hashtable.cpp

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/*
Copyright (C) 2002-2023 UFO: Alien Invasion.

This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.

*/

#include "hashtable.h"

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

#include "common.h"
#include "mem.h"

/*
    The memory structure being build by the hash table looks like this:

    T = hashTable_s
    B = hashBucket_s
    I = hashItem_s
    0 = NULL

    [T]
      ...
      [0]
      [B]
        [I]->[0]
      [B]
        [I]->[0]
      [0]
      ...
      [B]
        [I]->[I]->[I]->[0]
      [0]
      ...
*/

// the hash table index size */
#define HASH_TABLE_SIZE 256

// forward declarations
struct hashBucket_s;

struct hashItem_s {
    void* key;
    int nkey;
    void* value;
    int nvalue;
    hashItem_s* next;
    hashBucket_s* root;
};

struct hashBucket_s {
    int count;
    hashItem_s* root;
};

struct hashTable_s {
    hashBucket_s* table[HASH_TABLE_SIZE];
    hashTable_hash hash;
    hashTable_compare compare;
    bool ownsKeys;
    bool ownsValues;
    bool duplicateOverwrite;
    memPool_t* keyPool;
    memPool_t* valuePool;
    memPool_t* internalPool;
};

#ifdef __DEBUG__
static unsigned long _num_allocs = 0u;
#endif // __DEBUG__

static void* _hash_alloc (memPool_t* pool, int n, size_t s) {
    #ifdef __DEBUG__
    _num_allocs++;
    #endif // __DEBUG__
    if (pool) return Mem_PoolAlloc (n * s, pool, 0);
    return Mem_Alloc(n * s);
}

static void _hash_free (void* p) {
    #ifdef __DEBUG__
    _num_allocs--;
    #endif // __DEBUG__
    Mem_Free(p);
}

static HASH_INDEX default_hash(const void* key, int len) {
    const unsigned char* p = (const unsigned char*) key;
    unsigned int h = 2166136261u;
    int i;

    for (i = 0; i < len; i++) {
        h = (h*16777619u) ^ p[i];
    }

    return (h % HASH_TABLE_SIZE);
}

static int default_compare(const void* key1, int len1, const void* key2, int len2) {
    int n = (len1 < len2) ? len1 : len2;
    return memcmp(key1, key2, n);
}

static hashItem_s* _find_bucket_entry (hashBucket_s* b, hashTable_compare c, const void* key, int nkey, hashItem_s** prev) {
    hashItem_s* p = NULL; // points to preceding item in linked list or NULL if there is none
    hashItem_s* i = b->root; // points to current item in linked list
    while (i) {
        if (c(key, nkey, i->key, i->nkey) == 0) {
                // return preceding item only if reference for this value is supplied
                if (prev) (*prev) = p;
                return i;
        }
        p = i;
        i = i->next;
    }
    if (prev) (*prev) = NULL;
    return NULL;
}

static void _release_entry (hashItem_s** i, bool ownsKeys, bool ownsValues) {
    if (ownsKeys) _hash_free ((*i)->key);
    if (ownsValues) _hash_free ((*i)->value);
    _hash_free (*i);
    (*i)=NULL;
}

static void _release_bucket (hashBucket_s** b, bool ownsKeys, bool ownsValues) {
    // delete entries
    hashItem_s* i = (*b)->root;
    while (i) {
        hashItem_s* p=i;
        i = i->next;
        _release_entry(&p, ownsKeys, ownsValues);
    }
    (*b)->root = NULL;
    // delete the bucket
    _hash_free (*b);
    (*b) = NULL;
}

static void _release_table (hashTable_s** t, bool full) {
    // delete buckets
    for (int i=0; i<HASH_TABLE_SIZE; i++) {
        if ((*t)->table[i]) _release_bucket(&((*t)->table[i]), (*t)->ownsKeys, (*t)->ownsValues);
    }
    if (full) {
        // delete table
        _hash_free ((*t));
        (*t) = NULL;
    }
}
static hashItem_s* _iterator_first (hashTable_s* t) {
    if (t) {
        for (int ti = 0; ti < HASH_TABLE_SIZE; ti++) {
            if (t->table[ti]) return t->table[ti]->root;
        }
    }
    return nullptr;
}

static hashItem_s* _iterator_next (hashTable_s* t, hashItem_s* i) {
    if (i) {
        if (i->next) {
            return i->next;
        }
        // compute the hash key of the last item iterated
        int h = t->hash(i->key, i->nkey);
        // now get the next filled bucket in the array
        h++;
        while (h < HASH_TABLE_SIZE) {
            hashBucket_s* b = (t->table)[h];
            if (b) {
                return b->root;
            }
            h++;
        }
    }
    return nullptr;
}

hashTable_s* HASH_NewTable (bool ownsKeys, bool ownsValues, bool duplicateOverwrite) {
    return HASH_NewTable (ownsKeys, ownsValues, duplicateOverwrite, &default_hash, &default_compare);
}


hashTable_s* HASH_NewTable (bool ownsKeys, bool ownsValues, bool duplicateOverwrite, hashTable_hash h, hashTable_compare c) {
    return HASH_NewTable(ownsKeys, ownsValues, duplicateOverwrite, h, c, nullptr, nullptr, nullptr);
}

hashTable_s* HASH_NewTable (bool ownsKeys, bool ownsValues, bool duplicateOverwrite, hashTable_hash h, hashTable_compare c, memPool_t* keys, memPool_t* values, memPool_t* table) {
    // allocate table
    hashTable_s* t = (hashTable_s*) _hash_alloc (table, 1, sizeof(hashTable_s));
    t->hash = h;
    t->compare = c;
    t->ownsKeys = ownsKeys;
    t->ownsValues = ownsValues;
    t->duplicateOverwrite = duplicateOverwrite;
    t->keyPool = keys;
    t->valuePool = values;
    t->internalPool = table;
    return t;
}

hashTable_s* HASH_CloneTable (hashTable_s* source) {
    hashTable_s* t = HASH_NewTable(source->ownsKeys, source->ownsValues, source->duplicateOverwrite, source->hash, source->compare);

    hashItem_s* item = _iterator_first (source);
    while (item) {
        HASH_Insert (t, item->key, item->nkey, item->value, item->nvalue);
        item = _iterator_next (source, item);
    }
    return t;
}

void HASH_DeleteTable (hashTable_s** t) {
    _release_table (t, true);
}

bool HASH_Insert (hashTable_s* t, const void* key, int nkey, const void* value, int nvalue) {
    // compute hash index
    int idx=t->hash(key, nkey);
    // find the bucket, if no bucket available create a new one
    hashBucket_s* b = t->table[idx];
    if (b == NULL) {
        t->table[idx] = b = (hashBucket_s*)_hash_alloc (t->internalPool, 1, sizeof(hashBucket_s));
    }
    // find entry
    hashItem_s* i = _find_bucket_entry(b, t->compare, key, nkey, NULL);
    if (i) {
        // entry already found, so we are overwriting the current value here
        // check table settings to see if we need to assert here
        if (!t->duplicateOverwrite) {
            assert(false);
            return false;
        }
        // if the table owns the items, create a copy
        if (t->ownsValues) {
            i->value = _hash_alloc (t->valuePool, 1, nvalue);
            memcpy (i->value, value, nvalue);
        }
        else {
            i->value = const_cast<void*>(value);
        }
        i->nvalue = nvalue;
    }
    else {
        // create a new entry, add it to the top of the list
        i = (hashItem_s*) _hash_alloc (t->internalPool, 1, sizeof(hashItem_s));
        if (t->ownsKeys) {
            i->key = _hash_alloc (t->keyPool, 1, nkey);
            memcpy (i->key, key, nkey);
        }
        else {
            i->key = const_cast<void*>(key);
        }
        i->nkey = nkey;
        if (t->ownsValues) {
            i->value = _hash_alloc (t->valuePool, 1, nvalue);
            memcpy (i->value, value, nvalue);
        }
        else {
            i->value = const_cast<void*>(value);
        }
        i->nvalue = nvalue;

        i->next = b->root;
        b->root = i;
    }
    // increase the count of the bucket
    b->count++;

    return true;
}

void* HASH_Remove (hashTable_s* t, const void* key, int nkey) {
    // return value
    void* v = NULL;
    // compute index
    int idx = t->hash (key, nkey);
    if (t->table[idx]) {
        // find hash entry
        hashItem_s* prev;
        hashItem_s* i=_find_bucket_entry (t->table[idx], t->compare, key, nkey, &prev);
        if (i) {
            if (!t->ownsValues) v = i->value;
            // link prev item with next item (effectively unchaining i from the linked list)
            if (prev) {
                prev->next = i->next;
                _release_entry (&i, t->ownsKeys, t->ownsValues);
            }
            else {
                // special case: the entry found was the root entry
                t->table[idx]->root = i->next;
                _release_entry (&i, t->ownsKeys, t->ownsValues);
            }
            // drop the count in this bucket by one
            t->table[idx]->count--;
        }
    }
    return v;
}

void HASH_Clear (hashTable_s* t) {
    _release_table (&t, false);
}

void* HASH_Get (hashTable_s* t, const void* key, int nkey) {
    // compute bucket index
    int idx = t->hash(key, nkey);
    if (t->table[idx]) {
        // from this bucket, scan for exact match
        hashItem_s* i = _find_bucket_entry(t->table[idx], t->compare, key, nkey, NULL);
        if (i) return i->value;
    }
    return NULL;
}

int HASH_Count (hashTable_s* t) {
    // iteratie the table
    int cnt=0;
    for (int i=0; i<HASH_TABLE_SIZE;i++) {
        if (t->table[i]) cnt += (t->table[i]->count);
    }
    return cnt;
}

#ifdef __DEBUG__

#include <time.h>
#include <stdlib.h>
#include <stdio.h>

bool HASH_test () {
    // return value
    bool result = true;

    /* test 1: create the hash table, delete the hash table */
    hashTable_s* table = HASH_NewTable(true, true, true);
    HASH_DeleteTable (&table);
    /* check table pointer is correctly set to nil */
    result = result && (table == NULL);
    if (!result) return false;
    /* check alloc total */
    result = result && (_num_allocs == 0);
    if (!result) return false;

    /* test 2: create the hash table, insert 3 values, delete the hash table */
    table = HASH_NewTable(true, true, true);
    HASH_Insert (table, "AAA", 4, "AAA", 4);
    HASH_Insert (table, "BBB", 4, "BBB", 4);
    HASH_Insert (table, "CCC", 4, "CCC", 4);
    if (HASH_Count(table) != 3) return false;
    HASH_Clear (table);
    if (HASH_Count(table) != 0) return false;
    HASH_DeleteTable (&table);
    /* check table pointer is correctly set to nil */
    result = result && (table == NULL);
    if (!result) return false;
    /* check alloc total */
    result = result && (_num_allocs == 0);
    if (!result) return false;

    /* test 3: create the hash table, insert/remove 3 values, delete the hash table */
    table = HASH_NewTable(true, true, true);
    HASH_Insert (table, "AAA", 4, "AAA", 4);
    HASH_Remove (table, "AAA", 4);
    HASH_Insert (table, "BBB", 4, "BBB", 4);
    HASH_Remove (table, "BBB", 4);
    HASH_Insert (table, "CCC", 4, "CCC", 4);
    HASH_Remove (table, "CCC", 4);
    HASH_DeleteTable (&table);
    /* check table pointer is correctly set to nil */
    result = result && (table == NULL);
    if (!result) return false;
    /* check alloc total */
    result = result && (_num_allocs == 0);
    if (!result) return false;

    /* test 4: create the hash table, insert/count/search/delete 3 values, delete the hash table */
    table = HASH_NewTable(true, true, true);
    HASH_Insert (table, "AAA", 4, "AAA", 4);
    HASH_Insert (table, "BBB", 4, "BBB", 4);
    HASH_Insert (table, "CCC", 4, "CCC", 4);
    /* check count items */
    if (HASH_Count(table) != 3) return false;
    char* aaa = (char*)HASH_Get(table, "AAA", 4);
    if (strncmp (aaa, "AAA", 4) != 0) return false;
    char* bbb = (char*)HASH_Get(table, "BBB", 4);
    if (strncmp (bbb, "BBB", 4) != 0) return false;
    char* ccc = (char*)HASH_Get(table, "CCC", 4);
    if (strncmp (ccc, "CCC", 4) != 0) return false;
    HASH_Remove (table, "AAA", 4);
    HASH_Remove (table, "BBB", 4);
    HASH_Remove (table, "CCC", 4);
    if (HASH_Count(table) != 0) return false;
    HASH_DeleteTable (&table);
    /* check table pointer is correctly set to nil */
    result = result && (table == NULL);
    if (!result) return false;
    /* check alloc total */
    result = result && (_num_allocs == 0);
    if (!result) return false;

    /* test 5: hash function test */
    const char AZ[] = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
    char buffer[26];
    /* compute the averag of the hash index of 400 random keys */
    int total = 0;
    srand(time(NULL));
    for(int i=0; i < 4000; i++) {
        /* create random key of random length between 4..23 charachters */
        int len = 4 + (rand() % 20);
        memset (buffer, 0, sizeof(buffer));
        for (int j=0; j < len; j++) {
            int v = rand() % sizeof(AZ);
            buffer[j]=AZ[v];
        }
        /* compute the hash index */
        int idx = default_hash (buffer, len);
        /* sum index */
        total += idx;
    }
    /* now compute the average of the indices */
    int avg = (total / 4000);
    /* the average idx should be somewhere halfway, allow a %10 error margin */
    int idx_low = (HASH_TABLE_SIZE/2) - (HASH_TABLE_SIZE/10);
    int idx_high = (HASH_TABLE_SIZE/2) + (HASH_TABLE_SIZE/10);
    if ( !((idx_low <= avg) && (idx_high >= avg)) ) return false;

    /* test 6: hash table without ownership test */
    table = HASH_NewTable(true, false, true);
    char item1[] = "AAA";
    char item2[] = "BBB";
    char item3[] = "CCC";
    HASH_Insert (table, item1, 4, item1, 4);
    HASH_Insert (table, item2, 4, item2, 4);
    HASH_Insert (table, item3, 4, item3, 4);
    /* check if we get the correct value pointers */
    aaa = (char*)HASH_Get(table, "AAA", 4);
    if (aaa != item1) return false;
    bbb = (char*)HASH_Get(table, "BBB", 4);
    if (bbb != item2) return false;
    ccc = (char*)HASH_Get(table, "CCC", 4);
    if (ccc != item3) return false;
    HASH_DeleteTable (&table);
    /* check table pointer is correctly set to nil */
    result = result && (table == NULL);
    if (!result) return false;
    /* check alloc total */
    result = result && (_num_allocs == 0);
    if (!result) return false;


    /* end of unit test, everything OK */
    return true;
}

#endif // __DEBUG__