gstreamer/gst/parse/grammar.y

%{
#include <glib-object.h>
#include <glib.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>

#include "../gst_private.h"
#include "../gst-i18n-lib.h"

#include "../gstconfig.h"
#include "../gstparse.h"
#include "../gstinfo.h"
#include "../gsterror.h"
#include "../gststructure.h"
#include "../gsturi.h"
#include "../gstutils.h"
#include "../gstvalue.h"
#include "../gstchildproxy.h"
#include "types.h"

/* All error messages in this file are user-visible and need to be translated.
 * Don't start the message with a capital, and don't end them with a period,
 * as they will be presented inside a sentence/error.
 */
  
#define YYERROR_VERBOSE 1
#define YYLEX_PARAM scanner

typedef void* yyscan_t;

int _gst_parse_yylex (void * yylval_param , yyscan_t yyscanner);
int _gst_parse_yylex_init (yyscan_t scanner);
int _gst_parse_yylex_destroy (yyscan_t scanner);
struct yy_buffer_state * _gst_parse_yy_scan_string (char* , yyscan_t);
void _gst_parse_yypush_buffer_state (void * new_buffer ,yyscan_t yyscanner );
void _gst_parse_yypop_buffer_state (yyscan_t yyscanner );


#ifdef __GST_PARSE_TRACE
static guint __strings;
static guint __links;
static guint __chains;
gchar *
__gst_parse_strdup (gchar *org)
{
  gchar *ret; 
  __strings++;
  ret = g_strdup (org);
  /* g_print ("ALLOCATED STR   (%3u): %p %s\n", __strings, ret, ret); */
  return ret;
}
void
__gst_parse_strfree (gchar *str)
{
  if (str) {
    /* g_print ("FREEING STR     (%3u): %p %s\n", __strings - 1, str, str); */
    g_free (str);
    g_return_if_fail (__strings > 0);
    __strings--;
  }
}
link_t *__gst_parse_link_new ()
{
  link_t *ret;
  __links++;
  ret = g_new0 (link_t, 1);
  /* g_print ("ALLOCATED LINK  (%3u): %p\n", __links, ret); */
  return ret;
}
void
__gst_parse_link_free (link_t *data)
{
  if (data) {
    /* g_print ("FREEING LINK    (%3u): %p\n", __links - 1, data); */
    g_free (data);
    g_return_if_fail (__links > 0);
    __links--;
  }
}
chain_t *
__gst_parse_chain_new ()
{
  chain_t *ret;
  __chains++;
  ret = g_new0 (chain_t, 1);
  /* g_print ("ALLOCATED CHAIN (%3u): %p\n", __chains, ret); */
  return ret;
}
void
__gst_parse_chain_free (chain_t *data)
{
  /* g_print ("FREEING CHAIN   (%3u): %p\n", __chains - 1, data); */
  g_free (data);
  g_return_if_fail (__chains > 0);
  __chains--;
}

#endif /* __GST_PARSE_TRACE */

typedef struct {
  gchar *src_pad;
  gchar *sink_pad;
  GstElement *sink;
  GstCaps *caps;
  gulong signal_id;
  /* FIXME: need to connect to "disposed" signal to clean up,
   * but there is no such signal */
} DelayedLink;

typedef struct {
  GstElement *parent;
  gchar *name;
  gchar *value_str;
  gulong signal_id;
} DelayedSet;

/*** define SET_ERROR and ERROR macros/functions */

#ifdef G_HAVE_ISO_VARARGS

#  define SET_ERROR(error, type, ...) \
G_STMT_START { \
  GST_CAT_ERROR (GST_CAT_PIPELINE, __VA_ARGS__); \
  if ((error) && !*(error)) { \
    g_set_error ((error), GST_PARSE_ERROR, (type), __VA_ARGS__); \
  } \
} G_STMT_END

#  define ERROR(type, ...) \
  SET_ERROR (graph->error, (type), __VA_ARGS__ )

#elif defined(G_HAVE_GNUC_VARARGS)

#  define SET_ERROR(error, type, args...) \
G_STMT_START { \
  GST_CAT_ERROR (GST_CAT_PIPELINE, args ); \
  if ((error) && !*(error)) { \
    g_set_error ((error), GST_PARSE_ERROR, (type), args ); \
  } \
} G_STMT_END

#  define ERROR(type, args...) \
  SET_ERROR (graph->error,(type) , args )

#else

static inline void
SET_ERROR (GError **error, gint type, const char *format, ...)
{
  if (error) {
    if (*error) {
      g_warning ("error while parsing");
    } else {
      va_list varargs;
      char *string;

      va_start (varargs, format);
      string = g_strdup_vprintf (format, varargs);
      va_end (varargs);
      
      g_set_error (error, GST_PARSE_ERROR, type, string);

      g_free (string);
    }
  }
}

#endif /* G_HAVE_ISO_VARARGS */

/*** define YYPRINTF macro/function if we're debugging */

/* bison 1.35 calls this macro with side effects, we need to make sure the
   side effects work - crappy bison */

#ifndef GST_DISABLE_GST_DEBUG
#  define YYDEBUG 1

#  ifdef G_HAVE_ISO_VARARGS

/* #  define YYFPRINTF(a, ...) GST_CAT_DEBUG (GST_CAT_PIPELINE, __VA_ARGS__) */
#    define YYFPRINTF(a, ...) \
G_STMT_START { \
     gchar *temp = g_strdup_printf (__VA_ARGS__); \
     GST_CAT_LOG (GST_CAT_PIPELINE, temp); \
     g_free (temp); \
} G_STMT_END

#  elif defined(G_HAVE_GNUC_VARARGS)

#    define YYFPRINTF(a, args...) \
G_STMT_START { \
     gchar *temp = g_strdup_printf ( args ); \
     GST_CAT_LOG (GST_CAT_PIPELINE, temp); \
     g_free (temp); \
} G_STMT_END

#  else

static inline void
YYPRINTF(const char *format, ...)
{
  va_list varargs;
  gchar *temp;
  
  va_start (varargs, format);
  temp = g_strdup_vprintf (format, varargs);
  GST_CAT_LOG (GST_CAT_PIPELINE, "%s", temp);
  g_free (temp);
  va_end (varargs);
}

#  endif /* G_HAVE_ISO_VARARGS */

#endif /* GST_DISABLE_GST_DEBUG */

#define ADD_MISSING_ELEMENT(graph,name) G_STMT_START {                      \
    if ((graph)->ctx) {                                                     \
      (graph)->ctx->missing_elements =                                      \
          g_list_append ((graph)->ctx->missing_elements, g_strdup (name));  \
    } } G_STMT_END

#define GST_BIN_MAKE(res, type, chainval, assign, free_string) \
G_STMT_START { \
  chain_t *chain = chainval; \
  GSList *walk; \
  GstBin *bin = (GstBin *) gst_element_factory_make (type, NULL); \
  if (!chain) { \
    SET_ERROR (graph->error, GST_PARSE_ERROR_EMPTY_BIN, \
        _("specified empty bin \"%s\", not allowed"), type); \
    g_slist_foreach (assign, (GFunc) gst_parse_strfree, NULL); \
    g_slist_free (assign); \
    gst_object_unref (bin); \
    if (free_string) \
      gst_parse_strfree (type); /* Need to clean up the string */ \
    YYERROR; \
  } else if (!bin) { \
    ADD_MISSING_ELEMENT(graph, type); \
    SET_ERROR (graph->error, GST_PARSE_ERROR_NO_SUCH_ELEMENT, \
        _("no bin \"%s\", skipping"), type); \
    g_slist_foreach (assign, (GFunc) gst_parse_strfree, NULL); \
    g_slist_free (assign); \
    res = chain; \
  } else { \
    for (walk = chain->elements; walk; walk = walk->next ) \
      gst_bin_add (bin, GST_ELEMENT (walk->data)); \
    g_slist_free (chain->elements); \
    chain->elements = g_slist_prepend (NULL, bin); \
    res = chain; \
    /* set the properties now */ \
    for (walk = assign; walk; walk = walk->next) \
      gst_parse_element_set ((gchar *) walk->data, GST_ELEMENT (bin), graph); \
    g_slist_free (assign); \
  } \
} G_STMT_END

#define MAKE_LINK(link, _src, _src_name, _src_pads, _sink, _sink_name, _sink_pads) \
G_STMT_START { \
  link = gst_parse_link_new (); \
  link->src = _src; \
  link->sink = _sink; \
  link->src_name = _src_name; \
  link->sink_name = _sink_name; \
  link->src_pads = _src_pads; \
  link->sink_pads = _sink_pads; \
  link->caps = NULL; \
} G_STMT_END

#define MAKE_REF(link, _src, _pads) \
G_STMT_START { \
  gchar *padname = _src; \
  GSList *pads = _pads; \
  if (padname) { \
    while (*padname != '.') padname++; \
    *padname = '\0'; \
    padname++; \
    if (*padname != '\0') \
      pads = g_slist_prepend (pads, gst_parse_strdup (padname)); \
  } \
  MAKE_LINK (link, NULL, _src, pads, NULL, NULL, NULL); \
} G_STMT_END

static void gst_parse_new_child(GstChildProxy *child_proxy, GObject *object,
                                gpointer data)
{
  DelayedSet *set = (DelayedSet *) data;
  GParamSpec *pspec;
  GValue v = { 0, }; 
  GstObject *target = NULL;
  GType value_type;

  if (gst_child_proxy_lookup (GST_OBJECT (set->parent), set->name, &target, &pspec)) { 
    gboolean got_value = FALSE;

    value_type = G_PARAM_SPEC_VALUE_TYPE (pspec);

    GST_CAT_LOG (GST_CAT_PIPELINE, "parsing delayed property %s as a %s from %s", pspec->name,
      g_type_name (value_type), set->value_str);
    g_value_init (&v, value_type);
    if (gst_value_deserialize (&v, set->value_str))
      got_value = TRUE;
    else if (g_type_is_a (value_type, GST_TYPE_ELEMENT)) {
       GstElement *bin;
       
       bin = gst_parse_bin_from_description (set->value_str, TRUE, NULL);
       if (bin) {
         g_value_set_object (&v, bin);
         got_value = TRUE;
       }
    }
    g_signal_handler_disconnect (child_proxy, set->signal_id);
    g_free(set->name);
    g_free(set->value_str);
    g_free(set);
    if (!got_value)
      goto error;
    g_object_set_property (G_OBJECT (target), pspec->name, &v);
  }

out:
  if (G_IS_VALUE (&v))
    g_value_unset (&v);
  if (target)
    gst_object_unref (target);
  return;

error:
  GST_CAT_ERROR (GST_CAT_PIPELINE, "could not set property \"%s\" in element \"%s\"",
	 pspec->name, GST_ELEMENT_NAME (target));
  goto out;
}


static void
gst_parse_element_set (gchar *value, GstElement *element, graph_t *graph)
{
  GParamSpec *pspec;
  gchar *pos = value;
  GValue v = { 0, }; 
  GstObject *target = NULL;
  GType value_type;

  /* do nothing if assignment is for missing element */
  if (element == NULL)
    goto out;

  /* parse the string, so the property name is null-terminated an pos points
     to the beginning of the value */
  while (!g_ascii_isspace (*pos) && (*pos != '=')) pos++; 
  if (*pos == '=') { 
    *pos = '\0'; 
  } else { 
    *pos = '\0'; 
    pos++;
    while (g_ascii_isspace (*pos)) pos++; 
  } 
  pos++; 
  while (g_ascii_isspace (*pos)) pos++; 
  if (*pos == '"') {
    pos++;
    pos[strlen (pos) - 1] = '\0';
  }
  gst_parse_unescape (pos);

  if (gst_child_proxy_lookup (GST_OBJECT (element), value, &target, &pspec)) { 
    gboolean got_value = FALSE;

    value_type = G_PARAM_SPEC_VALUE_TYPE (pspec); 

    GST_CAT_LOG (GST_CAT_PIPELINE, "parsing property %s as a %s", pspec->name,
      g_type_name (value_type));
    g_value_init (&v, value_type);
    if (gst_value_deserialize (&v, pos))
      got_value = TRUE;
    else if (g_type_is_a (value_type, GST_TYPE_ELEMENT)) {
       GstElement *bin;
       
       bin = gst_parse_bin_from_description (pos, TRUE, NULL);
       if (bin) {
         g_value_set_object (&v, bin);
         got_value = TRUE;
       }
    }
    if (!got_value)
      goto error;
    g_object_set_property (G_OBJECT (target), pspec->name, &v);
  } else { 
    /* do a delayed set */
    if (GST_IS_CHILD_PROXY (element)) {
      DelayedSet *data = g_new (DelayedSet, 1);
      
      data->parent = element;
      data->name = g_strdup(value);
      data->value_str = g_strdup(pos);
      data->signal_id = g_signal_connect(GST_OBJECT (element),"child-added", G_CALLBACK (gst_parse_new_child), data);
    }
    else {
      SET_ERROR (graph->error, GST_PARSE_ERROR_NO_SUCH_PROPERTY, \
          _("no property \"%s\" in element \"%s\""), value, \
          GST_ELEMENT_NAME (element));
    }
  }

out:
  gst_parse_strfree (value);
  if (G_IS_VALUE (&v))
    g_value_unset (&v);
  if (target)
    gst_object_unref (target);
  return;
  
error:
  SET_ERROR (graph->error, GST_PARSE_ERROR_COULD_NOT_SET_PROPERTY,
         _("could not set property \"%s\" in element \"%s\" to \"%s\""), 
	 value, GST_ELEMENT_NAME (element), pos); 
  goto out;
}
static inline void
gst_parse_free_link (link_t *link)
{
  gst_parse_strfree (link->src_name);
  gst_parse_strfree (link->sink_name);
  g_slist_foreach (link->src_pads, (GFunc) gst_parse_strfree, NULL);
  g_slist_foreach (link->sink_pads, (GFunc) gst_parse_strfree, NULL);
  g_slist_free (link->src_pads);
  g_slist_free (link->sink_pads);
  if (link->caps) gst_caps_unref (link->caps);
  gst_parse_link_free (link);  
}

static void
gst_parse_found_pad (GstElement *src, GstPad *pad, gpointer data)
{
  DelayedLink *link = (DelayedLink *) data;
  
  GST_CAT_INFO (GST_CAT_PIPELINE, "trying delayed linking %s:%s to %s:%s", 
                GST_STR_NULL (GST_ELEMENT_NAME (src)), GST_STR_NULL (link->src_pad),
                GST_STR_NULL (GST_ELEMENT_NAME (link->sink)), GST_STR_NULL (link->sink_pad));

  if (gst_element_link_pads_filtered (src, link->src_pad, link->sink,
      link->sink_pad, link->caps)) {
    /* do this here, we don't want to get any problems later on when
     * unlocking states */
    GST_CAT_DEBUG (GST_CAT_PIPELINE, "delayed linking %s:%s to %s:%s worked", 
               	   GST_STR_NULL (GST_ELEMENT_NAME (src)), GST_STR_NULL (link->src_pad),
               	   GST_STR_NULL (GST_ELEMENT_NAME (link->sink)), GST_STR_NULL (link->sink_pad));
    g_signal_handler_disconnect (src, link->signal_id);
    g_free (link->src_pad);
    g_free (link->sink_pad);
    if (link->caps) gst_caps_unref (link->caps);
    g_free (link);
  }
}
/* both padnames and the caps may be NULL */
static gboolean
gst_parse_perform_delayed_link (GstElement *src, const gchar *src_pad, 
                                GstElement *sink, const gchar *sink_pad,
                                GstCaps *caps)
{
  GList *templs = gst_element_class_get_pad_template_list (
      GST_ELEMENT_GET_CLASS (src));
	 
  for (; templs; templs = templs->next) {
    GstPadTemplate *templ = (GstPadTemplate *) templs->data;
    if ((GST_PAD_TEMPLATE_DIRECTION (templ) == GST_PAD_SRC) &&
        (GST_PAD_TEMPLATE_PRESENCE(templ) == GST_PAD_SOMETIMES))
    {
      DelayedLink *data = g_new (DelayedLink, 1); 
      
      /* TODO: maybe we should check if src_pad matches this template's names */

      GST_CAT_DEBUG (GST_CAT_PIPELINE, "trying delayed link %s:%s to %s:%s", 
                     GST_STR_NULL (GST_ELEMENT_NAME (src)), GST_STR_NULL (src_pad),
                     GST_STR_NULL (GST_ELEMENT_NAME (sink)), GST_STR_NULL (sink_pad));

      data->src_pad = g_strdup (src_pad);
      data->sink = sink;
      data->sink_pad = g_strdup (sink_pad);
      if (caps) {
      	data->caps = gst_caps_copy (caps);
      } else {
      	data->caps = NULL;
      }
      data->signal_id = g_signal_connect (G_OBJECT (src), "pad-added", 
          G_CALLBACK (gst_parse_found_pad), data);
      return TRUE;
    }
  }
  return FALSE;
}
/*
 * performs a link and frees the struct. src and sink elements must be given
 * return values   0 - link performed
 *                 1 - link delayed
 *                <0 - error
 */
static gint
gst_parse_perform_link (link_t *link, graph_t *graph)
{
  GstElement *src = link->src;
  GstElement *sink = link->sink;
  GSList *srcs = link->src_pads;
  GSList *sinks = link->sink_pads;
  g_assert (GST_IS_ELEMENT (src));
  g_assert (GST_IS_ELEMENT (sink));
  
  GST_CAT_INFO (GST_CAT_PIPELINE,
      "linking %s:%s to %s:%s (%u/%u) with caps \"%" GST_PTR_FORMAT "\"", 
      GST_ELEMENT_NAME (src), link->src_name ? link->src_name : "(any)",
      GST_ELEMENT_NAME (sink), link->sink_name ? link->sink_name : "(any)",
      g_slist_length (srcs), g_slist_length (sinks), link->caps);

  if (!srcs || !sinks) {
    if (gst_element_link_pads_filtered (src,
        srcs ? (const gchar *) srcs->data : NULL, sink,
        sinks ? (const gchar *) sinks->data : NULL, link->caps)) {
      goto success;
    } else {
      if (gst_parse_perform_delayed_link (src,
          srcs ? (const gchar *) srcs->data : NULL,
          sink, sinks ? (const gchar *) sinks->data : NULL, link->caps)) {
	goto success;
      } else {
        goto error;
      }
    }
  }
  if (g_slist_length (link->src_pads) != g_slist_length (link->src_pads)) {
    goto error;
  }
  while (srcs && sinks) {
    const gchar *src_pad = (const gchar *) srcs->data;
    const gchar *sink_pad = (const gchar *) sinks->data;
    srcs = g_slist_next (srcs);
    sinks = g_slist_next (sinks);
    if (gst_element_link_pads_filtered (src, src_pad, sink, sink_pad,
        link->caps)) {
      continue;
    } else {
      if (gst_parse_perform_delayed_link (src, src_pad,
                                          sink, sink_pad,
					  link->caps)) {
	continue;
      } else {
        goto error;
      }
    }
  }
  
success:
  gst_parse_free_link (link);
  return 0;
  
error:
  SET_ERROR (graph->error, GST_PARSE_ERROR_LINK,
      _("could not link %s to %s"), GST_ELEMENT_NAME (src),
      GST_ELEMENT_NAME (sink));
  gst_parse_free_link (link);
  return -1;
}


static int yyerror (void *scanner, graph_t *graph, const char *s);
%}

%union {
    gchar *s;
    chain_t *c;
    link_t *l;
    GstElement *e;
    GSList *p;
    graph_t *g;
}

%token <s> PARSE_URL
%token <s> IDENTIFIER
%left <s> REF PADREF BINREF
%token <s> ASSIGNMENT
%token <s> LINK

%type <g> graph
%type <c> chain bin
%type <l> reference
%type <l> linkpart link
%type <p> linklist
%type <e> element 
%type <p> padlist pads assignments

%left '(' ')'
%left ','
%right '.'
%left '!' '='

%parse-param { void *scanner }
%parse-param { graph_t *graph }
%pure-parser

%start graph
%%

element:	IDENTIFIER     		      { $$ = gst_element_factory_make ($1, NULL); 
						if ($$ == NULL) {
						  ADD_MISSING_ELEMENT (graph, $1);
						  SET_ERROR (graph->error, GST_PARSE_ERROR_NO_SUCH_ELEMENT, _("no element \"%s\""), $1);
						  /* if FATAL_ERRORS flag is set, we don't have to worry about backwards
						   * compatibility and can continue parsing and check for other missing
						   * elements */
						  if ((graph->flags & GST_PARSE_FLAG_FATAL_ERRORS) == 0) {
						    gst_parse_strfree ($1);
						    YYERROR;
						  }
						}
						gst_parse_strfree ($1);
                                              }
	|	element ASSIGNMENT	      { gst_parse_element_set ($2, $1, graph);
						$$ = $1;
	                                      }
	;
assignments:	/* NOP */		      { $$ = NULL; }
	|	assignments ASSIGNMENT	      { $$ = g_slist_prepend ($1, $2); }
	;		
bin:	        '(' assignments chain ')' { GST_BIN_MAKE ($$, "bin", $3, $2, FALSE); }
        |       BINREF assignments chain ')'  { GST_BIN_MAKE ($$, $1, $3, $2, TRUE); 
						gst_parse_strfree ($1);
					      }
        |       BINREF assignments ')'	      { GST_BIN_MAKE ($$, $1, NULL, $2, TRUE); 
						gst_parse_strfree ($1);
					      }
        |       BINREF assignments error ')'  { GST_BIN_MAKE ($$, $1, NULL, $2, TRUE); 
						gst_parse_strfree ($1);
					      }
	;
	
pads:		PADREF 			      { $$ = g_slist_prepend (NULL, $1); }
	|	PADREF padlist		      { $$ = $2;
						$$ = g_slist_prepend ($$, $1);
					      }				     
	;
padlist:	',' IDENTIFIER		      { $$ = g_slist_prepend (NULL, $2); }
	|	',' IDENTIFIER padlist	      { $$ = g_slist_prepend ($3, $2); }
	;
	
reference:	REF 			      { MAKE_REF ($$, $1, NULL); }
	|	REF padlist		      { MAKE_REF ($$, $1, $2); }
	;

linkpart:	reference		      { $$ = $1; }
	|	pads			      { MAKE_REF ($$, NULL, $1); }
	|	/* NOP */		      { MAKE_REF ($$, NULL, NULL); }
	;
	
link:		linkpart LINK linkpart	      { $$ = $1;
						if ($2) {
						  $$->caps = gst_caps_from_string ($2);
						  if ($$->caps == NULL)
						    SET_ERROR (graph->error, GST_PARSE_ERROR_LINK, _("could not parse caps \"%s\""), $2);
						  gst_parse_strfree ($2);
						}
						$$->sink_name = $3->src_name;
						$$->sink_pads = $3->src_pads;
						gst_parse_link_free ($3);
					      }
	;
	
linklist:	link			      { $$ = g_slist_prepend (NULL, $1); }
	|	link linklist		      { $$ = g_slist_prepend ($2, $1); }
	|	linklist error		      { $$ = $1; }
	;	

chain:   	element			      { $$ = gst_parse_chain_new ();
						$$->first = $$->last = $1;
						$$->front = $$->back = NULL;
						$$->elements = g_slist_prepend (NULL, $1);
					      }
	|	bin			      { $$ = $1; }
	|	chain chain		      { if ($1->back && $2->front) {
						  if (!$1->back->sink_name) {
						    SET_ERROR (graph->error, GST_PARSE_ERROR_LINK, _("link without source element"));
						    gst_parse_free_link ($1->back);
						  } else {
						    graph->links = g_slist_prepend (graph->links, $1->back);
						  }
						  if (!$2->front->src_name) {
						    SET_ERROR (graph->error, GST_PARSE_ERROR_LINK, _("link without sink element"));
						    gst_parse_free_link ($2->front);
						  } else {
						    graph->links = g_slist_prepend (graph->links, $2->front);
						  }
						  $1->back = NULL;
						} else if ($1->back) {
						  if (!$1->back->sink_name) {
						    $1->back->sink = $2->first;
						  }
						} else if ($2->front) {
						  if (!$2->front->src_name) {
						    $2->front->src = $1->last;
						  }
						  $1->back = $2->front;
						}
						
						if ($1->back) {
						  graph->links = g_slist_prepend (graph->links, $1->back);
						}
						$1->last = $2->last;
						$1->back = $2->back;
						$1->elements = g_slist_concat ($1->elements, $2->elements);
						if ($2)
						  gst_parse_chain_free ($2);
						$$ = $1;
					      }
	|	chain linklist		      { GSList *walk;
						if ($1->back) {
						  $2 = g_slist_prepend ($2, $1->back);
						  $1->back = NULL;
						} else {
						  if (!((link_t *) $2->data)->src_name) {
						    ((link_t *) $2->data)->src = $1->last;
						  }						  
						}
						for (walk = $2; walk; walk = walk->next) {
						  link_t *link = (link_t *) walk->data;
						  if (!link->sink_name && walk->next) {
						    SET_ERROR (graph->error, GST_PARSE_ERROR_LINK, _("link without sink element"));
						    gst_parse_free_link (link);
						  } else if (!link->src_name && !link->src) {
						    SET_ERROR (graph->error, GST_PARSE_ERROR_LINK, _("link without source element"));
						    gst_parse_free_link (link);
						  } else {
						    if (walk->next) {
						      graph->links = g_slist_prepend (graph->links, link);
						    } else {
						      $1->back = link;
						    }
						  }
						}
						g_slist_free ($2);
						$$ = $1;
					      }
	|	chain error		      { $$ = $1; }
	|	link chain		      { if ($2->front) {
						  if (!$2->front->src_name) {
						    SET_ERROR (graph->error, GST_PARSE_ERROR_LINK, _("link without source element"));
						    gst_parse_free_link ($2->front);
						  } else {
						    graph->links = g_slist_prepend (graph->links, $2->front);
						  }
						}
						if (!$1->sink_name) {
						  $1->sink = $2->first;
						}
						$2->front = $1;
						$$ = $2;
					      }
	|	PARSE_URL chain		      { $$ = $2;
						if ($$->front) {
						  GstElement *element = 
							  gst_element_make_from_uri (GST_URI_SRC, $1, NULL);
						  if (!element) {
						    SET_ERROR (graph->error, GST_PARSE_ERROR_NO_SUCH_ELEMENT, 
							    _("no source element for URI \"%s\""), $1);
						  } else {
						    $$->front->src = element;
						    graph->links = g_slist_prepend (
							    graph->links, $$->front);
						    $$->front = NULL;
						    $$->elements = g_slist_prepend ($$->elements, element);
						  }
						} else {
						  SET_ERROR (graph->error, GST_PARSE_ERROR_LINK, 
							  _("no element to link URI \"%s\" to"), $1);
						}
						g_free ($1);
					      }
	|	link PARSE_URL		      { GstElement *element =
							  gst_element_make_from_uri (GST_URI_SINK, $2, NULL);
						if (!element) {
						  SET_ERROR (graph->error, GST_PARSE_ERROR_NO_SUCH_ELEMENT, 
							  _("no sink element for URI \"%s\""), $2);
						  gst_parse_link_free ($1);
						  g_free ($2);
						  YYERROR;
						} else if ($1->sink_name || $1->sink_pads) {
                                                  gst_object_unref (element);
						  SET_ERROR (graph->error, GST_PARSE_ERROR_LINK, 
							  _("could not link sink element for URI \"%s\""), $2);
						  gst_parse_link_free ($1);
						  g_free ($2);
						  YYERROR;
						} else {
						  $$ = gst_parse_chain_new ();
						  $$->first = $$->last = element;
						  $$->front = $1;
						  $$->front->sink = element;
						  $$->elements = g_slist_prepend (NULL, element);
						}
						g_free ($2);
					      }
	;
graph:		/* NOP */		      { SET_ERROR (graph->error, GST_PARSE_ERROR_EMPTY, _("empty pipeline not allowed"));
						$$ = graph;
					      }
	|	chain			      { $$ = graph;
						if ($1->front) {
						  if (!$1->front->src_name) {
						    SET_ERROR (graph->error, GST_PARSE_ERROR_LINK, _("link without source element"));
						    gst_parse_free_link ($1->front);
						  } else {
						    $$->links = g_slist_prepend ($$->links, $1->front);
						  }
						  $1->front = NULL;
						}
						if ($1->back) {
						  if (!$1->back->sink_name) {
						    SET_ERROR (graph->error, GST_PARSE_ERROR_LINK, _("link without sink element"));
						    gst_parse_free_link ($1->back);
						  } else {
						    $$->links = g_slist_prepend ($$->links, $1->back);
						  }
						  $1->back = NULL;
						}
						$$->chain = $1;
					      }
	;

%%


static int
yyerror (void *scanner, graph_t *graph, const char *s)
{
  /* FIXME: This should go into the GError somehow, but how? */
  GST_WARNING ("Error during parsing: %s", s);
  return -1;
}


GstElement *
_gst_parse_launch (const gchar *str, GError **error, GstParseContext *ctx,
    GstParseFlags flags)
{
  graph_t g;
  gchar *dstr;
  GSList *walk;
  GstBin *bin = NULL;
  GstElement *ret;
  yyscan_t scanner;

  g_return_val_if_fail (str != NULL, NULL);
  g_return_val_if_fail (error == NULL || *error == NULL, NULL);

  g.chain = NULL;
  g.links = NULL;
  g.error = error;
  g.ctx = ctx;
  g.flags = flags;
  
#ifdef __GST_PARSE_TRACE
  GST_CAT_DEBUG (GST_CAT_PIPELINE, "TRACE: tracing enabled");
  __strings = __chains = __links = 0;
#endif /* __GST_PARSE_TRACE */

  dstr = g_strdup (str);
  _gst_parse_yylex_init (&scanner);
  _gst_parse_yy_scan_string (dstr, scanner);

#ifndef YYDEBUG
  yydebug = 1;
#endif

  if (yyparse (scanner, &g) != 0) {
    SET_ERROR (error, GST_PARSE_ERROR_SYNTAX,
        "Unrecoverable syntax error while parsing pipeline %s", str);
    
    _gst_parse_yylex_destroy (scanner);
    g_free (dstr);
  
    goto error1;
  }
  _gst_parse_yylex_destroy (scanner);
  g_free (dstr);
  
  GST_CAT_DEBUG (GST_CAT_PIPELINE, "got %u elements and %u links",
      g.chain ? g_slist_length (g.chain->elements) : 0,
      g_slist_length (g.links));
  
  if (!g.chain) {
    ret = NULL;
  } else if (!g.chain->elements->next) {
    /* only one toplevel element */  
    ret = (GstElement *) g.chain->elements->data;
    g_slist_free (g.chain->elements);
    if (GST_IS_BIN (ret))
      bin = GST_BIN (ret);
    gst_parse_chain_free (g.chain);
  } else {  
    /* put all elements in our bin */
    bin = GST_BIN (gst_element_factory_make ("pipeline", NULL));
    g_assert (bin);
    
    for (walk = g.chain->elements; walk; walk = walk->next) {
      if (walk->data != NULL)
        gst_bin_add (bin, GST_ELEMENT (walk->data));
    }
    
    g_slist_free (g.chain->elements);
    ret = GST_ELEMENT (bin);
    gst_parse_chain_free (g.chain);
  }
  
  /* remove links */
  for (walk = g.links; walk; walk = walk->next) {
    link_t *l = (link_t *) walk->data;
    if (!l->src) {
      if (l->src_name) {
        if (bin) {
          l->src = gst_bin_get_by_name_recurse_up (bin, l->src_name);
          if (l->src)
            gst_object_unref (l->src);
        } else {
          l->src = strcmp (GST_ELEMENT_NAME (ret), l->src_name) == 0 ? ret : NULL;
        }
      }
      if (!l->src) {
        if (l->src_name) {
          SET_ERROR (error, GST_PARSE_ERROR_NO_SUCH_ELEMENT,
              "No element named \"%s\" - omitting link", l->src_name);
        } else {
          /* probably a missing element which we've handled already */
        }
        gst_parse_free_link (l);
        continue;
      }
    }
    if (!l->sink) {
      if (l->sink_name) {
        if (bin) {
          l->sink = gst_bin_get_by_name_recurse_up (bin, l->sink_name);
          if (l->sink)
            gst_object_unref (l->sink);
        } else {
          l->sink = strcmp (GST_ELEMENT_NAME (ret), l->sink_name) == 0 ? ret : NULL;
        }
      }
      if (!l->sink) {
        if (l->sink_name) {
          SET_ERROR (error, GST_PARSE_ERROR_NO_SUCH_ELEMENT,
              "No element named \"%s\" - omitting link", l->sink_name);
        } else {
          /* probably a missing element which we've handled already */
        }
        gst_parse_free_link (l);
        continue;
      }
    }
    gst_parse_perform_link (l, &g);
  }
  g_slist_free (g.links);

out:
#ifdef __GST_PARSE_TRACE
  GST_CAT_DEBUG (GST_CAT_PIPELINE,
      "TRACE: %u strings, %u chains and %u links left", __strings, __chains,
      __links);
  if (__strings || __chains || __links) {
    g_warning ("TRACE: %u strings, %u chains and %u links left", __strings,
        __chains, __links);
  }
#endif /* __GST_PARSE_TRACE */

  return ret;
  
error1:
  if (g.chain) {
    g_slist_foreach (g.chain->elements, (GFunc)gst_object_unref, NULL);
    g_slist_free (g.chain->elements);
    gst_parse_chain_free (g.chain);
  }

  g_slist_foreach (g.links, (GFunc)gst_parse_free_link, NULL);
  g_slist_free (g.links);
  
  if (error)
    g_assert (*error);
  ret = NULL;
  
  goto out;
}