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 actual values collected
  55  */
  56 /**
  57  * GTypeCValue:
  58  * @v_int: the field for holding integer values
  59  * @v_long: the field for holding long integer values
  60  * @v_int64: the field for holding 64 bit integer values
  61  * @v_double: the field for holding floating point values
  62  * @v_pointer: the field for holding pointers
  63  *
  64  * A union holding one collected value.
  65  */
  66 union _GTypeCValue
  67 {
  68   gint     v_int;
  69   glong    v_long;
  70   gint64   v_int64;
  71   gdouble  v_double;
  72   gpointer v_pointer;
  73 };
  74
  75 /**
  76  * G_VALUE_COLLECT_INIT:
  77  * @value: a #GValue return location. @value must contain only 0 bytes.
  78  * @_value_type: the #GType to use for @value.
  79  * @var_args: the va_list variable; it may be evaluated multiple times
  80  * @flags: flags which are passed on to the collect_value() function of
  81  *  the #GTypeValueTable of @value.
  82  * @__error: a #gchar** variable that will be modified to hold a g_new()
  83  *  allocated error messages if something fails
  84  *
  85  * Collects a variable argument value from a va_list. We have to
  86  * implement the varargs collection as a macro, because on some systems
  87  * va_list variables cannot be passed by reference.
  88  *
  89  * Since: 2.24
  90  */
  91 #define G_VALUE_COLLECT_INIT(value, _value_type, var_args, flags, __error)              \
  92 G_STMT_START {                                                                          \
  93   GValue *_val = (value);                                                               \
  94   guint _flags = (flags);                                                               \
  95   GTypeValueTable *_vtab = g_type_value_table_peek (_value_type);                       \
  96   gchar *_collect_format = _vtab->collect_format;                                       \
  97   GTypeCValue _cvalues[G_VALUE_COLLECT_FORMAT_MAX_LENGTH] = { { 0, }, };                \
  98   guint _n_values = 0;                                                                  \
  99                                                                                         \
 100   _val->g_type = _value_type;           /* value_meminit() from gvalue.c */             \
 101   while (*_collect_format)                                                              \
 102     {                                                                                   \
 103       GTypeCValue *_cvalue = _cvalues + _n_values++;                                    \
 104                                                                                         \
 105       switch (*_collect_format++)                                                       \
 106         {                                                                               \
 107         case G_VALUE_COLLECT_INT:                                                       \
 108           _cvalue->v_int = va_arg ((var_args), gint);                                   \
 109           break;                                                                        \
 110         case G_VALUE_COLLECT_LONG:                                                      \
 111           _cvalue->v_long = va_arg ((var_args), glong);                                 \
 112           break;                                                                        \
 113         case G_VALUE_COLLECT_INT64:                                                     \
 114           _cvalue->v_int64 = va_arg ((var_args), gint64);                               \
 115           break;                                                                        \
 116         case G_VALUE_COLLECT_DOUBLE:                                                    \
 117           _cvalue->v_double = va_arg ((var_args), gdouble);                             \
 118           break;                                                                        \
 119         case G_VALUE_COLLECT_POINTER:                                                   \
 120           _cvalue->v_pointer = va_arg ((var_args), gpointer);                           \
 121           break;                                                                        \
 122         default:                                                                        \
 123           g_assert_not_reached ();                                                      \
 124         }                                                                               \
 125     }                                                                                   \
 126   *(__error) = _vtab->collect_value (_val,                                              \
 127                                        _n_values,                                       \
 128                                        _cvalues,                                        \
 129                                        _flags);                                         \
 130 } G_STMT_END
 131
 132 /**
 133  * G_VALUE_COLLECT:
 134  * @value: a #GValue return location. @value is supposed to be initialized
 135  *  according to the value type to be collected
 136  * @var_args: the va_list variable; it may be evaluated multiple times
 137  * @flags: flags which are passed on to the collect_value() function of
 138  *  the #GTypeValueTable of @value.
 139  * @__error: a #gchar** variable that will be modified to hold a g_new()
 140  *  allocated error messages if something fails
 141  *
 142  * Collects a variable argument value from a va_list. We have to
 143  * implement the varargs collection as a macro, because on some systems
 144  * va_list variables cannot be passed by reference.
 145  *
 146  * Note: If you are creating the @value argument just before calling this macro,
 147  * you should use the #G_VALUE_COLLECT_INIT variant and pass the unitialized
 148  * #GValue. That variant is faster than #G_VALUE_COLLECT.
 149  */
 150 #define G_VALUE_COLLECT(value, var_args, flags, __error) G_STMT_START {                 \
 151   GValue *_value = (value);                                                             \
 152   GType _value_type = G_VALUE_TYPE (_value);                                            \
 153   GTypeValueTable *_vtable = g_type_value_table_peek (_value_type);                     \
 154                                                                                         \
 155   if (_vtable->value_free)                                                              \
 156     _vtable->value_free (_value);                                                       \
 157   memset (_value->data, 0, sizeof (_value->data));                                      \
 158                                                                                         \
 159   G_VALUE_COLLECT_INIT(value, _value_type, var_args, flags, __error);                   \
 160 } G_STMT_END
 161
 162 /**
 163  * G_VALUE_LCOPY:
 164  * @value: a #GValue return location. @value is supposed to be initialized
 165  *  according to the value type to be collected
 166  * @var_args: the va_list variable; it may be evaluated multiple times
 167  * @flags: flags which are passed on to the lcopy_value() function of
 168  *  the #GTypeValueTable of @value.
 169  * @__error: a #gchar** variable that will be modified to hold a g_new()
 170  *  allocated error messages if something fails
 171  *
 172  * Collects a value's variable argument locations from a va_list. Usage is
 173  * analogous to G_VALUE_COLLECT().
 174  */
 175 #define G_VALUE_LCOPY(value, var_args, flags, __error)                                  \
 176 G_STMT_START {                                                                          \
 177   const GValue *_value = (value);                                                       \
 178   guint _flags = (flags);                                                               \
 179   GType _value_type = G_VALUE_TYPE (_value);                                            \
 180   GTypeValueTable *_vtable = g_type_value_table_peek (_value_type);                     \
 181   gchar *_lcopy_format = _vtable->lcopy_format;                                         \
 182   GTypeCValue _cvalues[G_VALUE_COLLECT_FORMAT_MAX_LENGTH] = { { 0, }, };                \
 183   guint _n_values = 0;                                                                  \
 184                                                                                         \
 185   while (*_lcopy_format)                                                                \
 186     {                                                                                   \
 187       GTypeCValue *_cvalue = _cvalues + _n_values++;                                    \
 188                                                                                         \
 189       switch (*_lcopy_format++)                                                         \
 190         {                                                                               \
 191         case G_VALUE_COLLECT_INT:                                                       \
 192           _cvalue->v_int = va_arg ((var_args), gint);                                   \
 193           break;                                                                        \
 194         case G_VALUE_COLLECT_LONG:                                                      \
 195           _cvalue->v_long = va_arg ((var_args), glong);                                 \
 196           break;                                                                        \
 197         case G_VALUE_COLLECT_INT64:                                                     \
 198           _cvalue->v_int64 = va_arg ((var_args), gint64);                               \
 199           break;                                                                        \
 200         case G_VALUE_COLLECT_DOUBLE:                                                    \
 201           _cvalue->v_double = va_arg ((var_args), gdouble);                             \
 202           break;                                                                        \
 203         case G_VALUE_COLLECT_POINTER:                                                   \
 204           _cvalue->v_pointer = va_arg ((var_args), gpointer);                           \
 205           break;                                                                        \
 206         default:                                                                        \
 207           g_assert_not_reached ();                                                      \
 208         }                                                                               \
 209     }                                                                                   \
 210   *(__error) = _vtable->lcopy_value (_value,                                            \
 211                                      _n_values,                                         \
 212                                      _cvalues,                                          \
 213                                      _flags);                                           \
 214 } G_STMT_END
 215
 216
 217 /**
 218  * G_VALUE_COLLECT_FORMAT_MAX_LENGTH:
 219  *
 220  * The maximal number of #GTypeCValue<!-- -->s which can be collected for a
 221  * single #GValue.
 222  */
 223 #define G_VALUE_COLLECT_FORMAT_MAX_LENGTH       (8)
 224
 225 G_END_DECLS
 226
 227 #endif /* __G_VALUE_COLLECTOR_H__ */