gobject/gvaluecollector.h

   1 /* GObject - GLib Type, Object, Parameter and Signal Library
   2  * Copyright (C) 1998-1999, 2000-2001 Tim Janik and Red Hat, Inc.
   3  *
   4  * This library is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU Lesser General Public
   6  * License as published by the Free Software Foundation; either
   7  * version 2 of the License, or (at your option) any later version.
   8  *
   9  * This library is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12  * Lesser General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU Lesser General
  15  * Public License along with this library; if not, write to the
  16  * Free Software Foundation, Inc., 59 Temple Place, Suite 330,
  17  * Boston, MA 02111-1307, USA.
  18  *
  19  * gvaluecollector.h: GValue varargs stubs
  20  */
  21 /**
  22  * SECTION:value_collection
  23  * @Short_description: Converting varargs to generic values
  24  * @See_also:#GValueTable
  25  * @Title: Varargs Value Collection
  26  *
  27  * The macros in this section provide the varargs parsing support needed
  28  * in variadic GObject functions such as g_object_new() or g_object_set().
  29  * They currently support the collection of integral types, floating point
  30  * types and pointers.
  31  */
  32 #ifndef __G_VALUE_COLLECTOR_H__
  33 #define __G_VALUE_COLLECTOR_H__
  34
  35 #include <glib-object.h>
  36
  37 G_BEGIN_DECLS
  38
  39 /* we may want to add aggregate types here some day, if requested
  40  * by users. the basic C types are covered already, everything
  41  * smaller than an int is promoted to an integer and floats are
  42  * always promoted to doubles for varargs call constructions.
  43  */
  44 enum    /*< skip >*/
  45 {
  46   G_VALUE_COLLECT_INT           = 'i',
  47   G_VALUE_COLLECT_LONG          = 'l',
  48   G_VALUE_COLLECT_INT64         = 'q',
  49   G_VALUE_COLLECT_DOUBLE        = 'd',
  50   G_VALUE_COLLECT_POINTER       = 'p'
  51 };
  52
  53
  54 /* vararg union holding actuall values collected
  55  */
  56 /**
  57  * GTypeCValue:
  58  *
  59  * A union holding one collected value.
  60  */
  61 union _GTypeCValue
  62 {
  63   gint     v_int;
  64   glong    v_long;
  65   gint64   v_int64;
  66   gdouble  v_double;
  67   gpointer v_pointer;
  68 };
  69
  70 /**
  71  * G_VALUE_COLLECT_INIT:
  72  * @value: a #GValue return location. @value must contain only 0 bytes.
  73  * @_value_type: the #GType to use for @value.
  74  * @var_args: the va_list variable; it may be evaluated multiple times
  75  * @flags: flags which are passed on to the collect_value() function of
  76  *  the #GTypeValueTable of @value.
  77  * @__error: a #gchar** variable that will be modified to hold a g_new()
  78  *  allocated error messages if something fails
  79  *
  80  * Collects a variable argument value from a va_list. We have to
  81  * implement the varargs collection as a macro, because on some systems
  82  * va_list variables cannot be passed by reference.
  83  *
  84  * Since: 2.24
  85  */
  86 #define G_VALUE_COLLECT_INIT(value, _value_type, var_args, flags, __error)              \
  87 G_STMT_START {                                                                          \
  88   GValue *_value = (value);                                                             \
  89   guint _flags = (flags);                                                               \
  90   GTypeValueTable *_vtable = g_type_value_table_peek (_value_type);                     \
  91   gchar *_collect_format = _vtable->collect_format;                                     \
  92   GTypeCValue _cvalues[G_VALUE_COLLECT_FORMAT_MAX_LENGTH] = { { 0, }, };                \
  93   guint _n_values = 0;                                                                  \
  94                                                                                         \
  95   _value->g_type = _value_type;         /* value_meminit() from gvalue.c */             \
  96   while (*_collect_format)                                                              \
  97     {                                                                                   \
  98       GTypeCValue *_cvalue = _cvalues + _n_values++;                                    \
  99                                                                                         \
 100       switch (*_collect_format++)                                                       \
 101         {                                                                               \
 102         case G_VALUE_COLLECT_INT:                                                       \
 103           _cvalue->v_int = va_arg ((var_args), gint);                                   \
 104           break;                                                                        \
 105         case G_VALUE_COLLECT_LONG:                                                      \
 106           _cvalue->v_long = va_arg ((var_args), glong);                                 \
 107           break;                                                                        \
 108         case G_VALUE_COLLECT_INT64:                                                     \
 109           _cvalue->v_int64 = va_arg ((var_args), gint64);                               \
 110           break;                                                                        \
 111         case G_VALUE_COLLECT_DOUBLE:                                                    \
 112           _cvalue->v_double = va_arg ((var_args), gdouble);                             \
 113           break;                                                                        \
 114         case G_VALUE_COLLECT_POINTER:                                                   \
 115           _cvalue->v_pointer = va_arg ((var_args), gpointer);                           \
 116           break;                                                                        \
 117         default:                                                                        \
 118           g_assert_not_reached ();                                                      \
 119         }                                                                               \
 120     }                                                                                   \
 121   *(__error) = _vtable->collect_value (_value,                                          \
 122                                        _n_values,                                       \
 123                                        _cvalues,                                        \
 124                                        _flags);                                         \
 125 } G_STMT_END
 126
 127 /**
 128  * G_VALUE_COLLECT:
 129  * @value: a #GValue return location. @value is supposed to be initialized
 130  *  according to the value type to be collected
 131  * @var_args: the va_list variable; it may be evaluated multiple times
 132  * @flags: flags which are passed on to the collect_value() function of
 133  *  the #GTypeValueTable of @value.
 134  * @__error: a #gchar** variable that will be modified to hold a g_new()
 135  *  allocated error messages if something fails
 136  *
 137  * Collects a variable argument value from a va_list. We have to
 138  * implement the varargs collection as a macro, because on some systems
 139  * va_list variables cannot be passed by reference.
 140  *
 141  * Note: If you are creating the @value argument just before calling this macro,
 142  * you should use the #G_VALUE_COLLECT_INIT variant and pass the unitialized
 143  * #GValue. That variant is faster than #G_VALUE_COLLECT.
 144  */
 145 #define G_VALUE_COLLECT(value, var_args, flags, __error) G_STMT_START {                 \
 146   GValue *_value = (value);                                                             \
 147   GType _value_type = G_VALUE_TYPE (_value);                                            \
 148   GTypeValueTable *_vtable = g_type_value_table_peek (_value_type);                     \
 149                                                                                         \
 150   if (_vtable->value_free)                                                              \
 151     _vtable->value_free (_value);                                                       \
 152   memset (_value->data, 0, sizeof (_value->data));                                      \
 153                                                                                         \
 154   G_VALUE_COLLECT_INIT(value, _value_type, var_args, flags, __error);                   \
 155 } G_STMT_END
 156
 157 /**
 158  * G_VALUE_LCOPY:
 159  * @value: a #GValue return location. @value is supposed to be initialized
 160  *  according to the value type to be collected
 161  * @var_args: the va_list variable; it may be evaluated multiple times
 162  * @flags: flags which are passed on to the lcopy_value() function of
 163  *  the #GTypeValueTable of @value.
 164  * @__error: a #gchar** variable that will be modified to hold a g_new()
 165  *  allocated error messages if something fails
 166  *
 167  * Collects a value's variable argument locations from a va_list. Usage is
 168  * analogous to G_VALUE_COLLECT().
 169  */
 170 #define G_VALUE_LCOPY(value, var_args, flags, __error)                                  \
 171 G_STMT_START {                                                                          \
 172   const GValue *_value = (value);                                                       \
 173   guint _flags = (flags);                                                               \
 174   GType _value_type = G_VALUE_TYPE (_value);                                            \
 175   GTypeValueTable *_vtable = g_type_value_table_peek (_value_type);                     \
 176   gchar *_lcopy_format = _vtable->lcopy_format;                                         \
 177   GTypeCValue _cvalues[G_VALUE_COLLECT_FORMAT_MAX_LENGTH] = { { 0, }, };                \
 178   guint _n_values = 0;                                                                  \
 179                                                                                         \
 180   while (*_lcopy_format)                                                                \
 181     {                                                                                   \
 182       GTypeCValue *_cvalue = _cvalues + _n_values++;                                    \
 183                                                                                         \
 184       switch (*_lcopy_format++)                                                         \
 185         {                                                                               \
 186         case G_VALUE_COLLECT_INT:                                                       \
 187           _cvalue->v_int = va_arg ((var_args), gint);                                   \
 188           break;                                                                        \
 189         case G_VALUE_COLLECT_LONG:                                                      \
 190           _cvalue->v_long = va_arg ((var_args), glong);                                 \
 191           break;                                                                        \
 192         case G_VALUE_COLLECT_INT64:                                                     \
 193           _cvalue->v_int64 = va_arg ((var_args), gint64);                               \
 194           break;                                                                        \
 195         case G_VALUE_COLLECT_DOUBLE:                                                    \
 196           _cvalue->v_double = va_arg ((var_args), gdouble);                             \
 197           break;                                                                        \
 198         case G_VALUE_COLLECT_POINTER:                                                   \
 199           _cvalue->v_pointer = va_arg ((var_args), gpointer);                           \
 200           break;                                                                        \
 201         default:                                                                        \
 202           g_assert_not_reached ();                                                      \
 203         }                                                                               \
 204     }                                                                                   \
 205   *(__error) = _vtable->lcopy_value (_value,                                            \
 206                                      _n_values,                                         \
 207                                      _cvalues,                                          \
 208                                      _flags);                                           \
 209 } G_STMT_END
 210
 211
 212 /**
 213  * G_VALUE_COLLECT_FORMAT_MAX_LENGTH:
 214  *
 215  * The maximal number of #GTypeCValue<!-- -->s which can be collected for a
 216  * single #GValue.
 217  */
 218 #define G_VALUE_COLLECT_FORMAT_MAX_LENGTH       (8)
 219
 220 G_END_DECLS
 221
 222 #endif /* __G_VALUE_COLLECTOR_H__ */