annotate vamp-hostsdk/PluginLoader.h @ 277:6d355f1b7eaf

* Patch from Richard Ash to make building the host optional, so you can
  at least build the SDK even if you don't have libsndfile

/* -*- 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 2006-2007 Chris Cannam and QMUL.
  
    Permission is hereby granted, free of charge, to any person
    obtaining a copy of this software and associated documentation
    files (the "Software"), to deal in the Software without
    restriction, including without limitation the rights to use, copy,
    modify, merge, publish, distribute, sublicense, and/or sell copies
    of the Software, and to permit persons to whom the Software is
    furnished to do so, subject to the following conditions:

    The above copyright notice and this permission notice shall be
    included in all copies or substantial portions of the Software.

    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
    EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
    MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
    NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR
    ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF
    CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
    WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

    Except as contained in this notice, the names of the Centre for
    Digital Music; Queen Mary, University of London; and Chris Cannam
    shall not be used in advertising or otherwise to promote the sale,
    use or other dealings in this Software without prior written
    authorization.
*/

#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.
 *
 * \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