gstreamer/gst/gstcaps.c

/* GStreamer
 * Copyright (C) <2003> David A. Schleef <ds@schleef.org>
 *
 * 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.
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include <string.h>

#include <gst/gst.h>

#define CAPS_POISON(caps) G_STMT_START{ \
  if (caps) { \
    GstCaps *_newcaps = gst_caps_copy (caps); \
    gst_caps_free(caps); \
    caps = _newcaps; \
  } \
} G_STMT_END
#define STRUCTURE_POISON(structure) G_STMT_START{ \
  if (structure) { \
    GstStructure *_newstruct = gst_structure_copy (structure); \
    gst_structure_free(structure); \
    structure = _newstruct; \
  } \
} G_STMT_END


static void gst_caps_transform_to_string (const GValue * src_value,
    GValue * dest_value);
static gboolean gst_caps_from_string_inplace (GstCaps * caps,
    const gchar * string);
static GstCaps *gst_caps_copy_conditional (const GstCaps * src);

GType
gst_caps_get_type (void)
{
  static GType gst_caps_type = 0;

  if (!gst_caps_type) {
    gst_caps_type = g_boxed_type_register_static ("GstCaps",
        (GBoxedCopyFunc) gst_caps_copy_conditional,
        (GBoxedFreeFunc) gst_caps_free);

    g_value_register_transform_func (gst_caps_type,
        G_TYPE_STRING, gst_caps_transform_to_string);
  }

  return gst_caps_type;
}

/* creation/deletion */

/**
 * gst_caps_new_empty:
 *
 * Creates a new #GstCaps that is empty.  That is, the returned
 * #GstCaps contains no media formats.
 *
 * Returns: the new #GstCaps
 */
GstCaps *
gst_caps_new_empty (void)
{
  GstCaps *caps = g_new0 (GstCaps, 1);

  caps->type = GST_TYPE_CAPS;
  caps->structs = g_ptr_array_new ();

  return caps;
}

/**
 * gst_caps_new_empty:
 *
 * Creates a new #GstCaps that indicates that it is compatible with
 * any media format.
 *
 * Returns: the new #GstCaps
 */
GstCaps *
gst_caps_new_any (void)
{
  GstCaps *caps = g_new0 (GstCaps, 1);

  caps->type = GST_TYPE_CAPS;
  caps->structs = g_ptr_array_new ();
  caps->flags = GST_CAPS_FLAGS_ANY;

  return caps;
}

/**
 * gst_caps_new_simple:
 * @media_type: the media type of the structure
 * @...: additional arguments
 *
 * Creates a new #GstCaps that contains one #GstStructure.  The
 * structure is defined by the arguments, which have the same format
 * as @gst_structure_new().
 *
 * Returns: the new #GstCaps
 */
GstCaps *
gst_caps_new_simple (const char *media_type, const char *fieldname, ...)
{
  GstCaps *caps;
  GstStructure *structure;
  va_list var_args;

  caps = g_new0 (GstCaps, 1);
  caps->type = GST_TYPE_CAPS;
  caps->structs = g_ptr_array_new ();

  va_start (var_args, fieldname);
  structure = gst_structure_new_valist (media_type, fieldname, var_args);
  va_end (var_args);

  gst_caps_append_structure (caps, structure);

  return caps;
}

/**
 * gst_caps_new_full:
 * @struct1: the first structure to add
 * @...: additional structures to add
 *
 * Creates a new #GstCaps and adds all the structures listed as
 * arguments.  The list must be NULL-terminated.  The structures
 * are not copied; the returned #GstCaps owns the structures.
 *
 * Returns: the new #GstCaps
 */
GstCaps *
gst_caps_new_full (GstStructure * struct1, ...)
{
  GstCaps *caps;
  va_list var_args;

  va_start (var_args, struct1);
  caps = gst_caps_new_full_valist (struct1, var_args);
  va_end (var_args);

  return caps;
}

/**
 * gst_caps_new_full_valist:
 * @struct1: the first structure to add
 * @var_args: additional structures to add
 *
 * Creates a new #GstCaps and adds all the structures listed as
 * arguments.  The list must be NULL-terminated.  The structures
 * are not copied; the returned #GstCaps owns the structures.
 *
 * Returns: the new #GstCaps
 */
GstCaps *
gst_caps_new_full_valist (GstStructure * structure, va_list var_args)
{
  GstCaps *caps;

  caps = g_new0 (GstCaps, 1);
  caps->type = GST_TYPE_CAPS;
  caps->structs = g_ptr_array_new ();

  while (structure) {
    gst_caps_append_structure (caps, structure);
    structure = va_arg (var_args, GstStructure *);
  }

  return caps;
}

/**
 * gst_caps_copy:
 * @caps: the #GstCaps to copy
 *
 * Deeply copies a #GstCaps, including all structures and all the
 * structures' values.
 *
 * Returns: the new #GstCaps
 */
GstCaps *
gst_caps_copy (const GstCaps * caps)
{
  GstCaps *newcaps;
  GstStructure *structure;
  int i;

  g_return_val_if_fail (caps != NULL, NULL);

  newcaps = g_new0 (GstCaps, 1);
  newcaps->type = GST_TYPE_CAPS;
  newcaps->flags = caps->flags;
  newcaps->structs = g_ptr_array_new ();

  for (i = 0; i < caps->structs->len; i++) {
    structure = gst_caps_get_structure (caps, i);
    gst_caps_append_structure (newcaps, gst_structure_copy (structure));
  }

  return newcaps;
}

/**
 * gst_caps_free:
 * @caps: the #GstCaps to free
 *
 * Frees a #GstCaps and all its structures and the structures'
 * values.
 */
void
gst_caps_free (GstCaps * caps)
{
  GstStructure *structure;
  int i;

  g_return_if_fail (caps != NULL);

  for (i = 0; i < caps->structs->len; i++) {
    structure = gst_caps_get_structure (caps, i);
    gst_structure_free (structure);
  }
  g_ptr_array_free (caps->structs, TRUE);
#ifdef USE_POISONING
  memset (caps, 0xff, sizeof (GstCaps));
#endif
  g_free (caps);
}

/**
 * gst_static_caps_get:
 * @static_caps: the #GstStaticCaps to convert
 *
 * Converts a #GstStaticCaps to a #GstCaps.
 *
 * Returns: the new #GstCaps
 */
const GstCaps *
gst_static_caps_get (GstStaticCaps * static_caps)
{
  GstCaps *caps = (GstCaps *) static_caps;
  gboolean ret;

  if (caps->type == 0) {
    caps->type = GST_TYPE_CAPS;
    caps->structs = g_ptr_array_new ();
    ret = gst_caps_from_string_inplace (caps, static_caps->string);

    if (!ret) {
      g_critical ("Could not convert static caps \"%s\"", static_caps->string);
    }
  }

  return caps;
}

/* manipulation */

/**
 * gst_caps_append:
 * @caps1: the #GstCaps that will be appended to
 * @caps2: the #GstCaps to append
 *
 * Appends the structures contained in @caps2 to @caps1.  The structures
 * in @caps2 are not copied -- they are transferred to @caps1, and then
 * @caps2 is freed.
 */
void
gst_caps_append (GstCaps * caps1, GstCaps * caps2)
{
  GstStructure *structure;
  int i;

  g_return_if_fail (caps1 != NULL);
  g_return_if_fail (caps2 != NULL);

#ifdef USE_POISONING
  CAPS_POISON (caps2);
#endif
  for (i = 0; i < caps2->structs->len; i++) {
    structure = gst_caps_get_structure (caps2, i);
    gst_caps_append_structure (caps1, structure);
  }
  g_ptr_array_free (caps2->structs, TRUE);
#ifdef USE_POISONING
  memset (caps2, 0xff, sizeof (GstCaps));
#endif
  g_free (caps2);
}

/**
 * gst_caps_append_structure:
 * @caps: the #GstCaps that will be appended to
 * @structure: the #GstStructure to append
 *
 * Appends @structure to @caps1.  The structure is not copied; @caps1
 * becomes the owner of @structure.
 */
void
gst_caps_append_structure (GstCaps * caps, GstStructure * structure)
{
  g_return_if_fail (caps != NULL);

  if (structure) {
#if 0
#ifdef USE_POISONING
    STRUCTURE_POISON (structure);
#endif
#endif
    g_ptr_array_add (caps->structs, structure);
  }
}

/**
 * gst_caps_split_one:
 * @caps: 
 *
 * Returns:
 */
GstCaps *
gst_caps_split_one (GstCaps * caps)
{
  /* FIXME */
  g_critical ("unimplemented");

  return NULL;
}

/**
 * gst_caps_split_one:
 * @caps: a #GstCaps
 *
 * Returns: the number of structures that @caps contains
 */
int
gst_caps_get_size (const GstCaps * caps)
{
  g_return_val_if_fail (caps != NULL, 0);

  return caps->structs->len;
}

/**
 * gst_caps_get_structure:
 * @caps: a #GstCaps
 * @index: the index of the structure
 *
 * Finds the structure in @caps that has the index @index, and 
 * returns it.
 *
 * WARNING: This function takes a const GstCaps *, but returns a
 * non-const GstStructure *.  This is for programming convenience --
 * the caller should be aware that structures inside a constant
 * @GstCaps should not be modified.
 *
 * Returns: a pointer to the #GstStructure corresponding to @index
 */
GstStructure *
gst_caps_get_structure (const GstCaps * caps, int index)
{
  g_return_val_if_fail (caps != NULL, NULL);
  g_return_val_if_fail (index >= 0, NULL);
  g_return_val_if_fail (index < caps->structs->len, NULL);

  return g_ptr_array_index (caps->structs, index);
}

/**
 * gst_caps_copy_1:
 * @caps: the @GstCaps to copy
 *
 * Creates a new @GstCaps and appends a copy of the first structure
 * contained in @caps.
 *
 * Returns: the new @GstCaps
 */
GstCaps *
gst_caps_copy_1 (const GstCaps * caps)
{
  GstCaps *newcaps;
  GstStructure *structure;

  g_return_val_if_fail (caps != NULL, NULL);

  newcaps = g_new0 (GstCaps, 1);
  newcaps->type = GST_TYPE_CAPS;
  newcaps->flags = caps->flags;
  newcaps->structs = g_ptr_array_new ();

  if (caps->structs->len > 0) {
    structure = gst_caps_get_structure (caps, 0);
    gst_caps_append_structure (newcaps, gst_structure_copy (structure));
  }

  return newcaps;
}

/**
 * gst_caps_set_simple:
 * @caps: the @GstCaps to set
 * @field: first field to set
 * @...: additional parameters
 *
 * Sets fields in a simple #GstCaps.  A simple #GstCaps is one that
 * only has one structure.  The arguments must be passed in the same
 * manner as @gst_structure_set(), and be NULL-terminated.
 */
void
gst_caps_set_simple (GstCaps * caps, char *field, ...)
{
  GstStructure *structure;
  va_list var_args;

  g_return_if_fail (caps != NULL);
  g_return_if_fail (caps->structs->len == 1);

  structure = gst_caps_get_structure (caps, 0);

  va_start (var_args, field);
  gst_structure_set_valist (structure, field, var_args);
  va_end (var_args);
}

/**
 * gst_caps_set_simple_valist:
 * @caps: the @GstCaps to copy
 * @field: first field to set
 * @varargs: additional parameters
 *
 * Sets fields in a simple #GstCaps.  A simple #GstCaps is one that
 * only has one structure.  The arguments must be passed in the same
 * manner as @gst_structure_set(), and be NULL-terminated.
 */
void
gst_caps_set_simple_valist (GstCaps * caps, char *field, va_list varargs)
{
  GstStructure *structure;

  g_return_if_fail (caps != NULL);
  g_return_if_fail (caps->structs->len != 1);

  structure = gst_caps_get_structure (caps, 0);

  gst_structure_set_valist (structure, field, varargs);
}

/* tests */

/**
 * gst_caps_is_any:
 * @caps: the @GstCaps to test
 *
 * Returns: TRUE if @caps represents any format.
 */
gboolean
gst_caps_is_any (const GstCaps * caps)
{
  g_return_val_if_fail (caps != NULL, FALSE);

  return (caps->flags & GST_CAPS_FLAGS_ANY);
}

/**
 * gst_caps_is_empty:
 * @caps: the @GstCaps to test
 *
 * Returns: TRUE if @caps represents no formats.
 */
gboolean
gst_caps_is_empty (const GstCaps * caps)
{
  g_return_val_if_fail (caps != NULL, FALSE);

  if (caps->flags & GST_CAPS_FLAGS_ANY)
    return FALSE;

  return (caps->structs == NULL) || (caps->structs->len == 0);
}

/**
 * gst_caps_is_chained:
 * @caps: the @GstCaps to test
 *
 * Returns: TRUE if @caps contains more than one structure
 */
gboolean
gst_caps_is_chained (const GstCaps * caps)
{
  g_return_val_if_fail (caps != NULL, FALSE);

  return (caps->structs->len > 1);
}

static gboolean
gst_caps_is_fixed_foreach (GQuark field_id, GValue * value, gpointer unused)
{
  GType type = G_VALUE_TYPE (value);

  if (G_TYPE_IS_FUNDAMENTAL (type))
    return TRUE;
  if (type == GST_TYPE_FOURCC)
    return TRUE;
  return FALSE;
}

/**
 * gst_caps_is_fixed:
 * @caps: the @GstCaps to test
 *
 * Fixed @GstCaps describe exactly one format, that is, they have exactly
 * one structure, and each field in the structure describes a fixed type.
 * Examples of non-fixed types are GST_TYPE_INT_RANGE and GST_TYPE_LIST.
 *
 * Returns: TRUE if @caps is fixed
 */
gboolean
gst_caps_is_fixed (const GstCaps * caps)
{
  GstStructure *structure;

  g_return_val_if_fail (caps != NULL, FALSE);

  if (caps->structs->len != 1)
    return FALSE;

  structure = gst_caps_get_structure (caps, 0);

  return gst_structure_foreach (structure, gst_caps_is_fixed_foreach, NULL);
}

static gboolean
gst_structure_is_equal_foreach (GQuark field_id, GValue * val2, gpointer data)
{
  GstStructure *struct1 = (GstStructure *) data;
  const GValue *val1 = gst_structure_id_get_value (struct1, field_id);

  if (val1 == NULL)
    return FALSE;
  if (gst_value_compare (val1, val2) == GST_VALUE_EQUAL) {
    return TRUE;
  }

  return FALSE;
}

/**
 * gst_caps_is_equal_fixed:
 * @caps1: the #GstCaps to test
 * @caps2: the #GstCaps to test
 *
 * Tests if two #GstCaps are equal.  This function only works on fixed
 * #GstCaps.
 *
 * Returns: TRUE if the arguments represent the same format
 */
gboolean
gst_caps_is_equal_fixed (const GstCaps * caps1, const GstCaps * caps2)
{
  GstStructure *struct1, *struct2;

  g_return_val_if_fail (gst_caps_is_fixed (caps1), FALSE);
  g_return_val_if_fail (gst_caps_is_fixed (caps2), FALSE);

  struct1 = gst_caps_get_structure (caps1, 0);
  struct2 = gst_caps_get_structure (caps2, 0);

  if (struct1->name != struct2->name) {
    return FALSE;
  }
  if (struct1->fields->len != struct2->fields->len) {
    return FALSE;
  }

  return gst_structure_foreach (struct1, gst_structure_is_equal_foreach,
      struct2);
}

static gboolean
gst_structure_field_has_compatible (GQuark field_id,
    GValue * val2, gpointer data)
{
  GValue dest = { 0 };
  GstStructure *struct1 = (GstStructure *) data;
  const GValue *val1 = gst_structure_id_get_value (struct1, field_id);

  if (val1 == NULL)
    return FALSE;
  if (gst_value_intersect (&dest, val1, val2)) {
    g_value_unset (&dest);
    return TRUE;
  }

  return FALSE;
}

static gboolean
gst_cap_is_always_compatible (const GstStructure * struct1,
    const GstStructure * struct2)
{
  if (struct1->name != struct2->name) {
    return FALSE;
  }

  /* the reversed order is important */
  return gst_structure_foreach ((GstStructure *) struct2,
      gst_structure_field_has_compatible, (gpointer) struct1);
}

static gboolean
gst_caps_cap_is_always_compatible (const GstStructure * struct1,
    const GstCaps * caps2)
{
  int i;

  for (i = 0; i < caps2->structs->len; i++) {
    GstStructure *struct2 = gst_caps_get_structure (caps2, i);

    if (gst_cap_is_always_compatible (struct1, struct2)) {
      return TRUE;
    }
  }

  return FALSE;
}

/**
 * gst_caps_is_always_compatible
 * @caps1: the #GstCaps to test
 * @caps2: the #GstCaps to test
 *
 * Returns: TRUE if @caps1 is a subset of @caps2.
 */
gboolean
gst_caps_is_always_compatible (const GstCaps * caps1, const GstCaps * caps2)
{
  int i;

  g_return_val_if_fail (caps1 != NULL, FALSE);
  g_return_val_if_fail (caps2 != NULL, FALSE);
  /* FIXME: is this right ? */
  g_return_val_if_fail (!gst_caps_is_empty (caps1), FALSE);
  g_return_val_if_fail (!gst_caps_is_empty (caps2), FALSE);

  if (gst_caps_is_any (caps2))
    return TRUE;
  if (gst_caps_is_any (caps1))
    return FALSE;

  for (i = 0; i < caps1->structs->len; i++) {
    GstStructure *struct1 = gst_caps_get_structure (caps1, i);

    if (gst_caps_cap_is_always_compatible (struct1, caps2) == FALSE) {
      return FALSE;
    }

  }

  return FALSE;
}

typedef struct
{
  GstStructure *dest;
  const GstStructure *intersect;
  gboolean first_run;
}
IntersectData;

static gboolean
gst_caps_structure_intersect_field (GQuark id, GValue * val1, gpointer data)
{
  IntersectData *idata = (IntersectData *) data;
  GValue dest_value = { 0 };
  const GValue *val2 = gst_structure_id_get_value (idata->intersect, id);

  if (val2 == NULL) {
    gst_structure_id_set_value (idata->dest, id, val1);
  } else if (idata->first_run) {
    if (gst_value_intersect (&dest_value, val1, val2)) {
      gst_structure_id_set_value (idata->dest, id, &dest_value);
      g_value_unset (&dest_value);
    } else {
      return FALSE;
    }
  }

  return TRUE;
}

static GstStructure *
gst_caps_structure_intersect (const GstStructure * struct1,
    const GstStructure * struct2)
{
  IntersectData data;

  g_return_val_if_fail (struct1 != NULL, NULL);
  g_return_val_if_fail (struct2 != NULL, NULL);

  if (struct1->name != struct2->name)
    return NULL;

  data.dest = gst_structure_id_empty_new (struct1->name);
  data.intersect = struct2;
  data.first_run = TRUE;
  if (!gst_structure_foreach ((GstStructure *) struct1,
          gst_caps_structure_intersect_field, &data))
    goto error;

  data.intersect = struct1;
  data.first_run = FALSE;
  if (!gst_structure_foreach ((GstStructure *) struct2,
          gst_caps_structure_intersect_field, &data))
    goto error;

  return data.dest;

error:
  gst_structure_free (data.dest);
  return NULL;
}

#if 0
static GstStructure *
gst_caps_structure_union (const GstStructure * struct1,
    const GstStructure * struct2)
{
  int i;
  GstStructure *dest;
  const GstStructureField *field1;
  const GstStructureField *field2;
  int ret;

  /* FIXME this doesn't actually work */

  if (struct1->name != struct2->name)
    return NULL;

  dest = gst_structure_id_empty_new (struct1->name);

  for (i = 0; i < struct1->fields->len; i++) {
    GValue dest_value = { 0 };

    field1 = GST_STRUCTURE_FIELD (struct1, i);
    field2 = gst_structure_id_get_field (struct2, field1->name);

    if (field2 == NULL) {
      continue;
    } else {
      if (gst_value_union (&dest_value, &field1->value, &field2->value)) {
        gst_structure_set_value (dest, g_quark_to_string (field1->name),
            &dest_value);
      } else {
        ret = gst_value_compare (&field1->value, &field2->value);
      }
    }
  }

  return dest;
}
#endif

/* operations */

/**
 * gst_caps_intersect:
 * @caps1: a #GstCaps to intersect
 * @caps2: a #GstCaps to intersect
 *
 * Creates a new #GstCaps that contains all the formats that are common
 * to both @caps1 and @caps2.
 *
 * Returns: the new #GstCaps
 */
GstCaps *
gst_caps_intersect (const GstCaps * caps1, const GstCaps * caps2)
{
  int i, j;
  GstStructure *struct1;
  GstStructure *struct2;
  GstCaps *dest;

#if 0
  GstCaps *caps;
#endif

  g_return_val_if_fail (caps1 != NULL, NULL);
  g_return_val_if_fail (caps2 != NULL, NULL);

  if (gst_caps_is_empty (caps1) || gst_caps_is_empty (caps2)) {
    return gst_caps_new_empty ();
  }
  if (gst_caps_is_any (caps1))
    return gst_caps_copy (caps2);
  if (gst_caps_is_any (caps2))
    return gst_caps_copy (caps1);

  dest = gst_caps_new_empty ();
  for (i = 0; i < caps1->structs->len; i++) {
    struct1 = gst_caps_get_structure (caps1, i);
    for (j = 0; j < caps2->structs->len; j++) {
      GstStructure *istruct;

      struct2 = gst_caps_get_structure (caps2, j);
      istruct = gst_caps_structure_intersect (struct1, struct2);

      gst_caps_append_structure (dest, istruct);
    }
  }

#if 0
  caps = gst_caps_simplify (dest);
  gst_caps_free (dest);

  return caps;
#else
  return dest;
#endif
}

/**
 * gst_caps_union:
 * @caps1: a #GstCaps to union
 * @caps2: a #GstCaps to union
 *
 * Creates a new #GstCaps that contains all the formats that are in
 * either @caps1 and @caps2.
 *
 * Returns: the new #GstCaps
 */
GstCaps *
gst_caps_union (const GstCaps * caps1, const GstCaps * caps2)
{
  GstCaps *dest1;
  GstCaps *dest2;

  dest1 = gst_caps_copy (caps1);
  dest2 = gst_caps_copy (caps2);
  gst_caps_append (dest1, dest2);

  /* FIXME: need a simplify function */

  return dest1;
}

typedef struct _NormalizeForeach
{
  GstCaps *caps;
  GstStructure *structure;
}
NormalizeForeach;

static gboolean
gst_caps_normalize_foreach (GQuark field_id, GValue * value, gpointer ptr)
{
  NormalizeForeach *nf = (NormalizeForeach *) ptr;
  GValue val = { 0 };
  int i;

  if (G_VALUE_TYPE (value) == GST_TYPE_LIST) {
    for (i = 1; i < gst_value_list_get_size (value); i++) {
      const GValue *v = gst_value_list_get_value (value, i);
      GstStructure *structure = gst_structure_copy (nf->structure);

      gst_structure_id_set_value (structure, field_id, v);
      gst_caps_append_structure (nf->caps, structure);
    }

    gst_value_init_and_copy (&val, gst_value_list_get_value (value, 0));
    gst_structure_id_set_value (nf->structure, field_id, &val);
    g_value_unset (&val);

    return FALSE;
  }
  return TRUE;
}

/**
 * gst_caps_normalize:
 * @caps: a #GstCaps to normalize
 *
 * Creates a new #GstCaps that represents the same set of formats as
 * @caps, but contains no lists.  Each list is expanded into separate
 * @GstStructures.
 *
 * Returns: the new #GstCaps
 */
GstCaps *
gst_caps_normalize (const GstCaps * caps)
{
  NormalizeForeach nf;
  GstCaps *newcaps;
  int i;

  g_return_val_if_fail (caps != NULL, NULL);

  newcaps = gst_caps_copy (caps);
  nf.caps = newcaps;

  for (i = 0; i < newcaps->structs->len; i++) {
    nf.structure = gst_caps_get_structure (newcaps, i);

    while (!gst_structure_foreach (nf.structure,
            gst_caps_normalize_foreach, &nf));
  }

  return newcaps;
}

static gboolean
simplify_foreach (GQuark field_id, GValue * value, gpointer user_data)
{
  GstStructure *s2 = (GstStructure *) user_data;
  const GValue *v2;

  v2 = gst_structure_id_get_value (s2, field_id);
  if (v2 == NULL)
    return FALSE;

  if (gst_value_compare (value, v2) == GST_VALUE_EQUAL)
    return TRUE;
  return FALSE;
}

static gboolean
gst_caps_structure_simplify (GstStructure * struct1,
    const GstStructure * struct2)
{
  /* FIXME this is just a simple compare.  Better would be to merge
   * the two structures */
  if (struct1->name != struct2->name)
    return FALSE;
  if (struct1->fields->len != struct2->fields->len)
    return FALSE;

  return gst_structure_foreach (struct1, simplify_foreach, (void *) struct2);
}

/**
 * gst_caps_simplify:
 * @caps: a #GstCaps to simplify
 *
 * Creates a new #GstCaps that represents the same set of formats as
 * @caps, but simpler.  Component structures that are identical are
 * merged.  Component structures that have ranges or lists that can
 * be merged are also merged.
 *
 * Returns: the new #GstCaps
 */
GstCaps *
gst_caps_simplify (const GstCaps * caps)
{
  int i;
  int j;
  GstCaps *newcaps;
  GstStructure *structure;
  GstStructure *struct2;

  if (gst_caps_get_size (caps) < 2) {
    return gst_caps_copy (caps);
  }

  newcaps = gst_caps_new_empty ();

  for (i = 0; i < gst_caps_get_size (caps); i++) {
    structure = gst_caps_get_structure (caps, i);

    for (j = 0; j < gst_caps_get_size (newcaps); j++) {
      struct2 = gst_caps_get_structure (caps, i);
      if (gst_caps_structure_simplify (struct2, structure)) {
        break;
      }
    }
    if (j == gst_caps_get_size (newcaps)) {
      gst_caps_append_structure (newcaps, gst_structure_copy (structure));
    }
  }

  return newcaps;
}

#ifndef GST_DISABLE_LOADSAVE
xmlNodePtr
gst_caps_save_thyself (const GstCaps * caps, xmlNodePtr parent)
{

  return 0;
}

GstCaps *
gst_caps_load_thyself (xmlNodePtr parent)
{

  return NULL;
}
#endif

/* utility */

/**
 * gst_caps_replace:
 * @caps: a pointer to #GstCaps
 * @newcaps: a #GstCaps to replace *caps
 *
 * Replaces *caps with @newcaps.  Frees the #GstCaps in the location
 * pointed to by @caps, if applicable, then modifies @caps to point to
 * @newcaps.
 */
void
gst_caps_replace (GstCaps ** caps, GstCaps * newcaps)
{
#if 0                           /* disable this, since too many plugins rely on undefined behavior */
#ifdef USE_POISONING
  //if (newcaps) CAPS_POISON (newcaps);
#endif
#endif
  if (*caps)
    gst_caps_free (*caps);
  *caps = newcaps;
}

/**
 * gst_caps_to_string:
 * @caps: a #GstCaps
 *
 * Converts @caps to a string representation.  This string representation
 * can be converted back to a #GstCaps by #gst_caps_from_string().
 *
 * Returns: a string representing @caps
 */
gchar *
gst_caps_to_string (const GstCaps * caps)
{
  int i;
  GstStructure *structure;
  GString *s;
  char *sstr;

  /* NOTE:  This function is potentially called by the debug system,
   * so any calls to gst_log() (and GST_DEBUG(), GST_LOG(), etc.)
   * should be careful to avoid recursion.  This includes any functions
   * called by gst_caps_to_string.  In particular, calls should
   * not use the GST_PTR_FORMAT extension.  */

  /* FIXME does this leak? */

  if (caps == NULL) {
    return g_strdup ("NULL");
  }
  if (gst_caps_is_any (caps)) {
    return g_strdup ("ANY");
  }
  if (gst_caps_is_empty (caps)) {
    return g_strdup ("EMPTY");
  }
  s = g_string_new ("");
  structure = gst_caps_get_structure (caps, 0);
  sstr = gst_structure_to_string (structure);
  g_string_append (s, sstr);
  g_free (sstr);

  for (i = 1; i < caps->structs->len; i++) {
    structure = gst_caps_get_structure (caps, i);

    g_string_append (s, "; ");
    sstr = gst_structure_to_string (structure);
    g_string_append (s, sstr);
    g_free (sstr);
  }

  return g_string_free (s, FALSE);
}

static gboolean
gst_caps_from_string_inplace (GstCaps * caps, const gchar * string)
{
  GstStructure *structure;
  gchar *s;

  if (strcmp ("ANY", string) == 0) {
    caps->flags = GST_CAPS_FLAGS_ANY;
    return TRUE;
  }
  if (strcmp ("NONE", string) == 0) {
    return TRUE;
  }

  structure = gst_structure_from_string (string, &s);
  if (structure == NULL) {
    return FALSE;
  }
  gst_caps_append_structure (caps, structure);

  while (*s == ';') {
    s++;
    while (g_ascii_isspace (*s))
      s++;
    structure = gst_structure_from_string (s, &s);
    if (structure == NULL) {
      return FALSE;
    }
    gst_caps_append_structure (caps, structure);
    while (g_ascii_isspace (*s))
      s++;
  }

  if (*s != 0) {
    return FALSE;
  }

  return TRUE;
}

/**
 * gst_caps_from_string:
 * @caps: a string to convert to #GstCaps
 *
 * Converts @caps from a string representation.
 *
 * Returns: a new #GstCaps
 */
GstCaps *
gst_caps_from_string (const gchar * string)
{
  GstCaps *caps;

  caps = gst_caps_new_empty ();
  if (gst_caps_from_string_inplace (caps, string)) {
    return caps;
  } else {
    gst_caps_free (caps);
    return NULL;
  }
}

static void
gst_caps_transform_to_string (const GValue * src_value, GValue * dest_value)
{
  g_return_if_fail (src_value != NULL);
  g_return_if_fail (dest_value != NULL);

  dest_value->data[0].v_pointer =
      gst_caps_to_string (src_value->data[0].v_pointer);
}

static GstCaps *
gst_caps_copy_conditional (const GstCaps * src)
{
  if (src) {
    return gst_caps_copy (src);
  } else {
    return NULL;
  }
}

/* fixate utility functions */

gboolean
gst_caps_structure_fixate_field_nearest_int (GstStructure * structure,
    const char *field_name, int target)
{
  const GValue *value;

  g_return_val_if_fail (gst_structure_has_field (structure, field_name), FALSE);

  value = gst_structure_get_value (structure, field_name);

  if (G_VALUE_TYPE (value) == G_TYPE_INT) {
    /* already fixed */
    return FALSE;
  } else if (G_VALUE_TYPE (value) == GST_TYPE_INT_RANGE) {
    int x;

    x = gst_value_get_int_range_min (value);
    if (target < x)
      target = x;
    x = gst_value_get_int_range_max (value);
    if (target > x)
      target = x;
    gst_structure_set (structure, field_name, G_TYPE_INT, target, NULL);
    return TRUE;
  } else if (G_VALUE_TYPE (value) == GST_TYPE_LIST) {
    const GValue *list_value;
    int i, n;
    int best = 0;
    int best_index = -1;

    n = gst_value_list_get_size (value);
    for (i = 0; i < n; i++) {
      list_value = gst_value_list_get_value (value, i);
      if (G_VALUE_TYPE (list_value) == G_TYPE_INT) {
        int x = g_value_get_int (list_value);

        if (best_index == -1 || (ABS (target - x) < ABS (best - x))) {
          best_index = i;
          best = x;
        }
      }
    }
    if (best_index != -1) {
      gst_structure_set (structure, field_name, G_TYPE_INT, best, NULL);
      return TRUE;
    }
    return FALSE;
  }

  return FALSE;
}

gboolean
gst_caps_structure_fixate_field_nearest_double (GstStructure * structure,
    const char *field_name, double target)
{
  const GValue *value;

  g_return_val_if_fail (gst_structure_has_field (structure, field_name), FALSE);

  value = gst_structure_get_value (structure, field_name);

  if (G_VALUE_TYPE (value) == G_TYPE_DOUBLE) {
    /* already fixed */
    return FALSE;
  } else if (G_VALUE_TYPE (value) == GST_TYPE_DOUBLE_RANGE) {
    double x;

    x = gst_value_get_double_range_min (value);
    if (target < x)
      target = x;
    x = gst_value_get_double_range_max (value);
    if (target > x)
      target = x;
    gst_structure_set (structure, field_name, G_TYPE_DOUBLE, target, NULL);
    return TRUE;
  } else if (G_VALUE_TYPE (value) == GST_TYPE_LIST) {
    const GValue *list_value;
    int i, n;
    double best = 0;
    int best_index = -1;

    n = gst_value_list_get_size (value);
    for (i = 0; i < n; i++) {
      list_value = gst_value_list_get_value (value, i);
      if (G_VALUE_TYPE (list_value) == G_TYPE_DOUBLE) {
        double x = g_value_get_double (list_value);

        if (best_index == -1 || (ABS (target - x) < ABS (best - x))) {
          best_index = i;
          best = x;
        }
      }
    }
    if (best_index != -1) {
      gst_structure_set (structure, field_name, G_TYPE_DOUBLE, best, NULL);
      return TRUE;
    }
    return FALSE;
  }

  return FALSE;

}