gstreamer_core/tools/grammar.y
changeset 11 1373546e05c6
parent 0 0e761a78d257
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gstreamer_core/tools/grammar.y	Thu May 27 13:09:21 2010 +0300
@@ -0,0 +1,932 @@
+%{
+
+
+#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 "../gsturi.h"
+#include "../gstutils.h"
+#include "../gstvalue.h"
+#include "../gstchildproxy.h"
+#include "types.h"
+
+#include <glib_global.h>
+#include <glib_object.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_t *) 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_t *) 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 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_t *) 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) { \
+    SET_ERROR (((graph_t *) 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)) { 
+    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)) {
+      g_object_set_property (G_OBJECT (target), pspec->name, &v);
+    }
+    g_signal_handler_disconnect (child_proxy, set->signal_id);
+    g_free(set->name);
+    g_free(set->value_str);
+    g_free(set);
+  }
+
+  if (G_IS_VALUE (&v))
+    g_value_unset (&v);
+  if (target)
+    gst_object_unref (target);
+  return;
+}
+
+
+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;
+
+  /* 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)) { 
+    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))
+      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_t *) 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_t *) 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_t *) 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) {
+						  SET_ERROR (((graph_t *) graph)->error, GST_PARSE_ERROR_NO_SUCH_ELEMENT, _("no element \"%s\""), $1);
+						  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 ($$->caps == NULL)
+						    SET_ERROR (((graph_t *) graph)->error, GST_PARSE_ERROR_LINK, _("could not parse caps \"%s\""), $2);
+						  gst_parse_strfree ($2);
+						}
+						$$->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			      { $$ = $1; }
+	|	chain chain		      { if ($1->back && $2->front) {
+						  if (!$1->back->sink_name) {
+						    SET_ERROR (((graph_t *) graph)->error, GST_PARSE_ERROR_LINK, _("link without source element"));
+						    gst_parse_free_link ($1->back);
+						  } else {
+						    ((graph_t *) graph)->links = g_slist_prepend (((graph_t *) graph)->links, $1->back);
+						  }
+						  if (!$2->front->src_name) {
+						    SET_ERROR (((graph_t *) graph)->error, GST_PARSE_ERROR_LINK, _("link without sink element"));
+						    gst_parse_free_link ($2->front);
+						  } else {
+						    ((graph_t *) graph)->links = g_slist_prepend (((graph_t *) graph)->links, $2->front);
+						  }
+						  $1->back = NULL;
+						} else if ($1->back) {
+						  if (!$1->back->sink_name) {
+						    $1->back->sink = $2->first;
+						  }
+						} else if ($2->front) {
+						  if (!$2->front->src_name) {
+						    $2->front->src = $1->last;
+						  }
+						  $1->back = $2->front;
+						}
+						
+						if ($1->back) {
+						  ((graph_t *) graph)->links = g_slist_prepend (((graph_t *) graph)->links, $1->back);
+						}
+						$1->last = $2->last;
+						$1->back = $2->back;
+						$1->elements = g_slist_concat ($1->elements, $2->elements);
+						if ($2)
+						  gst_parse_chain_free ($2);
+						$$ = $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_t *) 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_t *) graph)->error, GST_PARSE_ERROR_LINK, _("link without source element"));
+						    gst_parse_free_link (link);
+						  } else {
+						    if (walk->next) {
+						      ((graph_t *) graph)->links = g_slist_prepend (((graph_t *) 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_t *) graph)->error, GST_PARSE_ERROR_LINK, _("link without source element"));
+						    gst_parse_free_link ($2->front);
+						  } else {
+						    ((graph_t *) graph)->links = g_slist_prepend (((graph_t *) graph)->links, $2->front);
+						  }
+						}
+						if (!$1->sink_name) {
+						  $1->sink = $2->first;
+						}
+						$2->front = $1;
+						$$ = $2;
+					      }
+	|	PARSE_URL chain		      { $$ = $2;
+						if ($$->front) {
+						  GstElement *element = 
+							  gst_element_make_from_uri (GST_URI_SRC, $1, NULL);
+						  if (!element) {
+						    SET_ERROR (((graph_t *) graph)->error, GST_PARSE_ERROR_NO_SUCH_ELEMENT, 
+							    _("no source element for URI \"%s\""), $1);
+						  } else {
+						    $$->front->src = element;
+						    ((graph_t *) graph)->links = g_slist_prepend (
+							    ((graph_t *) graph)->links, $$->front);
+						    $$->front = NULL;
+						    $$->elements = g_slist_prepend ($$->elements, element);
+						  }
+						} else {
+						  SET_ERROR (((graph_t *) 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_t *) 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_t *) 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_t *) graph)->error, GST_PARSE_ERROR_EMPTY, _("empty pipeline not allowed"));
+						$$ = (graph_t *) graph;
+					      }
+	|	chain			      { $$ = (graph_t *) graph;
+						if ($1->front) {
+						  if (!$1->front->src_name) {
+						    SET_ERROR (((graph_t *) 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_t *) 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)
+{
+  graph_t g;
+  gchar *dstr;
+  GSList *walk;
+  GstBin *bin = NULL;
+  GstElement *ret;
+  yyscan_t scanner;
+
+  g_return_val_if_fail (str != NULL, NULL);
+
+  g.chain = NULL;
+  g.links = NULL;
+  g.error = error;
+  
+#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 (!(((chain_t *) g.chain)->elements->next)) {
+    /* only one toplevel element */  
+    ret = (GstElement *) ((chain_t *) g.chain)->elements->data;
+    g_slist_free (((chain_t *) 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) {
+        SET_ERROR (error, GST_PARSE_ERROR_NO_SUCH_ELEMENT,
+            "No element named \"%s\" - omitting link", l->src_name);
+        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) {
+        SET_ERROR (error, GST_PARSE_ERROR_NO_SUCH_ELEMENT,
+            "No element named \"%s\" - omitting link", l->sink_name);
+        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;
+}