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/* Copyright (c) 2006, 2010, Oracle and/or its affiliates.
Copyright (c) 2009, 2016, MariaDB
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; version 2 of the License.
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 St, Fifth Floor, Boston, MA 02110-1301 USA */
/*
extensible hash
TODO
try to get rid of dummy nodes ?
for non-unique hash, count only _distinct_ values
(but how to do it in lf_hash_delete ?)
*/
#include <my_global.h>
#include <m_string.h>
#include <my_sys.h>
#include <mysys_err.h>
#include <my_bit.h>
#include <lf.h>
/* An element of the list */
typedef struct {
intptr volatile link; /* a pointer to the next element in a list and a flag */
uint32 hashnr; /* reversed hash number, for sorting */
const uchar *key;
size_t keylen;
/*
data is stored here, directly after the keylen.
thus the pointer to data is (void*)(slist_element_ptr+1)
*/
} LF_SLIST;
const int LF_HASH_OVERHEAD= sizeof(LF_SLIST);
/*
a structure to pass the context (pointers two the three successive elements
in a list) from l_find to l_insert/l_delete
*/
typedef struct {
intptr volatile *prev;
LF_SLIST *curr, *next;
} CURSOR;
/*
the last bit in LF_SLIST::link is a "deleted" flag.
the helper macros below convert it to a pure pointer or a pure flag
*/
#define PTR(V) (LF_SLIST *)((V) & (~(intptr)1))
#define DELETED(V) ((V) & 1)
/** walk the list, searching for an element or invoking a callback
Search for hashnr/key/keylen in the list starting from 'head' and
position the cursor. The list is ORDER BY hashnr, key
@param head start walking the list from this node
@param cs charset for comparing keys, NULL if callback is used
@param hashnr hash number to search for
@param key key to search for OR data for the callback
@param keylen length of the key to compare, 0 if callback is used
@param cursor for returning the found element
@param pins see lf_alloc-pin.c
@param callback callback action, invoked for every element
@note
cursor is positioned in either case
pins[0..2] are used, they are NOT removed on return
callback might see some elements twice (because of retries)
@return
if find: 0 - not found
1 - found
if callback:
0 - ok
1 - error (callbck returned 1)
*/
static int l_find(LF_SLIST * volatile *head, CHARSET_INFO *cs, uint32 hashnr,
const uchar *key, size_t keylen, CURSOR *cursor, LF_PINS *pins,
my_hash_walk_action callback)
{
uint32 cur_hashnr;
const uchar *cur_key;
size_t cur_keylen;
intptr link;
DBUG_ASSERT(!cs || !callback); /* should not be set both */
DBUG_ASSERT(!keylen || !callback); /* should not be set both */
retry:
cursor->prev= (intptr *)head;
do { /* PTR() isn't necessary below, head is a dummy node */
cursor->curr= (LF_SLIST *)(*cursor->prev);
lf_pin(pins, 1, cursor->curr);
} while (*cursor->prev != (intptr)cursor->curr && LF_BACKOFF());
for (;;)
{
if (unlikely(!cursor->curr))
return 0; /* end of the list */
cur_hashnr= cursor->curr->hashnr;
cur_keylen= cursor->curr->keylen;
cur_key= cursor->curr->key;
do {
link= cursor->curr->link;
cursor->next= PTR(link);
lf_pin(pins, 0, cursor->next);
} while (link != cursor->curr->link && LF_BACKOFF());
if (!DELETED(link))
{
if (unlikely(callback))
{
if (cur_hashnr & 1 && callback(cursor->curr + 1, (void*)key))
return 1;
}
else if (cur_hashnr >= hashnr)
{
int r= 1;
if (cur_hashnr > hashnr ||
(r= my_strnncoll(cs, cur_key, cur_keylen, key, keylen)) >= 0)
return !r;
}
cursor->prev= &(cursor->curr->link);
if (!(cur_hashnr & 1)) /* dummy node */
head= (LF_SLIST **)cursor->prev;
lf_pin(pins, 2, cursor->curr);
}
else
{
/*
we found a deleted node - be nice, help the other thread
and remove this deleted node
*/
if (my_atomic_casptr((void **) cursor->prev,
(void **) &cursor->curr, cursor->next) && LF_BACKOFF())
lf_alloc_free(pins, cursor->curr);
else
goto retry;
}
cursor->curr= cursor->next;
lf_pin(pins, 1, cursor->curr);
}
}
/*
DESCRIPTION
insert a 'node' in the list that starts from 'head' in the correct
position (as found by l_find)
RETURN
0 - inserted
not 0 - a pointer to a duplicate (not pinned and thus unusable)
NOTE
it uses pins[0..2], on return all pins are removed.
if there're nodes with the same key value, a new node is added before them.
*/
static LF_SLIST *l_insert(LF_SLIST * volatile *head, CHARSET_INFO *cs,
LF_SLIST *node, LF_PINS *pins, uint flags)
{
CURSOR cursor;
int res;
for (;;)
{
if (l_find(head, cs, node->hashnr, node->key, node->keylen,
&cursor, pins, 0) &&
(flags & LF_HASH_UNIQUE))
{
res= 0; /* duplicate found */
break;
}
else
{
node->link= (intptr)cursor.curr;
DBUG_ASSERT(node->link != (intptr)node); /* no circular references */
DBUG_ASSERT(cursor.prev != &node->link); /* no circular references */
if (my_atomic_casptr((void **) cursor.prev,
(void **)(char*) &cursor.curr, node))
{
res= 1; /* inserted ok */
break;
}
}
}
lf_unpin(pins, 0);
lf_unpin(pins, 1);
lf_unpin(pins, 2);
/*
Note that cursor.curr is not pinned here and the pointer is unreliable,
the object may disappear anytime. But if it points to a dummy node, the
pointer is safe, because dummy nodes are never freed - initialize_bucket()
uses this fact.
*/
return res ? 0 : cursor.curr;
}
/*
DESCRIPTION
deletes a node as identified by hashnr/keey/keylen from the list
that starts from 'head'
RETURN
0 - ok
1 - not found
NOTE
it uses pins[0..2], on return all pins are removed.
*/
static int l_delete(LF_SLIST * volatile *head, CHARSET_INFO *cs, uint32 hashnr,
const uchar *key, uint keylen, LF_PINS *pins)
{
CURSOR cursor;
int res;
for (;;)
{
if (!l_find(head, cs, hashnr, key, keylen, &cursor, pins, 0))
{
res= 1; /* not found */
break;
}
else
{
/* mark the node deleted */
if (my_atomic_casptr((void **) (char*) &(cursor.curr->link),
(void **) (char*) &cursor.next,
(void *)(((intptr)cursor.next) | 1)))
{
/* and remove it from the list */
if (my_atomic_casptr((void **)cursor.prev,
(void **)(char*)&cursor.curr, cursor.next))
lf_alloc_free(pins, cursor.curr);
else
{
/*
somebody already "helped" us and removed the node ?
Let's check if we need to help that someone too!
(to ensure the number of "set DELETED flag" actions
is equal to the number of "remove from the list" actions)
*/
l_find(head, cs, hashnr, key, keylen, &cursor, pins, 0);
}
res= 0;
break;
}
}
}
lf_unpin(pins, 0);
lf_unpin(pins, 1);
lf_unpin(pins, 2);
return res;
}
/*
DESCRIPTION
searches for a node as identified by hashnr/keey/keylen in the list
that starts from 'head'
RETURN
0 - not found
node - found
NOTE
it uses pins[0..2], on return the pin[2] keeps the node found
all other pins are removed.
*/
static LF_SLIST *l_search(LF_SLIST * volatile *head, CHARSET_INFO *cs,
uint32 hashnr, const uchar *key, uint keylen,
LF_PINS *pins)
{
CURSOR cursor;
int res= l_find(head, cs, hashnr, key, keylen, &cursor, pins, 0);
if (res)
lf_pin(pins, 2, cursor.curr);
else
lf_unpin(pins, 2);
lf_unpin(pins, 1);
lf_unpin(pins, 0);
return res ? cursor.curr : 0;
}
static inline const uchar* hash_key(const LF_HASH *hash,
const uchar *record, size_t *length)
{
if (hash->get_key)
return (*hash->get_key)(record, length, 0);
*length= hash->key_length;
return record + hash->key_offset;
}
/*
Compute the hash key value from the raw key.
@note, that the hash value is limited to 2^31, because we need one
bit to distinguish between normal and dummy nodes.
*/
static inline my_hash_value_type calc_hash(CHARSET_INFO *cs,
const uchar *key,
size_t keylen)
{
ulong nr1= 1, nr2= 4;
cs->coll->hash_sort(cs, (uchar*) key, keylen, &nr1, &nr2);
return nr1;
}
#define MAX_LOAD 1.0 /* average number of elements in a bucket */
static int initialize_bucket(LF_HASH *, LF_SLIST * volatile*, uint, LF_PINS *);
static void default_initializer(LF_HASH *hash, void *dst, const void *src)
{
memcpy(dst, src, hash->element_size);
}
/*
Initializes lf_hash, the arguments are compatible with hash_init
@note element_size sets both the size of allocated memory block for
lf_alloc and a size of memcpy'ed block size in lf_hash_insert. Typically
they are the same, indeed. But LF_HASH::element_size can be decreased
after lf_hash_init, and then lf_alloc will allocate larger block that
lf_hash_insert will copy over. It is desirable if part of the element
is expensive to initialize - for example if there is a mutex or
DYNAMIC_ARRAY. In this case they should be initialize in the
LF_ALLOCATOR::constructor, and lf_hash_insert should not overwrite them.
The above works well with PODS. For more complex cases (e.g. C++ classes
with private members) use initializer function.
*/
void lf_hash_init(LF_HASH *hash, uint element_size, uint flags,
uint key_offset, uint key_length, my_hash_get_key get_key,
CHARSET_INFO *charset)
{
lf_alloc_init(&hash->alloc, sizeof(LF_SLIST)+element_size,
offsetof(LF_SLIST, key));
lf_dynarray_init(&hash->array, sizeof(LF_SLIST *));
hash->size= 1;
hash->count= 0;
hash->element_size= element_size;
hash->flags= flags;
hash->charset= charset ? charset : &my_charset_bin;
hash->key_offset= key_offset;
hash->key_length= key_length;
hash->get_key= get_key;
hash->initializer= default_initializer;
hash->hash_function= calc_hash;
DBUG_ASSERT(get_key ? !key_offset && !key_length : key_length);
}
void lf_hash_destroy(LF_HASH *hash)
{
LF_SLIST *el, **head= (LF_SLIST **)lf_dynarray_value(&hash->array, 0);
if (head)
{
el= *head;
while (el)
{
intptr next= el->link;
if (el->hashnr & 1)
lf_alloc_direct_free(&hash->alloc, el); /* normal node */
else
my_free(el); /* dummy node */
el= (LF_SLIST *)next;
}
}
lf_alloc_destroy(&hash->alloc);
lf_dynarray_destroy(&hash->array);
}
/*
DESCRIPTION
inserts a new element to a hash. it will have a _copy_ of
data, not a pointer to it.
RETURN
0 - inserted
1 - didn't (unique key conflict)
-1 - out of memory
NOTE
see l_insert() for pin usage notes
*/
int lf_hash_insert(LF_HASH *hash, LF_PINS *pins, const void *data)
{
int csize, bucket, hashnr;
LF_SLIST *node, * volatile *el;
node= (LF_SLIST *)lf_alloc_new(pins);
if (unlikely(!node))
return -1;
hash->initializer(hash, node + 1, data);
node->key= hash_key(hash, (uchar *)(node+1), &node->keylen);
hashnr= hash->hash_function(hash->charset, node->key, node->keylen) & INT_MAX32;
bucket= hashnr % hash->size;
el= lf_dynarray_lvalue(&hash->array, bucket);
if (unlikely(!el))
return -1;
if (*el == NULL && unlikely(initialize_bucket(hash, el, bucket, pins)))
return -1;
node->hashnr= my_reverse_bits(hashnr) | 1; /* normal node */
if (l_insert(el, hash->charset, node, pins, hash->flags))
{
lf_alloc_free(pins, node);
return 1;
}
csize= hash->size;
if ((my_atomic_add32(&hash->count, 1)+1.0) / csize > MAX_LOAD)
my_atomic_cas32(&hash->size, &csize, csize*2);
return 0;
}
/*
DESCRIPTION
deletes an element with the given key from the hash (if a hash is
not unique and there're many elements with this key - the "first"
matching element is deleted)
RETURN
0 - deleted
1 - didn't (not found)
NOTE
see l_delete() for pin usage notes
*/
int lf_hash_delete(LF_HASH *hash, LF_PINS *pins, const void *key, uint keylen)
{
LF_SLIST * volatile *el;
uint bucket, hashnr;
hashnr= hash->hash_function(hash->charset, (uchar *)key, keylen) & INT_MAX32;
/* hide OOM errors - if we cannot initialize a bucket, try the previous one */
for (bucket= hashnr % hash->size; ;bucket= my_clear_highest_bit(bucket))
{
el= lf_dynarray_lvalue(&hash->array, bucket);
if (el && (*el || initialize_bucket(hash, el, bucket, pins) == 0))
break;
if (unlikely(bucket == 0))
return 1; /* if there's no bucket==0, the hash is empty */
}
if (l_delete(el, hash->charset, my_reverse_bits(hashnr) | 1,
(uchar *)key, keylen, pins))
{
return 1;
}
my_atomic_add32(&hash->count, -1);
return 0;
}
/*
RETURN
a pointer to an element with the given key (if a hash is not unique and
there're many elements with this key - the "first" matching element)
NULL if nothing is found
NOTE
see l_search() for pin usage notes
*/
void *lf_hash_search_using_hash_value(LF_HASH *hash, LF_PINS *pins,
my_hash_value_type hashnr,
const void *key, uint keylen)
{
LF_SLIST * volatile *el, *found;
uint bucket;
/* hide OOM errors - if we cannot initialize a bucket, try the previous one */
for (bucket= hashnr % hash->size; ;bucket= my_clear_highest_bit(bucket))
{
el= lf_dynarray_lvalue(&hash->array, bucket);
if (el && (*el || initialize_bucket(hash, el, bucket, pins) == 0))
break;
if (unlikely(bucket == 0))
return 0; /* if there's no bucket==0, the hash is empty */
}
found= l_search(el, hash->charset, my_reverse_bits(hashnr) | 1,
(uchar *)key, keylen, pins);
return found ? found+1 : 0;
}
/**
Iterate over all elements in hash and call function with the element
@note
If one of 'action' invocations returns 1 the iteration aborts.
'action' might see some elements twice!
@retval 0 ok
@retval 1 error (action returned 1)
*/
int lf_hash_iterate(LF_HASH *hash, LF_PINS *pins,
my_hash_walk_action action, void *argument)
{
CURSOR cursor;
uint bucket= 0;
int res;
LF_SLIST * volatile *el;
el= lf_dynarray_lvalue(&hash->array, bucket);
if (unlikely(!el))
return 0; /* if there's no bucket==0, the hash is empty */
if (*el == NULL && unlikely(initialize_bucket(hash, el, bucket, pins)))
return 0; /* if there's no bucket==0, the hash is empty */
res= l_find(el, 0, 0, (uchar*)argument, 0, &cursor, pins, action);
lf_unpin(pins, 2);
lf_unpin(pins, 1);
lf_unpin(pins, 0);
return res;
}
void *lf_hash_search(LF_HASH *hash, LF_PINS *pins, const void *key, uint keylen)
{
return lf_hash_search_using_hash_value(hash, pins,
hash->hash_function(hash->charset,
(uchar*) key,
keylen) & INT_MAX32,
key, keylen);
}
static const uchar *dummy_key= (uchar*)"";
/*
RETURN
0 - ok
-1 - out of memory
*/
static int initialize_bucket(LF_HASH *hash, LF_SLIST * volatile *node,
uint bucket, LF_PINS *pins)
{
uint parent= my_clear_highest_bit(bucket);
LF_SLIST *dummy= (LF_SLIST *)my_malloc(sizeof(LF_SLIST), MYF(MY_WME));
LF_SLIST **tmp= 0, *cur;
LF_SLIST * volatile *el= lf_dynarray_lvalue(&hash->array, parent);
if (unlikely(!el || !dummy))
return -1;
if (*el == NULL && bucket &&
unlikely(initialize_bucket(hash, el, parent, pins)))
{
my_free(dummy);
return -1;
}
dummy->hashnr= my_reverse_bits(bucket) | 0; /* dummy node */
dummy->key= dummy_key;
dummy->keylen= 0;
if ((cur= l_insert(el, hash->charset, dummy, pins, LF_HASH_UNIQUE)))
{
my_free(dummy);
dummy= cur;
}
my_atomic_casptr((void **)node, (void **)(char*) &tmp, dummy);
/*
note that if the CAS above failed (after l_insert() succeeded),
it would mean that some other thread has executed l_insert() for
the same dummy node, its l_insert() failed, it picked up our
dummy node (in "dummy= cur") and executed the same CAS as above.
Which means that even if CAS above failed we don't need to retry,
and we should not free(dummy) - there's no memory leak here
*/
return 0;
}
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