completion_hash.cc

/* Copyright (c) 2000, 2023, Oracle and/or its affiliates.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License, version 2.0,
   as published by the Free Software Foundation.

   This program is also distributed with certain software (including
   but not limited to OpenSSL) that is licensed under separate terms,
   as designated in a particular file or component or in included license
   documentation.  The authors of MySQL hereby grant you an additional
   permission to link the program and your derivative works with the
   separately licensed software that they have included with MySQL.

   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, version 2.0, 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 */

/* Quick & light hash implementation for tab completion purposes
 *
 * by  Andi Gutmans <andi@zend.com>
 * and Zeev Suraski <zeev@zend.com>
 * Small portability changes by Monty. Changed also to use my_malloc/my_free
 */

#include <my_global.h>
#include <m_string.h>
#include <my_sys.h>
#include "completion_hash.h"

uint hashpjw(const char *arKey, uint nKeyLength)
{
  uint h = 0, g, i;

  for (i = 0; i < nKeyLength; i++) {
    h = (h << 4) + arKey[i];
    if ((g = (h & 0xF0000000))) {
      h = h ^ (g >> 24);
      h = h ^ g;
    }
  }
  return h;
}

int completion_hash_init(HashTable *ht, uint nSize)
{
  ht->arBuckets = (Bucket **) my_malloc(PSI_NOT_INSTRUMENTED,
                                        nSize* sizeof(Bucket *),
					MYF(MY_ZEROFILL | MY_WME));

  if (!ht->arBuckets)
  {
    ht->initialized = 0;
    return FAILURE;
  }
  init_alloc_root(PSI_NOT_INSTRUMENTED, &ht->mem_root, 8192, 0);
  ht->pHashFunction = hashpjw;
  ht->nTableSize = nSize;
  ht->initialized = 1;
  return SUCCESS;
}


int completion_hash_update(HashTable *ht, char *arKey, uint nKeyLength,
			   char *str)
{
  uint h, nIndex;

  Bucket *p;

  h = ht->pHashFunction(arKey, nKeyLength);
  nIndex = h % ht->nTableSize;

  if (nKeyLength <= 0) {
    return FAILURE;
  }
  p = ht->arBuckets[nIndex];
  while (p)
  {
    if ((p->h == h) && (p->nKeyLength == nKeyLength)) {
      if (!memcmp(p->arKey, arKey, nKeyLength)) {
	entry *n;

	if (!(n = (entry *) alloc_root(&ht->mem_root,sizeof(entry))))
          return FAILURE;
	n->pNext = p->pData;
	n->str = str;
	p->pData = n;
	p->count++;

	return SUCCESS;
      }
    }
    p = p->pNext;
  }

  if (!(p = (Bucket *) alloc_root(&ht->mem_root, sizeof(Bucket))))
    return FAILURE;

  p->arKey = arKey;
  p->nKeyLength = nKeyLength;
  p->h = h;

  if (!(p->pData = (entry*) alloc_root(&ht->mem_root, sizeof(entry))))
    return FAILURE;

  p->pData->str = str;
  p->pData->pNext = 0;
  p->count = 1;

  p->pNext = ht->arBuckets[nIndex];
  ht->arBuckets[nIndex] = p;

  return SUCCESS;
}

static Bucket *completion_hash_find(HashTable *ht, const char *arKey,
				    uint nKeyLength)
{
  uint h, nIndex;
  Bucket *p;

  h = ht->pHashFunction(arKey, nKeyLength);
  nIndex = h % ht->nTableSize;

  p = ht->arBuckets[nIndex];
  while (p)
  {
    if ((p->h == h) && (p->nKeyLength == nKeyLength)) {
      if (!memcmp(p->arKey, arKey, nKeyLength)) {
	return p;
      }
    }
    p = p->pNext;
  }
  return (Bucket*) 0;
}


int completion_hash_exists(HashTable *ht, char *arKey, uint nKeyLength)
{
  uint h, nIndex;
  Bucket *p;

  h = ht->pHashFunction(arKey, nKeyLength);
  nIndex = h % ht->nTableSize;

  p = ht->arBuckets[nIndex];
  while (p)
  {
    if ((p->h == h) && (p->nKeyLength == nKeyLength))
    {
      if (!strcmp(p->arKey, arKey)) {
	return 1;
      }
    }
    p = p->pNext;
  }
  return 0;
}

Bucket *find_all_matches(HashTable *ht, const char *str, uint length,
			 uint *res_length)
{
  Bucket *b;

  b = completion_hash_find(ht,str,length);
  if (!b) {
    *res_length = 0;
    return (Bucket*) 0;
  } else {
    *res_length = length;
    return b;
  }
}

Bucket *find_longest_match(HashTable *ht, char *str, uint length,
			   uint *res_length)
{
  Bucket *b,*return_b;
  char *s;
  uint count;
  uint lm;

  b = completion_hash_find(ht,str,length);
  if (!b) {
    *res_length = 0;
    return (Bucket*) 0;
  }

  count = b->count;
  lm = length;
  s = b->pData->str;

  return_b = b;
  while (s[lm]!=0 && (b=completion_hash_find(ht,s,lm+1))) {
    if (b->count<count) {
      *res_length=lm;
      return return_b;
    }
    return_b=b;
    lm++;
  }
  *res_length=lm;
  return return_b;
}


void completion_hash_clean(HashTable *ht)
{
  free_root(&ht->mem_root,MYF(0));
  memset(ht->arBuckets, 0, ht->nTableSize * sizeof(Bucket *));
}


void completion_hash_free(HashTable *ht)
{
  completion_hash_clean(ht);
  my_free(ht->arBuckets);
}


void add_word(HashTable *ht,char *str)
{
  int i;
  char *pos=str;
  for (i=1; *pos; i++, pos++)
    completion_hash_update(ht, str, i, str);
}