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 2.1 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  *
  27  * They currently support the collection of integral types, floating point
  28  * types and pointers.
  29  */
  30 #ifndef __G_VALUE_COLLECTOR_H__
  31 #define __G_VALUE_COLLECTOR_H__
  32
  33 #include <glib-object.h>
  34
  35 G_BEGIN_DECLS
  36
  37 /* we may want to add aggregate types here some day, if requested
  38  * by users. the basic C types are covered already, everything
  39  * smaller than an int is promoted to an integer and floats are
  40  * always promoted to doubles for varargs call constructions.
  41  */
  42 enum    /*< skip >*/
  43 {
  44   G_VALUE_COLLECT_INT           = 'i',
  45   G_VALUE_COLLECT_LONG          = 'l',
  46   G_VALUE_COLLECT_INT64         = 'q',
  47   G_VALUE_COLLECT_DOUBLE        = 'd',
  48   G_VALUE_COLLECT_POINTER       = 'p'
  49 };
  50
  51
  52 /* vararg union holding actual values collected
  53  */
  54 /**
  55  * GTypeCValue:
  56  * @v_int: the field for holding integer values
  57  * @v_long: the field for holding long integer values
  58  * @v_int64: the field for holding 64 bit integer values
  59  * @v_double: the field for holding floating point values
  60  * @v_pointer: the field for holding pointers
  61  *
  62  * A union holding one collected value.
  63  */
  64 union _GTypeCValue
  65 {
  66   gint     v_int;
  67   glong    v_long;
  68   gint64   v_int64;
  69   gdouble  v_double;
  70   gpointer v_pointer;
  71 };
  72
  73 /**
  74  * G_VALUE_COLLECT_INIT:
  75  * @value: a #GValue return location. @value must contain only 0 bytes.
  76  * @_value_type: the #GType to use for @value.
  77  * @var_args: the va_list variable; it may be evaluated multiple times
  78  * @flags: flags which are passed on to the collect_value() function of
  79  *  the #GTypeValueTable of @value.
  80  * @__error: a #gchar** variable that will be modified to hold a g_new()
  81  *  allocated error messages if something fails
  82  *
  83  * Collects a variable argument value from a `va_list`.
  84  *
  85  * We have to implement the varargs collection as a macro, because on some
  86  * systems `va_list` variables cannot be passed by reference.
  87  *
  88  * Since: 2.24
  89  */
  90 #define G_VALUE_COLLECT_INIT(value, _value_type, var_args, flags, __error)              \
  91 G_STMT_START {                                                                          \
  92   GValue *g_vci_val = (value);                                                          \
  93   guint g_vci_flags = (flags);                                                          \
  94   GTypeValueTable *g_vci_vtab = g_type_value_table_peek (_value_type);                  \
  95   const gchar *g_vci_collect_format = g_vci_vtab->collect_format;                                       \
  96   GTypeCValue g_vci_cvalues[G_VALUE_COLLECT_FORMAT_MAX_LENGTH] = { { 0, }, };           \
  97   guint g_vci_n_values = 0;                                                                     \
  98                                                                                         \
  99   g_vci_val->g_type = _value_type;              /* value_meminit() from gvalue.c */             \
 100   while (*g_vci_collect_format)                                                         \
 101     {                                                                                   \
 102       GTypeCValue *g_vci_cvalue = g_vci_cvalues + g_vci_n_values++;                                     \
 103                                                                                         \
 104       switch (*g_vci_collect_format++)                                                  \
 105         {                                                                               \
 106         case G_VALUE_COLLECT_INT:                                                       \
 107           g_vci_cvalue->v_int = va_arg ((var_args), gint);                                      \
 108           break;                                                                        \
 109         case G_VALUE_COLLECT_LONG:                                                      \
 110           g_vci_cvalue->v_long = va_arg ((var_args), glong);                                    \
 111           break;                                                                        \
 112         case G_VALUE_COLLECT_INT64:                                                     \
 113           g_vci_cvalue->v_int64 = va_arg ((var_args), gint64);                          \
 114           break;                                                                        \
 115         case G_VALUE_COLLECT_DOUBLE:                                                    \
 116           g_vci_cvalue->v_double = va_arg ((var_args), gdouble);                                \
 117           break;                                                                        \
 118         case G_VALUE_COLLECT_POINTER:                                                   \
 119           g_vci_cvalue->v_pointer = va_arg ((var_args), gpointer);                              \
 120           break;                                                                        \
 121         default:                                                                        \
 122           g_assert_not_reached ();                                                      \
 123         }                                                                               \
 124     }                                                                                   \
 125   *(__error) = g_vci_vtab->collect_value (g_vci_val,                                            \
 126                                        g_vci_n_values,                                  \
 127                                        g_vci_cvalues,                                   \
 128                                        g_vci_flags);                                            \
 129 } G_STMT_END
 130
 131 /**
 132  * G_VALUE_COLLECT:
 133  * @value: a #GValue return location. @value is supposed to be initialized
 134  *  according to the value type to be collected
 135  * @var_args: the va_list variable; it may be evaluated multiple times
 136  * @flags: flags which are passed on to the collect_value() function of
 137  *  the #GTypeValueTable of @value.
 138  * @__error: a #gchar** variable that will be modified to hold a g_new()
 139  *  allocated error messages if something fails
 140  *
 141  * Collects a variable argument value from a `va_list`.
 142  *
 143  * We have to 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 uninitialized
 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 *g_vc_value = (value);                                                         \
 152   GType g_vc_value_type = G_VALUE_TYPE (g_vc_value);                                            \
 153   GTypeValueTable *g_vc_vtable = g_type_value_table_peek (g_vc_value_type);                     \
 154                                                                                         \
 155   if (g_vc_vtable->value_free)                                                          \
 156     g_vc_vtable->value_free (g_vc_value);                                                       \
 157   memset (g_vc_value->data, 0, sizeof (g_vc_value->data));                                      \
 158                                                                                         \
 159   G_VALUE_COLLECT_INIT(value, g_vc_value_type, var_args, flags, __error);                       \
 160 } G_STMT_END
 161
 162 /**
 163  * G_VALUE_COLLECT_SKIP:
 164  * @_value_type: the #GType of the value to skip
 165  * @var_args: the va_list variable; it may be evaluated multiple times
 166  *
 167  * Skip an argument of type @_value_type from @var_args.
 168  */
 169 #define G_VALUE_COLLECT_SKIP(_value_type, var_args)                                     \
 170 G_STMT_START {                                                                          \
 171   GTypeValueTable *g_vcs_vtable = g_type_value_table_peek (_value_type);                        \
 172   const gchar *g_vcs_collect_format = g_vcs_vtable->collect_format;                             \
 173                                                                                         \
 174   while (*g_vcs_collect_format)                                                         \
 175     {                                                                                   \
 176       switch (*g_vcs_collect_format++)                                                  \
 177         {                                                                               \
 178         case G_VALUE_COLLECT_INT:                                                       \
 179           va_arg ((var_args), gint);                                                    \
 180           break;                                                                        \
 181         case G_VALUE_COLLECT_LONG:                                                      \
 182           va_arg ((var_args), glong);                                                   \
 183           break;                                                                        \
 184         case G_VALUE_COLLECT_INT64:                                                     \
 185           va_arg ((var_args), gint64);                                                  \
 186           break;                                                                        \
 187         case G_VALUE_COLLECT_DOUBLE:                                                    \
 188           va_arg ((var_args), gdouble);                                                 \
 189           break;                                                                        \
 190         case G_VALUE_COLLECT_POINTER:                                                   \
 191           va_arg ((var_args), gpointer);                                                \
 192           break;                                                                        \
 193         default:                                                                        \
 194           g_assert_not_reached ();                                                      \
 195         }                                                                               \
 196     }                                                                                   \
 197 } G_STMT_END
 198
 199 /**
 200  * G_VALUE_LCOPY:
 201  * @value: a #GValue to store into the @var_args; this must be initialized
 202  *  and set
 203  * @var_args: the va_list variable; it may be evaluated multiple times
 204  * @flags: flags which are passed on to the lcopy_value() function of
 205  *  the #GTypeValueTable of @value.
 206  * @__error: a #gchar** variable that will be modified to hold a g_new()
 207  *  allocated error message if something fails
 208  *
 209  * Stores a value’s value into one or more argument locations from a `va_list`.
 210  *
 211  * This is the inverse of G_VALUE_COLLECT().
 212  */
 213 #define G_VALUE_LCOPY(value, var_args, flags, __error)                                  \
 214 G_STMT_START {                                                                          \
 215   const GValue *g_vl_value = (value);                                                   \
 216   guint g_vl_flags = (flags);                                                           \
 217   GType g_vl_value_type = G_VALUE_TYPE (g_vl_value);                                            \
 218   GTypeValueTable *g_vl_vtable = g_type_value_table_peek (g_vl_value_type);                     \
 219   const gchar *g_vl_lcopy_format = g_vl_vtable->lcopy_format;                                   \
 220   GTypeCValue g_vl_cvalues[G_VALUE_COLLECT_FORMAT_MAX_LENGTH] = { { 0, }, };            \
 221   guint g_vl_n_values = 0;                                                                      \
 222                                                                                         \
 223   while (*g_vl_lcopy_format)                                                            \
 224     {                                                                                   \
 225       GTypeCValue *g_vl_cvalue = g_vl_cvalues + g_vl_n_values++;                                        \
 226                                                                                         \
 227       switch (*g_vl_lcopy_format++)                                                             \
 228         {                                                                               \
 229         case G_VALUE_COLLECT_INT:                                                       \
 230           g_vl_cvalue->v_int = va_arg ((var_args), gint);                                       \
 231           break;                                                                        \
 232         case G_VALUE_COLLECT_LONG:                                                      \
 233           g_vl_cvalue->v_long = va_arg ((var_args), glong);                                     \
 234           break;                                                                        \
 235         case G_VALUE_COLLECT_INT64:                                                     \
 236           g_vl_cvalue->v_int64 = va_arg ((var_args), gint64);                           \
 237           break;                                                                        \
 238         case G_VALUE_COLLECT_DOUBLE:                                                    \
 239           g_vl_cvalue->v_double = va_arg ((var_args), gdouble);                         \
 240           break;                                                                        \
 241         case G_VALUE_COLLECT_POINTER:                                                   \
 242           g_vl_cvalue->v_pointer = va_arg ((var_args), gpointer);                               \
 243           break;                                                                        \
 244         default:                                                                        \
 245           g_assert_not_reached ();                                                      \
 246         }                                                                               \
 247     }                                                                                   \
 248   *(__error) = g_vl_vtable->lcopy_value (g_vl_value,                                            \
 249                                      g_vl_n_values,                                             \
 250                                      g_vl_cvalues,                                              \
 251                                      g_vl_flags);                                               \
 252 } G_STMT_END
 253
 254
 255 /**
 256  * G_VALUE_COLLECT_FORMAT_MAX_LENGTH:
 257  *
 258  * The maximal number of #GTypeCValues which can be collected for a
 259  * single #GValue.
 260  */
 261 #define G_VALUE_COLLECT_FORMAT_MAX_LENGTH       (8)
 262
 263 G_END_DECLS
 264
 265 #endif /* __G_VALUE_COLLECTOR_H__ */