annotate data/fileio/MatrixFile.h @ 537:3cc4b7cd2aa5

* Merge from one-fftdataserver-per-fftmodel branch.  This bit of
reworking (which is not described very accurately by the title of
the branch) turns the MatrixFile object into something that either
reads or writes, but not both, and separates the FFT file cache
reader and writer implementations separately.  This allows the
FFT data server to have a single thread owning writers and one reader
per "customer" thread, and for all locking to be vastly simplified
and concentrated in the data server alone (because none of the
classes it makes use of is used in more than one thread at a time).
The result is faster and more trustworthy code.

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

/*
    Sonic Visualiser
    An audio file viewer and annotation editor.
    Centre for Digital Music, Queen Mary, University of London.
    This file copyright 2006-2009 Chris Cannam and QMUL.
    
    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.  See the file
    COPYING included with this distribution for more information.
*/

#ifndef _MATRIX_FILE_CACHE_H_
#define _MATRIX_FILE_CACHE_H_

#include "base/ResizeableBitset.h"

#include "FileReadThread.h"

#include <sys/types.h>
#include <QString>
#include <QMutex>
#include <map>

class MatrixFile : public QObject
{
    Q_OBJECT

public:
    enum Mode { ReadOnly, WriteOnly };

    /**
     * Construct a MatrixFile object reading from and/or writing to
     * the matrix file with the given base name in the application's
     * temporary directory.
     *
     * If mode is ReadOnly, the file must exist and be readable.
     *
     * If mode is WriteOnly, the file must not exist.
     *
     * cellSize specifies the size in bytes of the object type stored
     * in the matrix.  For example, use cellSize = sizeof(float) for a
     * matrix of floats.  The MatrixFile object doesn't care about the
     * objects themselves, it just deals with raw data of a given size.
     *
     * width and height specify the dimensions of the file.  These
     * cannot be changed after construction.
     *
     * MatrixFiles are reference counted by name.  When the last
     * MatrixFile with a given name is destroyed, the file is removed.
     * These are temporary files; the normal usage is to have one
     * MatrixFile of WriteOnly type creating the file and then
     * persisting until all readers are complete.
     *
     * MatrixFile has no built-in cache and is not thread-safe.  Use a
     * separate MatrixFile in each thread.
     */
    MatrixFile(QString fileBase, Mode mode, size_t cellSize,
               size_t width, size_t height);
    virtual ~MatrixFile();

    Mode getMode() const { return m_mode; }

    size_t getWidth() const { return m_width; }
    size_t getHeight() const { return m_height; }
    size_t getCellSize() const { return m_cellSize; }
    
    void close(); // does not decrement ref count; that happens in dtor

    bool haveSetColumnAt(size_t x) const;
    void getColumnAt(size_t x, void *data); // may throw FileReadFailed
    void setColumnAt(size_t x, const void *data);

protected:
    int     m_fd;
    Mode    m_mode;
    int     m_flags;
    mode_t  m_fmode;
    size_t  m_cellSize;
    size_t  m_width;
    size_t  m_height;
    size_t  m_headerSize;
    QString m_fileName;

    static std::map<QString, int> m_refcount;
    static QMutex m_createMutex;

    void initialise();
    bool seekTo(size_t x, size_t y) const;
};

#endif