/* Copyright (c) 2006, 2010, Oracle and/or its affiliates. All rights reserved. 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 #include #include #include #include LF_REQUIRE_PINS(3) /* An element of the list */ typedef struct { intptr volatile link; /* a pointer to the next element in a listand 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 lfind to linsert/ldelete */ 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) /* DESCRIPTION Search for hashnr/key/keylen in the list starting from 'head' and position the cursor. The list is ORDER BY hashnr, key RETURN 0 - not found 1 - found NOTE cursor is positioned in either case pins[0..2] are used, they are NOT removed on return */ static int lfind(LF_SLIST * volatile *head, CHARSET_INFO *cs, uint32 hashnr, const uchar *key, uint keylen, CURSOR *cursor, LF_PINS *pins) { uint32 cur_hashnr; const uchar *cur_key; uint cur_keylen; intptr link; 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 */ do { /* QQ: XXX or goto retry ? */ link= cursor->curr->link; cursor->next= PTR(link); _lf_pin(pins, 0, cursor->next); } while (link != cursor->curr->link && LF_BACKOFF); cur_hashnr= cursor->curr->hashnr; cur_key= cursor->curr->key; cur_keylen= cursor->curr->keylen; if (*cursor->prev != (intptr)cursor->curr) { (void)LF_BACKOFF; goto retry; } if (!DELETED(link)) { if (cur_hashnr >= hashnr) { int r= 1; if (cur_hashnr > hashnr || (r= my_strnncoll(cs, (uchar*) cur_key, cur_keylen, (uchar*) key, keylen)) >= 0) return !r; } cursor->prev= &(cursor->curr->link); _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 **)(char*) &cursor->curr, cursor->next)) _lf_alloc_free(pins, cursor->curr); else { (void)LF_BACKOFF; 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 lfind) 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 *linsert(LF_SLIST * volatile *head, CHARSET_INFO *cs, LF_SLIST *node, LF_PINS *pins, uint flags) { CURSOR cursor; int res; for (;;) { if (lfind(head, cs, node->hashnr, node->key, node->keylen, &cursor, pins) && (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 dissapear 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 ldelete(LF_SLIST * volatile *head, CHARSET_INFO *cs, uint32 hashnr, const uchar *key, uint keylen, LF_PINS *pins) { CURSOR cursor; int res; for (;;) { if (!lfind(head, cs, hashnr, key, keylen, &cursor, pins)) { 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) */ lfind(head, cs, hashnr, key, keylen, &cursor, pins); } 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 *lsearch(LF_SLIST * volatile *head, CHARSET_INFO *cs, uint32 hashnr, const uchar *key, uint keylen, LF_PINS *pins) { CURSOR cursor; int res= lfind(head, cs, hashnr, key, keylen, &cursor, pins); if (res) _lf_pin(pins, 2, cursor.curr); _lf_unpin(pins, 0); _lf_unpin(pins, 1); 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 uint calc_hash(LF_HASH *hash, const uchar *key, uint keylen) { ulong nr1= 1, nr2= 4; hash->charset->coll->hash_sort(hash->charset, (uchar*) key, keylen, &nr1, &nr2); return nr1 & INT_MAX32; } #define MAX_LOAD 1.0 /* average number of elements in a bucket */ static int initialize_bucket(LF_HASH *, LF_SLIST * volatile*, uint, LF_PINS *); /* 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 desireable 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. See wt_init() for example. */ 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; 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 linsert() 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; lf_rwlock_by_pins(pins); node= (LF_SLIST *)_lf_alloc_new(pins); if (unlikely(!node)) return -1; memcpy(node+1, data, hash->element_size); node->key= hash_key(hash, (uchar *)(node+1), &node->keylen); hashnr= calc_hash(hash, node->key, node->keylen); 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 (linsert(el, hash->charset, node, pins, hash->flags)) { _lf_alloc_free(pins, node); lf_rwunlock_by_pins(pins); 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); lf_rwunlock_by_pins(pins); 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) -1 - out of memory NOTE see ldelete() 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= calc_hash(hash, (uchar *)key, keylen); bucket= hashnr % hash->size; lf_rwlock_by_pins(pins); el= _lf_dynarray_lvalue(&hash->array, bucket); if (unlikely(!el)) return -1; /* note that we still need to initialize_bucket here, we cannot return "node not found", because an old bucket of that node may've been split and the node was assigned to a new bucket that was never accessed before and thus is not initialized. */ if (*el == NULL && unlikely(initialize_bucket(hash, el, bucket, pins))) return -1; if (ldelete(el, hash->charset, my_reverse_bits(hashnr) | 1, (uchar *)key, keylen, pins)) { lf_rwunlock_by_pins(pins); return 1; } my_atomic_add32(&hash->count, -1); lf_rwunlock_by_pins(pins); 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 MY_ERRPTR if OOM NOTE see lsearch() for pin usage notes */ void *lf_hash_search(LF_HASH *hash, LF_PINS *pins, const void *key, uint keylen) { LF_SLIST * volatile *el, *found; uint bucket, hashnr= calc_hash(hash, (uchar *)key, keylen); bucket= hashnr % hash->size; lf_rwlock_by_pins(pins); el= _lf_dynarray_lvalue(&hash->array, bucket); if (unlikely(!el)) return MY_ERRPTR; if (*el == NULL && unlikely(initialize_bucket(hash, el, bucket, pins))) return MY_ERRPTR; found= lsearch(el, hash->charset, my_reverse_bits(hashnr) | 1, (uchar *)key, keylen, pins); lf_rwunlock_by_pins(pins); return found ? found+1 : 0; } 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))) return -1; dummy->hashnr= my_reverse_bits(bucket) | 0; /* dummy node */ dummy->key= dummy_key; dummy->keylen= 0; if ((cur= linsert(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 linsert() succeeded), it would mean that some other thread has executed linsert() for the same dummy node, its linsert() 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; }