ossp-pkg/act/act_hash_lh.c
1.6
/*
** Act - Abstract Container Type Library
** Copyright (c) 1999-2000 Ralf S. Engelschall <rse@engelschall.com>
**
** This file is part of Act, a library for dealing with Abstract
** Container Types which can be found at http://www.ossp.org/pkg/act/.
**
** 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 ANY EXPRESSED 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 AUTHORS AND COPYRIGHT HOLDERS AND THEIR
** 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.
**
** act_hash_lh.c: Linear Hashing (dynamic)
*/
/*
** This module implements a Dynamic Hash Table, based on WITOLD LITWIN
** and PER-AKE LARSON's ``Linear Hashing'' algorithm (1980/1988),
** implemented on top of a two-level virtual array with separate
** collision chains as the backend data structure. Some ideas were
** taken over from MIKAEL PETTERSON's Linear Hashing enhancements
** (1993).
**
** The internal structure of the linear hashing table is illustrated in
** the following figure:
**
** -----BEGIN EMBEDDED OBJECT-----
** Content-type: application/fig
** Description: linear hashing structure layout
** Version: eo/1.0
** H4sIAKaXnjkCA5WRzwrCMAyHz+YpAp430nR/3FlQBrv5BGMWFWSI2/tjG9uuNy2l
** 9Gt/5SMk+1N/Rl0yDON8XabxZeBo5tW8oZ+nu1lgMKu9IYIiKong8phvTwMFg2Ii
** ZGBkJFR2t1iTPQrL9qfD78WuGnZY2dTtjrYzZZ//L1TaG1WTgtQl2UZZXla+Gq5S
** ELlkG+V5D75MTZRA49rooghZVq2DLDRYwMkkipBnbYMsjEZAZG2dQJa14jDnMDoB
** J5MoQv681IHCnCJJeyXdyKVWrX+rtVOLsAtNFYpv8AGUMVDTPQMAAA==
** -----END EMBEDDED OBJECT-----
**
** As you can see, it consists of four levels of memory chunks:
** 1. the top-level structure one sees in the API
** 2. the hash table consisting of a single directory and one or
** more directory segments
** 3. the collision chain consisting of element structures
** 4. the actual elements consisting of key and value structures
*/
#include "act_p.h"
/* fixed size (number of pointers) of the directory and of each segment */
#define INITDIRSIZE 256 /* can be an arbitrary value */
#define SEGMENTSIZE 512 /* = 2^9, must be a power of 2 for below fast arithmetic */
/* calculate index in directory and segment from virtual array index */
#define DIRINDEX(addr) ((addr) >> 9) /* == ((addr) / SEGMENTSIZE) */
#define SEGINDEX(addr) ((addr) & (512-1)) /* == ((addr) % SEGMENTSIZE) */
/* load of hash table (maximum should be between 2 and 4) */
#define MINLOADFCTR 1
#define MAXLOADFCTR 2
/* the per-element structure (keep this as small as possible!) */
typedef struct element_st element_t;
struct element_st {
element_t *e_next; /* pointer to next element in collision chain */
unsigned long e_hash; /* cached hash value of element (rehashing optimization) */
void *e_keyptr; /* pointer to key (= also pointer to key+data memory chunk) */
void *e_datptr; /* pointer to data in key+data memory chunk */
void *e_endptr; /* pointer to end of key+data memory chunk */
};
/* on-the-fly calculate lengths of key and data to reduce memory in element_t */
#define el_keylen(el) ((char *)((el)->e_datptr)-(char *)((el)->e_keyptr))
#define el_datlen(el) ((char *)((el)->e_endptr)-(char *)((el)->e_datptr))
/* the hash table segments */
typedef struct segment_st segment_t;
struct segment_st {
element_t *s_element[SEGMENTSIZE]; /* array of pointers to elements */
};
/* the top-level hash table structure */
typedef struct act_hash_lh_st act_hash_lh_t;
struct act_hash_lh_st {
act_ctx_t *h_ctx; /* context structure */
act_hash_fct_t h_func; /* hash function (copied from context) */
unsigned int h_p; /* pointer to start of unsplit region */
unsigned int h_pmax; /* pointer to end of unsplit region */
int h_slack; /* grow/shrink indicator */
unsigned h_dirsize; /* current size of directory */
segment_t **h_dir; /* pointer to directory */
};
/* create the hash table structure */
static act_hash_lh_t *
act_hash_lh_new(
act_ctx_t *ctx)
{
act_hash_lh_t *h;
/* allocate hash structure */
if ((h = (act_hash_lh_t *)act_mem_alloc_ctx(ctx, sizeof(act_hash_lh_t))) == NULL)
return NULL;
h->h_ctx = ctx;
/* allocate and clear hash table directory */
h->h_dirsize = INITDIRSIZE;
if ((h->h_dir = (segment_t **)act_mem_alloc_ctx(ctx, h->h_dirsize * sizeof(segment_t *))) == NULL) {
errno_safe(act_mem_free_ctx(ctx, h));
return NULL;
}
act_mem_set(h->h_dir, 0, h->h_dirsize * sizeof(segment_t *));
/* allocate and clear first segment of hash table array */
if ((h->h_dir[0] = (segment_t *)act_mem_alloc_ctx(ctx, sizeof(segment_t))) == NULL) {
errno_safe(act_mem_free_ctx(ctx, h->h_dir); act_mem_free_ctx(ctx, h));
return NULL;
}
act_mem_set(h->h_dir[0], 0, sizeof(segment_t));
/* initialize hash table control attributes */
h->h_p = 0;
h->h_pmax = SEGMENTSIZE;
h->h_slack = SEGMENTSIZE * MAXLOADFCTR;
/* inline values from context (for performance reasons only) */
if (!act_ctx_get(ctx, ACT_HASH_FUNC, &h->h_func))
h->h_func = act_hash_fct(djbx33a);
return h;
}
/* expand the hash table */
static void
act_hash_lh_expand(
act_ctx_t *ctx,
act_hash_lh_t *h)
{
unsigned int pmax0;
unsigned int newaddr;
segment_t *seg;
element_t **pelold;
element_t *el, *headofold, *headofnew, *next;
unsigned int n;
/* calculate next new address */
pmax0 = h->h_pmax;
newaddr = pmax0 + h->h_p;
/* have to enlarge directory? */
if (h->h_dirsize <= DIRINDEX(newaddr)) {
n = h->h_dirsize * sizeof(segment_t *);
h->h_dirsize *= 2;
if ((h->h_dir = (segment_t **)act_mem_realloc_ctx(ctx,
h->h_dir, h->h_dirsize*sizeof(segment_t *))) == NULL)
return;
act_mem_set((char *)h->h_dir+n, 0, n);
}
/* have to create a new table segment? */
if (SEGINDEX(newaddr) == 0) {
if ((seg = (segment_t *)act_mem_alloc_ctx(ctx, sizeof(segment_t))) == NULL)
return;
act_mem_set(seg, 0, sizeof(segment_t));
h->h_dir[DIRINDEX(newaddr)] = seg;
}
/* locate P-element */
pelold = &h->h_dir[DIRINDEX(h->h_p)]->s_element[SEGINDEX(h->h_p)];
/* adjust the state variables */
if (++(h->h_p) >= h->h_pmax) {
h->h_pmax = (h->h_pmax << 1); /* == h->h_pmax * 2 */
h->h_p = 0;
}
h->h_slack += MAXLOADFCTR;
/* relocate and split between P-element new element */
headofold = NULL;
headofnew = NULL;
for (el = *pelold; el != NULL; el = next) {
next = el->e_next;
if (el->e_hash & pmax0) {
el->e_next = headofnew;
headofnew = el;
} else {
el->e_next = headofold;
headofold = el;
}
}
*pelold = headofold;
h->h_dir[DIRINDEX(newaddr)]->s_element[SEGINDEX(newaddr)] = headofnew;
return;
}
/* shrink hash table */
static void
act_hash_lh_shrink(
act_ctx_t *ctx,
act_hash_lh_t *h)
{
segment_t *lastseg;
element_t **pel;
unsigned int oldlast;
unsigned int dirsize;
void *dir;
/* calculate old last element */
oldlast = h->h_p + h->h_pmax - 1;
/* we cannot shrink below one segment */
if (oldlast == 0)
return;
/* adjust the state variables */
if (h->h_p == 0) {
h->h_pmax = (h->h_pmax >> 1); /* == h->h_pmax / 2 */;
h->h_p = h->h_pmax - 1;
} else
h->h_p--;
h->h_slack -= MAXLOADFCTR;
/* relocate the lost old last element to the end of the P-element */
pel = &h->h_dir[DIRINDEX(h->h_p)]->s_element[SEGINDEX(h->h_p)];
while (*pel != NULL)
pel = &((*pel)->e_next);
lastseg = h->h_dir[DIRINDEX(oldlast)];
*pel = lastseg->s_element[SEGINDEX(oldlast)];
lastseg->s_element[SEGINDEX(oldlast)] = NULL;
/* if possible, deallocate the last segment */
if (SEGINDEX(oldlast) == 0) {
h->h_dir[DIRINDEX(oldlast)] = NULL;
free(lastseg);
}
/* if possible, deallocate the end of the directory */
if (h->h_dirsize > INITDIRSIZE && DIRINDEX(oldlast) < h->h_dirsize/2) {
dirsize = (h->h_dirsize >> 1); /* == h->h_dirsize / 2 */
if ((dir = (segment_t **)act_mem_realloc_ctx(ctx,
h->h_dir, dirsize*sizeof(segment_t *))) != NULL) {
h->h_dirsize = dirsize;
h->h_dir = dir;
}
}
return;
}
/* insert element into hash table */
static int
act_hash_lh_insert(
act_ctx_t *ctx,
act_hash_lh_t *h,
void *keyptr, int keylen,
void *datptr, int datlen,
int override)
{
unsigned int hash, addr;
element_t *el, **pel;
int bFound;
void *vp;
/* argument consistency check */
if (h == NULL || keyptr == NULL || keylen <= 0)
return_errno(FALSE, EINVAL);
/* calculate hash address */
hash = h->h_func(keyptr, keylen);
addr = hash % h->h_pmax; /* unsplit region */
if (addr < h->h_p)
addr = hash % (h->h_pmax << 1); /* split region */
/* locate hash element's collision list */
pel = &h->h_dir[DIRINDEX(addr)]->s_element[SEGINDEX(addr)];
/* check whether element is already in the hash table */
bFound = FALSE;
for (el = *pel; el != NULL; el = el->e_next) {
if ( el->e_hash == hash
&& el_keylen(el) == keylen
&& act_mem_cmp(el->e_keyptr, keyptr, el_keylen(el)) == 0) {
bFound = TRUE;
break;
}
}
/* only override on request */
if (bFound && !override)
return FALSE;
/* create a duplicate of key and data */
if ((vp = act_mem_alloc_ctx(ctx, keylen+datlen)) == NULL)
return FALSE;
act_mem_move(vp, keyptr, keylen);
act_mem_move((char *)vp+keylen, datptr, datlen);
keyptr = vp;
datptr = (char *)vp+keylen;
if (bFound) {
/* reuse existing element by freeing old contents */
if (el->e_keyptr != NULL)
act_mem_free_ctx(ctx, el->e_keyptr);
}
else {
/* allocate new element and chain into list */
if ((el = (element_t *)act_mem_alloc_ctx(ctx, sizeof(element_t))) == 0) {
act_mem_free_ctx(ctx, vp);
return FALSE;
}
while (*pel != NULL)
pel = &((*pel)->e_next);
el->e_next = *pel;
*pel = el;
}
/* insert contents into element structure */
el->e_keyptr = keyptr;
el->e_datptr = datptr;
el->e_endptr = (char *)datptr+datlen;
el->e_hash = hash;
/* do we need to expand the table now? */
if (--(h->h_slack) < 0)
act_hash_lh_expand(ctx, h);
return TRUE;
}
/* lookup an element in hash table */
static int
act_hash_lh_lookup(
act_ctx_t *ctx,
act_hash_lh_t *h,
void *keyptr, int keylen,
void **datptr, int *datlen)
{
unsigned int hash, addr;
element_t *el, **pel;
/* argument consistency check */
if (h == NULL || keyptr == NULL || keylen <= 0)
return_errno(FALSE, EINVAL);
/* calculate hash address */
hash = h->h_func(keyptr, keylen);
addr = hash % h->h_pmax; /* unsplit region */
if (addr < h->h_p)
addr = hash % (h->h_pmax << 1); /* split region */
/* locate hash element collision list */
pel = &h->h_dir[DIRINDEX(addr)]->s_element[SEGINDEX(addr)];
/* search for element in collision list */
for (el = *pel; el != NULL; el = el->e_next) {
if ( el->e_hash == hash
&& el_keylen(el) == keylen
&& act_mem_cmp(el->e_keyptr, keyptr, el_keylen(el)) == 0) {
/* provide results */
if (datptr != NULL)
*datptr = el->e_datptr;
if (datlen != NULL)
*datlen = el_datlen(el);
return TRUE;
}
}
return FALSE;
}
/* delete an element in hash table */
static int
act_hash_lh_delete(
act_ctx_t *ctx,
act_hash_lh_t *h,
void *keyptr, int keylen)
{
unsigned int hash, addr;
element_t *el, *lel, **pel;
int rv;
/* argument consistency check */
if (h == NULL || keyptr == NULL || keylen <= 0)
return_errno(FALSE, EINVAL);
/* calculate hash address */
hash = h->h_func(keyptr, keylen);
addr = hash % h->h_pmax; /* unsplit region */
if (addr < h->h_p)
addr = hash % (h->h_pmax << 1); /* split region */
/* locate hash element collision chain */
pel = &h->h_dir[DIRINDEX(addr)]->s_element[SEGINDEX(addr)];
/* search for element in collision chain */
rv = FALSE;
for (lel = NULL, el = *pel; el != NULL; lel = el, el = el->e_next) {
if ( el->e_hash == hash
&& el_keylen(el) == keylen
&& act_mem_cmp(el->e_keyptr, keyptr, el_keylen(el)) == 0) {
/* free key+data memory chunk */
if (el->e_keyptr != NULL)
act_mem_free_ctx(ctx, el->e_keyptr);
/* remove element from collision chain */
if (lel == NULL)
*pel = el->e_next;
else
lel->e_next = el->e_next;
/* deallocate element structure */
act_mem_free_ctx(ctx, el);
rv = TRUE;
break;
}
}
/* do we need to shrink the table now? */
if (++(h->h_slack) > ((h->h_pmax + h->h_p) * (MAXLOADFCTR-MINLOADFCTR)))
act_hash_lh_shrink(ctx, h);
return rv;
}
/* calculate total size of hash table */
static int
act_hash_lh_size(
act_ctx_t *ctx,
act_hash_lh_t *h,
long *pbytes, long *pelements)
{
long bytes, elements;
int i, j;
element_t *el;
/* argument consistency check */
if (h == NULL)
return_errno(FALSE, EINVAL);
/* start with 0 bytes and elements */
bytes = 0;
elements = 0;
/* add bytes for top-level structure and directory */
bytes += sizeof(act_hash_lh_t);
bytes += h->h_dirsize * sizeof(segment_t *);
/* add size for segments */
for (i = 0; i < h->h_dirsize; i++) {
if (h->h_dir[i] == NULL)
continue;
bytes += sizeof(segment_t);
/* add size of elements */
for (j = 0; j < SEGMENTSIZE; j++) {
if (h->h_dir[i]->s_element[j] == NULL)
continue;
el = h->h_dir[i]->s_element[j];
for (; el != NULL; el = el->e_next) {
elements++;
/* add size of key+data */
bytes += sizeof(element_t);
bytes += el_keylen(el);
bytes += el_datlen(el);
}
}
}
/* provide results */
if (pbytes != NULL)
*pbytes = bytes;
if (pelements != NULL)
*pelements = elements;
return TRUE;
}
/* destroy the whole hash table */
static int
act_hash_lh_free(
act_ctx_t *ctx,
act_hash_lh_t *h)
{
element_t *el, **pel;
unsigned int i, j;
/* argument consistency check */
if (h == NULL)
return_errno(FALSE, EINVAL);
/* deallocate all segment's entries */
for (i = 0; i < h->h_dirsize; i++) {
if (h->h_dir[i] == NULL)
continue;
/* deallocate all collision chains */
for (j = 0; j < SEGMENTSIZE; j++) {
if (h->h_dir[i]->s_element[j] == NULL)
continue;
/* deallocate all elements in collision chain */
pel = &h->h_dir[i]->s_element[j];
for (el = *pel; el != NULL; el = el->e_next) {
/* deallocate key+data memory chunk */
if (el->e_keyptr != NULL)
act_mem_free_ctx(ctx, el->e_keyptr);
}
}
act_mem_free_ctx(ctx, h->h_dir[i]);
}
/* deallocate hash table directory */
act_mem_free_ctx(ctx, h->h_dir);
/* deallocate hash table top-level structure */
act_mem_free_ctx(ctx, h);
return TRUE;
}
/* the ACT dispatch structure for the hashing API */
intern act_hash_method_t act_hash_lh = {
ACT_HASH_METHOD_TAG,
(act_hash_new_t) act_hash_lh_new,
(act_hash_insert_t) act_hash_lh_insert,
(act_hash_lookup_t) act_hash_lh_lookup,
(act_hash_delete_t) act_hash_lh_delete,
(act_hash_size_t) act_hash_lh_size,
(act_hash_free_t) act_hash_lh_free
};