write_buf.c

[詳解]

/*++
/* NAME
/*  write_buf 3
/* SUMMARY
/*  write buffer or bust
/* SYNOPSIS
/*  #include <iostuff.h>
/*
/*  ssize_t write_buf(fd, buf, len, timeout)
/*  int fd;
/*  const char *buf;
/*  ssize_t len;
/*  int timeout;
/* DESCRIPTION
/*  write_buf() writes a buffer to the named stream in as many
/*  fragments as needed, and returns the number of bytes written,
/*  which is always the number requested or an error indication.
/*
/*  Arguments:
/* .IP fd
/*  File descriptor in the range 0..FD_SETSIZE.
/* .IP buf
/*  Address of data to be written.
/* .IP len
/*  Amount of data to be written.
/* .IP timeout
/*  Bounds the time in seconds to wait until \fIfd\fD becomes writable.
/*  A value <= 0 means do not wait; this is useful only when \fIfd\fR
/*  uses blocking I/O.
/* DIAGNOSTICS
/*  write_buf() returns -1 in case of trouble. The global \fIerrno\fR
/*  variable reflects the nature of the problem.
/* LICENSE
/* .ad
/* .fi
/*  The Secure Mailer license must be distributed with this software.
/* AUTHOR(S)
/*  Wietse Venema
/*  IBM T.J. Watson Research
/*  P.O. Box 704
/*  Yorktown Heights, NY 10598, USA
/*--*/

/* System library. */

#include <sys_defs.h>
#include <unistd.h>
#include <errno.h>
#include <time.h>

/* Utility library. */

#include <msg.h>
#include <iostuff.h>

/* write_buf - write buffer or bust */

ssize_t write_buf(int fd, const char *buf, ssize_t len, int timeout)
{
    const char *start = buf;
    ssize_t count;
    time_t  expire;
    int     time_left = timeout;

    if (time_left > 0)
    expire = time((time_t *) 0) + time_left;

    while (len > 0) {
    if (time_left > 0 && write_wait(fd, time_left) < 0)
        return (-1);
    if ((count = write(fd, buf, len)) < 0) {
        if ((errno == EAGAIN && time_left > 0) || errno == EINTR)
         /* void */ ;
        else
        return (-1);
    } else {
        buf += count;
        len -= count;
    }
    if (len > 0 && time_left > 0) {
        time_left = expire - time((time_t *) 0);
        if (time_left <= 0) {
        errno = ETIMEDOUT;
        return (-1);
        }
    }
    }
    return (buf - start);
}