sysdeps/mach/hurd/sendfile64.c

   1 /* sendfile -- copy data directly from one file descriptor to another
   2    Copyright (C) 2002-2024 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <sys/sendfile.h>
  20 #include <hurd.h>
  21 #include <hurd/fd.h>
  22 #include <sys/mman.h>
  23
  24 /* Send COUNT bytes from file associated with IN_FD starting at OFFSET to
  25    descriptor OUT_FD.  */
  26 ssize_t
  27 __sendfile64 (int out_fd, int in_fd, off64_t *offset, size_t count)
  28 {
  29   /* We just do a vanilla io_read followed by a vanilla io_write here.
  30      In theory the IN_FD filesystem can return us out-of-line data that
  31      we then send out-of-line to the OUT_FD filesystem and no copying
  32      takes place until those pages need to be flushed or packaged by
  33      that filesystem (e.g. packetized by a network socket).  However,
  34      we momentarily consume COUNT bytes of our local address space,
  35      which might blow if it's huge or address space is real tight.  */
  36
  37   char *data = 0;
  38   mach_msg_type_number_t datalen = 0;
  39   error_t err = HURD_DPORT_USE (in_fd,
  40                                 __io_read (port, &data, &datalen,
  41                                            offset ? *offset : (off_t) -1,
  42                                            count));
  43   if (err == 0)
  44     {
  45       vm_size_t nwrote;
  46       if (datalen == 0)
  47         return 0;
  48       err = HURD_DPORT_USE (out_fd, __io_write (port, data, datalen,
  49                                                 (off_t) -1, &nwrote));
  50       __munmap (data, datalen);
  51       if (err == 0)
  52         {
  53           if (offset)
  54             *offset += datalen;
  55           return nwrote;
  56         }
  57     }
  58   return __hurd_fail (err);
  59 }
  60 strong_alias (__sendfile64, sendfile64)