1  /* sendfile -- copy data directly from one file descriptor to another
       2     Copyright (C) 2002-2023 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)