annotate vamp-client/ProcessQtTransport.h @ 127:5b113c87b6e6

Add and implement the "from" param for list request. The simple-server implementation is not yet correct.

/* -*- c-basic-offset: 4 indent-tabs-mode: nil -*-  vi:set ts=8 sts=4 sw=4: */
/*
  Piper C++

  An API for audio analysis and feature extraction plugins.

  Centre for Digital Music, Queen Mary, University of London.
  Copyright 2006-2016 Chris Cannam and QMUL.
  
  Permission is hereby granted, free of charge, to any person
  obtaining a copy of this software and associated documentation
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  of the Software, and to permit persons to whom the Software is
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  The above copyright notice and this permission notice shall be
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*/
 
#ifndef PIPER_PROCESS_QT_TRANSPORT_H
#define PIPER_PROCESS_QT_TRANSPORT_H

#include "SynchronousTransport.h"

#include <QProcess>
#include <QString>
#include <QMutex>

#include <iostream>

//#define DEBUG_TRANSPORT 1

namespace piper_vamp {
namespace client {

/**
 * A SynchronousTransport implementation that spawns a sub-process
 * using Qt's QProcess abstraction and talks to it via stdin/stdout
 * channels. Calls are completely serialized; the protocol only
 * supports one call in process at a time, and therefore the transport
 * only allows one at a time.
 *
 * This class is thread-safe, but in practice you can only use it from
 * within a single thread, because the underlying QProcess does not
 * support switching threads.
 */
class ProcessQtTransport : public SynchronousTransport
{
public:
    ProcessQtTransport(std::string processName, std::string formatArg) :
        m_completenessChecker(0),
        m_crashed(false) {

        m_process = new QProcess();
        m_process->setReadChannel(QProcess::StandardOutput);
        m_process->setProcessChannelMode(QProcess::ForwardedErrorChannel);

        m_process->start(QString::fromStdString(processName),
                         { QString::fromStdString(formatArg) });
        
        if (!m_process->waitForStarted()) {
            if (m_process->state() == QProcess::NotRunning) {
                QProcess::ProcessError err = m_process->error();
                if (err == QProcess::FailedToStart) {
                    std::cerr << "Unable to start server process "
                              << processName << std::endl;
                } else if (err == QProcess::Crashed) {
                    std::cerr << "Server process " << processName
                              << " crashed on startup" << std::endl;
                } else {
                    std::cerr << "Server process " << processName
                              << " failed on startup with error code "
                              << err << std::endl;
                }
                delete m_process;
                m_process = nullptr;
            }
        }
    }

    ~ProcessQtTransport() {
        if (m_process) {
            if (m_process->state() != QProcess::NotRunning) {
                m_process->closeWriteChannel();
                m_process->waitForFinished(200);
                m_process->close();
                m_process->waitForFinished();
#ifdef DEBUG_TRANSPORT
                std::cerr << "server exited" << std::endl;
#endif
            }
            delete m_process;
        }
    }

    void
    setCompletenessChecker(MessageCompletenessChecker *checker) override {
        m_completenessChecker = checker;
    }
    
    bool
    isOK() const override {
        return (m_process != nullptr) && !m_crashed;
    }
    
    std::vector<char>
    call(const char *ptr, size_t size, bool slow) override {

        QMutexLocker locker(&m_mutex);
        
        if (!m_completenessChecker) {
            throw std::logic_error("No completeness checker set on transport");
        }
        if (!isOK()) {
            throw std::logic_error("Transport is not OK");
        }
        
#ifdef DEBUG_TRANSPORT
        std::cerr << "writing " << size << " bytes to server" << std::endl;
#endif
        m_process->write(ptr, size);
        m_process->waitForBytesWritten();
        
        std::vector<char> buffer;
        bool complete = false;
        
        while (!complete) {

            qint64 byteCount = m_process->bytesAvailable();

            if (!byteCount) {
#ifdef DEBUG_TRANSPORT
                std::cerr << "waiting for data from server..." << std::endl;
#endif
                if (slow) {
                    m_process->waitForReadyRead(1000);
                } else {
#ifdef _WIN32
                    // This is most unsatisfactory -- if we give a non-zero
                    // arg here, then we end up sleeping way beyond the arrival
                    // of the data to read -- can end up using less than 10%
                    // CPU during processing which is crazy. So for Windows
                    // only, we busy-wait during "fast" calls. It works out
                    // much faster in the end. Could do with a simpler native
                    // blocking API really.
                    m_process->waitForReadyRead(0);
#else
                    m_process->waitForReadyRead(100);
#endif
                }
                if (m_process->state() == QProcess::NotRunning &&
                    // don't give up until we've read all that's been buffered!
                    !m_process->bytesAvailable()) {
                    QProcess::ProcessError err = m_process->error();
                    if (err == QProcess::Crashed) {
                        std::cerr << "Server crashed during request" << std::endl;
                    } else {
                        std::cerr << "Server failed during request with error code "
                                  << err << std::endl;
                    }
                    m_crashed = true;
                    throw ServerCrashed();
                }
            } else {
                size_t formerSize = buffer.size();
                buffer.resize(formerSize + byteCount);
                m_process->read(buffer.data() + formerSize, byteCount);
                complete = m_completenessChecker->isComplete(buffer);
            }
        }

        return buffer;
    }
    
private:
    MessageCompletenessChecker *m_completenessChecker; //!!! I don't own this (currently)
    QProcess *m_process; // I own this
    QMutex m_mutex;
    bool m_crashed;
};

}
}

#endif