vlc_preparser.h

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/*****************************************************************************
 * preparser.h
 *****************************************************************************
 * Copyright (C) 1999-2023 VLC authors and VideoLAN
 *
 * Authors: Samuel Hocevar <sam@zoy.org>
 *          Clément Stenac <zorglub@videolan.org>
 *
 * This program 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 program 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 program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
 *****************************************************************************/
 
#ifndef VLC_PREPARSER_H
#define VLC_PREPARSER_H 1
 
#include <vlc_input_item.h>
 
/**
 * @defgroup vlc_preparser Preparser
 * @ingroup input
 * @{
 * @file
 * VLC Preparser API
 */
 
/**
 * Preparser opaque structure.
 *
 * The preparser object will retrieve the meta data of any given input item in
 * an asynchronous way.
 * It will also issue art fetching requests.
 */
typedef struct vlc_preparser_t vlc_preparser_t;
 
/**
 * Preparser request opaque handle.
 *
 * Identifies a request created by vlc_preparser_req_NewParse(),
 * vlc_preparser_req_NewThumbnail() or vlc_preparser_req_NewThumbnailToFiles()
 * and started with vlc_preparser_Submit().
 * It can be passed to vlc_preparser_Cancel() to cancel that request.
 *
 * @note
 * - Ownership of the handle is transferred to the caller by the
 *   vlc_preparser_req_New*() functions. The caller must release it with
 *   vlc_preparser_req_Release() once it is no longer needed, whether or not it
 *   was submitted.
 *
 * - The caller must ensure that the callbacks and their context remain valid
 *   until the request terminates.
 */
typedef struct vlc_preparser_req vlc_preparser_req;
 
#define VLC_PREPARSER_TYPE_PARSE            0x01
#define VLC_PREPARSER_TYPE_FETCHMETA_LOCAL  0x02
#define VLC_PREPARSER_TYPE_FETCHMETA_NET    0x04
#define VLC_PREPARSER_TYPE_THUMBNAIL        0x08
#define VLC_PREPARSER_TYPE_THUMBNAIL_TO_FILES 0x10
#define VLC_PREPARSER_TYPE_FETCHMETA_ALL \
    (VLC_PREPARSER_TYPE_FETCHMETA_LOCAL|VLC_PREPARSER_TYPE_FETCHMETA_NET)
 
#define VLC_PREPARSER_OPTION_INTERACT 0x1000
#define VLC_PREPARSER_OPTION_SUBITEMS 0x2000
 
struct vlc_preparser_cbs
{
    /**
     * Event received when the parser ends
     *
     * @note This callback is mandatory.
     *
     * @param req request handle returned by vlc_preparser_req_NewParse()
     * @param status VLC_SUCCESS in case of success, VLC_ETIMEOUT in case of
     * timeout, -EINTR if cancelled, an error otherwise
     * @param data opaque pointer passed by vlc_preparser_req_NewParse()
     */
    void (*on_ended)(vlc_preparser_req *req, int status, void *data);
 
    /**
     * Event received when a new subtree is added
     *
     * @note This callback is optional.
     *
     * @param req request handle returned by vlc_preparser_req_NewParse()
     * @param subtree sub items of the current item (the listener gets the ownership)
     * @param data opaque pointer passed by vlc_preparser_req_NewParse()
     */
    void (*on_subtree_added)(vlc_preparser_req *req, input_item_node_t *subtree,
                             void *data);
 
    /**
     * Event received when new attachments are added
     *
     * @note This callback is optional. It can be called several times for one
     * parse request. The array contains only new elements after a second call.
     *
     * @param req request handle returned by vlc_preparser_req_NewParse()
     * @param array valid array containing new elements, should only be used
     * within the callback. One and all elements can be held and stored on a
     * new variable or new array.
     * @param count number of elements in the array
     * @param data opaque pointer passed by vlc_preparser_req_NewParse()
     */
    void (*on_attachments_added)(vlc_preparser_req *req,
                                 input_attachment_t *const *array,
                                 size_t count, void *data);
};
 
/**
 * Preparser thumbnailer callbacks
 *
 * Used by vlc_preparser_req_NewThumbnail()
 */
struct vlc_thumbnailer_cbs
{
    /**
     * Event received on thumbnailing completion or error
     *
     * This callback is invoked exactly once for each request successfully
     * submitted with vlc_preparser_Submit().
     *
     * @note This callback is mandatory if calling
     * vlc_preparser_req_NewThumbnail()
     *
     * In case of failure, timeout or cancellation, thumbnail will be NULL.
     * The picture, if any, is owned by the thumbnailer, and must be acquired
     * by using \link picture_Hold \endlink to use it pass the callback's
     * scope.
     *
     * @param req request handle returned by vlc_preparser_req_NewThumbnail()
     * @param status VLC_SUCCESS in case of success, VLC_ETIMEOUT in case of
     * timeout, -EINTR if cancelled, an error otherwise
     * @param thumbnail The generated thumbnail, or NULL in case of failure,
     * timeout or cancellation
     * @param data opaque pointer passed by
     * vlc_preparser_req_NewThumbnail()
     */
    void (*on_ended)(vlc_preparser_req *req, int status, picture_t* thumbnail, void *data);
};
 
/**
 * Preparser thumbnailer to file callbacks
 *
 * Used by vlc_preparser_req_NewThumbnailToFiles()
 */
struct vlc_thumbnailer_to_files_cbs
{
    /**
     * Event received on thumbnailing completion or error
     *
     * This callback is invoked exactly once for each request successfully
     * submitted with vlc_preparser_Submit().
     *
     * @note This callback is mandatory if calling
     * vlc_preparser_req_NewThumbnailToFiles()
     *
     * In case of failure, timeout or cancellation, result_array will be NULL
     * and result_count will be 0.
     *
     * @param req request handle returned by vlc_preparser_req_NewThumbnailToFiles()
     * @param status VLC_SUCCESS in case of success, VLC_ETIMEOUT in case of
     * timeout, -EINTR if cancelled, an error otherwise. A success mean that an
     * image was generated but it is still possible that the export failed,
     * check result_array to assure export were successful.
     * @param result_array array of results, if result_array[i] is true, the
     * outputs[i] from vlc_preparser_req_NewThumbnailToFiles() succeeded. NULL
     * if the status is not VLC_SUCCESS.
     * @param result_count size of the array, same than the output_count arg
     * from vlc_preparser_req_NewThumbnailToFiles(), or 0 if the status is not
     * VLC_SUCCESS
     * @param data opaque pointer passed by
     * vlc_preparser_req_NewThumbnailToFiles()
     */
    void (*on_ended)(vlc_preparser_req *req, int status,
                     const bool *result_array, size_t result_count, void *data);
};
 
/**
 * Thumbnailer argument
 *
 * Used by vlc_preparser_req_NewThumbnail() and
 * vlc_preparser_req_NewThumbnailToFiles()
 */
struct vlc_thumbnailer_arg
{
    /** Seek argument */
    struct seek
    {
        enum
        {
            /** Don't seek (default) */
            VLC_THUMBNAILER_SEEK_NONE,
            /** Seek by time */
            VLC_THUMBNAILER_SEEK_TIME,
            /** Seek by position */
            VLC_THUMBNAILER_SEEK_POS,
        } type;
        union
        {
            /** Seek time if type == VLC_THUMBNAILER_SEEK_TIME */
            vlc_tick_t time;
            /** Seek position if type == VLC_THUMBNAILER_SEEK_POS */
            double pos;
        };
        enum
        {
            /** Precise, but potentially slow */
            VLC_THUMBNAILER_SEEK_PRECISE,
            /** Fast, but potentially imprecise */
            VLC_THUMBNAILER_SEEK_FAST,
        } speed;
    } seek;
 
    /** True to enable hardware decoder (false by default) */
    bool hw_dec;
};
 
/**
 * Thumbnailer output format
 */
enum vlc_thumbnailer_format
{
    VLC_THUMBNAILER_FORMAT_PNG,
    VLC_THUMBNAILER_FORMAT_WEBP,
    VLC_THUMBNAILER_FORMAT_JPEG,
    VLC_THUMBNAILER_FORMAT_RGBA,
    VLC_THUMBNAILER_FORMAT_ARGB,
};
 
/**
 * Thumbnailer output argument
 *
 * Used by vlc_preparser_req_NewThumbnailToFiles()
 */
struct vlc_thumbnailer_output
{
    /**
     * Thumbnailer output format
     */
    enum vlc_thumbnailer_format format;
 
    /**
     * Requested width of the thumbnail
     *
     * cf. picture_Export() documentation.
     */
    int width;
 
    /**
     * Requested Height of the thumbnail
     *
     * cf. picture_Export() documentation.
     */
    int height;
 
    /**
     * True if the thumbnail should be cropped
     *
     * cf. picture_Export() documentation.
     */
    bool crop;
 
    /** File output path of the thumbnail */
    const char *file_path;
    /** File mode bits (cf. "mode_t mode" in `man 2 open`) */
    unsigned int creat_mode;
};
 
/**
 * Preparser creation configuration
 */
struct vlc_preparser_cfg
{
    /**
     * A combination of VLC_PREPARSER_TYPE_* flags, it is used to
     * setup the executors for each domain. Its possible to select more than
     * one type
     */
    int types;
 
    /**
     * The maximum number of threads used by the parser, 0 for default
     * (1 thread)
     */
    unsigned max_parser_threads;
 
    /**
     * The maximum number of threads used by the thumbnailer, 0 for default
     * (1 thread)
     */
    unsigned max_thumbnailer_threads;
 
    /**
     * Timeout of the preparser and/or thumbnailer, 0 for no limits.
     */
    vlc_tick_t timeout;
 
    /**
     * Indicate if the preparser will use external process or not.
     */
    bool external_process;
};
 
/**
 * This function creates the preparser object and thread.
 *
 * @param obj the parent object
 * @param cfg a pointer to a valid confiuration struct
 * @return a valid preparser object or NULL in case of error
 */
VLC_API vlc_preparser_t *vlc_preparser_New( vlc_object_t *obj,
                                            const struct vlc_preparser_cfg *cfg );
 
/**
 * Get the best possible format
 *
 * @param[out] format pointer to the best format
 * @param[out] out_ext pointer to the extension of the format
 * @return 0 if a format was found, VLC_ENOENT otherwise (in case there are no
 * "image encoder" modules)
 */
VLC_API int
vlc_preparser_GetBestThumbnailerFormat(enum vlc_thumbnailer_format *format,
                                       const char **out_ext);
 
/**
 * Check if the format is handled by VLC
 *
 * @param format format to check
 * @return 0 if the format was found, VLC_ENOENT otherwise (in case there are
 * no "image encoder" modules)
 */
VLC_API int
vlc_preparser_CheckThumbnailerFormat(enum vlc_thumbnailer_format format);
 
/**
 * Create a parse/fetch request.
 *
 * The request is created idle, nothing runs and no callback can fire until it
 * is handed to vlc_preparser_Submit(). The caller owns the returned handle
 * from the moment this function returns.
 *
 * @param preparser the preparser object
 * @param item a valid item to preparse
 * @param type_option a combination of VLC_PREPARSER_TYPE_* and
 * VLC_PREPARSER_OPTION_* flags. The type must be in the set specified in
 * vlc_preparser_New() (it is possible to select less types).
 * @param cbs callback to listen to events (can't be NULL)
 * @param cbs_userdata opaque pointer used by the callbacks
 * @return a request handle owned by the caller, or NULL in case of error. It
 * must be released with vlc_preparser_req_Release(), whether or not it is
 * submitted.
 *
 * @note The provided input_item will be held by the preparser and can safely be
 * released after calling this function.
 */
VLC_API vlc_preparser_req *
vlc_preparser_req_NewParse( vlc_preparser_t *preparser, input_item_t *item,
                            int type_option,
                            const struct vlc_preparser_cbs *cbs,
                            void *cbs_userdata );
 
/**
 * Create a thumbnail generation request.
 *
 * The request is created idle, nothing runs and no callback can fire until it
 * is handed to vlc_preparser_Submit(). The caller owns the returned handle
 * from the moment this function returns.
 *
 * @param preparser the preparser object
 * @param item a valid item to generate the thumbnail for
 * @param arg pointer to the arg struct, NULL for default options
 * @param cbs callback to listen to events (can't be NULL)
 * @param cbs_userdata opaque pointer used by the callbacks
 * @return a request handle owned by the caller, or NULL in case of error. It
 * must be released with vlc_preparser_req_Release(), whether or not it is
 * submitted.
 *
 * @note The provided input_item will be held by the preparser and can safely be
 * released after calling this function.
 */
VLC_API vlc_preparser_req *
vlc_preparser_req_NewThumbnail( vlc_preparser_t *preparser, input_item_t *item,
                                const struct vlc_thumbnailer_arg *arg,
                                const struct vlc_thumbnailer_cbs *cbs,
                                void *cbs_userdata );
 
/**
 * Create a request generating a thumbnail to one or several files.
 *
 * The request is created idle, nothing runs and no callback can fire until it
 * is handed to vlc_preparser_Submit(). The caller owns the returned handle
 * from the moment this function returns.
 *
 * @param preparser the preparser object
 * @param item a valid item to generate the thumbnail for
 * @param arg pointer to the arg struct, NULL for default options
 * @param outputs array of outputs, one file will be generated per output for a
 * single thumbnail
 * @param output_count outputs array size, must be > 0
 * @param cbs callback to listen to events (can't be NULL)
 * @param cbs_userdata opaque pointer used by the callbacks
 * @return a request handle owned by the caller, or NULL in case of error. It
 * must be released with vlc_preparser_req_Release(), whether or not it is
 * submitted.
 *
 * @note The provided input_item will be held by the preparser and can safely be
 * released after calling this function.
 */
VLC_API vlc_preparser_req *
vlc_preparser_req_NewThumbnailToFiles( vlc_preparser_t *preparser,
                                       input_item_t *item,
                                       const struct vlc_thumbnailer_arg *arg,
                                       const struct vlc_thumbnailer_output *outputs,
                                       size_t output_count,
                                       const struct vlc_thumbnailer_to_files_cbs *cbs,
                                       void *cbs_userdata );
 
/**
 * Submit a request created by one of the vlc_preparser_req_New*() functions.
 *
 * @param preparser the preparser object the request was created from
 * @param req a request handle that has never been submitted successfully
 * @return VLC_SUCCESS if the request was queued, VLC_EGENERIC otherwise
 *
 * @note
 * - On success the `on_ended` callback is guaranteed to be invoked exactly
 *   once. It may be invoked even before this function returns.
 *
 * - On failure the request was not queued and no callback will be invoked.
 *   The caller keeps its reference and may submit the request again.
 *
 * - A request may be submitted at most once, and may only be re-submitted if
 *   the previous attempt failed. Submitting a request that was already queued
 *   successfully is undefined behaviour.
 *
 * - Submitting the same request concurrently from several threads is
 *   undefined behaviour.
 */
VLC_API int
vlc_preparser_Submit( vlc_preparser_t *preparser, vlc_preparser_req *req );
 
/**
 * This function cancels ongoing or queued preparsing/thumbnail generation
 * for a given request handle.
 *
 * @param preparser the preparser object
 * @param req request handle returned by a vlc_preparser_req_New*() function.
 * Pass NULL to cancel all pending and running tasks.
 * @return number of tasks cancelled
 *
 * @note
 * - When a request is cancelled, the `on_ended` callback will be triggered
 *   with -EINTR status.
 *
 * - That callback may run synchronously, on the thread calling this function,
 *   if the request had not started yet. The caller must be careful not to hold
 *   any lock that the callback needs, or it will deadlock against itself.
 *
 * - If the request is already in a terminated state (finished, cancelled or
 *   error), or if it was never submitted, the call is a no-op and no callback
 *   will be invoked.
 */
VLC_API size_t vlc_preparser_Cancel( vlc_preparser_t *preparser,
                                     vlc_preparser_req *req );
 
/**
 * Fetch the input item associated with the request.
 *
 * @param req request handle returned by a vlc_preparser_req_New*() function.
 * @return input_item_t associated with the request
 *
 * @note The returned input item is held by the request, it must not be
 * released by the caller.
 */
VLC_API input_item_t *vlc_preparser_req_GetItem(vlc_preparser_req *req);
 
/**
 * Release a preparser request handle.
 *
 * @param req the preparser request handle
 *
 * @note
 * - Mandatory to call to avoid memory leaks.
 *
 * - It is safe to call this API from within the on_ended callback.
 *
 * - The request handle should not be used after calling this function.
 *
 * - If called on an active request, it doesn't cancel the preparsing request,
 *   use vlc_preparser_Cancel() for that.
 */
VLC_API void vlc_preparser_req_Release( vlc_preparser_req *req );
 
/**
 * This function destroys the preparser object and thread.
 *
 * @param preparser the preparser object
 * All pending input items will be released.
 */
VLC_API void vlc_preparser_Delete( vlc_preparser_t *preparser );
 
/** @} vlc_preparser */
 
#endif