common/fdconnector.cc

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//
// The FDConnector class - handle I/O on a file descriptor
//
// ***** BEGIN LICENSE BLOCK *****
// Version: MPL 1.1/GPL 2.0/LGPL 2.1
// 
// The contents of this file are subject to the Mozilla Public License
// Version 1.1 (the "License"); you may not use this file except in
// compliance with the License. You may obtain a copy of the License at
// http://www.mozilla.org/MPL/
// 
// Software distributed under the License is distributed on an "AS IS"
// basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
// the License for the specific language governing rights and limitations
// under the License.
// 
// The Original Code is the consmgr network/serial-line monitoring package.
// 
// The Initial Developer of the Original Code is Chris P. Ross.
// Portions created by the Initial Developer are Copyright (C) 2000-2008
// the Initial Developer.  All Rights Reserved.
// 
// Contributor(s):
//   Geoff Adams
// 
// Alternatively, the contents of this file may be used under the terms of
// either the GNU General Public License Version 2 or later (the "GPL"), or
// the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
// in which case the provisions of the GPL or the LGPL are applicable instead
// of those above. If you wish to allow use of your version of this file only
// under the terms of either the GPL or the LGPL, and not to allow others to
// use your version of this file under the terms of the MPL, indicate your
// decision by deleting the provisions above and replace them with the notice
// and other provisions required by the GPL or the LGPL. If you do not delete
// the provisions above, a recipient may use your version of this file under
// the terms of any one of the MPL, the GPL or the LGPL.
// 
// ***** END LICENSE BLOCK *****

//
// Note the implementation of synchronization between threads: We lock the
// mutex for making changes to the fd, but we don't need to lock it for
// reading. Locking for writing wouldn't buy us anything; the fd data member
// is an int, so it's atomic.
//

extern "C" {
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <netinet/in.h>
}

#include <sstream>

#include "consmgr.h"
#include "fdconnector.h"
#include "guard.h"

FDConnector::FDConnector()
        : fd(-1)
{
    // Instantiate our mutex
    int ret = pthread_mutex_init(&mutex, NULL);
    PTHREAD_CHECK_AND_THROW(ret, "mutex_init(mutex)");
}

FDConnector::FDConnector(int the_fd)
        : fd(the_fd)
{
    // Instantiate our mutex
    int ret = pthread_mutex_init(&mutex, NULL);
    PTHREAD_CHECK_AND_THROW(ret, "mutex_init(mutex)");
}

FDConnector::~FDConnector(void)
{
    disconnect();

    int ret = pthread_mutex_destroy(&mutex);
    if (ret != 0)
        cerr << "FDConnector::~FDConnector: Unable to destroy mutex ("
             << &mutex << "): " << strerror(ret) << endl;
}

#if 0
void
FDConnector::notify_on_disconnect(const Messageable *owner)
{
    add_recipient(owner);
}
#endif

std::string
FDConnector::get_id() const
{
    std::ostringstream  strs;
    
    strs << "FDConnector[";
    if (fd >= 0)
        strs << "fd#" << fd;
    else
        strs << "disconnected";
    strs << "]";
    return(strs.str());
}

//
// Set/initialize functions...
//

void
FDConnector::connect(int new_fd)
{
    // Proper thread safety requires that we lock the mutex *before* we test
    // the fd; otherwise someone else could be trying to close it on us while
    // we're here. Race.
    Guard g(&mutex);

    if (connected())
        throw(CMUnsupported("Already connected in call to FDConnector::connect!"));

    fd = new_fd;
}

void
FDConnector::disconnect()
{
    clog << "In FDConnector::disconnect" << endl;

    // Close our fd if it's open

    // Proper thread safety requires that we lock the mutex *before* we test
    // the fd; otherwise someone else could be trying to close it on us while
    // we're here. Race.
    Guard g(&mutex);

    if (connected()) {
        close(fd);
        fd = -1;
    }

    clog << "returning from FDConnector::disconnect()" << endl;
}

bool
FDConnector::connected() const
{
    return fd >= 0;
}

Data *
FDConnector::read()
{
    char *buf = new char[Connector::BufSize];
    int len;
    while ((len = ::read(fd, buf, Connector::BufSize)) <= 0) {
        if (errno != EINTR && errno != EAGAIN) {
            disconnect();
            // Throw an exception to indicate closure...
            throw CMStateChange();
        }
        // So, it's just an EINTR or an EAGAIN, in which case we should just
        // try again.
    }

    // Now return a Blob wrapping that data...
    return new Data((u_char *)buf, len);
}

ssize_t
FDConnector::write(const Data &d)
{
    const size_t        dlen = d.len();
    size_t              total = 0;
    int                 len;
    
    do {
        len = ::write(fd, (d.data() + total), (dlen - total));
        if (len < 0) {
            // XXX - check for error, throw exception, etc
            if (errno == EAGAIN || errno == EINTR)
                continue;
            // What else might be wrong?
            //  EPIPE - writing to an fd noone's reading
            //  EBADF - not an open/valid fd
            // If we're connected, which I think we must be here,
            // consider this a sign-of-disconnection, and throw
            // a state-change notification.
            disconnect();
            // XXX - Is this right, or are some of these cases
            // errors that should be handled differently?
            throw CMStateChange();
        }
        total += len;
    } while (total < dlen);
    
    return total; 
}

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