misc/fd_to_filename.c

   1 /* Construct a pathname under /proc/self/fd (or /dev/fd for Hurd).
   2    Copyright (C) 2020-2021 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 <fd_to_filename.h>
  20
  21 #include <assert.h>
  22 #include <string.h>
  23
  24 char *
  25 __fd_to_filename (int descriptor, struct fd_to_filename *storage)
  26 {
  27   assert (descriptor >= 0);
  28
  29   char *p = mempcpy (storage->buffer, FD_TO_FILENAME_PREFIX,
  30                      strlen (FD_TO_FILENAME_PREFIX));
  31
  32   for (int d = descriptor; p++, (d /= 10) != 0; )
  33     continue;
  34   *p = '\0';
  35   for (int d = descriptor; *--p = '0' + d % 10, (d /= 10) != 0; )
  36     continue;
  37   return storage->buffer;
  38 }