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emacs/lib/careadlinkat.h

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/* Read symbolic links into a buffer without size limitation, relative to fd.
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Copyright (C) 2011-2024 Free Software Foundation, Inc.
This file is free software: you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as
published by the Free Software Foundation; either version 2.1 of the
License, or (at your option) any later version.
This file is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>. */
/* Written by Paul Eggert, Bruno Haible, and Jim Meyering. */
#ifndef _GL_CAREADLINKAT_H
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#define _GL_CAREADLINKAT_H
/* This file uses HAVE_READLINKAT. */
#if !_GL_CONFIG_H_INCLUDED
#error "Please include config.h first."
#endif
#include <fcntl.h>
#include <unistd.h>
#ifdef __cplusplus
extern "C" {
#endif
struct allocator;
/* Assuming the current directory is FD, get the symbolic link value
of FILENAME as a null-terminated string and put it into a buffer.
If FD is AT_FDCWD, FILENAME is interpreted relative to the current
working directory, as in openat.
If the link is small enough to fit into BUFFER put it there.
BUFFER's size is BUFFER_SIZE, and BUFFER can be null
if BUFFER_SIZE is zero.
If the link is not small, put it into a dynamically allocated
buffer managed by ALLOC. It is the caller's responsibility to free
the returned value if it is nonnull and is not BUFFER.
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The PREADLINKAT function specifies how to read links. It operates
like POSIX readlinkat()
<https://pubs.opengroup.org/onlinepubs/9699919799/functions/readlink.html>
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but can assume that its first argument is the same as FD.
If successful, return the buffer address; otherwise return NULL and
set errno. */
char *careadlinkat (int fd, char const *filename,
char *restrict buffer, size_t buffer_size,
struct allocator const *alloc,
ssize_t (*preadlinkat) (int, char const *,
char *, size_t));
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/* Suitable value for careadlinkat's FD argument. */
#if HAVE_READLINKAT
/* AT_FDCWD is declared in <fcntl.h>. */
#else
/* Define AT_FDCWD independently, so that the careadlinkat module does
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not depend on the fcntl-h module. We might as well use the same value
as fcntl-h. */
# ifndef AT_FDCWD
# define AT_FDCWD (-3041965)
# endif
#endif
#ifdef __cplusplus
}
#endif
#endif /* _GL_CAREADLINKAT_H */