == 0)
            break; /* Success */
        if (close(listenfd) < 0) { /* Bind failed, try the next */
            fprintf(stderr, "open_listenfd close failed: %s\n", strerror(errno));
            return -1;
        }
    }


    /* Clean up */
    freeaddrinfo(listp);
    if (!p) /* No address worked */
        return -1;

    /* Make it a listening socket ready to accept connection requests */
    if (listen(listenfd, LISTENQ) < 0) {
        close(listenfd);
	return -1;
    }
    return listenfd;
}
/* $end open_listenfd */

//https://man7.org/tlpi/code/online/dist/sockets/read_line.c
ssize_t readLine(int fd, void *buffer, size_t n)
{
    ssize_t numRead;                    /* # of bytes fetched by last read() */
    size_t totRead;                     /* Total bytes read so far */
    char *buf;
    char ch;

    if (n <= 0 || buffer == NULL) {
        errno = EINVAL;
        return -1;
    }

    buf = buffer;                       /* No pointer arithmetic on "void *" */

    totRead = 0;
    for (;;) {
        numRead = read(fd, &ch, 1);

        if (numRead == -1) {
            if (errno == EINTR)         /* Interrupted --> restart read() */
                continue;
            else
                return -1;              /* Some other error */

        } else if (numRead == 0) {      /* EOF */
            if (totRead == 0)           /* No bytes read; return 0 */
                return 0;
            else                        /* Some bytes read; add '\0' */
                break;

        } else {                        /* 'numRead' must be 1 if we get here */
            if (totRead < n - 1) {      /* Discard > (n - 1) bytes */
                totRead++;
                *buf++ = ch;
            }

            if (ch == '\n')
                break;
        }
    }

    *buf = '\0';
    return totRead;
}

/* $end csapp.c */