[thirdparty/glibc.git] / sysdeps / posix / shm-directory.h

/* Header for directory for shm/sem files.
   Copyright (C) 2014-2021 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library 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.

   The GNU C Library 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 the GNU C Library; if not, see
   <https://www.gnu.org/licenses/>.  */

#ifndef _SHM_DIRECTORY_H

#include <errno.h>
#include <limits.h>
#include <stdbool.h>
#include <stdlib.h>
#include <string.h>

extern const char *__shm_directory (size_t *len);

/* This defines local variables SHM_DIR and SHM_DIRLEN, giving the
   directory prefix (with trailing slash) and length (not including '\0'
   terminator) of the directory used for shm files.  If that cannot be
   determined, it sets errno to ENOSYS and returns RETVAL_FOR_INVALID.

   This uses the local variable NAME as an lvalue, and increments it past
   any leading slashes.  It then defines the local variable NAMELEN, giving
   strlen (NAME) + 1.  If NAME is invalid, it sets errno to
   ERRNO_FOR_INVALID and returns RETVAL_FOR_INVALID.  Finally, it defines
   the local variable SHM_NAME, giving the absolute file name of the shm
   file corresponding to NAME.  PREFIX is a string constant used as a
   prefix on NAME.  */

#define SHM_GET_NAME(errno_for_invalid, retval_for_invalid, prefix)           \
  size_t shm_dirlen;							      \
  const char *shm_dir = __shm_directory (&shm_dirlen);			      \
  /* If we don't know what directory to use, there is nothing we can do.  */  \
  if (__glibc_unlikely (shm_dir == NULL))				      \
    {									      \
      __set_errno (ENOSYS);						      \
      return retval_for_invalid;					      \
    }									      \
  /* Construct the filename.  */					      \
  while (name[0] == '/')						      \
    ++name;								      \
  size_t namelen = strlen (name) + 1;					      \
  /* Validate the filename.  */						      \
  if (namelen == 1 || namelen >= NAME_MAX || strchr (name, '/') != NULL)      \
    {									      \
      __set_errno (errno_for_invalid);					      \
      return retval_for_invalid;					      \
    }									      \
  char *shm_name = __alloca (shm_dirlen + sizeof prefix - 1 + namelen);	      \
  __mempcpy (__mempcpy (__mempcpy (shm_name, shm_dir, shm_dirlen),	      \
                        prefix, sizeof prefix - 1),			      \
             name, namelen)

#endif	/* shm-directory.h */
Commit	Line	Data
78e21c5d	1	/* Header for directory for shm/sem files.
2b778ceb	2	Copyright (C) 2014-2021 Free Software Foundation, Inc.
78e21c5d RM	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
5a82c748	17	<https://www.gnu.org/licenses/>. */
78e21c5d RM	18
	19	#ifndef _SHM_DIRECTORY_H
	20
	21	#include <errno.h>
	22	#include <limits.h>
	23	#include <stdbool.h>
	24	#include <stdlib.h>
	25	#include <string.h>
	26
	27	extern const char __shm_directory (size_t len);
	28
	29	/* This defines local variables SHM_DIR and SHM_DIRLEN, giving the
	30	directory prefix (with trailing slash) and length (not including '\0'
	31	terminator) of the directory used for shm files. If that cannot be
	32	determined, it sets errno to ENOSYS and returns RETVAL_FOR_INVALID.
	33
	34	This uses the local variable NAME as an lvalue, and increments it past
	35	any leading slashes. It then defines the local variable NAMELEN, giving
	36	strlen (NAME) + 1. If NAME is invalid, it sets errno to
	37	ERRNO_FOR_INVALID and returns RETVAL_FOR_INVALID. Finally, it defines
	38	the local variable SHM_NAME, giving the absolute file name of the shm
e4f639e4 RM	39	file corresponding to NAME. PREFIX is a string constant used as a
e4f639e4 RM	40	prefix on NAME. */
78e21c5d	41
e4f639e4	42	#define SHM_GET_NAME(errno_for_invalid, retval_for_invalid, prefix) \
78e21c5d RM	43	size_t shm_dirlen; \
	44	const char *shm_dir = __shm_directory (&shm_dirlen); \
	45	/* If we don't know what directory to use, there is nothing we can do. */ \
	46	if (__glibc_unlikely (shm_dir == NULL)) \
	47	{ \
	48	__set_errno (ENOSYS); \
	49	return retval_for_invalid; \
	50	} \
	51	/* Construct the filename. */ \
	52	while (name[0] == '/') \
	53	++name; \
	54	size_t namelen = strlen (name) + 1; \
	55	/* Validate the filename. */ \
	56	if (namelen == 1 \|\| namelen >= NAME_MAX \|\| strchr (name, '/') != NULL) \
	57	{ \
	58	__set_errno (errno_for_invalid); \
	59	return retval_for_invalid; \
	60	} \
e4f639e4 RM	61	char *shm_name = __alloca (shm_dirlen + sizeof prefix - 1 + namelen); \
	62	__mempcpy (__mempcpy (__mempcpy (shm_name, shm_dir, shm_dirlen), \
	63	prefix, sizeof prefix - 1), \
	64	name, namelen)
78e21c5d RM	65
78e21c5d RM	66	#endif /* shm-directory.h */