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glibc  2.9
sendfile64.c
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00001 /* sendfile -- copy data directly from one file descriptor to another
00002    Copyright (C) 2002 Free Software Foundation, Inc.
00003    This file is part of the GNU C Library.
00004 
00005    The GNU C Library is free software; you can redistribute it and/or
00006    modify it under the terms of the GNU Lesser General Public
00007    License as published by the Free Software Foundation; either
00008    version 2.1 of the License, or (at your option) any later version.
00009 
00010    The GNU C Library is distributed in the hope that it will be useful,
00011    but WITHOUT ANY WARRANTY; without even the implied warranty of
00012    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00013    Lesser General Public License for more details.
00014 
00015    You should have received a copy of the GNU Lesser General Public
00016    License along with the GNU C Library; if not, write to the Free
00017    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
00018    02111-1307 USA.  */
00019 
00020 #include <sys/sendfile.h>
00021 #include <hurd.h>
00022 #include <hurd/fd.h>
00023 #include <sys/mman.h>
00024 
00025 /* Send COUNT bytes from file associated with IN_FD starting at OFFSET to
00026    descriptor OUT_FD.  */
00027 ssize_t
00028 sendfile64 (int out_fd, int in_fd, off64_t *offset, size_t count)
00029 {
00030   /* We just do a vanilla io_read followed by a vanilla io_write here.
00031      In theory the IN_FD filesystem can return us out-of-line data that
00032      we then send out-of-line to the OUT_FD filesystem and no copying
00033      takes place until those pages need to be flushed or packaged by
00034      that filesystem (e.g. packetized by a network socket).  However,
00035      we momentarily consume COUNT bytes of our local address space,
00036      which might blow if it's huge or address space is real tight.  */
00037 
00038   char *data = 0;
00039   size_t datalen = 0;
00040   error_t err = HURD_DPORT_USE (in_fd,
00041                             __io_read (port, &data, &datalen,
00042                                       offset ? *offset : (off_t) -1,
00043                                       count));
00044   if (err == 0)
00045     {
00046       size_t nwrote;
00047       if (datalen == 0)
00048        return 0;
00049       err = HURD_DPORT_USE (out_fd, __io_write (port, data, datalen,
00050                                           (off_t) -1, &nwrote));
00051       munmap (data, datalen);
00052       if (err == 0)
00053        {
00054          if (offset)
00055            *offset += datalen;
00056          return nwrote;
00057        }
00058     }
00059   return __hurd_fail (err);
00060 }