MarshallerThread.cc

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// -*- mode: c++; c-basic-offset:4 -*-
 
// This file is part of libdap, A C++ implementation of the OPeNDAP Data
// Access Protocol.
 
// Copyright (c) 2015 OPeNDAP, Inc.
// Author: James Gallagher <jgallagher@opendap.org>
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
//
// This library 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
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
//
// You can contact OPeNDAP, Inc. at PO Box 112, Saunderstown, RI. 02874-0112.
 
/*
 * MarshallerThread.cc
 *
 *  Created on: Aug 27, 2015
 *      Author: jimg
 */
 
#include "config.h"
 
#include <fcntl.h>
#include <pthread.h>
#include <sys/time.h>
#include <unistd.h>
 
#include <ostream>
#include <sstream>
 
#include "Error.h"
#include "InternalErr.h"
#include "MarshallerThread.h"
#include "debug.h"
 
using namespace libdap;
using namespace std;
 
// Set TIMING to 1 to enable timing output
#define TIMING 0
 
#if TIMING
bool MarshallerThread::print_time = false;

static double time_diff_to_hundredths(struct timeval *stop, struct timeval *start) {
    /* Perform the carry for the later subtraction by updating y. */
    if (stop->tv_usec < start->tv_usec) {
        int nsec = (start->tv_usec - stop->tv_usec) / 1000000 + 1;
        start->tv_usec -= 1000000 * nsec;
        start->tv_sec += nsec;
    }
    if (stop->tv_usec - start->tv_usec > 1000000) {
        int nsec = (start->tv_usec - stop->tv_usec) / 1000000;
        start->tv_usec += 1000000 * nsec;
        start->tv_sec -= nsec;
    }
 
    double result = stop->tv_sec - start->tv_sec;
    result += double(stop->tv_usec - start->tv_usec) / 1000000;
    return result;
}
#endif

Locker::Locker(pthread_mutex_t &lock, pthread_cond_t &cond, int &count) : m_mutex(lock) {
    int status = pthread_mutex_lock(&m_mutex);
 
    DBG(cerr << "Locking the mutex! (waiting; " << pthread_self() << ")" << endl);
 
    if (status != 0)
        throw InternalErr(__FILE__, __LINE__, "Could not lock m_mutex");
    while (count != 0) {
        status = pthread_cond_wait(&cond, &m_mutex);
        if (status != 0)
            throw InternalErr(__FILE__, __LINE__, "Could not wait on m_cond");
    }
 
    DBG(cerr << "Locked! (" << pthread_self() << ")" << endl);
}

Locker::~Locker() {
    DBG(cerr << "Unlocking the mutex! (" << pthread_self() << ")" << endl);
 
    (void)pthread_mutex_unlock(&m_mutex);
}

 
ChildLocker::ChildLocker(pthread_mutex_t &lock, pthread_cond_t &cond, int &count)
    : m_mutex(lock), m_cond(cond), m_count(count) {
    int status = pthread_mutex_lock(&m_mutex);
 
    DBG(cerr << "Locking the mutex! (simple; " << pthread_self() << ")" << endl);
 
    if (status != 0)
        throw InternalErr(__FILE__, __LINE__, "Could not lock m_mutex");
 
    DBG(cerr << "Locked! (" << pthread_self() << ")" << endl);
}
 
ChildLocker::~ChildLocker() {
    DBG(cerr << "Unlocking the mutex! (" << pthread_self() << ")" << endl);
 
    m_count = 0;
 
    (void)pthread_cond_signal(&m_cond);
    (void)pthread_mutex_unlock(&m_mutex);
}
 
MarshallerThread::MarshallerThread() {
    if (pthread_attr_init(&d_thread_attr) != 0)
        throw Error(internal_error, "Failed to initialize pthread attributes.");
    if (pthread_attr_setdetachstate(&d_thread_attr, PTHREAD_CREATE_DETACHED /*PTHREAD_CREATE_JOINABLE*/) != 0)
        throw Error(internal_error, "Failed to complete pthread attribute initialization.");
 
    if (pthread_mutex_init(&d_out_mutex, nullptr) != 0)
        throw Error(internal_error, "Failed to initialize mutex.");
    if (pthread_cond_init(&d_out_cond, nullptr) != 0)
        throw Error(internal_error, "Failed to initialize cond.");
}
 
MarshallerThread::~MarshallerThread() {
    (void)pthread_mutex_lock(&d_out_mutex);
    // d_child_thread_count is passed into the thread in a structure (see write_thread())
    // and is decremented by the ChildLocker dtor when write_thread() exits. jhrg 2/7/19
    if (d_child_thread_count != 0) {
        (void)pthread_cond_wait(&d_out_cond, &d_out_mutex);
        d_child_thread_count = 0;
    }
 
    (void)pthread_mutex_unlock(&d_out_mutex);
 
    pthread_mutex_destroy(&d_out_mutex);
    pthread_cond_destroy(&d_out_cond);
 
    pthread_attr_destroy(&d_thread_attr);
}
 
// not a static method
void MarshallerThread::start_thread(void *(*thread)(void *arg), ostream &out, char *byte_buf, std::streamsize bytes) {
    auto *args = new write_args(d_out_mutex, d_out_cond, d_child_thread_count, d_thread_error, out, byte_buf, bytes);
    int status = pthread_create(&d_thread, &d_thread_attr, thread, args);
    if (status != 0)
        throw InternalErr(__FILE__, __LINE__, "Could not start child thread");
}

void MarshallerThread::start_thread(void *(*thread)(void *arg), int fd, char *byte_buf, std::streamsize bytes) {
    auto *args = new write_args(d_out_mutex, d_out_cond, d_child_thread_count, d_thread_error, fd, byte_buf, bytes);
    int status = pthread_create(&d_thread, &d_thread_attr, thread, args);
    if (status != 0)
        throw InternalErr(__FILE__, __LINE__, "Could not start child thread");
}

void *MarshallerThread::write_thread(void *arg) {
    auto *args = reinterpret_cast<write_args *>(arg);
 
    ChildLocker lock(args->d_mutex, args->d_cond, args->d_count); // RAII; will unlock on exit
 
#if TIMING
    struct timeval tp_s;
    if (print_time && gettimeofday(&tp_s, 0) != 0)
        cerr << "could not read time" << endl;
#endif
 
    // force an error
    // return (void*)-1;
 
    if (args->d_out_file != -1) {
        auto bytes_written = write(args->d_out_file, args->d_buf, args->d_num);
        if (bytes_written != args->d_num)
            return (void *)-1;
    } else {
        args->d_out.write(args->d_buf, args->d_num);
        if (args->d_out.fail()) {
            ostringstream oss;
            oss << "Could not write data: " << __FILE__ << ":" << __LINE__;
            args->d_error = oss.str();
            return (void *)-1;
        }
    }
 
    delete[] args->d_buf;
    delete args;
 
#if TIMING
    struct timeval tp_e;
    if (print_time) {
        if (gettimeofday(&tp_e, 0) != 0)
            cerr << "could not read time" << endl;
 
        cerr << "time for child thread write: " << time_diff_to_hundredths(&tp_e, &tp_s) << endl;
    }
#endif
 
    return nullptr;
}

void *MarshallerThread::write_thread_part(void *arg) {
    auto *args = reinterpret_cast<write_args *>(arg);
 
    ChildLocker lock(args->d_mutex, args->d_cond, args->d_count); // RAII; will unlock on exit
 
    if (args->d_out_file != -1) {
        auto bytes_written = write(args->d_out_file, args->d_buf, args->d_num);
        if (bytes_written != args->d_num)
            return (void *)-1;
    } else {
        args->d_out.write(args->d_buf + 4, args->d_num);
        if (args->d_out.fail()) {
            ostringstream oss;
            oss << "Could not write data: " << __FILE__ << ":" << __LINE__;
            args->d_error = oss.str();
            return (void *)-1;
        }
    }
 
    delete[] args->d_buf;
    delete args;
 
    return nullptr;
}