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, see <http://www.gnu.org/licenses/>.
  16  *
  17  * gvaluecollector.h: GValue varargs stubs
  18  */
  19 /**
  20  * SECTION:value_collection
  21  * @Short_description: Converting varargs to generic values
  22  * @Title: Varargs Value Collection
  23  *
  24  * The macros in this section provide the varargs parsing support needed
  25  * in variadic GObject functions such as g_object_new() or g_object_set().
  26  * They currently support the collection of integral types, floating point
  27  * types and pointers.
  28  */
  29 #ifndef __G_VALUE_COLLECTOR_H__
  30 #define __G_VALUE_COLLECTOR_H__
  31
  32 #include <glib-object.h>
  33
  34 G_BEGIN_DECLS
  35
  36 /* we may want to add aggregate types here some day, if requested
  37  * by users. the basic C types are covered already, everything
  38  * smaller than an int is promoted to an integer and floats are
  39  * always promoted to doubles for varargs call constructions.
  40  */
  41 enum    /*< skip >*/
  42 {
  43   G_VALUE_COLLECT_INT           = 'i',
  44   G_VALUE_COLLECT_LONG          = 'l',
  45   G_VALUE_COLLECT_INT64         = 'q',
  46   G_VALUE_COLLECT_DOUBLE        = 'd',
  47   G_VALUE_COLLECT_POINTER       = 'p'
  48 };
  49
  50
  51 /* vararg union holding actual values collected
  52  */
  53 /**
  54  * GTypeCValue:
  55  * @v_int: the field for holding integer values
  56  * @v_long: the field for holding long integer values
  57  * @v_int64: the field for holding 64 bit integer values
  58  * @v_double: the field for holding floating point values
  59  * @v_pointer: the field for holding pointers
  60  *
  61  * A union holding one collected value.
  62  */
  63 union _GTypeCValue
  64 {
  65   gint     v_int;
  66   glong    v_long;
  67   gint64   v_int64;
  68   gdouble  v_double;
  69   gpointer v_pointer;
  70 };
  71
  72 /**
  73  * G_VALUE_COLLECT_INIT:
  74  * @value: a #GValue return location. @value must contain only 0 bytes.
  75  * @_value_type: the #GType to use for @value.
  76  * @var_args: the va_list variable; it may be evaluated multiple times
  77  * @flags: flags which are passed on to the collect_value() function of
  78  *  the #GTypeValueTable of @value.
  79  * @__error: a #gchar** variable that will be modified to hold a g_new()
  80  *  allocated error messages if something fails
  81  *
  82  * Collects a variable argument value from a va_list. We have to
  83  * implement the varargs collection as a macro, because on some systems
  84  * va_list variables cannot be passed by reference.
  85  *
  86  * Since: 2.24
  87  */
  88 #define G_VALUE_COLLECT_INIT(value, _value_type, var_args, flags, __error)              \
  89 G_STMT_START {                                                                          \
  90   GValue *_val = (value);                                                               \
  91   guint _flags = (flags);                                                               \
  92   GTypeValueTable *_vtab = g_type_value_table_peek (_value_type);                       \
  93   const gchar *_collect_format = _vtab->collect_format;                                 \
  94   GTypeCValue _cvalues[G_VALUE_COLLECT_FORMAT_MAX_LENGTH] = { { 0, }, };                \
  95   guint _n_values = 0;                                                                  \
  96                                                                                         \
  97   _val->g_type = _value_type;           /* value_meminit() from gvalue.c */             \
  98   while (*_collect_format)                                                              \
  99     {                                                                                   \
 100       GTypeCValue *_cvalue = _cvalues + _n_values++;                                    \
 101                                                                                         \
 102       switch (*_collect_format++)                                                       \
 103         {                                                                               \
 104         case G_VALUE_COLLECT_INT:                                                       \
 105           _cvalue->v_int = va_arg ((var_args), gint);                                   \
 106           break;                                                                        \
 107         case G_VALUE_COLLECT_LONG:                                                      \
 108           _cvalue->v_long = va_arg ((var_args), glong);                                 \
 109           break;                                                                        \
 110         case G_VALUE_COLLECT_INT64:                                                     \
 111           _cvalue->v_int64 = va_arg ((var_args), gint64);                               \
 112           break;                                                                        \
 113         case G_VALUE_COLLECT_DOUBLE:                                                    \
 114           _cvalue->v_double = va_arg ((var_args), gdouble);                             \
 115           break;                                                                        \
 116         case G_VALUE_COLLECT_POINTER:                                                   \
 117           _cvalue->v_pointer = va_arg ((var_args), gpointer);                           \
 118           break;                                                                        \
 119         default:                                                                        \
 120           g_assert_not_reached ();                                                      \
 121         }                                                                               \
 122     }                                                                                   \
 123   *(__error) = _vtab->collect_value (_val,                                              \
 124                                        _n_values,                                       \
 125                                        _cvalues,                                        \
 126                                        _flags);                                         \
 127 } G_STMT_END
 128
 129 /**
 130  * G_VALUE_COLLECT:
 131  * @value: a #GValue return location. @value is supposed to be initialized
 132  *  according to the value type to be collected
 133  * @var_args: the va_list variable; it may be evaluated multiple times
 134  * @flags: flags which are passed on to the collect_value() function of
 135  *  the #GTypeValueTable of @value.
 136  * @__error: a #gchar** variable that will be modified to hold a g_new()
 137  *  allocated error messages if something fails
 138  *
 139  * Collects a variable argument value from a va_list. We have to
 140  * implement the varargs collection as a macro, because on some systems
 141  * va_list variables cannot be passed by reference.
 142  *
 143  * Note: If you are creating the @value argument just before calling this macro,
 144  * you should use the #G_VALUE_COLLECT_INIT variant and pass the unitialized
 145  * #GValue. That variant is faster than #G_VALUE_COLLECT.
 146  */
 147 #define G_VALUE_COLLECT(value, var_args, flags, __error) G_STMT_START {                 \
 148   GValue *_value = (value);                                                             \
 149   GType _value_type = G_VALUE_TYPE (_value);                                            \
 150   GTypeValueTable *_vtable = g_type_value_table_peek (_value_type);                     \
 151                                                                                         \
 152   if (_vtable->value_free)                                                              \
 153     _vtable->value_free (_value);                                                       \
 154   memset (_value->data, 0, sizeof (_value->data));                                      \
 155                                                                                         \
 156   G_VALUE_COLLECT_INIT(value, _value_type, var_args, flags, __error);                   \
 157 } G_STMT_END
 158
 159 #define G_VALUE_COLLECT_SKIP(_value_type, var_args)                                     \
 160 G_STMT_START {                                                                          \
 161   GTypeValueTable *_vtable = g_type_value_table_peek (_value_type);                     \
 162   const gchar *_collect_format = _vtable->collect_format;                               \
 163                                                                                         \
 164   while (*_collect_format)                                                              \
 165     {                                                                                   \
 166       switch (*_collect_format++)                                                       \
 167         {                                                                               \
 168         case G_VALUE_COLLECT_INT:                                                       \
 169           va_arg ((var_args), gint);                                                    \
 170           break;                                                                        \
 171         case G_VALUE_COLLECT_LONG:                                                      \
 172           va_arg ((var_args), glong);                                                   \
 173           break;                                                                        \
 174         case G_VALUE_COLLECT_INT64:                                                     \
 175           va_arg ((var_args), gint64);                                                  \
 176           break;                                                                        \
 177         case G_VALUE_COLLECT_DOUBLE:                                                    \
 178           va_arg ((var_args), gdouble);                                                 \
 179           break;                                                                        \
 180         case G_VALUE_COLLECT_POINTER:                                                   \
 181           va_arg ((var_args), gpointer);                                                \
 182           break;                                                                        \
 183         default:                                                                        \
 184           g_assert_not_reached ();                                                      \
 185         }                                                                               \
 186     }                                                                                   \
 187 } G_STMT_END
 188
 189 /**
 190  * G_VALUE_LCOPY:
 191  * @value: a #GValue return location. @value is supposed to be initialized
 192  *  according to the value type to be collected
 193  * @var_args: the va_list variable; it may be evaluated multiple times
 194  * @flags: flags which are passed on to the lcopy_value() function of
 195  *  the #GTypeValueTable of @value.
 196  * @__error: a #gchar** variable that will be modified to hold a g_new()
 197  *  allocated error messages if something fails
 198  *
 199  * Collects a value's variable argument locations from a va_list. Usage is
 200  * analogous to G_VALUE_COLLECT().
 201  */
 202 #define G_VALUE_LCOPY(value, var_args, flags, __error)                                  \
 203 G_STMT_START {                                                                          \
 204   const GValue *_value = (value);                                                       \
 205   guint _flags = (flags);                                                               \
 206   GType _value_type = G_VALUE_TYPE (_value);                                            \
 207   GTypeValueTable *_vtable = g_type_value_table_peek (_value_type);                     \
 208   const gchar *_lcopy_format = _vtable->lcopy_format;                                   \
 209   GTypeCValue _cvalues[G_VALUE_COLLECT_FORMAT_MAX_LENGTH] = { { 0, }, };                \
 210   guint _n_values = 0;                                                                  \
 211                                                                                         \
 212   while (*_lcopy_format)                                                                \
 213     {                                                                                   \
 214       GTypeCValue *_cvalue = _cvalues + _n_values++;                                    \
 215                                                                                         \
 216       switch (*_lcopy_format++)                                                         \
 217         {                                                                               \
 218         case G_VALUE_COLLECT_INT:                                                       \
 219           _cvalue->v_int = va_arg ((var_args), gint);                                   \
 220           break;                                                                        \
 221         case G_VALUE_COLLECT_LONG:                                                      \
 222           _cvalue->v_long = va_arg ((var_args), glong);                                 \
 223           break;                                                                        \
 224         case G_VALUE_COLLECT_INT64:                                                     \
 225           _cvalue->v_int64 = va_arg ((var_args), gint64);                               \
 226           break;                                                                        \
 227         case G_VALUE_COLLECT_DOUBLE:                                                    \
 228           _cvalue->v_double = va_arg ((var_args), gdouble);                             \
 229           break;                                                                        \
 230         case G_VALUE_COLLECT_POINTER:                                                   \
 231           _cvalue->v_pointer = va_arg ((var_args), gpointer);                           \
 232           break;                                                                        \
 233         default:                                                                        \
 234           g_assert_not_reached ();                                                      \
 235         }                                                                               \
 236     }                                                                                   \
 237   *(__error) = _vtable->lcopy_value (_value,                                            \
 238                                      _n_values,                                         \
 239                                      _cvalues,                                          \
 240                                      _flags);                                           \
 241 } G_STMT_END
 242
 243
 244 /**
 245  * G_VALUE_COLLECT_FORMAT_MAX_LENGTH:
 246  *
 247  * The maximal number of #GTypeCValues which can be collected for a
 248  * single #GValue.
 249  */
 250 #define G_VALUE_COLLECT_FORMAT_MAX_LENGTH       (8)
 251
 252 G_END_DECLS
 253
 254 #endif /* __G_VALUE_COLLECTOR_H__ */