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glibc  2.9
pread64.c
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00001 /* Copyright (C) 1997, 1998, 2000, 2002, 2003, 2004, 2006
00002    Free Software Foundation, Inc.
00003    This file is part of the GNU C Library.
00004    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
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 <errno.h>
00022 #include <unistd.h>
00023 #include <endian.h>
00024 
00025 #include <sysdep-cancel.h>
00026 #include <sys/syscall.h>
00027 #include <bp-checks.h>
00028 
00029 #include <kernel-features.h>
00030 
00031 #ifdef __NR_pread64             /* Newer kernels renamed but it's the same.  */
00032 # ifdef __NR_pread
00033 #  error "__NR_pread and __NR_pread64 both defined???"
00034 # endif
00035 # define __NR_pread __NR_pread64
00036 #endif
00037 
00038 #if defined __NR_pread || __ASSUME_PREAD_SYSCALL > 0
00039 
00040 # if __ASSUME_PREAD_SYSCALL == 0
00041 static ssize_t __emulate_pread64 (int fd, void *buf, size_t count,
00042                               off64_t offset) internal_function;
00043 # endif
00044 
00045 ssize_t
00046 __libc_pread64 (fd, buf, count, offset)
00047      int fd;
00048      void *buf;
00049      size_t count;
00050      off64_t offset;
00051 {
00052   ssize_t result;
00053 
00054   if (SINGLE_THREAD_P)
00055     {
00056      /* First try the syscall.  */
00057      result = INLINE_SYSCALL (pread, 6, fd, CHECK_N (buf, count), count, 0,
00058                            __LONG_LONG_PAIR ((off_t) (offset >> 32),
00059                            (off_t) (offset & 0xffffffff)));
00060 # if __ASSUME_PREAD_SYSCALL == 0
00061      if (result == -1 && errno == ENOSYS)
00062      /* No system call available.  Use the emulation.  */
00063      result = __emulate_pread64 (fd, buf, count, offset);
00064 # endif
00065      return result;
00066     }
00067 
00068   int oldtype = LIBC_CANCEL_ASYNC ();
00069 
00070   /* First try the syscall.  */
00071   result = INLINE_SYSCALL (pread, 6, fd, CHECK_N (buf, count), count, 0,
00072                         __LONG_LONG_PAIR ((off_t) (offset >> 32),
00073                                         (off_t) (offset & 0xffffffff)));
00074 # if __ASSUME_PREAD_SYSCALL == 0
00075   if (result == -1 && errno == ENOSYS)
00076     /* No system call available.  Use the emulation.  */
00077     result = __emulate_pread64 (fd, buf, count, offset);
00078 # endif
00079 
00080   LIBC_CANCEL_RESET (oldtype);
00081 
00082   return result;
00083 }
00084 
00085 weak_alias (__libc_pread64, __pread64)
00086 weak_alias (__libc_pread64, pread64)
00087 
00088 # define __libc_pread64(fd, buf, count, offset) \
00089      static internal_function __emulate_pread64 (fd, buf, count, offset)
00090 #endif
00091 
00092 #if __ASSUME_PREAD_SYSCALL == 0
00093 # include <sysdeps/posix/pread64.c>
00094 #endif