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  * SPDX-License-Identifier: LGPL-2.1-or-later
   5  *
   6  * This library is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU Lesser General Public
   8  * License as published by the Free Software Foundation; either
   9  * version 2.1 of the License, or (at your option) any later version.
  10  *
  11  * This library is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  * Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General
  17  * Public License along with this library; if not, see <http://www.gnu.org/licenses/>.
  18  *
  19  * gvaluecollector.h: GValue varargs stubs
  20  */
  21 /**
  22  * SECTION:value_collection
  23  * @Short_description: Converting varargs to generic values
  24  * @Title: Varargs Value Collection
  25  *
  26  * The macros in this section provide the varargs parsing support needed
  27  * in variadic GObject functions such as g_object_new() or g_object_set().
  28  *
  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`.
  86  *
  87  * We have to implement the varargs collection as a macro, because on some
  88  * systems `va_list` variables cannot be passed by reference.
  89  *
  90  * Since: 2.24
  91  */
  92 #define G_VALUE_COLLECT_INIT(value, _value_type, var_args, flags, __error) \
  93   G_STMT_START { \
  94     GTypeValueTable *g_vci_vtab; \
  95     G_VALUE_COLLECT_INIT2(value, g_vci_vtab, _value_type, var_args, flags, __error); \
  96 } G_STMT_END
  97
  98 /**
  99  * G_VALUE_COLLECT_INIT2:
 100  * @value: a #GValue return location. @value must contain only 0 bytes.
 101  * @g_vci_vtab: a #GTypeValueTable pointer that will be set to the value table
 102  *   for @_value_type
 103  * @_value_type: the #GType to use for @value.
 104  * @var_args: the va_list variable; it may be evaluated multiple times
 105  * @flags: flags which are passed on to the collect_value() function of
 106  *  the #GTypeValueTable of @value.
 107  * @__error: a #gchar** variable that will be modified to hold a g_new()
 108  *  allocated error messages if something fails
 109  *
 110  * A variant of G_VALUE_COLLECT_INIT() that provides the #GTypeValueTable
 111  * to the caller.
 112  *
 113  * Since: 2.74
 114  */
 115 #define G_VALUE_COLLECT_INIT2(value, g_vci_vtab, _value_type, var_args, flags, __error)         \
 116 G_STMT_START {                                                                          \
 117   GValue *g_vci_val = (value);                                                          \
 118   guint g_vci_flags = (flags);                                                          \
 119   const gchar *g_vci_collect_format; \
 120   GTypeCValue g_vci_cvalues[G_VALUE_COLLECT_FORMAT_MAX_LENGTH] = { { 0, }, };           \
 121   guint g_vci_n_values = 0;                                                                     \
 122   g_vci_vtab = g_type_value_table_peek (_value_type);                   \
 123   g_vci_collect_format = g_vci_vtab->collect_format;                                    \
 124   g_vci_val->g_type = _value_type;              /* value_meminit() from gvalue.c */             \
 125   while (*g_vci_collect_format)                                                         \
 126     {                                                                                   \
 127       GTypeCValue *g_vci_cvalue = g_vci_cvalues + g_vci_n_values++;                                     \
 128                                                                                         \
 129       switch (*g_vci_collect_format++)                                                  \
 130         {                                                                               \
 131         case G_VALUE_COLLECT_INT:                                                       \
 132           g_vci_cvalue->v_int = va_arg ((var_args), gint);                                      \
 133           break;                                                                        \
 134         case G_VALUE_COLLECT_LONG:                                                      \
 135           g_vci_cvalue->v_long = va_arg ((var_args), glong);                                    \
 136           break;                                                                        \
 137         case G_VALUE_COLLECT_INT64:                                                     \
 138           g_vci_cvalue->v_int64 = va_arg ((var_args), gint64);                          \
 139           break;                                                                        \
 140         case G_VALUE_COLLECT_DOUBLE:                                                    \
 141           g_vci_cvalue->v_double = va_arg ((var_args), gdouble);                                \
 142           break;                                                                        \
 143         case G_VALUE_COLLECT_POINTER:                                                   \
 144           g_vci_cvalue->v_pointer = va_arg ((var_args), gpointer);                              \
 145           break;                                                                        \
 146         default:                                                                        \
 147           g_assert_not_reached ();                                                      \
 148         }                                                                               \
 149     }                                                                                   \
 150   *(__error) = g_vci_vtab->collect_value (g_vci_val,                                            \
 151                                        g_vci_n_values,                                  \
 152                                        g_vci_cvalues,                                   \
 153                                        g_vci_flags);                                            \
 154 } G_STMT_END
 155
 156 /**
 157  * G_VALUE_COLLECT:
 158  * @value: a #GValue return location. @value is supposed to be initialized
 159  *  according to the value type to be collected
 160  * @var_args: the va_list variable; it may be evaluated multiple times
 161  * @flags: flags which are passed on to the collect_value() function of
 162  *  the #GTypeValueTable of @value.
 163  * @__error: a #gchar** variable that will be modified to hold a g_new()
 164  *  allocated error messages if something fails
 165  *
 166  * Collects a variable argument value from a `va_list`.
 167  *
 168  * We have to implement the varargs collection as a macro, because on some systems
 169  * `va_list` variables cannot be passed by reference.
 170  *
 171  * Note: If you are creating the @value argument just before calling this macro,
 172  * you should use the G_VALUE_COLLECT_INIT() variant and pass the uninitialized
 173  * #GValue. That variant is faster than G_VALUE_COLLECT().
 174  */
 175 #define G_VALUE_COLLECT(value, var_args, flags, __error) G_STMT_START {                 \
 176   GValue *g_vc_value = (value);                                                         \
 177   GType g_vc_value_type = G_VALUE_TYPE (g_vc_value);                                            \
 178   GTypeValueTable *g_vc_vtable = g_type_value_table_peek (g_vc_value_type);                     \
 179                                                                                         \
 180   if (g_vc_vtable->value_free)                                                          \
 181     g_vc_vtable->value_free (g_vc_value);                                                       \
 182   memset (g_vc_value->data, 0, sizeof (g_vc_value->data));                                      \
 183                                                                                         \
 184   G_VALUE_COLLECT_INIT(value, g_vc_value_type, var_args, flags, __error);                       \
 185 } G_STMT_END
 186
 187 /**
 188  * G_VALUE_COLLECT_SKIP:
 189  * @_value_type: the #GType of the value to skip
 190  * @var_args: the va_list variable; it may be evaluated multiple times
 191  *
 192  * Skip an argument of type @_value_type from @var_args.
 193  */
 194 #define G_VALUE_COLLECT_SKIP(_value_type, var_args)                                     \
 195 G_STMT_START {                                                                          \
 196   GTypeValueTable *g_vcs_vtable = g_type_value_table_peek (_value_type);                        \
 197   const gchar *g_vcs_collect_format = g_vcs_vtable->collect_format;                             \
 198                                                                                         \
 199   while (*g_vcs_collect_format)                                                         \
 200     {                                                                                   \
 201       switch (*g_vcs_collect_format++)                                                  \
 202         {                                                                               \
 203         case G_VALUE_COLLECT_INT:                                                       \
 204           va_arg ((var_args), gint);                                                    \
 205           break;                                                                        \
 206         case G_VALUE_COLLECT_LONG:                                                      \
 207           va_arg ((var_args), glong);                                                   \
 208           break;                                                                        \
 209         case G_VALUE_COLLECT_INT64:                                                     \
 210           va_arg ((var_args), gint64);                                                  \
 211           break;                                                                        \
 212         case G_VALUE_COLLECT_DOUBLE:                                                    \
 213           va_arg ((var_args), gdouble);                                                 \
 214           break;                                                                        \
 215         case G_VALUE_COLLECT_POINTER:                                                   \
 216           va_arg ((var_args), gpointer);                                                \
 217           break;                                                                        \
 218         default:                                                                        \
 219           g_assert_not_reached ();                                                      \
 220         }                                                                               \
 221     }                                                                                   \
 222 } G_STMT_END
 223
 224 /**
 225  * G_VALUE_LCOPY:
 226  * @value: a #GValue to store into the @var_args; this must be initialized
 227  *  and set
 228  * @var_args: the va_list variable; it may be evaluated multiple times
 229  * @flags: flags which are passed on to the lcopy_value() function of
 230  *  the #GTypeValueTable of @value.
 231  * @__error: a #gchar** variable that will be modified to hold a g_new()
 232  *  allocated error message if something fails
 233  *
 234  * Stores a value’s value into one or more argument locations from a `va_list`.
 235  *
 236  * This is the inverse of G_VALUE_COLLECT().
 237  */
 238 #define G_VALUE_LCOPY(value, var_args, flags, __error)                                  \
 239 G_STMT_START {                                                                          \
 240   const GValue *g_vl_value = (value);                                                   \
 241   guint g_vl_flags = (flags);                                                           \
 242   GType g_vl_value_type = G_VALUE_TYPE (g_vl_value);                                            \
 243   GTypeValueTable *g_vl_vtable = g_type_value_table_peek (g_vl_value_type);                     \
 244   const gchar *g_vl_lcopy_format = g_vl_vtable->lcopy_format;                                   \
 245   GTypeCValue g_vl_cvalues[G_VALUE_COLLECT_FORMAT_MAX_LENGTH] = { { 0, }, };            \
 246   guint g_vl_n_values = 0;                                                                      \
 247                                                                                         \
 248   while (*g_vl_lcopy_format)                                                            \
 249     {                                                                                   \
 250       GTypeCValue *g_vl_cvalue = g_vl_cvalues + g_vl_n_values++;                                        \
 251                                                                                         \
 252       switch (*g_vl_lcopy_format++)                                                             \
 253         {                                                                               \
 254         case G_VALUE_COLLECT_INT:                                                       \
 255           g_vl_cvalue->v_int = va_arg ((var_args), gint);                                       \
 256           break;                                                                        \
 257         case G_VALUE_COLLECT_LONG:                                                      \
 258           g_vl_cvalue->v_long = va_arg ((var_args), glong);                                     \
 259           break;                                                                        \
 260         case G_VALUE_COLLECT_INT64:                                                     \
 261           g_vl_cvalue->v_int64 = va_arg ((var_args), gint64);                           \
 262           break;                                                                        \
 263         case G_VALUE_COLLECT_DOUBLE:                                                    \
 264           g_vl_cvalue->v_double = va_arg ((var_args), gdouble);                         \
 265           break;                                                                        \
 266         case G_VALUE_COLLECT_POINTER:                                                   \
 267           g_vl_cvalue->v_pointer = va_arg ((var_args), gpointer);                               \
 268           break;                                                                        \
 269         default:                                                                        \
 270           g_assert_not_reached ();                                                      \
 271         }                                                                               \
 272     }                                                                                   \
 273   *(__error) = g_vl_vtable->lcopy_value (g_vl_value,                                            \
 274                                      g_vl_n_values,                                             \
 275                                      g_vl_cvalues,                                              \
 276                                      g_vl_flags);                                               \
 277 } G_STMT_END
 278
 279
 280 /**
 281  * G_VALUE_COLLECT_FORMAT_MAX_LENGTH:
 282  *
 283  * The maximal number of #GTypeCValues which can be collected for a
 284  * single #GValue.
 285  */
 286 #define G_VALUE_COLLECT_FORMAT_MAX_LENGTH       (8)
 287
 288 G_END_DECLS
 289
 290 #endif /* __G_VALUE_COLLECTOR_H__ */