(split) LDP v3.24 -> v3.29 の定型的な変更内容を反映。

[linuxjm/LDP_man-pages.git] / release / man2 / select_tut.2

.\" This manpage is copyright (C) 2001 Paul Sheer.
.\"
.\" Permission is granted to make and distribute verbatim copies of this
.\" manual provided the copyright notice and this permission notice are
.\" preserved on all copies.
.\"
.\" Permission is granted to copy and distribute modified versions of this
.\" manual under the conditions for verbatim copying, provided that the
.\" entire resulting derived work is distributed under the terms of a
.\" permission notice identical to this one.
.\"
.\" Since the Linux kernel and libraries are constantly changing, this
.\" manual page may be incorrect or out-of-date.  The author(s) assume no
.\" responsibility for errors or omissions, or for damages resulting from
.\" the use of the information contained herein.  The author(s) may not
.\" have taken the same level of care in the production of this manual,
.\" which is licensed free of charge, as they might when working
.\" professionally.
.\"
.\" Formatted or processed versions of this manual, if unaccompanied by
.\" the source, must acknowledge the copyright and authors of this work.
.\"
.\" very minor changes, aeb
.\"
.\" Modified 5 June 2002, Michael Kerrisk <mtk.manpages@gmail.com>
.\" 2006-05-13, mtk, removed much material that is redundant with select.2
.\"             various other changes
.\" 2008-01-26, mtk, substantial changes and rewrites
.\"
.\" Translated 2002-02-21, NAKANO Takeo <nakano@apm.seikei.ac.jp>
.\" Updated 2002-09-23, Akihiro MOTOKI <amotoki@dd.iij4u.or.jp>
.\" Updated 2005-03-15, Akihiro MOTOKI <amotoki@dd.iij4u.or.jp>
.\" Updated 2006-07-21, Akihiro MOTOKI, LDP v2.36
.\" Updated 2009-02-13, Akihiro MOTOKI, LDP v3.18
.\"
.\"WORD:        file descriptor         ¥Õ¥¡¥¤¥ë¥Ç¥£¥¹¥¯¥ê¥×¥¿
.\"WORD:        exceptional condition   Îã³°¾õÂÖ
.\"
.TH SELECT_TUT 2 2010-06-10 "Linux" "Linux Programmer's Manual"
.SH ̾Á°
select, pselect, FD_CLR, FD_ISSET, FD_SET, FD_ZERO \- Ʊ´ü I/O ¤Î¿½Å²½
.SH ½ñ¼°
.nf
/* POSIX.1-2001 ¤Ë½¾¤¦¾ì¹ç */
.br
.B #include <sys/select.h>
.sp
/* °ÊÁ°¤Îµ¬³Ê¤Ë½¾¤¦¾ì¹ç */
.br
.B #include <sys/time.h>
.br
.B #include <sys/types.h>
.br
.B #include <unistd.h>
.sp
.BI "int select(int " nfds ", fd_set *" readfds ", fd_set *" writefds ,
.BI "           fd_set *" exceptfds ", struct timeval *" utimeout );
.sp
.BI "void FD_CLR(int " fd ", fd_set *" set );
.br
.BI "int  FD_ISSET(int " fd ", fd_set *" set );
.br
.BI "void FD_SET(int " fd ", fd_set *" set );
.br
.BI "void FD_ZERO(fd_set *" set );
.sp
.B #include <sys/select.h>
.sp
.BI "int pselect(int " nfds ", fd_set *" readfds ", fd_set *" writefds ,
.BI "            fd_set *" exceptfds ", const struct timespec *" ntimeout ,
.BI "            const sigset_t *" sigmask );
.fi
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.SH ÀâÌÀ
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.nf
struct timeval {
    time_t tv_sec;    /* seconds */
    long tv_usec;     /* microseconds */
};
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.nf
struct timespec {
    long tv_sec;    /* seconds */
    long tv_nsec;   /* nanoseconds */
};
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.nf
static volatile sig_atomic_t got_SIGCHLD = 0;

static void
child_sig_handler(int sig)
{
    got_SIGCHLD = 1;
}

int
main(int argc, char *argv[])
{
    sigset_t sigmask, empty_mask;
    struct sigaction sa;
    fd_set readfds, writefds, exceptfds;
    int r;

    sigemptyset(&sigmask);
    sigaddset(&sigmask, SIGCHLD);
    if (sigprocmask(SIG_BLOCK, &sigmask, NULL) == \-1) {
        perror("sigprocmask");
        exit(EXIT_FAILURE);
    }

    sa.sa_flags = 0;
    sa.sa_handler = child_sig_handler;
    sigemptyset(&sa.sa_mask);
    if (sigaction(SIGCHLD, &sa, NULL) == \-1) {
        perror("sigaction");
        exit(EXIT_FAILURE);
    }

    sigemptyset(&empty_mask);

    for (;;) {          /* main loop */
        /* Initialize readfds, writefds, and exceptfds
           before the pselect() call. (Code omitted.) */

        r = pselect(nfds, &readfds, &writefds, &exceptfds,
                    NULL, &empty_mask);
        if (r == \-1 && errno != EINTR) {
            /* Handle error */
        }

        if (got_SIGCHLD) {
            got_SIGCHLD = 0;

            /* Handle signalled event here; e.g., wait() for all
               terminated children. (Code omitted.) */
        }

        /* main body of program */
    }
}
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    struct timeval tv;
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.nf
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/time.h>
#include <sys/types.h>
#include <string.h>
#include <signal.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <errno.h>

static int forward_port;

#undef max
#define max(x,y) ((x) > (y) ? (x) : (y))

static int
listen_socket(int listen_port)
{
    struct sockaddr_in a;
    int s;
    int yes;

    if ((s = socket(AF_INET, SOCK_STREAM, 0)) == \-1) {
        perror("socket");
        return \-1;
    }
    yes = 1;
    if (setsockopt(s, SOL_SOCKET, SO_REUSEADDR,
            (char *) &yes, sizeof(yes)) == \-1) {
        perror("setsockopt");
        close(s);
        return \-1;
    }
    memset(&a, 0, sizeof(a));
    a.sin_port = htons(listen_port);
    a.sin_family = AF_INET;
    if (bind(s, (struct sockaddr *) &a, sizeof(a)) == \-1) {
        perror("bind");
        close(s);
        return \-1;
    }
    printf("accepting connections on port %d\\n", listen_port);
    listen(s, 10);
    return s;
}

static int
connect_socket(int connect_port, char *address)
{
    struct sockaddr_in a;
    int s;

    if ((s = socket(AF_INET, SOCK_STREAM, 0)) == \-1) {
        perror("socket");
        close(s);
        return \-1;
    }

    memset(&a, 0, sizeof(a));
    a.sin_port = htons(connect_port);
    a.sin_family = AF_INET;

    if (!inet_aton(address, (struct in_addr *) &a.sin_addr.s_addr)) {
        perror("bad IP address format");
        close(s);
        return \-1;
    }

    if (connect(s, (struct sockaddr *) &a, sizeof(a)) == \-1) {
        perror("connect()");
        shutdown(s, SHUT_RDWR);
        close(s);
        return \-1;
    }
    return s;
}

#define SHUT_FD1 do {                                \\
                     if (fd1 >= 0) {                 \\
                         shutdown(fd1, SHUT_RDWR);   \\
                         close(fd1);                 \\
                         fd1 = \-1;                   \\
                     }                               \\
                 } while (0)

#define SHUT_FD2 do {                                \\
                     if (fd2 >= 0) {                 \\
                         shutdown(fd2, SHUT_RDWR);   \\
                         close(fd2);                 \\
                         fd2 = \-1;                   \\
                     }                               \\
                 } while (0)

#define BUF_SIZE 1024

int
main(int argc, char *argv[])
{
    int h;
    int fd1 = \-1, fd2 = \-1;
    char buf1[BUF_SIZE], buf2[BUF_SIZE];
    int buf1_avail, buf1_written;
    int buf2_avail, buf2_written;

    if (argc != 4) {
        fprintf(stderr, "Usage\\n\\tfwd <listen-port> "
                 "<forward-to-port> <forward-to-ip-address>\\n");
        exit(EXIT_FAILURE);
    }

    signal(SIGPIPE, SIG_IGN);

    forward_port = atoi(argv[2]);

    h = listen_socket(atoi(argv[1]));
    if (h == \-1)
        exit(EXIT_FAILURE);

    for (;;) {
        int r, nfds = 0;
        fd_set rd, wr, er;

        FD_ZERO(&rd);
        FD_ZERO(&wr);
        FD_ZERO(&er);
        FD_SET(h, &rd);
        nfds = max(nfds, h);
        if (fd1 > 0 && buf1_avail < BUF_SIZE) {
            FD_SET(fd1, &rd);
            nfds = max(nfds, fd1);
        }
        if (fd2 > 0 && buf2_avail < BUF_SIZE) {
            FD_SET(fd2, &rd);
            nfds = max(nfds, fd2);
        }
        if (fd1 > 0 && buf2_avail \- buf2_written > 0) {
            FD_SET(fd1, &wr);
            nfds = max(nfds, fd1);
        }
        if (fd2 > 0 && buf1_avail \- buf1_written > 0) {
            FD_SET(fd2, &wr);
            nfds = max(nfds, fd2);
        }
        if (fd1 > 0) {
            FD_SET(fd1, &er);
            nfds = max(nfds, fd1);
        }
        if (fd2 > 0) {
            FD_SET(fd2, &er);
            nfds = max(nfds, fd2);
        }

        r = select(nfds + 1, &rd, &wr, &er, NULL);

        if (r == \-1 && errno == EINTR)
            continue;

        if (r == \-1) {
            perror("select()");
            exit(EXIT_FAILURE);
        }

        if (FD_ISSET(h, &rd)) {
            unsigned int l;
            struct sockaddr_in client_address;

            memset(&client_address, 0, l = sizeof(client_address));
            r = accept(h, (struct sockaddr *) &client_address, &l);
            if (r == \-1) {
                perror("accept()");
            } else {
                SHUT_FD1;
                SHUT_FD2;
                buf1_avail = buf1_written = 0;
                buf2_avail = buf2_written = 0;
                fd1 = r;
                fd2 = connect_socket(forward_port, argv[3]);
                if (fd2 == \-1)
                    SHUT_FD1;
                else
                    printf("connect from %s\\n",
                            inet_ntoa(client_address.sin_addr));
            }
        }

        /* NB: read oob data before normal reads */

        if (fd1 > 0)
            if (FD_ISSET(fd1, &er)) {
                char c;

                r = recv(fd1, &c, 1, MSG_OOB);
                if (r < 1)
                    SHUT_FD1;
                else
                    send(fd2, &c, 1, MSG_OOB);
            }
        if (fd2 > 0)
            if (FD_ISSET(fd2, &er)) {
                char c;

                r = recv(fd2, &c, 1, MSG_OOB);
                if (r < 1)
                    SHUT_FD2;
                else
                    send(fd1, &c, 1, MSG_OOB);
            }
        if (fd1 > 0)
            if (FD_ISSET(fd1, &rd)) {
                r = read(fd1, buf1 + buf1_avail,
                          BUF_SIZE \- buf1_avail);
                if (r < 1)
                    SHUT_FD1;
                else
                    buf1_avail += r;
            }
        if (fd2 > 0)
            if (FD_ISSET(fd2, &rd)) {
                r = read(fd2, buf2 + buf2_avail,
                          BUF_SIZE \- buf2_avail);
                if (r < 1)
                    SHUT_FD2;
                else
                    buf2_avail += r;
            }
        if (fd1 > 0)
            if (FD_ISSET(fd1, &wr)) {
                r = write(fd1, buf2 + buf2_written,
                           buf2_avail \- buf2_written);
                if (r < 1)
                    SHUT_FD1;
                else
                    buf2_written += r;
            }
        if (fd2 > 0)
            if (FD_ISSET(fd2, &wr)) {
                r = write(fd2, buf1 + buf1_written,
                           buf1_avail \- buf1_written);
                if (r < 1)
                    SHUT_FD2;
                else
                    buf1_written += r;
            }

        /* check if write data has caught read data */

        if (buf1_written == buf1_avail)
            buf1_written = buf1_avail = 0;
        if (buf2_written == buf2_avail)
            buf2_written = buf2_avail = 0;

        /* one side has closed the connection, keep
           writing to the other side until empty */

        if (fd1 < 0 && buf1_avail \- buf1_written == 0)
            SHUT_FD2;
        if (fd2 < 0 && buf2_avail \- buf2_written == 0)
            SHUT_FD1;
    }
    exit(EXIT_SUCCESS);
}
.fi
.PP
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.SH ´ØÏ¢¹àÌÜ
.BR accept (2),
.BR connect (2),
.BR ioctl (2),
.BR poll (2),
.BR read (2),
.BR recv (2),
.BR select (2),
.BR send (2),
.BR sigprocmask (2),
.BR write (2),
.BR sigaddset (3),
.BR sigdelset (3),
.BR sigemptyset (3),
.BR sigfillset (3),
.BR sigismember (3),
.BR epoll (7)
.\" .SH AUTHORS
.\" This man page was written by Paul Sheer.