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/* sharefile.c -- open files just once.
Copyright (C) 2008-2022 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/>.
*/
/* config.h always comes first. */
#include <config.h>
/* system headers. */
#include <assert.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/types.h>
/* gnulib headers. */
#include "cloexec.h"
#include "hash.h"
#include "stdio--.h"
/* find headers. */
#include "sharefile.h"
#include "defs.h"
enum
{
DefaultHashTableSize = 11
};
struct sharefile
{
char *mode;
Hash_table *table;
};
/*
* We cannot use the name to determine that two strings represent the
* same file, since that test would be fooled by symbolic links.
* Instead we use the device and inode number.
*
* However, we remember the name of each file that we opened. This
* allows us to issue a fatal error message when (flushing and)
* closing a file fails.
*/
struct SharefileEntry
{
dev_t device;
ino_t inode;
char *name; /* not the only name for this file; error messages only */
FILE *fp;
};
static bool
entry_comparator (const void *av, const void *bv)
{
const struct SharefileEntry *a=av, *b=bv;
return (a->inode == b->inode) && (a->device == b->device);
}
static void
entry_free (void *pv)
{
struct SharefileEntry *p = pv;
if (p->fp)
{
if (0 != fclose (p->fp))
fatal_nontarget_file_error (errno, p->name);
}
free (p->name);
free (p);
}
static size_t
entry_hashfunc (const void *pv, size_t buckets)
{
const struct SharefileEntry *p = pv;
return (p->device ^ p->inode) % buckets;
}
sharefile_handle
sharefile_init (const char *mode)
{
struct Hash_tuning;
struct sharefile *p = malloc (sizeof (struct sharefile));
if (p)
{
p->mode = strdup (mode);
if (p->mode)
{
p->table = hash_initialize (DefaultHashTableSize, NULL,
entry_hashfunc,
entry_comparator,
entry_free);
if (p->table)
{
return p;
}
else
{
free (p->mode);
free (p);
}
}
else
{
free (p);
}
}
return NULL;
}
void
sharefile_destroy (sharefile_handle pv)
{
struct sharefile *p = pv;
free (p->mode);
hash_free (p->table);
}
FILE *
sharefile_fopen (sharefile_handle h, const char *filename)
{
struct sharefile *p = h;
struct SharefileEntry *new_entry;
new_entry = malloc (sizeof (struct SharefileEntry));
if (!new_entry)
return NULL;
new_entry->name = strdup (filename);
if (NULL == new_entry->name)
{
free (new_entry);
return NULL;
}
if (NULL == (new_entry->fp = fopen (filename, p->mode)))
{
entry_free (new_entry);
return NULL;
}
else
{
struct stat st;
const int fd = fileno (new_entry->fp);
assert (fd >= 0);
set_cloexec_flag (fd, true);
if (fstat (fd, &st) < 0)
{
entry_free (new_entry);
return NULL;
}
else
{
void *existing;
new_entry->device = st.st_dev;
new_entry->inode = st.st_ino;
existing = hash_lookup (p->table, new_entry);
if (existing) /* We have previously opened that file. */
{
entry_free (new_entry); /* don't need new_entry. */
return ((const struct SharefileEntry*)existing)->fp;
}
else /* We didn't open it already */
{
if (hash_insert (p->table, new_entry))
{
return new_entry->fp;
}
else /* failed to insert in hashtable. */
{
const int save_errno = errno;
entry_free (new_entry);
errno = save_errno;
return NULL;
}
}
}
}
}
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