libvirt/src/hash.c

/*
 * hash.c: chained hash tables
 *
 * Reference: Your favorite introductory book on algorithms
 *
 * Copyright (C) 2000 Bjorn Reese and Daniel Veillard.
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
 * MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE AUTHORS AND
 * CONTRIBUTORS ACCEPT NO RESPONSIBILITY IN ANY CONCEIVABLE MANNER.
 *
 * Author: breese@users.sourceforge.net
 */

#define IN_LIBXML

#include <string.h>
#include "hash.h"

#define MAX_HASH_LEN 8

/* #define DEBUG_GROW */

/*
 * A single entry in the hash table
 */
typedef struct _virHashEntry virHashEntry;
typedef virHashEntry *virHashEntryPtr;
struct _virHashEntry {
    struct _virHashEntry *next;
    char *name;
    void *payload;
    int valid;
};

/*
 * The entire hash table
 */
struct _virHashTable {
    struct _virHashEntry *table;
    int size;
    int nbElems;
};

/*
 * virHashComputeKey:
 * Calculate the hash key
 */
static unsigned long
virHashComputeKey(virHashTablePtr table, const char *name) {
    unsigned long value = 0L;
    char ch;
    
    if (name != NULL) {
	value += 30 * (*name);
	while ((ch = *name++) != 0) {
	    value = value ^ ((value << 5) + (value >> 3) + (unsigned long)ch);
	}
    }
    return (value % table->size);
}

/**
 * virHashCreate:
 * @size: the size of the hash table
 *
 * Create a new virHashTablePtr.
 *
 * Returns the newly created object, or NULL if an error occured.
 */
virHashTablePtr
virHashCreate(int size) {
    virHashTablePtr table;
  
    if (size <= 0)
        size = 256;
  
    table = malloc(sizeof(virHashTable));
    if (table) {
        table->size = size;
	table->nbElems = 0;
        table->table = malloc(size * sizeof(virHashEntry));
        if (table->table) {
  	    memset(table->table, 0, size * sizeof(virHashEntry));
  	    return(table);
        }
        free(table);
    }
    return(NULL);
}

/**
 * virHashGrow:
 * @table: the hash table
 * @size: the new size of the hash table
 *
 * resize the hash table
 *
 * Returns 0 in case of success, -1 in case of failure
 */
static int
virHashGrow(virHashTablePtr table, int size) {
    unsigned long key;
    int oldsize, i;
    virHashEntryPtr iter, next;
    struct _virHashEntry *oldtable;
#ifdef DEBUG_GROW
    unsigned long nbElem = 0;
#endif
  
    if (table == NULL)
	return(-1);
    if (size < 8)
        return(-1);
    if (size > 8 * 2048)
	return(-1);

    oldsize = table->size;
    oldtable = table->table;
    if (oldtable == NULL)
        return(-1);
  
    table->table = malloc(size * sizeof(virHashEntry));
    if (table->table == NULL) {
	table->table = oldtable;
	return(-1);
    }
    memset(table->table, 0, size * sizeof(virHashEntry));
    table->size = size;

    /*	If the two loops are merged, there would be situations where
	a new entry needs to allocated and data copied into it from 
	the main table. So instead, we run through the array twice, first
	copying all the elements in the main array (where we can't get
	conflicts) and then the rest, so we only free (and don't allocate)
    */
    for (i = 0; i < oldsize; i++) {
	if (oldtable[i].valid == 0) 
	    continue;
	key = virHashComputeKey(table, oldtable[i].name);
	memcpy(&(table->table[key]), &(oldtable[i]), sizeof(virHashEntry));
	table->table[key].next = NULL;
    }

    for (i = 0; i < oldsize; i++) {
	iter = oldtable[i].next;
	while (iter) {
	    next = iter->next;

	    /*
	     * put back the entry in the new table
	     */

	    key = virHashComputeKey(table, iter->name);
	    if (table->table[key].valid == 0) {
		memcpy(&(table->table[key]), iter, sizeof(virHashEntry));
		table->table[key].next = NULL;
		free(iter);
	    } else {
	    	iter->next = table->table[key].next;
	    	table->table[key].next = iter;
	    }

#ifdef DEBUG_GROW
	    nbElem++;
#endif

	    iter = next;
	}
    }

    free(oldtable);

#ifdef DEBUG_GROW
    xmlGenericError(xmlGenericErrorContext,
	    "virHashGrow : from %d to %d, %d elems\n", oldsize, size, nbElem);
#endif

    return(0);
}

/**
 * virHashFree:
 * @table: the hash table
 * @f:  the deallocator function for items in the hash
 *
 * Free the hash @table and its contents. The userdata is
 * deallocated with @f if provided.
 */
void
virHashFree(virHashTablePtr table, virHashDeallocator f) {
    int i;
    virHashEntryPtr iter;
    virHashEntryPtr next;
    int inside_table = 0;
    int nbElems;

    if (table == NULL)
	return;
    if (table->table) {
	nbElems = table->nbElems;
	for(i = 0; (i < table->size) && (nbElems > 0); i++) {
	    iter = &(table->table[i]);
	    if (iter->valid == 0)
		continue;
	    inside_table = 1;
	    while (iter) {
		next = iter->next;
		if ((f != NULL) && (iter->payload != NULL))
		    f(iter->payload, iter->name);
		if (iter->name)
		    free(iter->name);
		iter->payload = NULL;
		if (!inside_table)
		    free(iter);
		nbElems--;
		inside_table = 0;
		iter = next;
	    }
	    inside_table = 0;
	}
	free(table->table);
    }
    free(table);
}

/**
 * virHashAddEntry3:
 * @table: the hash table
 * @name: the name of the userdata
 * @userdata: a pointer to the userdata
 *
 * Add the @userdata to the hash @table. This can later be retrieved
 * by using @name. Duplicate entries generate errors.
 *
 * Returns 0 the addition succeeded and -1 in case of error.
 */
int
virHashAddEntry(virHashTablePtr table, const char *name,
		 void *userdata) {
    unsigned long key, len = 0;
    virHashEntryPtr entry;
    virHashEntryPtr insert;

    if ((table == NULL) || (name == NULL))
	return(-1);

    /*
     * Check for duplicate and insertion location.
     */
    key = virHashComputeKey(table, name);
    if (table->table[key].valid == 0) {
	insert = NULL;
    } else {
	for (insert = &(table->table[key]); insert->next != NULL;
	     insert = insert->next) {
	    if (!strcmp(insert->name, name))
		return(-1);
	    len++;
	}
	if (!strcmp(insert->name, name))
	    return(-1);
    }

    if (insert == NULL) {
	entry = &(table->table[key]);
    } else {
	entry = malloc(sizeof(virHashEntry));
	if (entry == NULL)
	     return(-1);
    }

    entry->name = strdup(name);
    entry->payload = userdata;
    entry->next = NULL;
    entry->valid = 1;


    if (insert != NULL) 
	insert->next = entry;

    table->nbElems++;

    if (len > MAX_HASH_LEN)
	virHashGrow(table, MAX_HASH_LEN * table->size);

    return(0);
}

/**
 * virHashUpdateEntry:
 * @table: the hash table
 * @name: the name of the userdata
 * @userdata: a pointer to the userdata
 * @f: the deallocator function for replaced item (if any)
 *
 * Add the @userdata to the hash @table. This can later be retrieved
 * by using @name. Existing entry for this tuple
 * will be removed and freed with @f if found.
 *
 * Returns 0 the addition succeeded and -1 in case of error.
 */
int
virHashUpdateEntry(virHashTablePtr table, const char *name,
		   void *userdata, virHashDeallocator f) {
    unsigned long key;
    virHashEntryPtr entry;
    virHashEntryPtr insert;

    if ((table == NULL) || name == NULL)
	return(-1);

    /*
     * Check for duplicate and insertion location.
     */
    key = virHashComputeKey(table, name);
    if (table->table[key].valid == 0) {
	insert = NULL;
    } else {
	for (insert = &(table->table[key]); insert->next != NULL;
	     insert = insert->next) {
	    if (!strcmp(insert->name, name)) {
		if (f)
		    f(insert->payload, insert->name);
		insert->payload = userdata;
		return(0);
	    }
	}
	if (!strcmp(insert->name, name)) {
	    if (f)
		f(insert->payload, insert->name);
	    insert->payload = userdata;
	    return(0);
	}
    }

    if (insert == NULL) {
	entry =  &(table->table[key]);
    } else {
	entry = malloc(sizeof(virHashEntry));
	if (entry == NULL)
	     return(-1);
    }

    entry->name = strdup(name);
    entry->payload = userdata;
    entry->next = NULL;
    entry->valid = 1;
    table->nbElems++;


    if (insert != NULL) {
	insert->next = entry;
    }
    return(0);
}

/**
 * virHashLookup:
 * @table: the hash table
 * @name: the name of the userdata
 *
 * Find the userdata specified by the (@name, @name2, @name3) tuple.
 *
 * Returns the a pointer to the userdata
 */
void *
virHashLookup(virHashTablePtr table, const char *name) {
    unsigned long key;
    virHashEntryPtr entry;

    if (table == NULL)
	return(NULL);
    if (name == NULL)
	return(NULL);
    key = virHashComputeKey(table, name);
    if (table->table[key].valid == 0)
	return(NULL);
    for (entry = &(table->table[key]); entry != NULL; entry = entry->next) {
	if (!strcmp(entry->name, name))
	    return(entry->payload);
    }
    return(NULL);
}

/**
 * virHashSize:
 * @table: the hash table
 *
 * Query the number of elements installed in the hash @table.
 *
 * Returns the number of elements in the hash table or
 * -1 in case of error
 */
int
virHashSize(virHashTablePtr table) {
    if (table == NULL)
	return(-1);
    return(table->nbElems);
}

/**
 * virHashRemoveEntry:
 * @table: the hash table
 * @name: the name of the userdata
 * @f: the deallocator function for removed item (if any)
 *
 * Find the userdata specified by the @name and remove
 * it from the hash @table. Existing userdata for this tuple will be removed
 * and freed with @f.
 *
 * Returns 0 if the removal succeeded and -1 in case of error or not found.
 */
int
virHashRemoveEntry(virHashTablePtr table, const char *name,
                   virHashDeallocator f) {
    unsigned long key;
    virHashEntryPtr entry;
    virHashEntryPtr prev = NULL;

    if (table == NULL || name == NULL)
        return(-1);

    key = virHashComputeKey(table, name);
    if (table->table[key].valid == 0) {
        return(-1);
    } else {
        for (entry = &(table->table[key]); entry != NULL; entry = entry->next) {
            if (!strcmp(entry->name, name)) {
                if ((f != NULL) && (entry->payload != NULL))
                    f(entry->payload, entry->name);
                entry->payload = NULL;
		if(entry->name)
		    free(entry->name);
                if(prev) {
                    prev->next = entry->next;
		    free(entry);
		} else {
		    if (entry->next == NULL) {
			entry->valid = 0;
		    } else {
			entry = entry->next;
			memcpy(&(table->table[key]), entry, sizeof(virHashEntry));
			free(entry);
		    }
		}
                table->nbElems--;
                return(0);
            }
            prev = entry;
        }
        return(-1);
    }
}