openssl/crypto/lhash/lhash.c

/* crypto/lhash/lhash.c */
/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
 * All rights reserved.
 *
 * This package is an SSL implementation written
 * by Eric Young (eay@cryptsoft.com).
 * The implementation was written so as to conform with Netscapes SSL.
 * 
 * This library is free for commercial and non-commercial use as long as
 * the following conditions are aheared to.  The following conditions
 * apply to all code found in this distribution, be it the RC4, RSA,
 * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
 * included with this distribution is covered by the same copyright terms
 * except that the holder is Tim Hudson (tjh@cryptsoft.com).
 * 
 * Copyright remains Eric Young's, and as such any Copyright notices in
 * the code are not to be removed.
 * If this package is used in a product, Eric Young should be given attribution
 * as the author of the parts of the library used.
 * This can be in the form of a textual message at program startup or
 * in documentation (online or textual) provided with the package.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *    "This product includes cryptographic software written by
 *     Eric Young (eay@cryptsoft.com)"
 *    The word 'cryptographic' can be left out if the rouines from the library
 *    being used are not cryptographic related :-).
 * 4. If you include any Windows specific code (or a derivative thereof) from 
 *    the apps directory (application code) you must include an acknowledgement:
 *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
 * 
 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * 
 * The licence and distribution terms for any publically available version or
 * derivative of this code cannot be changed.  i.e. this code cannot simply be
 * copied and put under another distribution licence
 * [including the GNU Public Licence.]
 */

/* Code for dynamic hash table routines
 * Author - Eric Young v 2.0
 *
 * 2.2 eay - added #include "crypto.h" so the memory leak checking code is
 *	     present. eay 18-Jun-98
 *
 * 2.1 eay - Added an 'error in last operation' flag. eay 6-May-98
 *
 * 2.0 eay - Fixed a bug that occurred when using lh_delete
 *	     from inside lh_doall().  As entries were deleted,
 *	     the 'table' was 'contract()ed', making some entries
 *	     jump from the end of the table to the start, there by
 *	     skipping the lh_doall() processing. eay - 4/12/95
 *
 * 1.9 eay - Fixed a memory leak in lh_free, the LHASH_NODEs
 *	     were not being free()ed. 21/11/95
 *
 * 1.8 eay - Put the stats routines into a separate file, lh_stats.c
 *	     19/09/95
 *
 * 1.7 eay - Removed the fputs() for realloc failures - the code
 *           should silently tolerate them.  I have also fixed things
 *           lint complained about 04/05/95
 *
 * 1.6 eay - Fixed an invalid pointers in contract/expand 27/07/92
 *
 * 1.5 eay - Fixed a misuse of realloc in expand 02/03/1992
 *
 * 1.4 eay - Fixed lh_doall so the function can call lh_delete 28/05/91
 *
 * 1.3 eay - Fixed a few lint problems 19/3/1991
 *
 * 1.2 eay - Fixed lh_doall problem 13/3/1991
 *
 * 1.1 eay - Added lh_doall
 *
 * 1.0 eay - First version
 */
#include <limits.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <openssl/crypto.h>
#include <openssl/lhash.h>

const char lh_version[]="lhash" OPENSSL_VERSION_PTEXT;

#undef MIN_NODES 
#define MIN_NODES	16
#define UP_LOAD		(2*LH_LOAD_MULT) /* load times 256  (default 2) */
#define DOWN_LOAD	(LH_LOAD_MULT)   /* load times 256  (default 1) */

/* Maximum number of nodes to guarantee the load computations don't overflow */
#define MAX_LOAD_ITEMS   (UINT_MAX / LH_LOAD_MULT)

/* The field 'iteration_state' is used to hold data to ensure that a hash
 * table is not resized during an 'insert' or 'delete' operation performed
 * within a lh_doall/lh_doall_arg call.
 *
 * Conceptually, this records two things:
 *
 *   - A 'depth' count, which is incremented at the start of lh_doall*,
 *     and decremented just before it returns.
 *
 *   - A 'mutated' boolean flag, which is set in lh_insert() or lh_delete()
 *     when the operation is performed with a non-0 depth.
 *
 * The following are helper macros to handle this state in a more explicit
 * way.
 */

/* Reset the iteration state to its defaults. */
#define LH_ITERATION_RESET(lh) do { \
	(lh)->iteration_state = 0; \
	} while (0)

/* Returns 1 if the hash table is currently being iterated on, 0 otherwise. */
#define LH_ITERATION_IS_ACTIVE(lh)  ((lh)->iteration_state >= 2)

/* Increment iteration depth. This should always be followed by a paired call
 * to LH_ITERATION_DECREMENT_DEPTH(). */
#define LH_ITERATION_INCREMENT_DEPTH(lh) do { \
	(lh)->iteration_state += 2; \
	} while (0)

/* Decrement iteration depth. This should always be called after a paired call
 * to LH_ITERATION_INCREMENT_DEPTH(). */
#define LH_ITERATION_DECREMENT_DEPTH(lh) do { \
	(lh)->iteration_state -= 2; \
	} while (0)

/* Return 1 if the iteration 'mutated' flag is set, 0 otherwise. */
#define LH_ITERATION_IS_MUTATED(lh) (((lh)->iteration_state & 1) != 0)

/* Set the iteration 'mutated' flag to 1. LH_ITERATION_RESET() to reset it. */
#define LH_ITERATION_SET_MUTATED(lh) do { \
	(lh)->iteration_state |= 1; \
	} while (0)

/* This macro returns 1 if the hash table should be expanded due to its current
 * load, or 0 otherwise. The exact comparison to be performed is expressed by
 * the mathematical expression (where '//' denotes division over real numbers):
 *
 *      (num_items // num_nodes) >= (up_load // LOAD_MULT)    or
 *      (num_items * LOAD_MULT // num_nodes) >= up_load.
 *
 * Given that the C language operator '/' implements integer division, i.e:
 *     a // b == (a / b) + epsilon  (with 0 <= epsilon < 1, for positive a & b)
 *
 * This can be rewritten as:
 *     (num_items * LOAD_MULT / num_nodes) + epsilon >= up_load
 *     (num_items * LOAD_MULT / num_nodes) - up_load >= - epsilon
 *
 * Let's call 'A' the left-hand side of the equation above, it is an integer
 * and:
 *     - If A >= 0, the expression is true for any value of epsilon.
 *     - If A <= -1, the expression is also true for any value of epsilon.
 *
 * In other words, this is equivalent to 'A >= 0', or:
 *     (num_items * LOAD_MULT / num_nodes) >= up_load
 */
#define LH_SHOULD_EXPAND(lh) \
	((lh)->num_items < MAX_LOAD_ITEMS && \
	 (((lh)->num_items*LH_LOAD_MULT/(lh)->num_nodes) >= (lh)->up_load))

/* This macro returns 1 if the hash table should be contracted due to its
 * current load, or 0 otherwise. Abbreviated computations are:
 *
 *    (num_items // num_nodes) <= (down_load // LOAD_MULT)
 *    (num_items * LOAD_MULT // num_nodes) <= down_load
 *    (num_items * LOAD_MULT / num_nodes) + epsilon <= down_load
 *    (num_items * LOAD_MULT / num_nodes) - down_load <= -epsilon
 *
 * Let's call 'B' the left-hand side of the equation above:
 *    - If B <= -1, the expression is true for any value of epsilon.
 *    - If B >= 1, the expression is false for any value of epsilon.
 *    - If B == 0, the expression is true for 'epsilon == 0', and false
 *      otherwise, which is problematic.
 *
 * To work around this problem, while keeping the code simple, just change
 * the initial expression to use a strict inequality, i.e.:
 *
 *    (num_items // num_nodes) < (down_load // LOAD_MULT)
 *
 * Which leads to:
 *    (num_items * LOAD_MULT / num_nodes) - down_load < -epsilon
 *
 * Then:
 *    - If 'B <= -1', the expression is true for any value of epsilon.
 *    - If 'B' >= 0, the expression is false for any value of epsilon,
 *
 * In other words, this is equivalent to 'B < 0', or:
 *     (num_items * LOAD_MULT / num_nodes) < down_load
 */
#define LH_SHOULD_CONTRACT(lh) \
	(((lh)->num_nodes > MIN_NODES) && \
	 ((lh)->num_items < MAX_LOAD_ITEMS && \
	 ((lh)->num_items*LH_LOAD_MULT/(lh)->num_nodes) < (lh)->down_load))

static void expand(_LHASH *lh);
static void contract(_LHASH *lh);
static LHASH_NODE **getrn(_LHASH *lh, const void *data, unsigned long *rhash);

_LHASH *lh_new(LHASH_HASH_FN_TYPE h, LHASH_COMP_FN_TYPE c)
	{
	_LHASH *ret;
	int i;

	if ((ret=OPENSSL_malloc(sizeof(_LHASH))) == NULL)
		goto err0;
	if ((ret->b=OPENSSL_malloc(sizeof(LHASH_NODE *)*MIN_NODES)) == NULL)
		goto err1;
	for (i=0; i<MIN_NODES; i++)
		ret->b[i]=NULL;
	ret->comp=((c == NULL)?(LHASH_COMP_FN_TYPE)strcmp:c);
	ret->hash=((h == NULL)?(LHASH_HASH_FN_TYPE)lh_strhash:h);
	ret->num_nodes=MIN_NODES/2;
	ret->num_alloc_nodes=MIN_NODES;
	ret->p=0;
	ret->pmax=MIN_NODES/2;
	ret->up_load=UP_LOAD;
	ret->down_load=DOWN_LOAD;
	ret->num_items=0;

	ret->num_expands=0;
	ret->num_expand_reallocs=0;
	ret->num_contracts=0;
	ret->num_contract_reallocs=0;
	ret->num_hash_calls=0;
	ret->num_comp_calls=0;
	ret->num_insert=0;
	ret->num_replace=0;
	ret->num_delete=0;
	ret->num_no_delete=0;
	ret->num_retrieve=0;
	ret->num_retrieve_miss=0;
	ret->num_hash_comps=0;

	ret->error=0;
	LH_ITERATION_RESET(ret);
	return(ret);
err1:
	OPENSSL_free(ret);
err0:
	return(NULL);
	}

void lh_free(_LHASH *lh)
	{
	unsigned int i;
	LHASH_NODE *n,*nn;

	if (lh == NULL)
	    return;

	for (i=0; i<lh->num_nodes; i++)
		{
		n=lh->b[i];
		while (n != NULL)
			{
			nn=n->next;
			OPENSSL_free(n);
			n=nn;
			}
		}
	OPENSSL_free(lh->b);
	OPENSSL_free(lh);
	}

void *lh_insert(_LHASH *lh, void *data)
	{
	unsigned long hash;
	LHASH_NODE *nn,**rn;
	void *ret;

	lh->error=0;
	/* Do not expand the array if the table is being iterated on. */
	if (LH_ITERATION_IS_ACTIVE(lh))
		LH_ITERATION_SET_MUTATED(lh);
	else if (LH_SHOULD_EXPAND(lh))
		expand(lh);

	rn=getrn(lh,data,&hash);

	if (*rn == NULL)
		{
		if ((nn=(LHASH_NODE *)OPENSSL_malloc(sizeof(LHASH_NODE))) == NULL)
			{
			lh->error++;
			return(NULL);
			}
		nn->data=data;
		nn->next=NULL;
#ifndef OPENSSL_NO_HASH_COMP
		nn->hash=hash;
#endif
		*rn=nn;
		ret=NULL;
		lh->num_insert++;
		lh->num_items++;
		}
	else /* replace same key */
		{
		ret= (*rn)->data;
		(*rn)->data=data;
		lh->num_replace++;
		}
	return(ret);
	}

void *lh_delete(_LHASH *lh, const void *data)
	{
	unsigned long hash;
	LHASH_NODE *nn,**rn;
	void *ret;

	lh->error=0;
	rn=getrn(lh,data,&hash);

	if (*rn == NULL)
		{
		lh->num_no_delete++;
		return(NULL);
		}
	else
		{
		nn= *rn;
		*rn=nn->next;
		ret=nn->data;
		OPENSSL_free(nn);
		lh->num_delete++;
		}

	lh->num_items--;
	/* Do not contract the array if the table is being iterated on. */
	if (LH_ITERATION_IS_ACTIVE(lh))
		LH_ITERATION_SET_MUTATED(lh);
	else if (LH_SHOULD_CONTRACT(lh))
		contract(lh);

	return(ret);
	}

void *lh_retrieve(_LHASH *lh, const void *data)
	{
	unsigned long hash;
	LHASH_NODE **rn;
	void *ret;

	lh->error=0;
	rn=getrn(lh,data,&hash);

	if (*rn == NULL)
		{
		lh->num_retrieve_miss++;
		return(NULL);
		}
	else
		{
		ret= (*rn)->data;
		lh->num_retrieve++;
		}
	return(ret);
	}

static void doall_util_fn(_LHASH *lh, int use_arg, LHASH_DOALL_FN_TYPE func,
			  LHASH_DOALL_ARG_FN_TYPE func_arg, void *arg)
	{
	int i;
	LHASH_NODE *a,*n;

	if (lh == NULL)
		return;

	LH_ITERATION_INCREMENT_DEPTH(lh);
	/* reverse the order so we search from 'top to bottom'
	 * We were having memory leaks otherwise */
	for (i=lh->num_nodes-1; i>=0; i--)
		{
		a=lh->b[i];
		while (a != NULL)
			{
			/* note that 'a' can be deleted by the callback */
			n=a->next;
			if(use_arg)
				func_arg(a->data,arg);
			else
				func(a->data);
			a=n;
			}
		}

	LH_ITERATION_DECREMENT_DEPTH(lh);
	if (!LH_ITERATION_IS_ACTIVE(lh) && LH_ITERATION_IS_MUTATED(lh))
		{
		LH_ITERATION_RESET(lh);
		/* Resize the buckets array if necessary. Each expand() or
		 * contract() call will double/halve the size of the array,
		 * respectively, so call them in a loop. */
		while (LH_SHOULD_EXPAND(lh))
			expand(lh);
		while (LH_SHOULD_CONTRACT(lh))
			contract(lh);
		}
	}

void lh_doall(_LHASH *lh, LHASH_DOALL_FN_TYPE func)
	{
	doall_util_fn(lh, 0, func, (LHASH_DOALL_ARG_FN_TYPE)0, NULL);
	}

void lh_doall_arg(_LHASH *lh, LHASH_DOALL_ARG_FN_TYPE func, void *arg)
	{
	doall_util_fn(lh, 1, (LHASH_DOALL_FN_TYPE)0, func, arg);
	}

static void expand(_LHASH *lh)
	{
	LHASH_NODE **n,**n1,**n2,*np;
	unsigned int p,i,j;
	unsigned long hash,nni;

	lh->num_nodes++;
	lh->num_expands++;
	p=(int)lh->p++;
	n1= &(lh->b[p]);
	n2= &(lh->b[p+(int)lh->pmax]);
	*n2=NULL;        /* 27/07/92 - eay - undefined pointer bug */
	nni=lh->num_alloc_nodes;
	
	for (np= *n1; np != NULL; )
		{
#ifndef OPENSSL_NO_HASH_COMP
		hash=np->hash;
#else
		hash=lh->hash(np->data);
		lh->num_hash_calls++;
#endif
		if ((hash%nni) != p)
			{ /* move it */
			*n1= (*n1)->next;
			np->next= *n2;
			*n2=np;
			}
		else
			n1= &((*n1)->next);
		np= *n1;
		}

	if ((lh->p) >= lh->pmax)
		{
		j=(int)lh->num_alloc_nodes*2;
		n=(LHASH_NODE **)OPENSSL_realloc(lh->b,
			(int)(sizeof(LHASH_NODE *)*j));
		if (n == NULL)
			{
/*			fputs("realloc error in lhash",stderr); */
			lh->error++;
			lh->p=0;
			return;
			}
		/* else */
		for (i=(int)lh->num_alloc_nodes; i<j; i++)/* 26/02/92 eay */
			n[i]=NULL;			  /* 02/03/92 eay */
		lh->pmax=lh->num_alloc_nodes;
		lh->num_alloc_nodes=j;
		lh->num_expand_reallocs++;
		lh->p=0;
		lh->b=n;
		}
	}

static void contract(_LHASH *lh)
	{
	LHASH_NODE **n,*n1,*np;

	np=lh->b[lh->p+lh->pmax-1];
	lh->b[lh->p+lh->pmax-1]=NULL; /* 24/07-92 - eay - weird but :-( */
	if (lh->p == 0)
		{
		n=(LHASH_NODE **)OPENSSL_realloc(lh->b,
			(unsigned int)(sizeof(LHASH_NODE *)*lh->pmax));
		if (n == NULL)
			{
/*			fputs("realloc error in lhash",stderr); */
			lh->error++;
			return;
			}
		lh->num_contract_reallocs++;
		lh->num_alloc_nodes/=2;
		lh->pmax/=2;
		lh->p=lh->pmax-1;
		lh->b=n;
		}
	else
		lh->p--;

	lh->num_nodes--;
	lh->num_contracts++;

	n1=lh->b[(int)lh->p];
	if (n1 == NULL)
		lh->b[(int)lh->p]=np;
	else
		{
		while (n1->next != NULL)
			n1=n1->next;
		n1->next=np;
		}
	}

static LHASH_NODE **getrn(_LHASH *lh, const void *data, unsigned long *rhash)
	{
	LHASH_NODE **ret,*n1;
	unsigned long hash,nn;
	LHASH_COMP_FN_TYPE cf;

	hash=(*(lh->hash))(data);
	lh->num_hash_calls++;
	*rhash=hash;

	nn=hash%lh->pmax;
	if (nn < lh->p)
		nn=hash%lh->num_alloc_nodes;

	cf=lh->comp;
	ret= &(lh->b[(int)nn]);
	for (n1= *ret; n1 != NULL; n1=n1->next)
		{
#ifndef OPENSSL_NO_HASH_COMP
		lh->num_hash_comps++;
		if (n1->hash != hash)
			{
			ret= &(n1->next);
			continue;
			}
#endif
		lh->num_comp_calls++;
		if(cf(n1->data,data) == 0)
			break;
		ret= &(n1->next);
		}
	return(ret);
	}

/* The following hash seems to work very well on normal text strings
 * no collisions on /usr/dict/words and it distributes on %2^n quite
 * well, not as good as MD5, but still good.
 */
unsigned long lh_strhash(const char *c)
	{
	unsigned long ret=0;
	long n;
	unsigned long v;
	int r;

	if ((c == NULL) || (*c == '\0'))
		return(ret);
/*
	unsigned char b[16];
	MD5(c,strlen(c),b);
	return(b[0]|(b[1]<<8)|(b[2]<<16)|(b[3]<<24)); 
*/

	n=0x100;
	while (*c)
		{
		v=n|(*c);
		n+=0x100;
		r= (int)((v>>2)^v)&0x0f;
		ret=(ret<<r)|(ret>>(32-r));
		ret&=0xFFFFFFFFL;
		ret^=v*v;
		c++;
		}
	return((ret>>16)^ret);
	}

unsigned long lh_num_items(const _LHASH *lh)
	{
	return lh ? lh->num_items : 0;
	}