maphash.c

/******************************************************************************
 * $Id$
 *
 * Project:  MapServer
 * Purpose:  Implement hashTableObj class.
 * Author:   Sean Gillies, sgillies@frii.com
 *
 ******************************************************************************
 * Copyright (c) 1996-2005 Regents of the University of Minnesota.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in 
 * all copies of this Software or works derived from this Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 ****************************************************************************/

#include <ctype.h>

#include "mapserver.h"
#include "maphash.h"



static unsigned hash(const char *key)
{
  unsigned hashval;
  
  for(hashval=0; *key!='\0'; key++)
    hashval = tolower(*key) + 31 * hashval;

  return(hashval % MS_HASHSIZE);
}

hashTableObj *msCreateHashTable() 
{
    int i;
    hashTableObj *table;
    
    table = (hashTableObj *) msSmallMalloc(sizeof(hashTableObj));
    table->items = (struct hashObj **) msSmallMalloc(sizeof(struct hashObj *)*MS_HASHSIZE);
    
    for (i=0; i<MS_HASHSIZE; i++)
        table->items[i] = NULL;
    table->numitems = 0;
    
    return table;
}

int initHashTable( hashTableObj *table ) 
{
    int i;

    table->items = (struct hashObj **) malloc(sizeof(struct hashObj *)*MS_HASHSIZE);
    MS_CHECK_ALLOC(table->items, sizeof(struct hashObj *)*MS_HASHSIZE, MS_FAILURE);

    for (i=0; i<MS_HASHSIZE; i++)
        table->items[i] = NULL;
    table->numitems = 0;
    return MS_SUCCESS;
}

void msFreeHashTable( hashTableObj *table )
{
    if( table != NULL )
    {
        msFreeHashItems(table);
        free(table);
        table = NULL;
    }
}

int msHashIsEmpty( hashTableObj *table )
{
    if (table->numitems == 0 )
        return MS_TRUE;
    else
        return MS_FALSE;
}


void msFreeHashItems( hashTableObj *table )
{
    int i;
    struct hashObj *tp=NULL;
    struct hashObj *prev_tp=NULL;
    
    if (table) {
        if(table->items) {
            for (i=0; i<MS_HASHSIZE; i++) {
                if (table->items[i] != NULL) {
                    for (tp=table->items[i]; tp!=NULL; prev_tp=tp,tp=tp->next,free(prev_tp)) {
                      msFree(tp->key);
                      msFree(tp->data);
                    }
                }
                if (tp) free(tp);
            }
            free(table->items);
            table->items = NULL;
        } else {
          msSetError(MS_HASHERR, "No items allocated.", "msFreeHashItems()");
        }
    } else {
        msSetError(MS_HASHERR, "Can't free NULL table", "msFreeHashItems()");
    }
}

struct hashObj *msInsertHashTable(hashTableObj *table, 
                                  const char *key, const char *value)
{
    struct hashObj *tp;
    unsigned hashval;

    if (!table || !key || !value) {
        msSetError(MS_HASHERR, "Invalid hash table or key",
                               "msInsertHashTable");
        return NULL;
    }

    for (tp=table->items[hash(key)]; tp!=NULL; tp=tp->next)
        if(strcasecmp(key, tp->key) == 0)
            break;

    if (tp == NULL) { /* not found */
        tp = (struct hashObj *) malloc(sizeof(*tp));
        MS_CHECK_ALLOC(tp, sizeof(*tp), NULL);
        tp->key = msStrdup(key);
        hashval = hash(key);
        tp->next = table->items[hashval];
        table->items[hashval] = tp;
        table->numitems++;
    } else {
        free(tp->data);
    }

    if ((tp->data = msStrdup(value)) == NULL)
        return NULL;

    return tp;
}

char *msLookupHashTable(hashTableObj *table, const char *key)
{
    struct hashObj *tp;

    if (!table || !key) {
        return(NULL);
    }

    for (tp=table->items[hash(key)]; tp!=NULL; tp=tp->next)
        if (strcasecmp(key, tp->key) == 0)
            return(tp->data);

    return NULL;
}

int msRemoveHashTable(hashTableObj *table, const char *key)
{ 
    struct hashObj *tp;
    struct hashObj *prev_tp=NULL;
    int status = MS_FAILURE;

    if (!table || !key) {
        msSetError(MS_HASHERR, "No hash table", "msRemoveHashTable");
        return MS_FAILURE;
    }
  
    tp=table->items[hash(key)];
    if (!tp) {
        msSetError(MS_HASHERR, "No such hash entry", "msRemoveHashTable");
        return MS_FAILURE;
    }

    prev_tp = NULL;
    while (tp != NULL) {
        if (strcasecmp(key, tp->key) == 0) {
            status = MS_SUCCESS;
            if (prev_tp) {     
                prev_tp->next = tp->next;
                free(tp);
                break;
            }
            else {
                table->items[hash(key)] = tp->next;
                free(tp);
                break;
            }
        }
        prev_tp = tp;
        tp = tp->next;
    }

    if (status == MS_SUCCESS)
        table->numitems--;

    return status;
}
      
const char *msFirstKeyFromHashTable( hashTableObj *table )
{
    int hash_index;
    
    if (!table) {
        msSetError(MS_HASHERR, "No hash table", "msFirstKeyFromHashTable");
        return NULL;
    }
    
    for (hash_index = 0; hash_index < MS_HASHSIZE; hash_index++ ) {
        if (table->items[hash_index] != NULL )
            return table->items[hash_index]->key;
    }

    return NULL;
}

const char *msNextKeyFromHashTable( hashTableObj *table, const char *lastKey )
{
    int hash_index;
    struct hashObj *link;

    if (!table) {
        msSetError(MS_HASHERR, "No hash table", "msNextKeyFromHashTable");
        return NULL;
    }
    
    if ( lastKey == NULL )
        return msFirstKeyFromHashTable( table );

    hash_index = hash(lastKey);
    for ( link = table->items[hash_index]; 
         link != NULL && strcasecmp(lastKey,link->key) != 0;
         link = link->next ) {}
    
    if ( link != NULL && link->next != NULL )
        return link->next->key;

    while ( ++hash_index < MS_HASHSIZE ) {
        if ( table->items[hash_index] != NULL )
            return table->items[hash_index]->key;
    }

    return NULL;
}