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113 lines
4.4 KiB
C
113 lines
4.4 KiB
C
/* GLIB - Library of useful routines for C programming
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* Copyright (C) 1995-1997 Peter Mattis, Spencer Kimball and Josh MacDonald
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the
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* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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* Boston, MA 02111-1307, USA.
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*/
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/*
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* Modified by the GLib Team and others 1997-2000. See the AUTHORS
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* file for a list of people on the GLib Team. See the ChangeLog
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* files for a list of changes. These files are distributed with
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* GLib at ftp://ftp.gtk.org/pub/gtk/.
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*/
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#if !defined (__GLIB_H_INSIDE__) && !defined (GLIB_COMPILATION)
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#error "Only <glib.h> can be included directly."
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#endif
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#ifndef __G_ALLOCA_H__
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#define __G_ALLOCA_H__
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#include <glib/gtypes.h>
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#if defined(__BIONIC__) && defined (GLIB_HAVE_ALLOCA_H)
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# include <alloca.h>
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#elif defined(__GNUC__)
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/* GCC does the right thing */
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# undef alloca
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# define alloca(size) __builtin_alloca (size)
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#elif defined (GLIB_HAVE_ALLOCA_H)
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/* a native and working alloca.h is there */
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# include <alloca.h>
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#else /* !__GNUC__ && !GLIB_HAVE_ALLOCA_H */
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# if defined(_MSC_VER) || defined(__DMC__)
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# include <malloc.h>
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# define alloca _alloca
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# else /* !_MSC_VER && !__DMC__ */
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# ifdef _AIX
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# pragma alloca
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# else /* !_AIX */
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# ifndef alloca /* predefined by HP cc +Olibcalls */
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G_BEGIN_DECLS
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char *alloca ();
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G_END_DECLS
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# endif /* !alloca */
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# endif /* !_AIX */
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# endif /* !_MSC_VER && !__DMC__ */
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#endif /* !__GNUC__ && !GLIB_HAVE_ALLOCA_H */
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/**
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* g_alloca:
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* @size: number of bytes to allocate.
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*
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* Allocates @size bytes on the stack; these bytes will be freed when the current
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* stack frame is cleaned up. This macro essentially just wraps the alloca()
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* function present on most UNIX variants.
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* Thus it provides the same advantages and pitfalls as alloca():
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* <variablelist>
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* <varlistentry><term></term><listitem><para>
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* + alloca() is very fast, as on most systems it's implemented by just adjusting
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* the stack pointer register.
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* </para></listitem></varlistentry>
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* <varlistentry><term></term><listitem><para>
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* + It doesn't cause any memory fragmentation, within its scope, separate alloca()
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* blocks just build up and are released together at function end.
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* </para></listitem></varlistentry>
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* <varlistentry><term></term><listitem><para>
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* - Allocation sizes have to fit into the current stack frame. For instance in a
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* threaded environment on Linux, the per-thread stack size is limited to 2 Megabytes,
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* so be sparse with alloca() uses.
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* </para></listitem></varlistentry>
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* <varlistentry><term></term><listitem><para>
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* - Allocation failure due to insufficient stack space is not indicated with a %NULL
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* return like e.g. with malloc(). Instead, most systems probably handle it the same
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* way as out of stack space situations from infinite function recursion, i.e.
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* with a segmentation fault.
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* </para></listitem></varlistentry>
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* <varlistentry><term></term><listitem><para>
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* - Special care has to be taken when mixing alloca() with GNU C variable sized arrays.
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* Stack space allocated with alloca() in the same scope as a variable sized array
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* will be freed together with the variable sized array upon exit of that scope, and
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* not upon exit of the enclosing function scope.
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* </para></listitem></varlistentry>
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* </variablelist>
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*
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* Returns: space for @size bytes, allocated on the stack
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*/
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#define g_alloca(size) alloca (size)
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/**
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* g_newa:
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* @struct_type: Type of memory chunks to be allocated
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* @n_structs: Number of chunks to be allocated
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*
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* Wraps g_alloca() in a more typesafe manner.
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*
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* Returns: Pointer to stack space for @n_structs chunks of type @struct_type
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*/
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#define g_newa(struct_type, n_structs) ((struct_type*) g_alloca (sizeof (struct_type) * (gsize) (n_structs)))
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#endif /* __G_ALLOCA_H__ */
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