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/* Make a file's ancestor directories.
Copyright (C) 2006, 2009-2020 Free Software Foundation, Inc.
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program 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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>. */
/* Written by Paul Eggert. */
#include <config.h>
#include "mkancesdirs.h"
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <errno.h>
#include <unistd.h>
#include "dirname.h"
#include "savewd.h"
/* Ensure that the ancestor directories of FILE exist, using an
algorithm that should work even if two processes execute this
function in parallel. Modify FILE as necessary to access the
ancestor directories, but restore FILE to an equivalent value
if successful.
WD points to the working directory, using the conventions of
savewd.
Create any ancestor directories that don't already exist, by
invoking MAKE_DIR (FILE, COMPONENT, MAKE_DIR_ARG). This function
should return 0 if successful, -1 (setting errno) otherwise. If
COMPONENT is relative, it is relative to the temporary working
directory, which may differ from *WD.
Ordinarily MAKE_DIR is executed with the working directory changed
to reflect the already-made prefix, and mkancesdirs returns with
the working directory changed a prefix of FILE. However, if the
initial working directory cannot be saved in a file descriptor,
MAKE_DIR is invoked in a subprocess and this function returns in
both the parent and child process, so the caller should not assume
any changed state survives other than the EXITMAX component of WD,
and the caller should take care that the parent does not attempt to
do the work that the child is doing.
If successful and if this process can go ahead and create FILE,
return the length of the prefix of FILE that has already been made.
If successful so far but a child process is doing the actual work,
return -2. If unsuccessful, return -1 and set errno. */
ptrdiff_t
mkancesdirs (char *file, struct savewd *wd,
int (*make_dir) (char const *, char const *, void *),
void *make_dir_arg)
{
/* Address of the previous directory separator that follows an
ordinary byte in a file name in the left-to-right scan, or NULL
if no such separator precedes the current location P. */
char *sep = NULL;
/* Address of the leftmost file name component that has not yet
been processed. */
char *component = file;
char *p = file + FILE_SYSTEM_PREFIX_LEN (file);
char c;
bool made_dir = false;
/* Scan forward through FILE, creating and chdiring into directories
along the way. Try MAKE_DIR before chdir, so that the procedure
works even when two or more processes are executing it in
parallel. Isolate each file name component by having COMPONENT
point to its start and SEP point just after its end. */
while ((c = *p++))
if (ISSLASH (*p))
{
if (! ISSLASH (c))
sep = p;
}
else if (ISSLASH (c) && *p && sep)
{
/* Don't bother to make or test for "." since it does not
affect the algorithm. */
if (! (sep - component == 1 && component[0] == '.'))
{
int make_dir_errno = 0;
int savewd_chdir_options = 0;
int chdir_result;
/* Temporarily modify FILE to isolate this file name
component. */
*sep = '\0';
/* Invoke MAKE_DIR on this component, except don't bother
with ".." since it must exist if its "parent" does. */
if (sep - component == 2
&& component[0] == '.' && component[1] == '.')
made_dir = false;
else if (make_dir (file, component, make_dir_arg) < 0)
make_dir_errno = errno;
else
made_dir = true;
if (made_dir)
savewd_chdir_options |= SAVEWD_CHDIR_NOFOLLOW;
chdir_result =
savewd_chdir (wd, component, savewd_chdir_options, NULL);
/* Undo the temporary modification to FILE, unless there
was a failure. */
if (chdir_result != -1)
*sep = '/';
if (chdir_result != 0)
{
if (make_dir_errno != 0 && errno == ENOENT)
errno = make_dir_errno;
return chdir_result;
}
}
component = p;
}
return component - file;
}
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