hashtable.c

来自「linux编程指南源代码 适于Linux下C++的初学者」· C语言 代码 · 共 135 行

/*
The contents of this file are subject to the Mozilla Public License
Version 1.0 (the "License"); you may not use this file except in
csompliance with the License. You may obtain a copy of the License at
http://www.mozilla.org/MPL/

Software distributed under the License is distributed on an "AS IS"
basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See the
License for the specific language governing rights and limitations
under the License.

The Original Code is expat.

The Initial Developer of the Original Code is James Clark.
Portions created by James Clark are Copyright (C) 1998
James Clark. All Rights Reserved.

Contributor(s):
*/

#include <stdlib.h>
#include <string.h>

#include "xmldef.h"
#include "hashtable.h"

#ifdef XML_UNICODE
#define keycmp wcscmp
#else
#define keycmp strcmp
#endif

#define INIT_SIZE 64

static
unsigned long hash(KEY s)
{
  unsigned long h = 0;
  while (*s)
    h = (h << 5) + h + (unsigned char)*s++;
  return h;
}

NAMED *lookup(HASH_TABLE *table, KEY name, size_t createSize)
{
  size_t i;
  if (table->size == 0) {
    if (!createSize)
      return 0;
    table->v = calloc(INIT_SIZE, sizeof(NAMED *));
    if (!table->v)
      return 0;
    table->size = INIT_SIZE;
    table->usedLim = INIT_SIZE / 2;
    i = hash(name) & (table->size - 1);
  }
  else {
    unsigned long h = hash(name);
    for (i = h & (table->size - 1);
         table->v[i];
         i == 0 ? i = table->size - 1 : --i) {
      if (keycmp(name, table->v[i]->name) == 0)
	return table->v[i];
    }
    if (!createSize)
      return 0;
    if (table->used == table->usedLim) {
      /* check for overflow */
      size_t newSize = table->size * 2;
      NAMED **newV = calloc(newSize, sizeof(NAMED *));
      if (!newV)
	return 0;
      for (i = 0; i < table->size; i++)
	if (table->v[i]) {
	  size_t j;
	  for (j = hash(table->v[i]->name) & (newSize - 1);
	       newV[j];
	       j == 0 ? j = newSize - 1 : --j)
	    ;
	  newV[j] = table->v[i];
	}
      free(table->v);
      table->v = newV;
      table->size = newSize;
      table->usedLim = newSize/2;
      for (i = h & (table->size - 1);
	   table->v[i];
	   i == 0 ? i = table->size - 1 : --i)
	;
    }
  }
  table->v[i] = calloc(1, createSize);
  if (!table->v[i])
    return 0;
  table->v[i]->name = name;
  (table->used)++;
  return table->v[i];
}

void hashTableDestroy(HASH_TABLE *table)
{
  size_t i;
  for (i = 0; i < table->size; i++) {
    NAMED *p = table->v[i];
    if (p)
      free(p);
  }
  free(table->v);
}

void hashTableInit(HASH_TABLE *p)
{
  p->size = 0;
  p->usedLim = 0;
  p->used = 0;
  p->v = 0;
}

void hashTableIterInit(HASH_TABLE_ITER *iter, const HASH_TABLE *table)
{
  iter->p = table->v;
  iter->end = iter->p + table->size;
}

NAMED *hashTableIterNext(HASH_TABLE_ITER *iter)
{
  while (iter->p != iter->end) {
    NAMED *tem = *(iter->p)++;
    if (tem)
      return tem;
  }
  return 0;
}