source: cpp/frams/util/hashtable.cpp @ 151

// This file is a part of the Framsticks GDK.
// Copyright (C) 2002-2014  Maciej Komosinski and Szymon Ulatowski.  See LICENSE.txt for details.
// Refer to http://www.framsticks.com/ for further information.

#include "hashtable.h"

int HashTable::hash(const char *s)
{
int h=0;
char c;
while(c=*(s++))
    h=31*h+c;
return h&0x7fffffff;
}

void HashTable::init(int initsize,float lo)
{
size=initsize;
load=lo;
threshold=(int)(load*(float)size);
tab=(HashEntry**)calloc(size,sizeof(HashEntry*));
count=0;
sync=0;
}

void HashTable::rehash(int newsize)
{
if (newsize==size) return;
HashEntry **newtab=(HashEntry**)calloc(newsize,sizeof(HashEntry*));
HashEntry **te=tab,*e,*ne;
int i;
for (int s=size;s>0;s--,te++)
    for (e=*te;e;)
        {
            ne=e; e=e->next;
            i=ne->hash%newsize;
            ne->next=newtab[i];
            newtab[i]=ne;
        }
free(tab);
tab=newtab;
size=newsize;
threshold=int(load*(float)size);
sync++;
}

void HashTable::clear()
{
HashEntry *e,**te,*next;
int n;
for (n=size,te=tab;n>0;n--,te++)
        for (e=*te;e;e=next)
                {
                next=e->next;
                delete e;
                }
if (tab) free(tab);
tab=0; size=0;
sync++;
}

HashTable::~HashTable()
{
clear();
}

void* HashTable::put(const SString& key,void *value)
{
int h=hash(key);
int i=h%size;
for (HashEntry *e=tab[i];e;e=e->next)
    {
    if (e->key==key)
        {
        void *v=e->value;
        e->value=value;
        return v;
        }
    }
if (count>=threshold) { rehash(2*size+1); i=h%size; }
HashEntry *e=new HashEntry(h,key,value);
e->next=tab[i];
tab[i]=e;
count++;
sync++;
return 0;
}

void* HashTable::remove(const SString& key)
{
int i=hash(key)%size;
HashEntry **ptr=tab+i,*e;
for (;e=*ptr;ptr=&e->next)
    {
    if (e->key==key)
        {
        *ptr=e->next;
        void *v=e->value;
        delete e;
        count--;
        sync++;
        return v;
        }
    }
return 0;
}

void* HashTable::remove(HashEntryIterator& it)
{
if (!it.entry) return 0;
HashEntry **ptr=tab+it.hashindex,*e;
for (;e=*ptr;ptr=&e->next)
    {
    if (e == it.entry)
        {
        it++;
        *ptr=e->next;
        void *v=e->value;
        delete e;
        count--;
        sync++;
        it.sync++;
        return v;
        }
    }
   return NULL; 
}

void* HashTable::get(const SString& key,int *reallygot)
{
int i=hash(key)%size;
for (HashEntry *e=tab[i];e;e=e->next)
        if (e->key==key) {if (reallygot) *reallygot=1; return e->value;}
return 0;
}

/////////

void HashEntryIterator::findNext()
{
while (hashindex < (ht->size-1))
        {
        hashindex++;
        if (entry=ht->tab[hashindex]) return;
        }
}


void HashEntryIterator::operator++()
{
if (entry) entry=entry->next;
if (!entry) findNext();
}

//////////////////////////

void HashTable::debugprint()
{
printf("HashTable: %d/%d (max %d)\n",count,size,threshold);
HashEntry *e,**te;
int n;
for (n=0,te=tab;n<size;n++,te++)
        if (e=*te)
        {
        printf(" %d:",n);
        for (;e;e=e->next)
                printf(" (%x)%s=%p",e->hash,(const char*)e->key,e->value);
        printf("\n");
        }
}

/**
stats[0]=buckets used
stats[1]=min keys in bucket
stats[2]=avg keys in bucket
stats[3]=max keys in bucket
 */
void HashTable::getstats(float *stats)
{
HashEntry *e,**te;
int used=0, ma=0, mi=count;
int c,n;
for (n=size,te=tab;n>0;n--,te++)
        {
        c=0;
        for (e=*te;e;e=e->next) c++;
        if (c>ma) ma=c;
        if ((c<mi)&&(c>0)) mi=c;
        if (c>0) used++;
        }
stats[0]=(float)used;
stats[1]=(float)((mi==count)?0:mi);
stats[2]=(float)count/(float)used;
stats[3]=(float)ma;
}