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glibc  2.9
swapcontext.c
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00001 /* Swap to new context.
00002    Copyright (C) 2008 Free Software Foundation, Inc.
00003    This file is part of the GNU C Library.
00004    Contributed by Helge Deller <deller@gmx.de>, 2008.
00005 
00006    The GNU C Library is free software; you can redistribute it and/or
00007    modify it under the terms of the GNU Lesser General Public
00008    License as published by the Free Software Foundation; either
00009    version 2.1 of the License, or (at your option) any later version.
00010 
00011    The GNU C Library is distributed in the hope that it will be useful,
00012    but WITHOUT ANY WARRANTY; without even the implied warranty of
00013    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00014    Lesser General Public License for more details.
00015 
00016    You should have received a copy of the GNU Lesser General Public
00017    License along with the GNU C Library; if not, write to the Free
00018    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
00019    02111-1307 USA.  */
00020 
00021 #include <ucontext.h>
00022 
00023 extern int __getcontext (ucontext_t *ucp);
00024 extern int __setcontext (const ucontext_t *ucp);
00025 
00026 int
00027 __swapcontext (ucontext_t *oucp, const ucontext_t *ucp)
00028 {
00029   /* Save the current machine context to oucp.  */
00030   __getcontext (oucp);
00031 
00032   /* mark sc_sar flag to skip the setcontext call on reactivation.  */
00033   if (oucp->uc_mcontext.sc_sar == 0) {
00034        oucp->uc_mcontext.sc_sar++;
00035 
00036        /* Restore the machine context in ucp.  */
00037        __setcontext (ucp);
00038   }
00039 
00040   return 0;
00041 }
00042 
00043 weak_alias (__swapcontext, swapcontext)