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/* Copyright (C) 2005 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; 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */
/*
Implementation of trie and Aho-Corasick automaton.
Supports only charsets that can be compared byte-wise.
TODO:
Add character frequencies. Can increase lookup speed
up to 30%.
Implement character-wise comparision.
*/
#include "mysys_priv.h"
#include <m_string.h>
#include <my_trie.h>
#include <my_base.h>
/*
SYNOPSIS
TRIE *trie_init (TRIE *trie, CHARSET_INFO *charset);
DESCRIPTION
Allocates or initializes a `TRIE' object. If `trie' is a `NULL'
pointer, the function allocates, initializes, and returns a new
object. Otherwise, the object is initialized and the address of
the object is returned. If `trie_init()' allocates a new object,
it will be freed when `trie_free()' is called.
RETURN VALUE
An initialized `TRIE*' object. `NULL' if there was insufficient
memory to allocate a new object.
*/
TRIE *trie_init (TRIE *trie, CHARSET_INFO *charset)
{
MEM_ROOT mem_root;
DBUG_ENTER("trie_init");
DBUG_ASSERT(charset);
init_alloc_root(&mem_root,
(sizeof(TRIE_NODE) * 128) + ALLOC_ROOT_MIN_BLOCK_SIZE,
sizeof(TRIE_NODE) * 128);
if (! trie)
{
if (! (trie= (TRIE *)alloc_root(&mem_root, sizeof(TRIE))))
{
free_root(&mem_root, MYF(0));
DBUG_RETURN(NULL);
}
}
memcpy(&trie->mem_root, &mem_root, sizeof(MEM_ROOT));
trie->root.leaf= 0;
trie->root.c= 0;
trie->root.next= NULL;
trie->root.links= NULL;
trie->root.fail= NULL;
trie->charset= charset;
trie->nnodes= 0;
trie->nwords= 0;
DBUG_RETURN(trie);
}
/*
SYNOPSIS
void trie_free (TRIE *trie);
trie - valid pointer to `TRIE'
DESCRIPTION
Frees the memory allocated for a `trie'.
RETURN VALUE
None.
*/
void trie_free (TRIE *trie)
{
MEM_ROOT mem_root;
DBUG_ENTER("trie_free");
DBUG_ASSERT(trie);
memcpy(&mem_root, &trie->mem_root, sizeof(MEM_ROOT));
free_root(&mem_root, MYF(0));
DBUG_VOID_RETURN;
}
/*
SYNOPSIS
my_bool trie_insert (TRIE *trie, const uchar *key, uint keylen);
trie - valid pointer to `TRIE'
key - valid pointer to key to insert
keylen - non-0 key length
DESCRIPTION
Inserts new key into trie.
RETURN VALUE
Upon successful completion, `trie_insert' returns `FALSE'. Otherwise
`TRUE' is returned.
NOTES
If this function fails you must assume `trie' is broken.
However it can be freed with trie_free().
*/
my_bool trie_insert (TRIE *trie, const uchar *key, uint keylen)
{
TRIE_NODE *node;
TRIE_NODE *next;
uchar p;
uint k;
DBUG_ENTER("trie_insert");
DBUG_ASSERT(trie && key && keylen);
node= &trie->root;
trie->root.fail= NULL;
for (k= 0; k < keylen; k++)
{
p= key[k];
for (next= node->links; next; next= next->next)
if (next->c == p)
break;
if (! next)
{
TRIE_NODE *tmp= (TRIE_NODE *)alloc_root(&trie->mem_root,
sizeof(TRIE_NODE));
if (! tmp)
DBUG_RETURN(TRUE);
tmp->leaf= 0;
tmp->c= p;
tmp->links= tmp->fail= tmp->next= NULL;
trie->nnodes++;
if (! node->links)
{
node->links= tmp;
}
else
{
for (next= node->links; next->next; next= next->next) /* no-op */;
next->next= tmp;
}
node= tmp;
}
else
{
node= next;
}
}
node->leaf= keylen;
trie->nwords++;
DBUG_RETURN(FALSE);
}
/*
SYNOPSIS
my_bool trie_prepare (TRIE *trie);
trie - valid pointer to `TRIE'
DESCRIPTION
Constructs Aho-Corasick automaton.
RETURN VALUE
Upon successful completion, `trie_prepare' returns `FALSE'. Otherwise
`TRUE' is returned.
*/
my_bool ac_trie_prepare (TRIE *trie)
{
TRIE_NODE **tmp_nodes;
TRIE_NODE *node;
uint32 fnode= 0;
uint32 lnode= 0;
DBUG_ENTER("trie_prepare");
DBUG_ASSERT(trie);
tmp_nodes= (TRIE_NODE **)my_malloc(trie->nnodes * sizeof(TRIE_NODE *), MYF(0));
if (! tmp_nodes)
DBUG_RETURN(TRUE);
trie->root.fail= &trie->root;
for (node= trie->root.links; node; node= node->next)
{
node->fail= &trie->root;
tmp_nodes[lnode++]= node;
}
while (fnode < lnode)
{
TRIE_NODE *current= (TRIE_NODE *)tmp_nodes[fnode++];
for (node= current->links; node; node= node->next)
{
TRIE_NODE *fail= current->fail;
tmp_nodes[lnode++]= node;
while (! (node->fail= trie_goto(&trie->root, fail, node->c)))
fail= fail->fail;
}
}
my_free((uchar*)tmp_nodes, MYF(0));
DBUG_RETURN(FALSE);
}
/*
SYNOPSIS
void ac_trie_init (TRIE *trie, AC_TRIE_STATE *state);
trie - valid pointer to `TRIE'
state - value pointer to `AC_TRIE_STATE'
DESCRIPTION
Initializes `AC_TRIE_STATE' object.
*/
void ac_trie_init (TRIE *trie, AC_TRIE_STATE *state)
{
DBUG_ENTER("ac_trie_init");
DBUG_ASSERT(trie && state);
state->trie= trie;
state->node= &trie->root;
DBUG_VOID_RETURN;
}
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