path: root/gst/gstpad.h

/* GStreamer
 * Copyright (C) 1999,2000 Erik Walthinsen <omega@cse.ogi.edu>
 *                    2000 Wim Taymans <wim.taymans@chello.be>
 *
 * gstpad.h: Header for GstPad object
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library 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
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with this library; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */


#ifndef __GST_PAD_H__
#define __GST_PAD_H__

#include <gst/gstconfig.h>

typedef struct _GstPad GstPad;
typedef struct _GstPadPrivate GstPadPrivate;
typedef struct _GstPadClass GstPadClass;
typedef struct _GstPadProbeInfo GstPadProbeInfo;

/**
 * GstPadDirection:
 * @GST_PAD_UNKNOWN: direction is unknown.
 * @GST_PAD_SRC: the pad is a source pad.
 * @GST_PAD_SINK: the pad is a sink pad.
 *
 * The direction of a pad.
 */
typedef enum {
  GST_PAD_UNKNOWN,
  GST_PAD_SRC,
  GST_PAD_SINK
} GstPadDirection;

/**
 * GstPadMode:
 * @GST_PAD_MODE_NONE: Pad will not handle dataflow
 * @GST_PAD_MODE_PUSH: Pad handles dataflow in downstream push mode
 * @GST_PAD_MODE_PULL: Pad handles dataflow in upstream pull mode
 *
 * The status of a GstPad. After activating a pad, which usually happens when the
 * parent element goes from READY to PAUSED, the GstPadMode defines if the
 * pad operates in push or pull mode.
 */
typedef enum {
  GST_PAD_MODE_NONE,
  GST_PAD_MODE_PUSH,
  GST_PAD_MODE_PULL
} GstPadMode;

#include <gst/gstobject.h>
#include <gst/gstbuffer.h>
#include <gst/gstbufferlist.h>
#include <gst/gstcaps.h>
#include <gst/gstpadtemplate.h>
#include <gst/gstevent.h>
#include <gst/gstquery.h>
#include <gst/gsttask.h>

G_BEGIN_DECLS

/*
 * Pad base class
 */
#define GST_TYPE_PAD			(gst_pad_get_type ())
#define GST_IS_PAD(obj)			(G_TYPE_CHECK_INSTANCE_TYPE ((obj), GST_TYPE_PAD))
#define GST_IS_PAD_CLASS(klass)		(G_TYPE_CHECK_CLASS_TYPE ((klass), GST_TYPE_PAD))
#define GST_PAD(obj)			(G_TYPE_CHECK_INSTANCE_CAST ((obj), GST_TYPE_PAD, GstPad))
#define GST_PAD_CLASS(klass)		(G_TYPE_CHECK_CLASS_CAST ((klass), GST_TYPE_PAD, GstPadClass))
#define GST_PAD_CAST(obj)		((GstPad*)(obj))



/**
 * GstPadLinkReturn:
 * @GST_PAD_LINK_OK		: link succeeded
 * @GST_PAD_LINK_WRONG_HIERARCHY: pads have no common grandparent
 * @GST_PAD_LINK_WAS_LINKED	: pad was already linked
 * @GST_PAD_LINK_WRONG_DIRECTION: pads have wrong direction
 * @GST_PAD_LINK_NOFORMAT	: pads do not have common format
 * @GST_PAD_LINK_NOSCHED	: pads cannot cooperate in scheduling
 * @GST_PAD_LINK_REFUSED	: refused for some reason
 *
 * Result values from gst_pad_link and friends.
 */
typedef enum {
  GST_PAD_LINK_OK               =  0,
  GST_PAD_LINK_WRONG_HIERARCHY  = -1,
  GST_PAD_LINK_WAS_LINKED       = -2,
  GST_PAD_LINK_WRONG_DIRECTION  = -3,
  GST_PAD_LINK_NOFORMAT         = -4,
  GST_PAD_LINK_NOSCHED          = -5,
  GST_PAD_LINK_REFUSED          = -6
} GstPadLinkReturn;

/**
 * GST_PAD_LINK_FAILED:
 * @ret: the #GstPadLinkReturn value
 *
 * Macro to test if the given #GstPadLinkReturn value indicates a failed
 * link step.
 */
#define GST_PAD_LINK_FAILED(ret) ((ret) < GST_PAD_LINK_OK)

/**
 * GST_PAD_LINK_SUCCESSFUL:
 * @ret: the #GstPadLinkReturn value
 *
 * Macro to test if the given #GstPadLinkReturn value indicates a successful
 * link step.
 */
#define GST_PAD_LINK_SUCCESSFUL(ret) ((ret) >= GST_PAD_LINK_OK)

/**
 * GstFlowReturn:
 * @GST_FLOW_OK:		 Data passing was ok.
 * @GST_FLOW_NOT_LINKED:	 Pad is not linked.
 * @GST_FLOW_FLUSHING:	         Pad is flushing.
 * @GST_FLOW_EOS:                Pad is EOS.
 * @GST_FLOW_NOT_NEGOTIATED:	 Pad is not negotiated.
 * @GST_FLOW_ERROR:		 Some (fatal) error occured. Element generating
 *                               this error should post an error message with more
 *                               details.
 * @GST_FLOW_NOT_SUPPORTED:	 This operation is not supported.
 * @GST_FLOW_CUSTOM_SUCCESS:	 Elements can use values starting from
 *                               this (and higher) to define custom success
 *                               codes.
 * @GST_FLOW_CUSTOM_SUCCESS_1:	 Pre-defined custom success code (define your
 *                               custom success code to this to avoid compiler
 *                               warnings).
 * @GST_FLOW_CUSTOM_SUCCESS_2:	 Pre-defined custom success code.
 * @GST_FLOW_CUSTOM_ERROR:	 Elements can use values starting from
 *                               this (and lower) to define custom error codes.
 * @GST_FLOW_CUSTOM_ERROR_1:	 Pre-defined custom error code (define your
 *                               custom error code to this to avoid compiler
 *                               warnings).
 * @GST_FLOW_CUSTOM_ERROR_2:	 Pre-defined custom error code.
 *
 * The result of passing data to a pad.
 *
 * Note that the custom return values should not be exposed outside of the
 * element scope.
 */
/* FIXME 0.11: remove custom flow returns */
typedef enum {
  /* custom success starts here */
  GST_FLOW_CUSTOM_SUCCESS_2 = 102,
  GST_FLOW_CUSTOM_SUCCESS_1 = 101,
  GST_FLOW_CUSTOM_SUCCESS = 100,

  /* core predefined */
  GST_FLOW_OK		  =  0,
  /* expected failures */
  GST_FLOW_NOT_LINKED     = -1,
  GST_FLOW_FLUSHING       = -2,
  /* error cases */
  GST_FLOW_EOS            = -3,
  GST_FLOW_NOT_NEGOTIATED = -4,
  GST_FLOW_ERROR	  = -5,
  GST_FLOW_NOT_SUPPORTED  = -6,

  /* custom error starts here */
  GST_FLOW_CUSTOM_ERROR   = -100,
  GST_FLOW_CUSTOM_ERROR_1 = -101,
  GST_FLOW_CUSTOM_ERROR_2 = -102
} GstFlowReturn;

const gchar*	        gst_flow_get_name	(GstFlowReturn ret);
GQuark			gst_flow_to_quark	(GstFlowReturn ret);

/**
 * GstPadLinkCheck:
 * @GST_PAD_LINK_CHECK_NOTHING: Don't check hierarchy or caps compatibility.
 * @GST_PAD_LINK_CHECK_HIERARCHY: Check the pads have same parents/grandparents.
 *   Could be omitted if it is already known that the two elements that own the
 *   pads are in the same bin.
 * @GST_PAD_LINK_CHECK_TEMPLATE_CAPS: Check if the pads are compatible by using
 *   their template caps. This is much faster than @GST_PAD_LINK_CHECK_CAPS, but
 *   would be unsafe e.g. if one pad has %GST_CAPS_ANY.
 * @GST_PAD_LINK_CHECK_CAPS: Check if the pads are compatible by comparing the
 *   caps returned by gst_pad_query_caps().
 * @GST_PAD_LINK_CHECK_DEFAULT: The default checks done when linking
 *   pads (i.e. the ones used by gst_pad_link()).
 *
 * The amount of checking to be done when linking pads. @GST_PAD_LINK_CHECK_CAPS
 * and @GST_PAD_LINK_CHECK_TEMPLATE_CAPS are mutually exclusive. If both are
 * specified, expensive but safe @GST_PAD_LINK_CHECK_CAPS are performed.
 *
 * <warning><para>
 * Only disable some of the checks if you are 100% certain you know the link
 * will not fail because of hierarchy/caps compatibility failures. If uncertain,
 * use the default checks (%GST_PAD_LINK_CHECK_DEFAULT) or the regular methods
 * for linking the pads.
 * </para></warning>
 */

typedef enum {
  GST_PAD_LINK_CHECK_NOTHING       = 0,
  GST_PAD_LINK_CHECK_HIERARCHY     = 1 << 0,
  GST_PAD_LINK_CHECK_TEMPLATE_CAPS = 1 << 1,
  GST_PAD_LINK_CHECK_CAPS          = 1 << 2,

  GST_PAD_LINK_CHECK_DEFAULT       = GST_PAD_LINK_CHECK_HIERARCHY | GST_PAD_LINK_CHECK_CAPS
} GstPadLinkCheck;

/* pad states */
/**
 * GstPadActivateFunction:
 * @pad: a #GstPad
 * @parent: the parent of @pad
 *
 * This function is called when the pad is activated during the element
 * READY to PAUSED state change. By default this function will call the
 * activate function that puts the pad in push mode but elements can
 * override this function to activate the pad in pull mode if they wish.
 *
 * Returns: TRUE if the pad could be activated.
 */
typedef gboolean		(*GstPadActivateFunction)	(GstPad *pad, GstObject *parent);
/**
 * GstPadActivateModeFunction:
 * @pad: a #GstPad
 * @parent: the parent of @pad
 * @mode: the requested activation mode of @pad
 * @active: activate or deactivate the pad.
 *
 * The prototype of the push and pull activate functions.
 *
 * Returns: TRUE if the pad could be activated or deactivated.
 */
typedef gboolean		(*GstPadActivateModeFunction)	(GstPad *pad, GstObject *parent,
                                                                 GstPadMode mode, gboolean active);


/* data passing */
/**
 * GstPadChainFunction:
 * @pad: the sink #GstPad that performed the chain.
 * @parent: the parent of @pad. If the #GST_PAD_FLAG_NEED_PARENT flag is set,
 *          @parent is guaranteed to be not-NULL and remain valid during the
 *          execution of this function.
 * @buffer: the #GstBuffer that is chained, not %NULL.
 *
 * A function that will be called on sinkpads when chaining buffers.
 * The function typically processes the data contained in the buffer and
 * either consumes the data or passes it on to the internally linked pad(s).
 *
 * The implementer of this function receives a refcount to @buffer and should
 * gst_buffer_unref() when the buffer is no longer needed.
 *
 * When a chain function detects an error in the data stream, it must post an
 * error on the bus and return an appropriate #GstFlowReturn value.
 *
 * Returns: #GST_FLOW_OK for success
 */
typedef GstFlowReturn		(*GstPadChainFunction)		(GstPad *pad, GstObject *parent,
                                                                 GstBuffer *buffer);

/**
 * GstPadChainListFunction:
 * @pad: the sink #GstPad that performed the chain.
 * @parent: the parent of @pad. If the #GST_PAD_FLAG_NEED_PARENT flag is set,
 *          @parent is guaranteed to be not-NULL and remain valid during the
 *          execution of this function.
 * @list: the #GstBufferList that is chained, not %NULL.
 *
 * A function that will be called on sinkpads when chaining buffer lists.
 * The function typically processes the data contained in the buffer list and
 * either consumes the data or passes it on to the internally linked pad(s).
 *
 * The implementer of this function receives a refcount to @list and
 * should gst_buffer_list_unref() when the list is no longer needed.
 *
 * When a chainlist function detects an error in the data stream, it must
 * post an error on the bus and return an appropriate #GstFlowReturn value.
 *
 * Returns: #GST_FLOW_OK for success
 */
typedef GstFlowReturn		(*GstPadChainListFunction)	(GstPad *pad, GstObject *parent,
                                                                 GstBufferList *list);

/**
 * GstPadGetRangeFunction:
 * @pad: the src #GstPad to perform the getrange on.
 * @parent: the parent of @pad. If the #GST_PAD_FLAG_NEED_PARENT flag is set,
 *          @parent is guaranteed to be not-NULL and remain valid during the
 *          execution of this function.
 * @offset: the offset of the range
 * @length: the length of the range
 * @buffer: a memory location to hold the result buffer, cannot be NULL.
 *
 * This function will be called on source pads when a peer element
 * request a buffer at the specified @offset and @length. If this function
 * returns #GST_FLOW_OK, the result buffer will be stored in @buffer. The
 * contents of @buffer is invalid for any other return value.
 *
 * This function is installed on a source pad with
 * gst_pad_set_getrange_function() and can only be called on source pads after
 * they are successfully activated with gst_pad_activate_pull().
 *
 * @offset and @length are always given in byte units. @offset must normally be a value
 * between 0 and the length in bytes of the data available on @pad. The
 * length (duration in bytes) can be retrieved with a #GST_QUERY_DURATION or with a
 * #GST_QUERY_SEEKING.
 *
 * Any @offset larger or equal than the length will make the function return
 * #GST_FLOW_EOS, which corresponds to EOS. In this case @buffer does not
 * contain a valid buffer.
 *
 * The buffer size of @buffer will only be smaller than @length when @offset is
 * near the end of the stream. In all other cases, the size of @buffer must be
 * exactly the requested size.
 *
 * It is allowed to call this function with a 0 @length and valid @offset, in
 * which case @buffer will contain a 0-sized buffer and the function returns
 * #GST_FLOW_OK.
 *
 * When this function is called with a -1 @offset, the sequentially next buffer
 * of length @length in the stream is returned.
 *
 * When this function is called with a -1 @length, a buffer with a default
 * optimal length is returned in @buffer. The length might depend on the value
 * of @offset.
 *
 * Returns: #GST_FLOW_OK for success and a valid buffer in @buffer. Any other
 * return value leaves @buffer undefined.
 */
typedef GstFlowReturn		(*GstPadGetRangeFunction)	(GstPad *pad, GstObject *parent,
                                                                 guint64 offset, guint length,
                                                                 GstBuffer **buffer);

/**
 * GstPadEventFunction:
 * @pad: the #GstPad to handle the event.
 * @parent: the parent of @pad. If the #GST_PAD_FLAG_NEED_PARENT flag is set,
 *          @parent is guaranteed to be not-NULL and remain valid during the
 *          execution of this function.
 * @event: the #GstEvent to handle.
 *
 * Function signature to handle an event for the pad.
 *
 * Returns: TRUE if the pad could handle the event.
 */
typedef gboolean		(*GstPadEventFunction)		(GstPad *pad, GstObject *parent,
                                                                 GstEvent *event);


/* internal links */
/**
 * GstPadIterIntLinkFunction:
 * @pad: The #GstPad to query.
 * @parent: the parent of @pad. If the #GST_PAD_FLAG_NEED_PARENT flag is set,
 *          @parent is guaranteed to be not-NULL and remain valid during the
 *          execution of this function.
 *
 * The signature of the internal pad link iterator function.
 *
 * Returns: a new #GstIterator that will iterate over all pads that are
 * linked to the given pad on the inside of the parent element.
 *
 * the caller must call gst_iterator_free() after usage.
 */
typedef GstIterator*           (*GstPadIterIntLinkFunction)    (GstPad *pad, GstObject *parent);

/* generic query function */
/**
 * GstPadQueryFunction:
 * @pad: the #GstPad to query.
 * @parent: the parent of @pad. If the #GST_PAD_FLAG_NEED_PARENT flag is set,
 *          @parent is guaranteed to be not-NULL and remain valid during the
 *          execution of this function.
 * @query: the #GstQuery object to execute
 *
 * The signature of the query function.
 *
 * Returns: TRUE if the query could be performed.
 */
typedef gboolean		(*GstPadQueryFunction)		(GstPad *pad, GstObject *parent,
                                                                 GstQuery *query);


/* linking */
/**
 * GstPadLinkFunction:
 * @pad: the #GstPad that is linked.
 * @peer: the peer #GstPad of the link
 *
 * Function signature to handle a new link on the pad.
 *
 * Returns: the result of the link with the specified peer.
 */
typedef GstPadLinkReturn	(*GstPadLinkFunction)		(GstPad *pad, GstPad *peer);
/**
 * GstPadUnlinkFunction:
 * @pad: the #GstPad that is linked.
 *
 * Function signature to handle a unlinking the pad prom its peer.
 */
typedef void			(*GstPadUnlinkFunction)		(GstPad *pad);


/* misc */
/**
 * GstPadForwardFunction:
 * @pad: the #GstPad that is forwarded.
 * @user_data: the gpointer to optional user data.
 *
 * A forward function is called for all internally linked pads, see
 * gst_pad_forward().
 *
 * Returns: TRUE if the dispatching procedure has to be stopped.
 */
typedef gboolean		(*GstPadForwardFunction)	(GstPad *pad, gpointer user_data);

/**
 * GstPadProbeType:
 * @GST_PAD_PROBE_TYPE_INVALID: invalid probe type
 * @GST_PAD_PROBE_TYPE_IDLE: probe idle pads and block
 * @GST_PAD_PROBE_TYPE_BLOCK: probe and block pads
 * @GST_PAD_PROBE_TYPE_BUFFER: probe buffers
 * @GST_PAD_PROBE_TYPE_BUFFER_LIST: probe buffer lists
 * @GST_PAD_PROBE_TYPE_EVENT_DOWNSTREAM: probe downstream events
 * @GST_PAD_PROBE_TYPE_EVENT_UPSTREAM: probe upstream events
 * @GST_PAD_PROBE_TYPE_EVENT_FLUSH: probe flush events. This probe has to be
 *     explicitly enabled and is not included in the
 *     @@GST_PAD_PROBE_TYPE_EVENT_DOWNSTREAM or
 *     @@GST_PAD_PROBE_TYPE_EVENT_UPSTREAM probe types.
 * @GST_PAD_PROBE_TYPE_QUERY_DOWNSTREAM: probe downstream queries
 * @GST_PAD_PROBE_TYPE_QUERY_UPSTREAM: probe upstream queries
 * @GST_PAD_PROBE_TYPE_PUSH: probe push
 * @GST_PAD_PROBE_TYPE_PULL: probe pull
 *
 * The different probing types that can occur. When either one of
 * @GST_PAD_PROBE_TYPE_IDLE or @GST_PAD_PROBE_TYPE_BLOCK is used, the probe will be a
 * blocking probe.
 */
typedef enum
{
  GST_PAD_PROBE_TYPE_INVALID          = 0,
  /* flags to control blocking */
  GST_PAD_PROBE_TYPE_IDLE             = (1 << 0),
  GST_PAD_PROBE_TYPE_BLOCK            = (1 << 1),
  /* flags to select datatypes */
  GST_PAD_PROBE_TYPE_BUFFER           = (1 << 4),
  GST_PAD_PROBE_TYPE_BUFFER_LIST      = (1 << 5),
  GST_PAD_PROBE_TYPE_EVENT_DOWNSTREAM = (1 << 6),
  GST_PAD_PROBE_TYPE_EVENT_UPSTREAM   = (1 << 7),
  GST_PAD_PROBE_TYPE_EVENT_FLUSH      = (1 << 8),
  GST_PAD_PROBE_TYPE_QUERY_DOWNSTREAM = (1 << 9),
  GST_PAD_PROBE_TYPE_QUERY_UPSTREAM   = (1 << 10),
  /* flags to select scheduling mode */
  GST_PAD_PROBE_TYPE_PUSH             = (1 << 12),
  GST_PAD_PROBE_TYPE_PULL             = (1 << 13)
} GstPadProbeType;

#define GST_PAD_PROBE_TYPE_BLOCKING         (GST_PAD_PROBE_TYPE_IDLE | GST_PAD_PROBE_TYPE_BLOCK)
#define GST_PAD_PROBE_TYPE_BLOCK_DOWNSTREAM (GST_PAD_PROBE_TYPE_BLOCK | GST_PAD_PROBE_TYPE_DATA_DOWNSTREAM)
#define GST_PAD_PROBE_TYPE_BLOCK_UPSTREAM   (GST_PAD_PROBE_TYPE_BLOCK | GST_PAD_PROBE_TYPE_DATA_UPSTREAM)
#define GST_PAD_PROBE_TYPE_DATA_DOWNSTREAM  (GST_PAD_PROBE_TYPE_BUFFER | GST_PAD_PROBE_TYPE_BUFFER_LIST | \
                                             GST_PAD_PROBE_TYPE_EVENT_DOWNSTREAM)
#define GST_PAD_PROBE_TYPE_DATA_UPSTREAM    (GST_PAD_PROBE_TYPE_EVENT_UPSTREAM)
#define GST_PAD_PROBE_TYPE_DATA_BOTH        (GST_PAD_PROBE_TYPE_DATA_DOWNSTREAM | \
                                             GST_PAD_PROBE_TYPE_DATA_UPSTREAM)
#define GST_PAD_PROBE_TYPE_EVENT_BOTH       (GST_PAD_PROBE_TYPE_EVENT_DOWNSTREAM | \
                                             GST_PAD_PROBE_TYPE_EVENT_UPSTREAM)
#define GST_PAD_PROBE_TYPE_QUERY_BOTH       (GST_PAD_PROBE_TYPE_QUERY_DOWNSTREAM | \
                                             GST_PAD_PROBE_TYPE_QUERY_UPSTREAM)
#define GST_PAD_PROBE_TYPE_ALL_BOTH         (GST_PAD_PROBE_TYPE_DATA_BOTH | \
                                             GST_PAD_PROBE_TYPE_QUERY_BOTH)
#define GST_PAD_PROBE_TYPE_SCHEDULING       (GST_PAD_PROBE_TYPE_PUSH | GST_PAD_PROBE_TYPE_PULL)

/**
 * GstPadProbeReturn:
 * @GST_PAD_PROBE_OK: normal probe return value
 * @GST_PAD_PROBE_DROP: drop data in data probes. For push mode this means that
 *        the data item is not sent downstream. For pull mode, it means that the
 *        data item is not passed upstream. In both cases, this result code
 *        returns #GST_FLOW_OK or %TRUE to the caller.
 * @GST_PAD_PROBE_REMOVE: remove probe
 * @GST_PAD_PROBE_PASS: pass the data item in the block probe and block on
 *                         the next item
 *
 * Different return values for the #GstPadProbeCallback.
 */
typedef enum
{
  GST_PAD_PROBE_DROP,
  GST_PAD_PROBE_OK,
  GST_PAD_PROBE_REMOVE,
  GST_PAD_PROBE_PASS,
} GstPadProbeReturn;


/**
 * GstPadProbeInfo:
 * @type: the current probe type
 * @id: the id of the probe
 * @data: type specific data, check the @type field to know the datatype.
 *    This field can be NULL.
 * @offset: offset of pull probe, this field is valid when @type contains
 *    #GST_PAD_PROBE_TYPE_PULL
 * @size: size of pull probe, this field is valid when @type contains
 *    #GST_PAD_PROBE_TYPE_PULL
 *
 * Info passed in the #GstPadProbeCallback.
 */
struct _GstPadProbeInfo
{
  GstPadProbeType type;
  gulong id;
  gpointer data;
  guint64 offset;
  guint size;

  /*< private >*/
  gpointer _gst_reserved[GST_PADDING];
};

#define GST_PAD_PROBE_INFO_TYPE(d)         ((d)->type)
#define GST_PAD_PROBE_INFO_ID(d)           ((d)->id)
#define GST_PAD_PROBE_INFO_DATA(d)         ((d)->data)

#define GST_PAD_PROBE_INFO_BUFFER(d)       GST_BUFFER_CAST(GST_PAD_PROBE_INFO_DATA(d))
#define GST_PAD_PROBE_INFO_BUFFER_LIST(d)  GST_BUFFER_LIST_CAST(GST_PAD_PROBE_INFO_DATA(d))
#define GST_PAD_PROBE_INFO_EVENT(d)        GST_EVENT_CAST(GST_PAD_PROBE_INFO_DATA(d))
#define GST_PAD_PROBE_INFO_QUERY(d)        GST_QUERY_CAST(GST_PAD_PROBE_INFO_DATA(d))

#define GST_PAD_PROBE_INFO_OFFSET(d)       ((d)->offset)
#define GST_PAD_PROBE_INFO_SIZE(d)         ((d)->size)

/**
 * GstPadProbeCallback:
 * @pad: the #GstPad that is blocked
 * @info: #GstPadProbeInfo
 * @user_data: the gpointer to optional user data.
 *
 * Callback used by gst_pad_add_probe(). Gets called to notify about the current
 * blocking type.
 *
 * The callback is allowed to modify the data pointer in @info.
 */
typedef GstPadProbeReturn   (*GstPadProbeCallback)   (GstPad *pad, GstPadProbeInfo *info,
                                                      gpointer user_data);

/**
 * GstPadStickyEventsForeachFunction:
 * @pad: the #GstPad.
 * @event: a sticky #GstEvent.
 * @user_data: the #gpointer to optional user data.
 *
 * Callback used by gst_pad_sticky_events_foreach().
 *
 * When this function returns %TRUE, the next event will be
 * returned. When %FALSE is returned, gst_pad_sticky_events_foreach() will return.
 *
 * When @event is set to NULL, the item will be removed from the list of sticky events.
 * When @event has been made writable, the new buffer reference can be assigned
 * to @event. This function is responsible for unreffing the old event when
 * removing or modifying.
 *
 * Returns: %TRUE if the iteration should continue
 */
typedef gboolean  (*GstPadStickyEventsForeachFunction) (GstPad *pad, GstEvent **event,
                                                        gpointer user_data);

/**
 * GstPadFlags:
 * @GST_PAD_FLAG_BLOCKED: is dataflow on a pad blocked
 * @GST_PAD_FLAG_FLUSHING: is pad flushing
 * @GST_PAD_FLAG_EOS: is pad in EOS state
 * @GST_PAD_FLAG_BLOCKING: is pad currently blocking on a buffer or event
 * @GST_PAD_FLAG_NEED_PARENT: ensure that there is a parent object before calling
 *                       into the pad callbacks.
 * @GST_PAD_FLAG_NEED_RECONFIGURE: the pad should be reconfigured/renegotiated.
 *                            The flag has to be unset manually after
 *                            reconfiguration happened.
 * @GST_PAD_FLAG_PENDING_EVENTS: the pad has pending events
 * @GST_PAD_FLAG_FIXED_CAPS: the pad is using fixed caps this means that once the
 *                      caps are set on the pad, the caps query function only
 *                      returns those caps.
 * @GST_PAD_FLAG_PROXY_CAPS: the default event and query handler will forward
 *                      all events and queries to the internally linked pads
 *                      instead of discarding them.
 * @GST_PAD_FLAG_PROXY_ALLOCATION: the default query handler will forward
 *                      allocation queries to the internally linked pads
 *                      instead of discarding them.
 * @GST_PAD_FLAG_PROXY_SCHEDULING: the default query handler will forward
 *                      scheduling queries to the internally linked pads
 *                      instead of discarding them.
 * @GST_PAD_FLAG_LAST: offset to define more flags
 *
 * Pad state flags
 */
typedef enum {
  GST_PAD_FLAG_BLOCKED          = (GST_OBJECT_FLAG_LAST << 0),
  GST_PAD_FLAG_FLUSHING         = (GST_OBJECT_FLAG_LAST << 1),
  GST_PAD_FLAG_EOS              = (GST_OBJECT_FLAG_LAST << 2),
  GST_PAD_FLAG_BLOCKING         = (GST_OBJECT_FLAG_LAST << 3),
  GST_PAD_FLAG_NEED_PARENT      = (GST_OBJECT_FLAG_LAST << 4),
  GST_PAD_FLAG_NEED_RECONFIGURE = (GST_OBJECT_FLAG_LAST << 5),
  GST_PAD_FLAG_PENDING_EVENTS   = (GST_OBJECT_FLAG_LAST << 6),
  GST_PAD_FLAG_FIXED_CAPS       = (GST_OBJECT_FLAG_LAST << 7),
  GST_PAD_FLAG_PROXY_CAPS       = (GST_OBJECT_FLAG_LAST << 8),
  GST_PAD_FLAG_PROXY_ALLOCATION = (GST_OBJECT_FLAG_LAST << 9),
  GST_PAD_FLAG_PROXY_SCHEDULING = (GST_OBJECT_FLAG_LAST << 10),
  /* padding */
  GST_PAD_FLAG_LAST        = (GST_OBJECT_FLAG_LAST << 16)
} GstPadFlags;

/**
 * GstPad:
 * @element_private: private data owned by the parent element
 * @padtemplate: padtemplate for this pad
 * @direction: the direction of the pad, cannot change after creating
 *             the pad.
 *
 * The #GstPad structure. Use the functions to update the variables.
 */
struct _GstPad {
  GstObject                      object;

  /*< public >*/
  gpointer                       element_private;

  GstPadTemplate                *padtemplate;

  GstPadDirection                direction;

  /*< private >*/
  /* streaming rec_lock */
  GRecMutex		         stream_rec_lock;
  GstTask			*task;

  /* block cond, mutex is from the object */
  GCond				 block_cond;
  GHookList                      probes;

  GstPadMode		         mode;
  GstPadActivateFunction	 activatefunc;
  gpointer                       activatedata;
  GDestroyNotify                 activatenotify;
  GstPadActivateModeFunction	 activatemodefunc;
  gpointer                       activatemodedata;
  GDestroyNotify                 activatemodenotify;

  /* pad link */
  GstPad			*peer;
  GstPadLinkFunction		 linkfunc;
  gpointer                       linkdata;
  GDestroyNotify                 linknotify;
  GstPadUnlinkFunction		 unlinkfunc;
  gpointer                       unlinkdata;
  GDestroyNotify                 unlinknotify;

  /* data transport functions */
  GstPadChainFunction		 chainfunc;
  gpointer                       chaindata;
  GDestroyNotify                 chainnotify;
  GstPadChainListFunction        chainlistfunc;
  gpointer                       chainlistdata;
  GDestroyNotify                 chainlistnotify;
  GstPadGetRangeFunction	 getrangefunc;
  gpointer                       getrangedata;
  GDestroyNotify                 getrangenotify;
  GstPadEventFunction		 eventfunc;
  gpointer                       eventdata;
  GDestroyNotify                 eventnotify;

  /* pad offset */
  gint64                         offset;

  /* generic query method */
  GstPadQueryFunction		 queryfunc;
  gpointer                       querydata;
  GDestroyNotify                 querynotify;

  /* internal links */
  GstPadIterIntLinkFunction      iterintlinkfunc;
  gpointer                       iterintlinkdata;
  GDestroyNotify                 iterintlinknotify;

  /* counts number of probes attached. */
  gint				 num_probes;
  gint				 num_blocked;

  GstPadPrivate                 *priv;

  gpointer _gst_reserved[GST_PADDING];
};

struct _GstPadClass {
  GstObjectClass	parent_class;

  /* signal callbacks */
  void		(*linked)		(GstPad *pad, GstPad *peer);
  void		(*unlinked)		(GstPad *pad, GstPad *peer);

  /*< private >*/
  gpointer _gst_reserved[GST_PADDING];
};


/***** helper macros *****/
/* GstPad */
#define GST_PAD_NAME(pad)		(GST_OBJECT_NAME(pad))
#define GST_PAD_PARENT(pad)		(GST_ELEMENT_CAST(GST_OBJECT_PARENT(pad)))
#define GST_PAD_ELEMENT_PRIVATE(pad)    (GST_PAD_CAST(pad)->element_private)
#define GST_PAD_PAD_TEMPLATE(pad)	(GST_PAD_CAST(pad)->padtemplate)
#define GST_PAD_DIRECTION(pad)		(GST_PAD_CAST(pad)->direction)
#define GST_PAD_TASK(pad)		(GST_PAD_CAST(pad)->task)
#define GST_PAD_MODE(pad)	        (GST_PAD_CAST(pad)->mode)

#define GST_PAD_ACTIVATEFUNC(pad)	(GST_PAD_CAST(pad)->activatefunc)
#define GST_PAD_ACTIVATEMODEFUNC(pad)	(GST_PAD_CAST(pad)->activatemodefunc)
#define GST_PAD_CHAINFUNC(pad)		(GST_PAD_CAST(pad)->chainfunc)
#define GST_PAD_CHAINLISTFUNC(pad)      (GST_PAD_CAST(pad)->chainlistfunc)
#define GST_PAD_GETRANGEFUNC(pad)	(GST_PAD_CAST(pad)->getrangefunc)
#define GST_PAD_EVENTFUNC(pad)		(GST_PAD_CAST(pad)->eventfunc)
#define GST_PAD_QUERYFUNC(pad)		(GST_PAD_CAST(pad)->queryfunc)
#define GST_PAD_ITERINTLINKFUNC(pad)    (GST_PAD_CAST(pad)->iterintlinkfunc)

#define GST_PAD_PEER(pad)		(GST_PAD_CAST(pad)->peer)
#define GST_PAD_LINKFUNC(pad)		(GST_PAD_CAST(pad)->linkfunc)
#define GST_PAD_UNLINKFUNC(pad)		(GST_PAD_CAST(pad)->unlinkfunc)

#define GST_PAD_IS_SRC(pad)		(GST_PAD_DIRECTION(pad) == GST_PAD_SRC)
#define GST_PAD_IS_SINK(pad)		(GST_PAD_DIRECTION(pad) == GST_PAD_SINK)

#define GST_PAD_IS_LINKED(pad)		(GST_PAD_PEER(pad) != NULL)

#define GST_PAD_IS_ACTIVE(pad)          (GST_PAD_MODE(pad) != GST_PAD_MODE_NONE)

#define GST_PAD_IS_BLOCKED(pad)		(GST_OBJECT_FLAG_IS_SET (pad, GST_PAD_FLAG_BLOCKED))
#define GST_PAD_IS_BLOCKING(pad)	(GST_OBJECT_FLAG_IS_SET (pad, GST_PAD_FLAG_BLOCKING))

#define GST_PAD_IS_FLUSHING(pad)	(GST_OBJECT_FLAG_IS_SET (pad, GST_PAD_FLAG_FLUSHING))
#define GST_PAD_SET_FLUSHING(pad)	(GST_OBJECT_FLAG_SET (pad, GST_PAD_FLAG_FLUSHING))
#define GST_PAD_UNSET_FLUSHING(pad)	(GST_OBJECT_FLAG_UNSET (pad, GST_PAD_FLAG_FLUSHING))

#define GST_PAD_IS_EOS(pad)	        (GST_OBJECT_FLAG_IS_SET (pad, GST_PAD_FLAG_EOS))

#define GST_PAD_NEEDS_RECONFIGURE(pad)  (GST_OBJECT_FLAG_IS_SET (pad, GST_PAD_FLAG_NEED_RECONFIGURE))
#define GST_PAD_HAS_PENDING_EVENTS(pad) (GST_OBJECT_FLAG_IS_SET (pad, GST_PAD_FLAG_PENDING_EVENTS))
#define GST_PAD_IS_FIXED_CAPS(pad)	(GST_OBJECT_FLAG_IS_SET (pad, GST_PAD_FLAG_FIXED_CAPS))
#define GST_PAD_NEEDS_PARENT(pad)       (GST_OBJECT_FLAG_IS_SET (pad, GST_PAD_FLAG_NEED_PARENT))

#define GST_PAD_IS_PROXY_CAPS(pad)      (GST_OBJECT_FLAG_IS_SET (pad, GST_PAD_FLAG_PROXY_CAPS))
#define GST_PAD_SET_PROXY_CAPS(pad)     (GST_OBJECT_FLAG_SET (pad, GST_PAD_FLAG_PROXY_CAPS))
#define GST_PAD_UNSET_PROXY_CAPS(pad)   (GST_OBJECT_FLAG_UNSET (pad, GST_PAD_FLAG_PROXY_CAPS))

#define GST_PAD_IS_PROXY_ALLOCATION(pad)    (GST_OBJECT_FLAG_IS_SET (pad, GST_PAD_FLAG_PROXY_ALLOCATION))
#define GST_PAD_SET_PROXY_ALLOCATION(pad)   (GST_OBJECT_FLAG_SET (pad, GST_PAD_FLAG_PROXY_ALLOCATION))
#define GST_PAD_UNSET_PROXY_ALLOCATION(pad) (GST_OBJECT_FLAG_UNSET (pad, GST_PAD_FLAG_PROXY_ALLOCATION))

#define GST_PAD_IS_PROXY_SCHEDULING(pad)    (GST_OBJECT_FLAG_IS_SET (pad, GST_PAD_FLAG_PROXY_SCHEDULING))
#define GST_PAD_SET_PROXY_SCHEDULING(pad)   (GST_OBJECT_FLAG_SET (pad, GST_PAD_FLAG_PROXY_SCHEDULING))
#define GST_PAD_UNSET_PROXY_SCHEDULING(pad) (GST_OBJECT_FLAG_UNSET (pad, GST_PAD_FLAG_PROXY_SCHEDULING))

/**
 * GST_PAD_GET_STREAM_LOCK:
 * @pad: a #GstPad
 *
 * Get the stream lock of @pad. The stream lock is protecting the
 * resources used in the data processing functions of @pad.
 */
#define GST_PAD_GET_STREAM_LOCK(pad)    (&(GST_PAD_CAST(pad)->stream_rec_lock))
/**
 * GST_PAD_STREAM_LOCK:
 * @pad: a #GstPad
 *
 * Lock the stream lock of @pad.
 */
#define GST_PAD_STREAM_LOCK(pad)        g_rec_mutex_lock(GST_PAD_GET_STREAM_LOCK(pad))
/**
 * GST_PAD_STREAM_TRYLOCK:
 * @pad: a #GstPad
 *
 * Try to Lock the stream lock of the pad, return TRUE if the lock could be
 * taken.
 */
#define GST_PAD_STREAM_TRYLOCK(pad)     g_rec_mutex_trylock(GST_PAD_GET_STREAM_LOCK(pad))
/**
 * GST_PAD_STREAM_UNLOCK:
 * @pad: a #GstPad
 *
 * Unlock the stream lock of @pad.
 */
#define GST_PAD_STREAM_UNLOCK(pad)      g_rec_mutex_unlock(GST_PAD_GET_STREAM_LOCK(pad))

#define GST_PAD_BLOCK_GET_COND(pad)     (&GST_PAD_CAST(pad)->block_cond)
#define GST_PAD_BLOCK_WAIT(pad)         (g_cond_wait(GST_PAD_BLOCK_GET_COND (pad), GST_OBJECT_GET_LOCK (pad)))
#define GST_PAD_BLOCK_SIGNAL(pad)       (g_cond_signal(GST_PAD_BLOCK_GET_COND (pad)))
#define GST_PAD_BLOCK_BROADCAST(pad)    (g_cond_broadcast(GST_PAD_BLOCK_GET_COND (pad)))

GType			gst_pad_get_type			(void);

/* creating pads */
GstPad*			gst_pad_new				(const gchar *name, GstPadDirection direction);
GstPad*			gst_pad_new_from_template		(GstPadTemplate *templ, const gchar *name);
GstPad*			gst_pad_new_from_static_template	(GstStaticPadTemplate *templ, const gchar *name);


/**
 * gst_pad_get_name:
 * @pad: the pad to get the name from
 *
 * Get a copy of the name of the pad. g_free() after usage.
 *
 * MT safe.
 */
#define gst_pad_get_name(pad) gst_object_get_name (GST_OBJECT_CAST (pad))
/**
 * gst_pad_get_parent:
 * @pad: the pad to get the parent of
 *
 * Get the parent of @pad. This function increases the refcount
 * of the parent object so you should gst_object_unref() it after usage.
 * Can return NULL if the pad did not have a parent.
 *
 * MT safe.
 */
#define gst_pad_get_parent(pad) gst_object_get_parent (GST_OBJECT_CAST (pad))

GstPadDirection		gst_pad_get_direction			(GstPad *pad);

gboolean		gst_pad_set_active			(GstPad *pad, gboolean active);
gboolean		gst_pad_is_active			(GstPad *pad);
gboolean		gst_pad_activate_mode			(GstPad *pad, GstPadMode mode,
                                                                 gboolean active);

gulong                  gst_pad_add_probe                       (GstPad *pad,
								 GstPadProbeType mask,
								 GstPadProbeCallback callback,
                                                                 gpointer user_data,
                                                                 GDestroyNotify destroy_data);
void                    gst_pad_remove_probe                    (GstPad *pad, gulong id);

gboolean		gst_pad_is_blocked			(GstPad *pad);
gboolean		gst_pad_is_blocking			(GstPad *pad);

void                    gst_pad_mark_reconfigure                (GstPad *pad);
gboolean		gst_pad_check_reconfigure               (GstPad *pad);

void			gst_pad_set_element_private		(GstPad *pad, gpointer priv);
gpointer		gst_pad_get_element_private		(GstPad *pad);

GstPadTemplate*		gst_pad_get_pad_template		(GstPad *pad);

GstEvent*               gst_pad_get_sticky_event                (GstPad *pad, GstEventType event_type,
                                                                 guint idx);
void                    gst_pad_sticky_events_foreach           (GstPad *pad, GstPadStickyEventsForeachFunction foreach_func, gpointer user_data);

/* data passing setup functions */
void			gst_pad_set_activate_function_full	(GstPad *pad,
                                                                 GstPadActivateFunction activate,
                                                                 gpointer user_data,
                                                                 GDestroyNotify notify);
void			gst_pad_set_activatemode_function_full	(GstPad *pad,
                                                                 GstPadActivateModeFunction activatemode,
                                                                 gpointer user_data,
                                                                 GDestroyNotify notify);
/* data passing functions */
void			gst_pad_set_chain_function_full		(GstPad *pad,
                                                                 GstPadChainFunction chain,
                                                                 gpointer user_data,
                                                                 GDestroyNotify notify);
void			gst_pad_set_chain_list_function_full	(GstPad *pad,
                                                                 GstPadChainListFunction chainlist,
                                                                 gpointer user_data,
                                                                 GDestroyNotify notify);
void			gst_pad_set_getrange_function_full	(GstPad *pad,
                                                                 GstPadGetRangeFunction get,
                                                                 gpointer user_data,
                                                                 GDestroyNotify notify);
void			gst_pad_set_event_function_full		(GstPad *pad,
                                                                 GstPadEventFunction event,
                                                                 gpointer user_data,
                                                                 GDestroyNotify notify);

#define gst_pad_set_activate_function(p,f)      gst_pad_set_activate_function_full((p),(f),NULL,NULL)
#define gst_pad_set_activatemode_function(p,f)  gst_pad_set_activatemode_function_full((p),(f),NULL,NULL)
#define gst_pad_set_chain_function(p,f)         gst_pad_set_chain_function_full((p),(f),NULL,NULL)
#define gst_pad_set_chain_list_function(p,f)    gst_pad_set_chain_list_function_full((p),(f),NULL,NULL)
#define gst_pad_set_getrange_function(p,f)      gst_pad_set_getrange_function_full((p),(f),NULL,NULL)
#define gst_pad_set_event_function(p,f)         gst_pad_set_event_function_full((p),(f),NULL,NULL)

/* pad links */
void			gst_pad_set_link_function_full		(GstPad *pad,
                                                                 GstPadLinkFunction link,
                                                                 gpointer user_data,
                                                                 GDestroyNotify notify);
void			gst_pad_set_unlink_function_full        (GstPad *pad,
                                                                 GstPadUnlinkFunction unlink,
                                                                 gpointer user_data,
                                                                 GDestroyNotify notify);

#define gst_pad_set_link_function(p,f)          gst_pad_set_link_function_full((p),(f),NULL,NULL)
#define gst_pad_set_unlink_function(p,f)        gst_pad_set_unlink_function_full((p),(f),NULL,NULL)

gboolean                gst_pad_can_link                        (GstPad *srcpad, GstPad *sinkpad);
GstPadLinkReturn        gst_pad_link				(GstPad *srcpad, GstPad *sinkpad);
GstPadLinkReturn        gst_pad_link_full			(GstPad *srcpad, GstPad *sinkpad, GstPadLinkCheck flags);
gboolean		gst_pad_unlink				(GstPad *srcpad, GstPad *sinkpad);
gboolean		gst_pad_is_linked			(GstPad *pad);

GstPad*			gst_pad_get_peer			(GstPad *pad);

GstCaps*                gst_pad_get_pad_template_caps		(GstPad *pad);

/* capsnego function for linked/unlinked pads */
GstCaps *		gst_pad_get_current_caps                (GstPad * pad);
gboolean		gst_pad_has_current_caps                (GstPad * pad);

/* capsnego for linked pads */
GstCaps *		gst_pad_get_allowed_caps		(GstPad * pad);

/* pad offsets */
gint64                  gst_pad_get_offset                      (GstPad *pad);
void                    gst_pad_set_offset                      (GstPad *pad, gint64 offset);

/* data passing functions to peer */
GstFlowReturn		gst_pad_push				(GstPad *pad, GstBuffer *buffer);
GstFlowReturn		gst_pad_push_list			(GstPad *pad, GstBufferList *list);
GstFlowReturn		gst_pad_pull_range			(GstPad *pad, guint64 offset, guint size,
								 GstBuffer **buffer);
gboolean		gst_pad_push_event			(GstPad *pad, GstEvent *event);
gboolean		gst_pad_event_default			(GstPad *pad, GstObject *parent,
                                                                 GstEvent *event);

/* data passing functions on pad */
GstFlowReturn		gst_pad_chain				(GstPad *pad, GstBuffer *buffer);
GstFlowReturn		gst_pad_chain_list                      (GstPad *pad, GstBufferList *list);
GstFlowReturn		gst_pad_get_range			(GstPad *pad, guint64 offset, guint size,
								 GstBuffer **buffer);
gboolean		gst_pad_send_event			(GstPad *pad, GstEvent *event);

/* pad tasks */
gboolean		gst_pad_start_task			(GstPad *pad, GstTaskFunction func,
								 gpointer user_data, GDestroyNotify notify);
gboolean		gst_pad_pause_task			(GstPad *pad);
gboolean		gst_pad_stop_task			(GstPad *pad);

/* internal links */
void                    gst_pad_set_iterate_internal_links_function_full (GstPad * pad,
                                                                 GstPadIterIntLinkFunction iterintlink,
                                                                 gpointer user_data,
                                                                 GDestroyNotify notify);
GstIterator *           gst_pad_iterate_internal_links          (GstPad * pad);
GstIterator *           gst_pad_iterate_internal_links_default  (GstPad * pad, GstObject *parent);

#define gst_pad_set_iterate_internal_links_function(p,f) gst_pad_set_iterate_internal_links_function_full((p),(f),NULL,NULL)

/* generic query function */
gboolean		gst_pad_query				(GstPad *pad, GstQuery *query);
gboolean		gst_pad_peer_query			(GstPad *pad, GstQuery *query);
void			gst_pad_set_query_function_full		(GstPad *pad, GstPadQueryFunction query,
                                                                 gpointer user_data,
                                                                 GDestroyNotify notify);
gboolean		gst_pad_query_default			(GstPad *pad, GstObject *parent,
                                                                 GstQuery *query);

#define gst_pad_set_query_function(p,f)   gst_pad_set_query_function_full((p),(f),NULL,NULL)

/* misc helper functions */
gboolean		gst_pad_forward                         (GstPad *pad, GstPadForwardFunction forward,
								 gpointer user_data);

G_END_DECLS

#endif /* __GST_PAD_H__ */