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*** 0 ****
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+
+ /*
+ ** Act - Abstract Container Type Library
+ ** Copyright (c) 1999-2002 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.
+ */
+
+ /*
+ ** 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).
+ **
+ ** Linear Hashing can be summarized as following:
+ **
+ ** o drawback of classical hashing is that the hash table is of
+ ** fixed size; if table is filled, the table has to be expanded;
+ ** unfortunately this requires re-hashing of all existing elements.
+ **
+ ** o Extendible Hashing solves this problem by allowing the table
+ ** to grow without complete re-hashing of elements every time;
+ ** unfortunately the table must double in size to grow - not a
+ ** problem for small tables, but a disadvantage for large ones.
+ **
+ ** o Linear Hashing allows the table to grow one bucket at a time:
+ ** table is extended when its load factor passes a critical value; buckets
+ ** are split "in sequence" starting at index 0 and ending at 2^n; two
+ ** hashing functions are always "active" - one for split buckets and one
+ ** for unsplit; when last bucket (the 2^n-th one) is split, the table has
+ ** been doubled in size, and a new cycle of splitting begins starting at
+ ** bucket 0.
+ **
+ ** 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
+ ** H4sIACfenzkCA62WTYvbMBCGz+tfIeixJOhb9rnQsrC3XntxE7ExdZ0ldhf233dG
+ ** sr6aNllRE2K90USPpNGMRx8+P34hYs+bp346zof+xTaf7LTYS/M4HU52bp7sAr8I
+ ** aRile0qbr8P0PNpmxxvGKSW84QQ/jOwYMURRQlFx+CtK9wMb1TwQBlYB3R1NLX6x
+ ** P7TQX0OkK5IbmguNNGdLagXDT/jyzoM5PCLYRC6HzRIJ/+BKZYIJVGhLCoyVXNhm
+ ** 4EXFJV15SaG1Eu1Z5UPIsNSk0FDhZt6Gxaq4Aa86JDprUn8su725bIFdTOM68fgz
+ ** 1foTLZRWNWgd0UYVqo0xklQVWvKAlkIVCoHemlQduo3oThXKAVtaKI9mKxqOLJwj
+ ** zc8RbbJ5QMGgn2i0EshfTGjIIskV8Y4xmfDRmUXizWnMvVm06/KZHloMSPcakVvs
+ ** gwvYh49vE9PJxCCgmzlMUHSPgdmEKJVWZTz970Q64rtSubDgm00kecBLVSo30VWs
+ ** 7djNmfi7fIeK822oyVF6O2rmFb4htY3UNlHD60HQe+9LlzVGpdasRTC01yWJ/RsY
+ ** 0m896SBczXS2pGR90XA56EpFplp1/WC0zgnU+c2XikyZUCoyVedfHdFGFSpeLDJV
+ ** hXbp6oCuVGTKhFKRqTp0G9GdKpQJpSJTIYx9KKdjZLU1I5bQKGR5Ldpgji6go/BX
+ ** m3iNkd4L+GAaotU7CMDuPqkZ5BoDjovg43Cxh+V8eftGKbseyfbK0DaM1OFWgzey
+ ** 2T7/hHvx/PeB5ZTS1U6fOMv5ZTfaVzveGwgn28FAoXCtuPHDeRyHeThP5HDqh+k9
+ ** E7P19efi/od9+3jsl/4dEzNm0O04EkP9dbgsv/qRnPr5RJb++2gd4zf8ksj2KwwA
+ ** AA==
+ ** -----END EMBEDDED OBJECT-----
+ **
+ ** As you can see, it consists of four classes of memory chunks:
+ ** 1. a top-level structure which acts as the primary handle
+ ** 2. the virtual hash table consisting of a single (growing)
+ ** directory and one or more (fixed size) directory segments
+ ** 3. the collision chains consisting of element structures
+ ** 4. the actual elements consisting of key+value structures
+ */
+
+ #include <stdlib.h>
+ #include <string.h>
+
+ #ifndef FALSE
+ #define FALSE 0
+ #endif
+ #ifndef TRUE
+ #define TRUE !FALSE
+ #endif
+
+ #include "lmtp2nntp_lh.h"
+
+ /* fixed size (number of pointers) of the directory and of each segment */
+ #define INITDIRSIZE 256 /* can be an arbitrary value */
+ #define SEGMENTSIZE 512 /* has to be a power of 2 for below arithmetic */
+
+ /* the borders for the hash table load */
+ #define MINLOADFCTR 1 /* should be between 0 and 1 */
+ #define MAXLOADFCTR 2 /* should be between 2 and 4 */
+
+ /* the per-element structure (keep 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 */
+ };
+
+ /* 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 */
+ struct lh_st {
+ 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 */
+ };
+
+ /* on-the-fly calculate index into directory and segment from virtual array index */
+ #define DIRINDEX(addr) (int)((addr) / SEGMENTSIZE)
+ #define SEGINDEX(addr) (int)((addr) % SEGMENTSIZE)
+
+ /* 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))
+
+ /*
+ * BJDDJ Hash Function (Bob Jenkins, Dr. Dobbs Journal):
+ * This is a very complex but also very good hash function, as proposed
+ * in the March'97 issue of Dr. Dobbs Journal (DDJ) by Bob Jenkins (see
+ * http://burtleburtle.net/bob/hash/doobs.html for online version). He
+ * showed that this hash function has both very good distribution and
+ * performance and our own hash function comparison confirmed this. The
+ * only difference to the original function of B.J. here is that our
+ * version doesn't provide the `level' (= previous hash) argument for
+ * consistency reasons with the other hash functions (i.e. same function
+ * signature). It can be definetely recommended as a good general
+ * purpuse hash function.
+ */
+ static long
+ lh_hash(
+ register unsigned char *k,
+ register size_t length)
+ {
+ register long a,b,c,len;
+
+ /* some abbreviations */
+ #define ub4 long
+ #define mix(a,b,c) { \
+ a -= b; a -= c; a ^= (c>>13); \
+ b -= c; b -= a; b ^= (a<< 8); \
+ c -= a; c -= b; c ^= (b>>13); \
+ a -= b; a -= c; a ^= (c>>12); \
+ b -= c; b -= a; b ^= (a<<16); \
+ c -= a; c -= b; c ^= (b>> 5); \
+ a -= b; a -= c; a ^= (c>> 3); \
+ b -= c; b -= a; b ^= (a<<10); \
+ c -= a; c -= b; c ^= (b>>15); \
+ }
+
+ /* setup the internal state */
+ len = length;
+ a = b = 0x9e3779b9; /* the golden ratio; an arbitrary value */
+ c = 0;
+
+ /* handle most of the key */
+ while (len >= 12) {
+ a += (k[0] +((ub4)k[1]<<8) +((ub4)k[ 2]<<16) +((ub4)k[ 3]<<24));
+ b += (k[4] +((ub4)k[5]<<8) +((ub4)k[ 6]<<16) +((ub4)k[ 7]<<24));
+ c += (k[8] +((ub4)k[9]<<8) +((ub4)k[10]<<16) +((ub4)k[11]<<24));
+ mix(a,b,c);
+ k += 12; len -= 12;
+ }
+
+ /* handle the last 11 bytes */
+ c += length;
+ switch(len) {
+ /* all the case statements fall through */
+ case 11: c+=((ub4)k[10]<<24);
+ case 10: c+=((ub4)k[ 9]<<16);
+ case 9 : c+=((ub4)k[ 8]<< 8);
+ /* the first byte of c is reserved for the length */
+ case 8 : b+=((ub4)k[ 7]<<24);
+ case 7 : b+=((ub4)k[ 6]<<16);
+ case 6 : b+=((ub4)k[ 5]<< 8);
+ case 5 : b+=k[4];
+ case 4 : a+=((ub4)k[ 3]<<24);
+ case 3 : a+=((ub4)k[ 2]<<16);
+ case 2 : a+=((ub4)k[ 1]<< 8);
+ case 1 : a+=k[0];
+ /* case 0: nothing left to add */
+ }
+ mix(a,b,c);
+
+ #undef ub4
+ #undef mix
+
+ /* report the result */
+ return c;
+ }
+
+ /* create the hash table structure */
+ lh_t *lh_new(void)
+ {
+ lh_t *h;
+
+ /* allocate hash structure */
+ if ((h = (lh_t *)malloc(sizeof(lh_t))) == NULL)
+ return NULL;
+
+ /* allocate and clear hash table directory */
+ h->h_dirsize = INITDIRSIZE;
+ if ((h->h_dir = (segment_t **)malloc(h->h_dirsize * sizeof(segment_t *))) == NULL) {
+ free(h);
+ return NULL;
+ }
+ memset(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 *)malloc(sizeof(segment_t))) == NULL) {
+ free(h->h_dir);
+ free(h);
+ return NULL;
+ }
+ memset(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;
+
+ return h;
+ }
+
+ /* expand the hash table */
+ static void lh_expand(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 **)realloc(
+ h->h_dir, h->h_dirsize*sizeof(segment_t *))) == NULL)
+ return;
+ memset((char *)h->h_dir+n, 0, n);
+ }
+
+ /* have to create a new table segment? */
+ if (SEGINDEX(newaddr) == 0) {
+ if ((seg = (segment_t *)malloc(sizeof(segment_t))) == NULL)
+ return;
+ memset(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 lh_shrink(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 **)realloc(
+ h->h_dir, dirsize*sizeof(segment_t *))) != NULL) {
+ h->h_dirsize = dirsize;
+ h->h_dir = dir;
+ }
+ }
+ return;
+ }
+
+ /* insert element into hash table */
+ int lh_insert(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 FALSE;
+
+ /* calculate hash address */
+ hash = lh_hash(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
+ && memcmp(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 = malloc(keylen+datlen)) == NULL)
+ return FALSE;
+ memmove(vp, keyptr, keylen);
+ memmove((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)
+ free(el->e_keyptr);
+ }
+ else {
+ /* allocate new element and chain into list */
+ if ((el = (element_t *)malloc(sizeof(element_t))) == 0) {
+ free(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)
+ lh_expand(h);
+
+ return TRUE;
+ }
+
+ /* lookup an element in hash table */
+ int lh_lookup(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 FALSE;
+
+ /* calculate hash address */
+ hash = lh_hash(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
+ && memcmp(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 */
+ int lh_delete(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 FALSE;
+
+ /* calculate hash address */
+ hash = lh_hash(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
+ && memcmp(el->e_keyptr, keyptr, el_keylen(el)) == 0) {
+ /* free key+data memory chunk */
+ if (el->e_keyptr != NULL)
+ free(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 */
+ free(el);
+ rv = TRUE;
+ break;
+ }
+ }
+
+ /* do we need to shrink the table now? */
+ if (++(h->h_slack) > ((h->h_pmax + h->h_p) * (MAXLOADFCTR-MINLOADFCTR)))
+ lh_shrink(h);
+
+ return rv;
+ }
+
+ /* destroy the whole hash table */
+ int lh_free(lh_t *h)
+ {
+ element_t *el, **pel;
+ unsigned int i, j;
+
+ /* argument consistency check */
+ if (h == NULL)
+ return FALSE;
+
+ /* 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)
+ free(el->e_keyptr);
+ }
+ }
+ free(h->h_dir[i]);
+ }
+
+ /* deallocate hash table directory */
+ free(h->h_dir);
+
+ /* deallocate hash table top-level structure */
+ free(h);
+
+ return TRUE;
+ }
+
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