root / tags / 1.0.8 / xapian-core / net / remoteconnection.cc

/** @file  remoteconnection.cc
 *  @brief RemoteConnection class used by the remote backend.
 */
/* Copyright (C) 2006,2007 Olly Betts
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
 */

#include <config.h>

#include <xapian/error.h>

#include "safeerrno.h"
#include "safefcntl.h"
#include "safeunistd.h"

#include <string>

#include "omassert.h"
#include "omdebug.h"
#include "omtime.h"
#include "remoteconnection.h"
#include "serialise.h"

#ifndef __WIN32__
# include "safesysselect.h"
#endif

using namespace std;

#ifdef __WIN32__
// __STDC_SECURE_LIB__ doesn't appear to be publicly documented, but appears
// to be a good idea.  We cribbed this test from the python sources - see, for
// example, http://svn.python.org/view?rev=47223&view=rev
# if defined _MSC_VER && _MSC_VER >= 1400 && defined __STDC_SECURE_LIB__
#  include <stdlib.h> // For _set_invalid_parameter_handler(), etc.
#  include <crtdbg.h> // For _CrtSetReportMode, etc.

/** A dummy invalid parameter handler which ignores the error. */
static void dummy_handler(const wchar_t*,
                          const wchar_t*,
                          const wchar_t*,
                          unsigned int,
                          uintptr_t)
{
}

// Recent versions of MSVC call an "_invalid_parameter_handler" if a
// CRT function receives an invalid parameter.  However, there are cases
// where this is totally reasonable.  To avoid the application dying,
// you just need to instantiate the MSVCIgnoreInvalidParameter class in
// the scope where you want MSVC to ignore invalid parameters.
class MSVCIgnoreInvalidParameter {
    _invalid_parameter_handler old_handler;
    int old_report_mode;

  public:
    MSVCIgnoreInvalidParameter() {
        // Install a dummy handler to avoid the program dying.
        old_handler = _set_invalid_parameter_handler(dummy_handler);
        // Make sure that no dialog boxes appear.
        old_report_mode = _CrtSetReportMode(_CRT_ASSERT, 0);
    }

    ~MSVCIgnoreInvalidParameter() {
        // Restore the previous settings.
        _set_invalid_parameter_handler(old_handler);
        _CrtSetReportMode(_CRT_ASSERT, old_report_mode);
    }
};
# else
// Mingw seems to be free of this insanity, so for this and older MSVC versions
// define a dummy class to allow MSVCIgnoreInvalidParameter to be used
// unconditionally.
struct MSVCIgnoreInvalidParameter {
    // Provide an explicit constructor so this isn't a POD struct - this seems
    // to prevent GCC warning about an unused variable whenever we instantiate
    // this class.
    MSVCIgnoreInvalidParameter() { }
};
# endif

/// Convert an fd (which might be a socket) to a WIN32 HANDLE.
static HANDLE fd_to_handle(int fd) {
    MSVCIgnoreInvalidParameter invalid_handle_value_is_ok;
    HANDLE handle = (HANDLE)_get_osfhandle(fd);
    // On WIN32, a socket fd isn't the same as a non-socket fd - in fact
    // it's already a HANDLE!
    return (handle != INVALID_HANDLE_VALUE ? handle : (HANDLE)fd);
}

/// Close an fd, which might be a socket.
static void close_fd_or_socket(int fd) {
    MSVCIgnoreInvalidParameter invalid_fd_value_is_ok;
    if (close(fd) == -1 && errno == EBADF) {
        // Bad file descriptor - probably because the fd is actually
        // a socket.
        closesocket(fd);
    }
}
#else
// There's no distinction between sockets and other fds on UNIX.
inline void close_fd_or_socket(int fd) { close(fd); }
#endif

RemoteConnection::RemoteConnection(int fdin_, int fdout_,
                                   const string & context_)
    : fdin(fdin_), fdout(fdout_), context(context_)
{
#ifdef __WIN32__
    memset(&overlapped, 0, sizeof(overlapped));
    overlapped.hEvent = CreateEvent(NULL, FALSE, FALSE, NULL);
    if (!overlapped.hEvent)
        throw Xapian::NetworkError("Failed to setup OVERLAPPED",
                                   context, -(int)GetLastError());

#endif
}

RemoteConnection::~RemoteConnection()
{
#ifdef __WIN32__
    if (overlapped.hEvent)
        CloseHandle(overlapped.hEvent);
#endif
}

void
RemoteConnection::read_at_least(size_t min_len, const OmTime & end_time)
{
    DEBUGCALL(REMOTE, string, "RemoteConnection::read_at_least",
              min_len << ", " << end_time);

    if (buffer.length() >= min_len) return;

#ifdef __WIN32__
    HANDLE hin = fd_to_handle(fdin);
    do {
        char buf[4096];
        DWORD received;
        BOOL ok = ReadFile(hin, buf, sizeof(buf), &received, &overlapped);
        if (!ok) {
            int errcode = GetLastError();
            if (errcode != ERROR_IO_PENDING)
                throw Xapian::NetworkError("read failed", context, -errcode);
            // Is asynch - just wait for the data to be received or a timeout.
            DWORD waitrc;
            waitrc = WaitForSingleObject(overlapped.hEvent, calc_read_wait_msecs(end_time));
            if (waitrc != WAIT_OBJECT_0) {
                DEBUGLINE(REMOTE, "read: timeout has expired");
                throw Xapian::NetworkTimeoutError("Timeout expired while trying to read", context);
            }
            // Get the final result of the read.
            if (!GetOverlappedResult(hin, &overlapped, &received, FALSE))
                throw Xapian::NetworkError("Failed to get overlapped result",
                                           context, -(int)GetLastError());
        }

        if (received == 0)
            throw Xapian::NetworkError("Received EOF", context);

        buffer.append(buf, received);
    } while (buffer.length() < min_len);
#else
    // If there's no end_time, just use blocking I/O.
    if (fcntl(fdin, F_SETFL, end_time.is_set() ? O_NONBLOCK : 0) < 0) {
        throw Xapian::NetworkError("Failed to set fdin non-blocking-ness",
                                   context, errno);
    }

    while (true) {
        char buf[4096];
        ssize_t received = read(fdin, buf, sizeof(buf));

        if (received > 0) {
            buffer.append(buf, received);
            if (buffer.length() >= min_len) return;
            continue;
        }

        if (received == 0)
            throw Xapian::NetworkError("Received EOF", context);

        DEBUGLINE(REMOTE, "read gave errno = " << strerror(errno));
        if (errno == EINTR) continue;

        if (errno != EAGAIN)
            throw Xapian::NetworkError("read failed", context, errno);

        Assert(end_time.is_set());
        while (true) {
            // Calculate how far in the future end_time is.
            OmTime time_diff = end_time - OmTime::now();
            // Check if the timeout has expired.
            if (time_diff.sec < 0) {
                DEBUGLINE(REMOTE, "read: timeout has expired");
                throw Xapian::NetworkTimeoutError("Timeout expired while trying to read", context);
            }

            struct timeval tv;
            tv.tv_sec = time_diff.sec;
            tv.tv_usec = time_diff.usec;

            // Use select to wait until there is data or the timeout is reached.
            fd_set fdset;
            FD_ZERO(&fdset);
            FD_SET(fdin, &fdset);

            int select_result = select(fdin + 1, &fdset, 0, &fdset, &tv);
            if (select_result > 0) break;

            if (select_result == 0)
                throw Xapian::NetworkTimeoutError("Timeout expired while trying to read", context);

            // EINTR means select was interrupted by a signal.
            if (errno != EINTR)
                throw Xapian::NetworkError("select failed during read", context, errno);
        }
    }
#endif
}

bool
RemoteConnection::ready_to_read() const
{
    DEBUGCALL(REMOTE, bool, "RemoteConnection::ready_to_read", "");

    if (!buffer.empty()) RETURN(true);

    // Use select to see if there's data available to be read.
    fd_set fdset;
    FD_ZERO(&fdset);
    FD_SET(fdin, &fdset);

    // Set a 0.1 second timeout to avoid a busy loop.
    // FIXME: this would be much better done by exposing the fd so that the
    // matcher can call select on all the fds involved...
    struct timeval tv;
    tv.tv_sec = 0;
    tv.tv_usec = 100000;
    RETURN(select(fdin + 1, &fdset, 0, &fdset, &tv) > 0);
}

void
RemoteConnection::send_message(char type, const string &message, const OmTime & end_time)
{
    DEBUGCALL(REMOTE, void, "RemoteConnection::send_message",
              type << ", " << message << ", " << end_time);

    string header;
    header += type;
    header += encode_length(message.size());

#ifdef __WIN32__
    HANDLE hout = fd_to_handle(fdout);
    const string * str = &header;

    size_t count = 0;
    while (true) {
        DWORD n;
        BOOL ok = WriteFile(hout, str->data() + count, str->size() - count, &n, &overlapped);
        if (!ok) {
            int errcode = GetLastError();
            if (errcode != ERROR_IO_PENDING)
                throw Xapian::NetworkError("write failed", context, -errcode);
            // Just wait for the data to be received, or a timeout.
            DWORD waitrc;
            waitrc = WaitForSingleObject(overlapped.hEvent, calc_read_wait_msecs(end_time));
            if (waitrc != WAIT_OBJECT_0) {
                DEBUGLINE(REMOTE, "write: timeout has expired");
                throw Xapian::NetworkTimeoutError("Timeout expired while trying to write", context);
            }
            // Get the final result.
            if (!GetOverlappedResult(hout, &overlapped, &n, FALSE))
                throw Xapian::NetworkError("Failed to get overlapped result",
                                           context, -(int)GetLastError());
        }

        count += n;
        if (count == str->size()) {
            if (str == &message || message.empty()) return;
            str = &message;
            count = 0;
        }
    }
#else
    // If there's no end_time, just use blocking I/O.
    if (fcntl(fdout, F_SETFL, end_time.is_set() ? O_NONBLOCK : 0) < 0) {
        throw Xapian::NetworkError("Failed to set fdout non-blocking-ness",
                                   context, errno);
    }

    const string * str = &header;

    fd_set fdset;
    size_t count = 0;
    while (true) {
        // We've set write to non-blocking, so just try writing as there
        // will usually be space.
        ssize_t n = write(fdout, str->data() + count, str->size() - count);

        if (n >= 0) {
            count += n;
            if (count == str->size()) {
                if (str == &message || message.empty()) return;
                str = &message;
                count = 0;
            }
            continue;
        }

        DEBUGLINE(REMOTE, "write gave errno = " << strerror(errno));
        if (errno == EINTR) continue;

        if (errno != EAGAIN)
            throw Xapian::NetworkError("write failed", context, errno);

        // Use select to wait until there is space or the timeout is reached.
        FD_ZERO(&fdset);
        FD_SET(fdout, &fdset);

        OmTime time_diff(end_time - OmTime::now());
        if (time_diff.sec < 0) {
            DEBUGLINE(REMOTE, "write: timeout has expired");
            throw Xapian::NetworkTimeoutError("Timeout expired while trying to write", context);
        }

        struct timeval tv;
        tv.tv_sec = time_diff.sec;
        tv.tv_usec = time_diff.usec;

        int select_result = select(fdout + 1, 0, &fdset, &fdset, &tv);

        if (select_result < 0) {
            if (errno == EINTR) {
                // EINTR means select was interrupted by a signal.
                // We could just retry the select, but it's easier to just
                // retry the write.
                continue;
            }
            throw Xapian::NetworkError("select failed during write", context, errno);
        }

        if (select_result == 0)
            throw Xapian::NetworkTimeoutError("Timeout expired while trying to write", context);
    }
#endif
}

char
RemoteConnection::get_message(string &result, const OmTime & end_time)
{
    DEBUGCALL(REMOTE, char, "RemoteConnection::get_message",
              "[result], " << end_time);

    read_at_least(2, end_time);
    size_t len = static_cast<unsigned char>(buffer[1]);
    read_at_least(len + 2, end_time);
    if (len != 0xff) {
        result.assign(buffer.data() + 2, len);
        char type = buffer[0];
        buffer.erase(0, len + 2);
        RETURN(type);
    }
    len = 0;
    string::const_iterator i = buffer.begin() + 2;
    unsigned char ch;
    int shift = 0;
    do {
        if (i == buffer.end() || shift > 28) {
            // Something is very wrong...
            throw Xapian::NetworkError("Insane message length specified!");
        }
        ch = *i++;
        len |= size_t(ch & 0x7f) << shift;
        shift += 7;
    } while ((ch & 0x80) == 0);
    len += 255;
    size_t header_len = (i - buffer.begin());
    read_at_least(header_len + len, end_time);
    result.assign(buffer.data() + header_len, len);
    char type = buffer[0];
    buffer.erase(0, header_len + len);
    RETURN(type);
}

void
RemoteConnection::do_close(bool wait)
{
    DEBUGCALL(REMOTE, void, "RemoteConnection::do_close", wait);

    if (fdout == -1) return;
    // We can be called from a destructor, so we can't throw an exception.
    if (wait) {
        try {
            send_message(MSG_SHUTDOWN, string(), OmTime());
        } catch (...) {
        }
#ifdef __WIN32__
        HANDLE hin = fd_to_handle(fdin);
        char dummy;
        DWORD received;
        BOOL ok = ReadFile(hin, &dummy, 1, &received, &overlapped);
        if (!ok && GetLastError() == ERROR_IO_PENDING) {
            // Wait for asynchronous read to complete.
            (void)WaitForSingleObject(overlapped.hEvent, INFINITE);
        }
#else
        // Wait for the connection to be closed - when this happens
        // select() will report that a read won't block.
        fd_set fdset;
        FD_ZERO(&fdset);
        FD_SET(fdin, &fdset);
        int res;
        do {
            res = select(fdin + 1, &fdset, 0, &fdset, NULL);
        } while (res < 0 && errno == EINTR);
#endif
    }
    close_fd_or_socket(fdin);
    if (fdin != fdout) close_fd_or_socket(fdout);
    fdout = -1;
}

#ifdef __WIN32__
DWORD
RemoteConnection::calc_read_wait_msecs(const OmTime & end_time)
{
    if (!end_time.is_set())
        return INFINITE;

    // Calculate how far in the future end_time is.
    OmTime now(OmTime::now());

    DWORD msecs;

    // msecs is unsigned, so we mustn't try and return a negative value
    if (now > end_time) {
        throw Xapian::NetworkTimeoutError("Timeout expired before starting read", context);
    }
    OmTime time_diff = end_time - now;
    msecs = time_diff.sec * 1000 + time_diff.usec / 1000;
    return msecs;
}
#endif