import base64
import errno
import hashlib
import logging
import os
import os.path
import re
import select
import signal
import socket
import subprocess
import threading
import time
import tempfile

logger = logging.getLogger("sshfuncs")

def log(msg, level, out = None, err = None):
    if out:
        msg += " - OUT: %s " % out

    if err:
        msg += " - ERROR: %s " % err

    logger.log(level, msg)


if hasattr(os, "devnull"):
    DEV_NULL = os.devnull
else:
    DEV_NULL = "/dev/null"

SHELL_SAFE = re.compile('^[-a-zA-Z0-9_=+:.,/]*$')

class STDOUT: 
    """
    Special value that when given to rspawn in stderr causes stderr to 
    redirect to whatever stdout was redirected to.
    """

class RUNNING:
    """
    Process is still running
    """

class FINISHED:
    """
    Process is finished
    """

class NOT_STARTED:
    """
    Process hasn't started running yet (this should be very rare)
    """

hostbyname_cache = dict()
hostbyname_cache_lock = threading.Lock()

def gethostbyname(host):
    global hostbyname_cache
    global hostbyname_cache_lock
    
    hostbyname = hostbyname_cache.get(host)
    if not hostbyname:
        with hostbyname_cache_lock:
            hostbyname = socket.gethostbyname(host)
            hostbyname_cache[host] = hostbyname

            msg = " Added hostbyname %s - %s " % (host, hostbyname)
            log(msg, logging.DEBUG)

    return hostbyname

OPENSSH_HAS_PERSIST = None

def openssh_has_persist():
    """ The ssh_config options ControlMaster and ControlPersist allow to
    reuse a same network connection for multiple ssh sessions. In this 
    way limitations on number of open ssh connections can be bypassed.
    However, older versions of openSSH do not support this feature.
    This function is used to determine if ssh connection persist features
    can be used.
    """
    global OPENSSH_HAS_PERSIST
    if OPENSSH_HAS_PERSIST is None:
        proc = subprocess.Popen(["ssh","-v"],
            stdout = subprocess.PIPE,
            stderr = subprocess.STDOUT,
            stdin = open("/dev/null","r") )
        out,err = proc.communicate()
        proc.wait()
        
        vre = re.compile(r'OpenSSH_(?:[6-9]|5[.][8-9]|5[.][1-9][0-9]|[1-9][0-9]).*', re.I)
        OPENSSH_HAS_PERSIST = bool(vre.match(out))
    return OPENSSH_HAS_PERSIST

def make_server_key_args(server_key, host, port):
    """ Returns a reference to a temporary known_hosts file, to which 
    the server key has been added. 
    
    Make sure to hold onto the temp file reference until the process is 
    done with it

    :param server_key: the server public key
    :type server_key: str

    :param host: the hostname
    :type host: str

    :param port: the ssh port
    :type port: str

    """
    if port is not None:
        host = '%s:%s' % (host, str(port))

    # Create a temporary server key file
    tmp_known_hosts = tempfile.NamedTemporaryFile()
   
    hostbyname = gethostbyname(host) 

    # Add the intended host key
    tmp_known_hosts.write('%s,%s %s\n' % (host, hostbyname, server_key))
    
    # If we're not in strict mode, add user-configured keys
    if os.environ.get('NEPI_STRICT_AUTH_MODE',"").lower() not in ('1','true','on'):
        user_hosts_path = '%s/.ssh/known_hosts' % (os.environ.get('HOME',""),)
        if os.access(user_hosts_path, os.R_OK):
            f = open(user_hosts_path, "r")
            tmp_known_hosts.write(f.read())
            f.close()
        
    tmp_known_hosts.flush()
    
    return tmp_known_hosts

def make_control_path(agent, forward_x11):
    ctrl_path = "/tmp/nepi_ssh"

    if agent:
        ctrl_path +="_a"

    if forward_x11:
        ctrl_path +="_x"

    ctrl_path += "-%r@%h:%p"

    return ctrl_path

def shell_escape(s):
    """ Escapes strings so that they are safe to use as command-line 
    arguments """
    if SHELL_SAFE.match(s):
        # safe string - no escaping needed
        return s
    else:
        # unsafe string - escape
        def escp(c):
            if (32 <= ord(c) < 127 or c in ('\r','\n','\t')) and c not in ("'",'"'):
                return c
            else:
                return "'$'\\x%02x''" % (ord(c),)
        s = ''.join(map(escp,s))
        return "'%s'" % (s,)

def eintr_retry(func):
    """Retries a function invocation when a EINTR occurs"""
    import functools
    @functools.wraps(func)
    def rv(*p, **kw):
        retry = kw.pop("_retry", False)
        for i in xrange(0 if retry else 4):
            try:
                return func(*p, **kw)
            except (select.error, socket.error), args:
                if args[0] == errno.EINTR:
                    continue
                else:
                    raise 
            except OSError, e:
                if e.errno == errno.EINTR:
                    continue
                else:
                    raise
        else:
            return func(*p, **kw)
    return rv

def rexec(command, host, user, 
        port = None, 
        agent = True,
        sudo = False,
        stdin = None,
        identity = None,
        server_key = None,
        env = None,
        tty = False,
        timeout = None,
        retry = 3,
        err_on_timeout = True,
        connect_timeout = 30,
        persistent = True,
        forward_x11 = False,
        strict_host_checking = True):
    """
    Executes a remote command, returns ((stdout,stderr),process)
    """
    
    tmp_known_hosts = None
    hostip = gethostbyname(host)

    args = ['ssh', '-C',
            # Don't bother with localhost. Makes test easier
            '-o', 'NoHostAuthenticationForLocalhost=yes',
            '-o', 'ConnectTimeout=%d' % (int(connect_timeout),),
            '-o', 'ConnectionAttempts=3',
            '-o', 'ServerAliveInterval=30',
            '-o', 'TCPKeepAlive=yes',
            '-l', user, hostip or host]

    if persistent and openssh_has_persist():
        args.extend([
            '-o', 'ControlMaster=auto',
            '-o', 'ControlPath=%s' % (make_control_path(agent, forward_x11),),
            '-o', 'ControlPersist=60' ])

    if not strict_host_checking:
        # Do not check for Host key. Unsafe.
        args.extend(['-o', 'StrictHostKeyChecking=no'])

    if agent:
        args.append('-A')

    if port:
        args.append('-p%d' % port)

    if identity:
        args.extend(('-i', identity))

    if tty:
        args.append('-t')
        args.append('-t')

    if forward_x11:
        args.append('-X')

    if server_key:
        # Create a temporary server key file
        tmp_known_hosts = make_server_key_args(server_key, host, port)
        args.extend(['-o', 'UserKnownHostsFile=%s' % (tmp_known_hosts.name,)])

    args.append(command)

    for x in xrange(retry):
        # connects to the remote host and starts a remote connection
        proc = subprocess.Popen(args,
                env = env,
                stdout = subprocess.PIPE,
                stdin = subprocess.PIPE, 
                stderr = subprocess.PIPE)
        
        # attach tempfile object to the process, to make sure the file stays
        # alive until the process is finished with it
        proc._known_hosts = tmp_known_hosts
    
        try:
            out, err = _communicate(proc, stdin, timeout, err_on_timeout)
            msg = " rexec - host %s - command %s " % (host, " ".join(args))
            log(msg, logging.DEBUG, out, err)

            if proc.poll():
                skip = False

                if err.strip().startswith('ssh: ') or err.strip().startswith('mux_client_hello_exchange: '):
                    # SSH error, can safely retry
                    skip = True 
                elif retry:
                    # Probably timed out or plain failed but can retry
                    skip = True 
                
                if skip:
                    t = x*2
                    msg = "SLEEPING %d ... ATEMPT %d - host %s - command %s " % ( 
                            t, x, host, " ".join(args))
                    log(msg, logging.DEBUG)

                    time.sleep(t)
                    continue
            break
        except RuntimeError, e:
            msg = " rexec EXCEPTION - host %s - command %s - TIMEOUT -> %s" % (host, " ".join(args), e.args)
            log(msg, logging.DEBUG, out, err)

            if retry <= 0:
                raise
            retry -= 1
        
    return ((out, err), proc)

def rcopy(source, dest,
        port = None, 
        agent = True, 
        recursive = False,
        identity = None,
        server_key = None,
        retry = 3,
        strict_host_checking = True):
    """
    Copies from/to remote sites.
    
    Source and destination should have the user and host encoded
    as per scp specs.
    
    If source is a file object, a special mode will be used to
    create the remote file with the same contents.
    
    If dest is a file object, the remote file (source) will be
    read and written into dest.
    
    In these modes, recursive cannot be True.
    
    Source can be a list of files to copy to a single destination,
    in which case it is advised that the destination be a folder.
    """
    
    if isinstance(source, file) and source.tell() == 0:
        source = source.name
    elif hasattr(source, 'read'):
        tmp = tempfile.NamedTemporaryFile()
        while True:
            buf = source.read(65536)
            if buf:
                tmp.write(buf)
            else:
                break
        tmp.seek(0)
        source = tmp.name
    
    if isinstance(source, file) or isinstance(dest, file) \
            or hasattr(source, 'read')  or hasattr(dest, 'write'):
        assert not recursive
        
        # Parse source/destination as <user>@<server>:<path>
        if isinstance(dest, basestring) and ':' in dest:
            remspec, path = dest.split(':',1)
        elif isinstance(source, basestring) and ':' in source:
            remspec, path = source.split(':',1)
        else:
            raise ValueError, "Both endpoints cannot be local"
        user,host = remspec.rsplit('@',1)
        
        tmp_known_hosts = None
        hostip = gethostbyname(host)
        
        args = ['ssh', '-l', user, '-C',
                # Don't bother with localhost. Makes test easier
                '-o', 'NoHostAuthenticationForLocalhost=yes',
                '-o', 'ConnectTimeout=60',
                '-o', 'ConnectionAttempts=3',
                '-o', 'ServerAliveInterval=30',
                '-o', 'TCPKeepAlive=yes',
                hostip or host ]

        if openssh_has_persist():
            args.extend([
                '-o', 'ControlMaster=auto',
                '-o', 'ControlPath=%s' % (make_control_path(agent, False),),
                '-o', 'ControlPersist=60' ])

        if port:
            args.append('-P%d' % port)

        if identity:
            args.extend(('-i', identity))

        if server_key:
            # Create a temporary server key file
            tmp_known_hosts = make_server_key_args(server_key, host, port)
            args.extend(['-o', 'UserKnownHostsFile=%s' % (tmp_known_hosts.name,)])
        
        if isinstance(source, file) or hasattr(source, 'read'):
            args.append('cat > %s' % (shell_escape(path),))
        elif isinstance(dest, file) or hasattr(dest, 'write'):
            args.append('cat %s' % (shell_escape(path),))
        else:
            raise AssertionError, "Unreachable code reached! :-Q"
        
        # connects to the remote host and starts a remote connection
        if isinstance(source, file):
            proc = subprocess.Popen(args, 
                    stdout = open('/dev/null','w'),
                    stderr = subprocess.PIPE,
                    stdin = source)
            err = proc.stderr.read()
            proc._known_hosts = tmp_known_hosts
            eintr_retry(proc.wait)()
            return ((None,err), proc)
        elif isinstance(dest, file):
            proc = subprocess.Popen(args, 
                    stdout = open('/dev/null','w'),
                    stderr = subprocess.PIPE,
                    stdin = source)
            err = proc.stderr.read()
            proc._known_hosts = tmp_known_hosts
            eintr_retry(proc.wait)()
            return ((None,err), proc)
        elif hasattr(source, 'read'):
            # file-like (but not file) source
            proc = subprocess.Popen(args, 
                    stdout = open('/dev/null','w'),
                    stderr = subprocess.PIPE,
                    stdin = subprocess.PIPE)
            
            buf = None
            err = []
            while True:
                if not buf:
                    buf = source.read(4096)
                if not buf:
                    #EOF
                    break
                
                rdrdy, wrdy, broken = select.select(
                    [proc.stderr],
                    [proc.stdin],
                    [proc.stderr,proc.stdin])
                
                if proc.stderr in rdrdy:
                    # use os.read for fully unbuffered behavior
                    err.append(os.read(proc.stderr.fileno(), 4096))
                
                if proc.stdin in wrdy:
                    proc.stdin.write(buf)
                    buf = None
                
                if broken:
                    break
            proc.stdin.close()
            err.append(proc.stderr.read())
                
            proc._known_hosts = tmp_known_hosts
            eintr_retry(proc.wait)()
            return ((None,''.join(err)), proc)
        elif hasattr(dest, 'write'):
            # file-like (but not file) dest
            proc = subprocess.Popen(args, 
                    stdout = subprocess.PIPE,
                    stderr = subprocess.PIPE,
                    stdin = open('/dev/null','w'))
            
            buf = None
            err = []
            while True:
                rdrdy, wrdy, broken = select.select(
                    [proc.stderr, proc.stdout],
                    [],
                    [proc.stderr, proc.stdout])
                
                if proc.stderr in rdrdy:
                    # use os.read for fully unbuffered behavior
                    err.append(os.read(proc.stderr.fileno(), 4096))
                
                if proc.stdout in rdrdy:
                    # use os.read for fully unbuffered behavior
                    buf = os.read(proc.stdout.fileno(), 4096)
                    dest.write(buf)
                    
                    if not buf:
                        #EOF
                        break
                
                if broken:
                    break
            err.append(proc.stderr.read())
                
            proc._known_hosts = tmp_known_hosts
            eintr_retry(proc.wait)()
            return ((None,''.join(err)), proc)
        else:
            raise AssertionError, "Unreachable code reached! :-Q"
    else:
        # Parse destination as <user>@<server>:<path>
        if isinstance(dest, basestring) and ':' in dest:
            remspec, path = dest.split(':',1)
        elif isinstance(source, basestring) and ':' in source:
            remspec, path = source.split(':',1)
        else:
            raise ValueError, "Both endpoints cannot be local"
        user,host = remspec.rsplit('@',1)
        
        # plain scp
        tmp_known_hosts = None

        args = ['scp', '-q', '-p', '-C',
                # Don't bother with localhost. Makes test easier
                '-o', 'NoHostAuthenticationForLocalhost=yes',
                '-o', 'ConnectTimeout=60',
                '-o', 'ConnectionAttempts=3',
                '-o', 'ServerAliveInterval=30',
                '-o', 'TCPKeepAlive=yes' ]
                
        if port:
            args.append('-P%d' % port)

        if recursive:
            args.append('-r')

        if identity:
            args.extend(('-i', identity))

        if server_key:
            # Create a temporary server key file
            tmp_known_hosts = make_server_key_args(server_key, host, port)
            args.extend(['-o', 'UserKnownHostsFile=%s' % (tmp_known_hosts.name,)])

        if not strict_host_checking:
            # Do not check for Host key. Unsafe.
            args.extend(['-o', 'StrictHostKeyChecking=no'])

        if isinstance(source,list):
            args.extend(source)
        else:
            if openssh_has_persist():
                args.extend([
                    '-o', 'ControlMaster=auto',
                    '-o', 'ControlPath=%s' % (make_control_path(agent, False),)
                    ])
            args.append(source)

        args.append(dest)

        for x in xrange(retry):
            # connects to the remote host and starts a remote connection
            proc = subprocess.Popen(args,
                    stdout = subprocess.PIPE,
                    stdin = subprocess.PIPE, 
                    stderr = subprocess.PIPE)
            
            # attach tempfile object to the process, to make sure the file stays
            # alive until the process is finished with it
            proc._known_hosts = tmp_known_hosts
        
            try:
                (out, err) = proc.communicate()
                eintr_retry(proc.wait)()
                msg = " rcopy - host %s - command %s " % (host, " ".join(args))
                log(msg, logging.DEBUG, out, err)

                if proc.poll():
                    t = x*2
                    msg = "SLEEPING %d ... ATEMPT %d - host %s - command %s " % ( 
                            t, x, host, " ".join(args))
                    log(msg, logging.DEBUG)

                    time.sleep(t)
                    continue

                break
            except RuntimeError, e:
                msg = " rcopy EXCEPTION - host %s - command %s - TIMEOUT -> %s" % (host, " ".join(args), e.args)
                log(msg, logging.DEBUG, out, err)

                if retry <= 0:
                    raise
                retry -= 1
            
        return ((out, err), proc)

def rspawn(command, pidfile, 
        stdout = '/dev/null', 
        stderr = STDOUT, 
        stdin = '/dev/null', 
        home = None, 
        create_home = False, 
        sudo = False,
        host = None, 
        port = None, 
        user = None, 
        agent = None, 
        identity = None, 
        server_key = None,
        tty = False):
    """
    Spawn a remote command such that it will continue working asynchronously.
    
    Parameters:
        command: the command to run - it should be a single line.
        
        pidfile: path of a (ideally unique to this task) pidfile for tracking the process.
        
        stdout: path of a file to redirect standard output to - must be a string.
            Defaults to /dev/null
        stderr: path of a file to redirect standard error to - string or the special STDOUT value
            to redirect to the same file stdout was redirected to. Defaults to STDOUT.
        stdin: path of a file with input to be piped into the command's standard input
        
        home: path of a folder to use as working directory - should exist, unless you specify create_home
        
        create_home: if True, the home folder will be created first with mkdir -p
        
        sudo: whether the command needs to be executed as root
        
        host/port/user/agent/identity: see rexec
    
    Returns:
        (stdout, stderr), process
        
        Of the spawning process, which only captures errors at spawning time.
        Usually only useful for diagnostics.
    """
    # Start process in a "daemonized" way, using nohup and heavy
    # stdin/out redirection to avoid connection issues
    if stderr is STDOUT:
        stderr = '&1'
    else:
        stderr = ' ' + stderr
    
    daemon_command = '{ { %(command)s  > %(stdout)s 2>%(stderr)s < %(stdin)s & } ; echo $! 1 > %(pidfile)s ; }' % {
        'command' : command,
        'pidfile' : shell_escape(pidfile),
        'stdout' : stdout,
        'stderr' : stderr,
        'stdin' : stdin,
    }
    
    cmd = "%(create)s%(gohome)s rm -f %(pidfile)s ; %(sudo)s nohup bash -c %(command)s " % {
            'command' : shell_escape(daemon_command),
            'sudo' : 'sudo -S' if sudo else '',
            'pidfile' : shell_escape(pidfile),
            'gohome' : 'cd %s ; ' % (shell_escape(home),) if home else '',
            'create' : 'mkdir -p %s ; ' % (shell_escape(home),) if create_home and home else '',
        }

    (out,err),proc = rexec(
        cmd,
        host = host,
        port = port,
        user = user,
        agent = agent,
        identity = identity,
        server_key = server_key,
        tty = tty ,
        )
    
    if proc.wait():
        raise RuntimeError, "Failed to set up application on host %s: %s %s" % (host, out,err,)

    return ((out, err), proc)

@eintr_retry
def rcheckpid(pidfile,
        host = None, 
        port = None, 
        user = None, 
        agent = None, 
        identity = None,
        server_key = None):
    """
    Check the pidfile of a process spawned with remote_spawn.
    
    Parameters:
        pidfile: the pidfile passed to remote_span
        
        host/port/user/agent/identity: see rexec
    
    Returns:
        
        A (pid, ppid) tuple useful for calling remote_status and remote_kill,
        or None if the pidfile isn't valid yet (maybe the process is still starting).
    """

    (out,err),proc = rexec(
        "cat %(pidfile)s" % {
            'pidfile' : pidfile,
        },
        host = host,
        port = port,
        user = user,
        agent = agent,
        identity = identity,
        server_key = server_key
        )
        
    if proc.wait():
        return None
    
    if out:
        try:
            return map(int,out.strip().split(' ',1))
        except:
            # Ignore, many ways to fail that don't matter that much
            return None

@eintr_retry
def rstatus(pid, ppid, 
        host = None, 
        port = None, 
        user = None, 
        agent = None, 
        identity = None,
        server_key = None):
    """
    Check the status of a process spawned with remote_spawn.
    
    Parameters:
        pid/ppid: pid and parent-pid of the spawned process. See remote_check_pid
        
        host/port/user/agent/identity: see rexec
    
    Returns:
        
        One of NOT_STARTED, RUNNING, FINISHED
    """

    (out,err),proc = rexec(
        # Check only by pid. pid+ppid does not always work (especially with sudo) 
        " (( ps --pid %(pid)d -o pid | grep -c %(pid)d && echo 'wait')  || echo 'done' ) | tail -n 1" % {
            'ppid' : ppid,
            'pid' : pid,
        },
        host = host,
        port = port,
        user = user,
        agent = agent,
        identity = identity,
        server_key = server_key
        )
    
    if proc.wait():
        return NOT_STARTED
    
    status = False
    if err:
        if err.strip().find("Error, do this: mount -t proc none /proc") >= 0:
            status = True
    elif out:
        status = (out.strip() == 'wait')
    else:
        return NOT_STARTED
    return RUNNING if status else FINISHED

@eintr_retry
def rkill(pid, ppid,
        host = None, 
        port = None, 
        user = None, 
        agent = None, 
        sudo = False,
        identity = None, 
        server_key = None, 
        nowait = False):
    """
    Kill a process spawned with remote_spawn.
    
    First tries a SIGTERM, and if the process does not end in 10 seconds,
    it sends a SIGKILL.
    
    Parameters:
        pid/ppid: pid and parent-pid of the spawned process. See remote_check_pid
        
        sudo: whether the command was run with sudo - careful killing like this.
        
        host/port/user/agent/identity: see rexec
    
    Returns:
        
        Nothing, should have killed the process
    """
    
    subkill = "$(ps --ppid %(pid)d -o pid h)" % { 'pid' : pid }
    cmd = """
SUBKILL="%(subkill)s" ;
%(sudo)s kill -- -%(pid)d $SUBKILL || /bin/true
%(sudo)s kill %(pid)d $SUBKILL || /bin/true
for x in 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 ; do 
    sleep 0.2 
    if [ `ps --pid %(pid)d -o pid | grep -c %(pid)d` == '0' ]; then
        break
    else
        %(sudo)s kill -- -%(pid)d $SUBKILL || /bin/true
        %(sudo)s kill %(pid)d $SUBKILL || /bin/true
    fi
    sleep 1.8
done
if [ `ps --pid %(pid)d -o pid | grep -c %(pid)d` != '0' ]; then
    %(sudo)s kill -9 -- -%(pid)d $SUBKILL || /bin/true
    %(sudo)s kill -9 %(pid)d $SUBKILL || /bin/true
fi
"""
    if nowait:
        cmd = "( %s ) >/dev/null 2>/dev/null </dev/null &" % (cmd,)

    (out,err),proc = rexec(
        cmd % {
            'ppid' : ppid,
            'pid' : pid,
            'sudo' : 'sudo -S' if sudo else '',
            'subkill' : subkill,
        },
        host = host,
        port = port,
        user = user,
        agent = agent,
        identity = identity,
        server_key = server_key
        )
    
    # wait, don't leave zombies around
    proc.wait()

    return (out, err), proc

# POSIX
def _communicate(self, input, timeout=None, err_on_timeout=True):
    read_set = []
    write_set = []
    stdout = None # Return
    stderr = None # Return
    
    killed = False
    
    if timeout is not None:
        timelimit = time.time() + timeout
        killtime = timelimit + 4
        bailtime = timelimit + 4

    if self.stdin:
        # Flush stdio buffer.  This might block, if the user has
        # been writing to .stdin in an uncontrolled fashion.
        self.stdin.flush()
        if input:
            write_set.append(self.stdin)
        else:
            self.stdin.close()
    if self.stdout:
        read_set.append(self.stdout)
        stdout = []
    if self.stderr:
        read_set.append(self.stderr)
        stderr = []

    input_offset = 0
    while read_set or write_set:
        if timeout is not None:
            curtime = time.time()
            if timeout is None or curtime > timelimit:
                if curtime > bailtime:
                    break
                elif curtime > killtime:
                    signum = signal.SIGKILL
                else:
                    signum = signal.SIGTERM
                # Lets kill it
                os.kill(self.pid, signum)
                select_timeout = 0.5
            else:
                select_timeout = timelimit - curtime + 0.1
        else:
            select_timeout = 1.0
        
        if select_timeout > 1.0:
            select_timeout = 1.0
            
        try:
            rlist, wlist, xlist = select.select(read_set, write_set, [], select_timeout)
        except select.error,e:
            if e[0] != 4:
                raise
            else:
                continue
        
        if not rlist and not wlist and not xlist and self.poll() is not None:
            # timeout and process exited, say bye
            break

        if self.stdin in wlist:
            # When select has indicated that the file is writable,
            # we can write up to PIPE_BUF bytes without risk
            # blocking.  POSIX defines PIPE_BUF >= 512
            bytes_written = os.write(self.stdin.fileno(), buffer(input, input_offset, 512))
            input_offset += bytes_written
            if input_offset >= len(input):
                self.stdin.close()
                write_set.remove(self.stdin)

        if self.stdout in rlist:
            data = os.read(self.stdout.fileno(), 1024)
            if data == "":
                self.stdout.close()
                read_set.remove(self.stdout)
            stdout.append(data)

        if self.stderr in rlist:
            data = os.read(self.stderr.fileno(), 1024)
            if data == "":
                self.stderr.close()
                read_set.remove(self.stderr)
            stderr.append(data)
    
    # All data exchanged.  Translate lists into strings.
    if stdout is not None:
        stdout = ''.join(stdout)
    if stderr is not None:
        stderr = ''.join(stderr)

    # Translate newlines, if requested.  We cannot let the file
    # object do the translation: It is based on stdio, which is
    # impossible to combine with select (unless forcing no
    # buffering).
    if self.universal_newlines and hasattr(file, 'newlines'):
        if stdout:
            stdout = self._translate_newlines(stdout)
        if stderr:
            stderr = self._translate_newlines(stderr)

    if killed and err_on_timeout:
        errcode = self.poll()
        raise RuntimeError, ("Operation timed out", errcode, stdout, stderr)
    else:
        if killed:
            self.poll()
        else:
            self.wait()
        return (stdout, stderr)