/**
 * \file rpmdb/rpmhash.c
 * Hash table implemenation
 */

#include "system.h"
#include "rpmlib.h"
#include "rpmhash.h"
#include "debug.h"

typedef	struct hashBucket_s * hashBucket;

/**
 */
struct hashBucket_s {
    hashBucket next;		/*!< pointer to next item in bucket */
    void *key;			/*!< hash key */
    int dataCount;		/*!< data entries */
    void *data[1];		/*!< data - grows by resizing whole bucket */
};

/**
 */
struct hashTable_s {
    int numBuckets;			/*!< number of hash buckets */
    int freeData;	/*!< should data be freed when table is destroyed? */
    hashBucket * buckets;		/*!< hash bucket array */
    hashFunctionType fn;		/*!< generate hash value for key */
    hashEqualityType eq;		/*!< compare hash keys for equality */
};

/**
 * Find entry in hash table.
 * @param ht            pointer to hash table
 * @param key           pointer to key value
 * @return pointer to hash bucket of key (or NULL)
 */
static /*@shared@*/ /*@null@*/
hashBucket findEntry(hashTable ht, const void * key)
	/*@*/
{
    unsigned int hash;
    hashBucket b;

    /*@-modunconnomods@*/
    hash = ht->fn(key) % ht->numBuckets;
    b = ht->buckets[hash];

    while (b && b->key && ht->eq(b->key, key))
	b = b->next;
    /*@=modunconnomods@*/

    return b;
}

int hashEqualityString(const void * key1, const void * key2)
{
    const char *k1 = (const char *)key1;
    const char *k2 = (const char *)key2;
    return strcmp(k1, k2);
}

unsigned int hashFunctionString(const void * string)
{
    char xorValue = 0;
    char sum = 0;
    short len;
    int i;
    const char * chp = string;

    len = strlen(string);
    for (i = 0; i < len; i++, chp++) {
	xorValue ^= *chp;
	sum += *chp;
    }

    return ((((unsigned)len) << 16) + (((unsigned)sum) << 8) + xorValue);
}

hashTable htCreate(int numBuckets, int freeData,
		hashFunctionType fn, hashEqualityType eq)
{
    hashTable ht;

    ht = xmalloc(sizeof(*ht));
    ht->numBuckets = numBuckets;
    ht->buckets = xcalloc(numBuckets, sizeof(*ht->buckets));
    ht->freeData = freeData;
    /*@-assignexpose@*/
    ht->fn = fn;
    ht->eq = eq;
    /*@=assignexpose@*/

    return ht;
}

void htAddEntry(hashTable ht, const void * key, const void * data)
{
    unsigned int hash = ht->fn(key) % ht->numBuckets;
    hashBucket b = ht->buckets[hash];
    hashBucket *b_addr = ht->buckets + hash;

    while (b && b->key && ht->eq(b->key, key)) {
	b_addr = &(b->next);
	b = b->next;
    }

    if (b == NULL) {
	b = xmalloc(sizeof(*b));
	b->key = key;
	b->dataCount = 1;
	b->data[0] = data;
	b->next = ht->buckets[hash];
	ht->buckets[hash] = b;
    }
    else {
	// Bucket_s already contains space for one dataset
	b = *b_addr = xrealloc(b, sizeof(*b) + sizeof(b->data[0]) * b->dataCount);
	// though increasing dataCount after the resize
	b->data[b->dataCount++] = data;
    }
}

void htFree(hashTable ht)
{
    hashBucket b, n;
    int i, j;

    for (i = 0; i < ht->numBuckets; i++) {
	b = ht->buckets[i];
	if (b == NULL)
	    continue;
	ht->buckets[i] = NULL;
	do {
	    n = b->next;
	    /*@-branchstate@*/
	    if (ht->freeData)
		for (j = 0; j < b->dataCount; j++)
		    b->data[j] = _free(b->data[j]);
	    /*@=branchstate@*/
	    b = _free(b);
	} while ((b = n) != NULL);
    }

    ht->buckets = _free(ht->buckets);
    ht = _free(ht);
}

int htHasEntry(hashTable ht, const void * key)
{
    hashBucket b;

    if (!(b = findEntry(ht, key))) return 0; else return 1;
}

int htGetEntry(hashTable ht, const void * key, const void *** data,
	       int * dataCount, const void ** tableKey)
{
    hashBucket b;

    if ((b = findEntry(ht, key)) == NULL)
	return 1;

    if (data)
	*data = (const void **) b->data;
    if (dataCount)
	*dataCount = b->dataCount;
    if (tableKey)
	*tableKey = b->key;

    return 0;
}