wshash.c

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/*
 *
 * wshash.c
 *
 * Author: Markku Rossi <mtr@iki.fi>
 *
 * Copyright (c) 1999-2000 WAPIT OY LTD.
 *       All rights reserved.
 *
 * A mapping from null-terminated strings to `void *' pointers.
 *
 */

#include "wsint.h"
#include "wshash.h"

/********************* Types and definitions ****************************/

/* The size of the hash table. */
#define WS_HASH_TABLE_SIZE  256

/* A hash item. */
struct WsHashItemRec
{
    struct WsHashItemRec *next;
    char *name;
    void *data;
};

typedef struct WsHashItemRec WsHashItem;

/* The hash object. */
struct WsHashRec
{
    WsHashItem *items[WS_HASH_TABLE_SIZE];
    WsHashItemDestructor destructor;
    void *destructor_context;
};

/********************* Prototypes for static functions ******************/

/* Hash function to count the hash value of string `string'.  */
static size_t count_hash(const char *string);

/********************* Global functions *********************************/

WsHashPtr ws_hash_create(WsHashItemDestructor destructor, void *context)
{
    WsHashPtr hash = ws_calloc(1, sizeof(*hash));

    if (hash) {
        hash->destructor = destructor;
        hash->destructor_context = context;
    }

    return hash;
}


void ws_hash_destroy(WsHashPtr hash)
{
    if (hash == NULL)
        return;

    ws_hash_clear(hash);
    ws_free(hash);
}


WsBool ws_hash_put(WsHashPtr hash, const char *name, void *data)
{
    WsHashItem *i;
    size_t h = count_hash(name);

    for (i = hash->items[h]; i; i = i->next) {
        if (strcmp(i->name, name) == 0) {
            /* Found it. */

            /* Destroy the old item */
            if (hash->destructor)
                (*hash->destructor)(i->data, hash->destructor_context);

            i->data = data;

            return WS_FALSE;
        }
    }

    /* Must create a new mapping. */
    i = ws_calloc(1, sizeof(*i));

    if (i == NULL)
        return WS_FALSE;

    i->name = ws_strdup(name);
    if (i->name == NULL) {
        ws_free(i);
        return WS_FALSE;
    }

    i->data = data;

    /* Link it to our hash. */
    i->next = hash->items[h];
    hash->items[h] = i;

    return WS_TRUE;
}


void *ws_hash_get(WsHashPtr hash, const char *name)
{
    WsHashItem *i;
    size_t h = count_hash(name);

    for (i = hash->items[h]; i; i = i->next)
        if (strcmp(i->name, name) == 0)
            return i->data;

    return NULL;
}


void ws_hash_clear(WsHashPtr hash)
{
    WsHashItem *i, *n;
    size_t j;

    for (j = 0; j < WS_HASH_TABLE_SIZE; j++) {
        for (i = hash->items[j]; i; i = n) {
            n = i->next;
            if (hash->destructor)
                (*hash->destructor)(i->data, hash->destructor_context);

            ws_free(i->name);
            ws_free(i);
        }
        hash->items[j] = NULL;
    }
}

/********************* Static functions *********************************/

static size_t count_hash(const char *string)
{
    size_t val = 0;
    int i;

    for (i = 0; string[i]; i++) {
        val <<= 3;
        val ^= string[i];
        val ^= (val & 0xff00) >> 5;
        val ^= (val & 0xff0000) >> 16;
    }

    return val % WS_HASH_TABLE_SIZE;
}