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/* -*- Mode: C; indent-tabs-mode: t; c-basic-offset: 8; tab-width: 8 -*- */
/*
* GData Client
* Copyright (C) Philip Withnall 2010 <philip@tecnocode.co.uk>
*
* GData Client is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* GData Client is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with GData Client. If not, see <http://www.gnu.org/licenses/>.
*/
/**
* SECTION:gdata-comparable
* @short_description: GData comparable interface
* @stability: Stable
* @include: gdata/gdata-comparable.h
*
* #GDataComparable is an interface which can be implemented by any object which needs to be compared to another object of the same type or of a
* derived type.
*
* When implementing the interface, classes must implement the <function>compare_with</function> function, and the implementation must be
* <ulink type="http" url="http://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html#index-g_t_0040code_007bpure_007d-function-attribute-2413">pure
* </ulink>.
*
* Since: 0.7.0
*/
#include <glib.h>
#include <glib-object.h>
#include "gdata-comparable.h"
GType
gdata_comparable_get_type (void)
{
static GType comparable_type = 0;
if (!comparable_type) {
comparable_type = g_type_register_static_simple (G_TYPE_INTERFACE, "GDataComparable",
sizeof (GDataComparableIface),
NULL, 0, NULL, 0);
}
return comparable_type;
}
/**
* gdata_comparable_compare:
* @self: (allow-none): a #GDataComparable, or %NULL
* @other: (allow-none): another #GDataComparable of the same type, or %NULL
*
* Compares the two objects, returning <code class="literal">-1</code> if @self is "less than" @other by some metric, <code class="literal">0</code>
* if they're equal, or <code class="literal">1</code> if @self is "greater than" @other.
*
* %NULL values are handled gracefully, with <code class="literal">0</code> returned if both @self and @other are %NULL,
* <code class="literal">-1</code> if @self is %NULL and <code class="literal">1</code> if @other is %NULL.
*
* The @other object must be of the same type as @self, or of a type derived from @self's type.
*
* Return value: %TRUE on success, %FALSE otherwise
*
* Since: 0.7.0
*/
gint
gdata_comparable_compare (GDataComparable *self, GDataComparable *other)
{
GDataComparableIface *iface;
g_return_val_if_fail (self == NULL || GDATA_IS_COMPARABLE (self), 0);
g_return_val_if_fail (other == NULL || GDATA_IS_COMPARABLE (other), 0);
g_return_val_if_fail (self == NULL || other == NULL || g_type_is_a (G_OBJECT_TYPE (other), G_OBJECT_TYPE (self)), 0);
/* Deal with NULL values */
if (self == NULL && other != NULL)
return -1;
else if (self != NULL && other == NULL)
return 1;
if (self == other)
return 0;
/* Use the comparator method for non-NULL values */
iface = GDATA_COMPARABLE_GET_IFACE (self);
g_assert (iface->compare_with != NULL);
return iface->compare_with (self, other);
}
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