lib/careadlinkat.h

   1 /* Read symbolic links into a buffer without size limitation, relative to fd.
   2
   3    Copyright (C) 2011 Free Software Foundation, Inc.
   4
   5    This program is free software: you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    the Free Software Foundation; either version 3 of the License, or
   8    (at your option) any later version.
   9
  10    This program 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
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  17
  18 /* Written by Paul Eggert, Bruno Haible, and Jim Meyering.  */
  19
  20 #ifndef _GL_CAREADLINKAT_H
  21
  22 #include <fcntl.h>
  23 #include <unistd.h>
  24
  25 struct allocator;
  26
  27 /* Assuming the current directory is FD, get the symbolic link value
  28    of FILENAME as a null-terminated string and put it into a buffer.
  29    If FD is AT_FDCWD, FILENAME is interpreted relative to the current
  30    working directory, as in openat.
  31
  32    If the link is small enough to fit into BUFFER put it there.
  33    BUFFER's size is BUFFER_SIZE, and BUFFER can be null
  34    if BUFFER_SIZE is zero.
  35
  36    If the link is not small, put it into a dynamically allocated
  37    buffer managed by ALLOC.  It is the caller's responsibility to free
  38    the returned value if it is nonnull and is not BUFFER.
  39
  40    The PREADLINKAT function specifies how to read links.
  41
  42    If successful, return the buffer address; otherwise return NULL and
  43    set errno.  */
  44
  45 char *careadlinkat (int fd, char const *filename,
  46                     char *buffer, size_t buffer_size,
  47                     struct allocator const *alloc,
  48                     ssize_t (*preadlinkat) (int, char const *,
  49                                             char *, size_t));
  50
  51 /* Suitable values for careadlinkat's FD and PREADLINKAT arguments,
  52    when doing a plain readlink.  */
  53 #if HAVE_READLINKAT
  54 # define careadlinkatcwd readlinkat
  55 #else
  56 /* Define AT_FDCWD independently, so that the careadlinkat module does
  57    not depend on the fcntl-h module.  The value does not matter, since
  58    careadlinkatcwd ignores it, but we might as well use the same value
  59    as fcntl-h.  */
  60 # ifndef AT_FDCWD
  61 #  define AT_FDCWD (-3041965)
  62 # endif
  63 ssize_t careadlinkatcwd (int fd, char const *filename,
  64                          char *buffer, size_t buffer_size);
  65 #endif
  66
  67 #endif /* _GL_CAREADLINKAT_H */