annotate vamp-hostsdk/PluginLoader.h @ 390:06988ce35ff0 vh

Initial draft of C API for plugin loading

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

/*
    Vamp

    An API for audio analysis and feature extraction plugins.

    Centre for Digital Music, Queen Mary, University of London.
    Copyright 2006-2009 Chris Cannam and QMUL.
  
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*/

#ifndef _VAMP_PLUGIN_LOADER_H_
#define _VAMP_PLUGIN_LOADER_H_

#include <vector>
#include <string>
#include <map>

#include "hostguard.h"
#include "PluginWrapper.h"

_VAMP_SDK_HOSTSPACE_BEGIN(PluginLoader.h)

namespace Vamp {

class Plugin;

namespace HostExt {

/**
 * \class PluginLoader PluginLoader.h <vamp-hostsdk/PluginLoader.h>
 * 
 * Vamp::HostExt::PluginLoader is a convenience class for discovering
 * and loading Vamp plugins using the typical plugin-path, library
 * naming, and categorisation conventions described in the Vamp SDK
 * documentation.  This class is intended to greatly simplify the task
 * of becoming a Vamp plugin host for any C++ application.
 * 
 * Hosts are not required by the Vamp specification to use the same
 * plugin search path and naming conventions as implemented by this
 * class, and are certainly not required to use this actual class.
 * But we do strongly recommend it.
 *
 * This class is not thread-safe; use it from a single application
 * thread, or guard access to it with a mutex.
 *
 * \note This class was introduced in version 1.1 of the Vamp plugin SDK.
 */

class PluginLoader
{
public:
    /**
     * Obtain a pointer to the singleton instance of PluginLoader.
     * Use this to obtain your loader object.
     */
    static PluginLoader *getInstance();

    /**
     * PluginKey is a string type that is used to identify a plugin
     * uniquely within the scope of "the current system".  It consists
     * of the lower-cased base name of the plugin library, a colon
     * separator, and the identifier string for the plugin.  It is
     * only meaningful in the context of a given plugin path (the one
     * returned by PluginHostAdapter::getPluginPath()).
     *
     * Use composePluginKey() to construct a plugin key from a known
     * plugin library name and identifier.
     *
     * Note: the fact that the library component of the key is
     * lower-cased implies that library names are matched
     * case-insensitively by the PluginLoader class, regardless of the
     * case sensitivity of the underlying filesystem.  (Plugin
     * identifiers _are_ case sensitive, however.)  Also, it is not
     * possible to portably extract a working library name from a
     * plugin key, as the result may fail on case-sensitive
     * filesystems.  Use getLibraryPathForPlugin() instead.
     */
    typedef std::string PluginKey;

    /**
     * PluginKeyList is a sequence of plugin keys, such as returned by
     * listPlugins().
     */
    typedef std::vector<PluginKey> PluginKeyList;

    /**
     * PluginCategoryHierarchy is a sequence of general->specific
     * category names, as may be associated with a single plugin.
     * This sequence describes the location of a plugin within a
     * category forest, containing the human-readable names of the
     * plugin's category tree root, followed by each of the nodes down
     * to the leaf containing the plugin.
     *
     * \see getPluginCategory()
     */
    typedef std::vector<std::string> PluginCategoryHierarchy;

    /**
     * Search for all available Vamp plugins, and return a list of
     * them in the order in which they were found.
     */
    PluginKeyList listPlugins();

    /**
     * AdapterFlags contains a set of values that may be OR'd together
     * to indicate in which circumstances PluginLoader should use a
     * plugin adapter to make a plugin easier to use for a host that
     * does not want to cater for complex features.
     *
     * The available flags are:
     * 
     * ADAPT_INPUT_DOMAIN - If the plugin expects frequency domain
     * input, wrap it in a PluginInputDomainAdapter that automatically
     * converts the plugin to one that expects time-domain input.
     * This enables a host to accommodate time- and frequency-domain
     * plugins without needing to do any conversion itself.
     *
     * ADAPT_CHANNEL_COUNT - Wrap the plugin in a PluginChannelAdapter
     * to handle any mismatch between the number of channels of audio
     * the plugin can handle and the number available in the host.
     * This enables a host to use plugins that may require the input
     * to be mixed down to mono, etc., without having to worry about
     * doing that itself.
     *
     * ADAPT_BUFFER_SIZE - Wrap the plugin in a PluginBufferingAdapter
     * permitting the host to provide audio input using any block
     * size, with no overlap, regardless of the plugin's preferred
     * block size (suitable for hosts that read from non-seekable
     * streaming media, for example).  This adapter introduces some
     * run-time overhead and also changes the semantics of the plugin
     * slightly (see the PluginBufferingAdapter header documentation
     * for details).
     *
     * ADAPT_ALL_SAFE - Perform all available adaptations that are
     * meaningful for the plugin and "safe".  Currently this means to
     * ADAPT_INPUT_DOMAIN if the plugin wants FrequencyDomain input;
     * ADAPT_CHANNEL_COUNT always; and ADAPT_BUFFER_SIZE never.
     * 
     * ADAPT_ALL - Perform all available adaptations that are
     * meaningful for the plugin.
     * 
     * See PluginInputDomainAdapter, PluginChannelAdapter and
     * PluginBufferingAdapter for more details of the classes that the
     * loader may use if these flags are set.
     */
    enum AdapterFlags {

        ADAPT_INPUT_DOMAIN  = 0x01,
        ADAPT_CHANNEL_COUNT = 0x02,
        ADAPT_BUFFER_SIZE   = 0x04,

        ADAPT_ALL_SAFE      = 0x03,

        ADAPT_ALL           = 0xff
    };

    /**
     * Load a Vamp plugin, given its identifying key.  If the plugin
     * could not be loaded, returns 0.
     *
     * The returned plugin should be deleted (using the standard C++
     * delete keyword) after use.
     *
     * \param adapterFlags a bitwise OR of the values in the AdapterFlags
     * enumeration, indicating under which circumstances an adapter should be
     * used to wrap the original plugin.  If adapterFlags is 0, no
     * optional adapters will be used.  Otherwise, the returned plugin
     * may be of an adapter class type which will behave identically
     * to the original plugin, apart from any particular features
     * implemented by the adapter itself.
     * 
     * \see AdapterFlags, PluginInputDomainAdapter, PluginChannelAdapter
     */
    Plugin *loadPlugin(PluginKey key,
                       float inputSampleRate,
                       int adapterFlags = 0);

    /**
     * Given a Vamp plugin library name and plugin identifier, return
     * the corresponding plugin key in a form suitable for passing in to
     * loadPlugin().
     */
    PluginKey composePluginKey(std::string libraryName,
                               std::string identifier);

    /**
     * Return the category hierarchy for a Vamp plugin, given its
     * identifying key.
     *
     * If the plugin has no category information, return an empty
     * hierarchy.
     *
     * \see PluginCategoryHierarchy
     */
    PluginCategoryHierarchy getPluginCategory(PluginKey plugin);

    /**
     * Return the file path of the dynamic library from which the
     * given plugin will be loaded (if available).
     */
    std::string getLibraryPathForPlugin(PluginKey plugin);

protected:
    PluginLoader();
    virtual ~PluginLoader();

    class Impl;
    Impl *m_impl;

    static PluginLoader *m_instance;
};

}

}

_VAMP_SDK_HOSTSPACE_END(PluginLoader.h)

#endif