mariadb/mysys/my_safehash.c
Michal Schorm 17b4f99928 Update FSF address
This commit is based on the work of Michal Schorm, rebased on the
earliest MariaDB version.

Th command line used to generate this diff was:

find ./ -type f \
  -exec sed -i -e 's/Foundation, Inc., 59 Temple Place, Suite 330, Boston, /Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, /g' {} \; \
  -exec sed -i -e 's/Foundation, Inc. 59 Temple Place.* Suite 330, Boston, /Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, /g' {} \; \
  -exec sed -i -e 's/MA.*.....-1307.*USA/MA 02110-1335 USA/g' {} \; \
  -exec sed -i -e 's/Foundation, Inc., 59 Temple/Foundation, Inc., 51 Franklin/g' {} \; \
  -exec sed -i -e 's/Place, Suite 330, Boston, MA.*02111-1307.*USA/Street, Fifth Floor, Boston, MA 02110-1335 USA/g' {} \; \
  -exec sed -i -e 's/MA.*.....-1307/MA 02110-1335/g' {} \;
2019-05-10 20:52:00 +03:00

297 lines
7.5 KiB
C

/* Copyright (C) 2003-2007 MySQL AB
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 2 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, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1335 USA */
/*
Handling of multiple key caches
The idea is to have a thread safe hash on the table name,
with a default key cache value that is returned if the table name is not in
the cache.
*/
#include "mysys_priv.h"
#include <m_string.h>
#include "my_safehash.h"
/*****************************************************************************
General functions to handle SAFE_HASH objects.
A SAFE_HASH object is used to store the hash, the mutex and default value
needed by the rest of the key cache code.
This is a separate struct to make it easy to later reuse the code for other
purposes
All entries are linked in a list to allow us to traverse all elements
and delete selected ones. (HASH doesn't allow any easy ways to do this).
*****************************************************************************/
/*
Free a SAFE_HASH_ENTRY
SYNOPSIS
safe_hash_entry_free()
entry The entry which should be freed
NOTE
This function is called by the hash object on delete
*/
static void safe_hash_entry_free(SAFE_HASH_ENTRY *entry)
{
DBUG_ENTER("safe_hash_entry_free");
my_free(entry);
DBUG_VOID_RETURN;
}
/*
Get key and length for a SAFE_HASH_ENTRY
SYNOPSIS
safe_hash_entry_get()
entry The entry for which the key should be returned
length Length of the key
RETURN
# reference on the key
*/
static uchar *safe_hash_entry_get(SAFE_HASH_ENTRY *entry, size_t *length,
my_bool not_used __attribute__((unused)))
{
*length= entry->length;
return (uchar*) entry->key;
}
/*
Init a SAFE_HASH object
SYNOPSIS
safe_hash_init()
hash safe_hash handler
elements Expected max number of elements
default_value default value
NOTES
In case of error we set hash->default_value to 0 to allow one to call
safe_hash_free on an object that couldn't be initialized.
RETURN
0 OK
1 error
*/
my_bool safe_hash_init(SAFE_HASH *hash, uint elements,
uchar *default_value)
{
DBUG_ENTER("safe_hash_init");
if (my_hash_init(&hash->hash, &my_charset_bin, elements,
0, 0, (my_hash_get_key) safe_hash_entry_get,
(void (*)(void*)) safe_hash_entry_free, 0))
{
hash->default_value= 0;
DBUG_RETURN(1);
}
mysql_rwlock_init(key_SAFEHASH_mutex, &hash->mutex);
hash->default_value= default_value;
hash->root= 0;
DBUG_RETURN(0);
}
/*
Free a SAFE_HASH object
SYNOPSIS
safe_hash_free()
hash Hash handle
NOTES
This is safe to call on any object that has been sent to safe_hash_init()
*/
void safe_hash_free(SAFE_HASH *hash)
{
/*
Test if safe_hash_init succeeded. This will also guard us against multiple
free calls.
*/
if (hash->default_value)
{
my_hash_free(&hash->hash);
mysql_rwlock_destroy(&hash->mutex);
hash->default_value=0;
}
}
/*
Return the value stored for a key or default value if no key
SYNOPSIS
safe_hash_search()
hash Hash handle
key key (path to table etc..)
length Length of key
def Default value of data
RETURN
# data associated with the key of default value if data was not found
*/
uchar *safe_hash_search(SAFE_HASH *hash, const uchar *key, uint length,
uchar *def)
{
uchar *result;
DBUG_ENTER("safe_hash_search");
mysql_rwlock_rdlock(&hash->mutex);
result= my_hash_search(&hash->hash, key, length);
mysql_rwlock_unlock(&hash->mutex);
if (!result)
result= def;
else
result= ((SAFE_HASH_ENTRY*) result)->data;
DBUG_PRINT("exit",("data: 0x%lx", (long) result));
DBUG_RETURN(result);
}
/*
Associate a key with some data
SYNOPSIS
safe_hash_set()
hash Hash handle
key key (path to table etc..)
length Length of key
data data to to associate with the data
NOTES
This can be used both to insert a new entry and change an existing
entry.
If one associates a key with the default key cache, the key is deleted
RETURN
0 OK
1 error (Can only be EOM). In this case my_message() is called.
*/
my_bool safe_hash_set(SAFE_HASH *hash, const uchar *key, uint length,
uchar *data)
{
SAFE_HASH_ENTRY *entry;
my_bool error= 0;
DBUG_ENTER("safe_hash_set");
DBUG_PRINT("enter",("key: %.*s data: 0x%lx", length, key, (long) data));
mysql_rwlock_wrlock(&hash->mutex);
entry= (SAFE_HASH_ENTRY*) my_hash_search(&hash->hash, key, length);
if (data == hash->default_value)
{
/*
The key is to be associated with the default entry. In this case
we can just delete the entry (if it existed) from the hash as a
search will return the default entry
*/
if (!entry) /* nothing to do */
goto end;
/* unlink entry from list */
if ((*entry->prev= entry->next))
entry->next->prev= entry->prev;
my_hash_delete(&hash->hash, (uchar*) entry);
goto end;
}
if (entry)
{
/* Entry existed; Just change the pointer to point at the new data */
entry->data= data;
}
else
{
if (!(entry= (SAFE_HASH_ENTRY *) my_malloc(sizeof(*entry) + length,
MYF(MY_WME))))
{
error= 1;
goto end;
}
entry->key= (uchar*) (entry +1);
memcpy((char*) entry->key, (char*) key, length);
entry->length= length;
entry->data= data;
/* Link entry to list */
if ((entry->next= hash->root))
entry->next->prev= &entry->next;
entry->prev= &hash->root;
hash->root= entry;
if (my_hash_insert(&hash->hash, (uchar*) entry))
{
/* This can only happen if hash got out of memory */
my_free(entry);
error= 1;
goto end;
}
}
end:
mysql_rwlock_unlock(&hash->mutex);
DBUG_RETURN(error);
}
/*
Change all entries with one data value to another data value
SYNOPSIS
safe_hash_change()
hash Hash handle
old_data Old data
new_data Change all 'old_data' to this
NOTES
We use the linked list to traverse all elements in the hash as
this allows us to delete elements in the case where 'new_data' is the
default value.
*/
void safe_hash_change(SAFE_HASH *hash, uchar *old_data, uchar *new_data)
{
SAFE_HASH_ENTRY *entry, *next;
DBUG_ENTER("safe_hash_change");
mysql_rwlock_wrlock(&hash->mutex);
for (entry= hash->root ; entry ; entry= next)
{
next= entry->next;
if (entry->data == old_data)
{
if (new_data == hash->default_value)
{
if ((*entry->prev= entry->next))
entry->next->prev= entry->prev;
my_hash_delete(&hash->hash, (uchar*) entry);
}
else
entry->data= new_data;
}
}
mysql_rwlock_unlock(&hash->mutex);
DBUG_VOID_RETURN;
}