hash.c

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/*-
 * Copyright (c) 1990, 1993, 1994
 * The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Margo Seltzer.
 *
 * 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 above 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 software developed by the University of
 * California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``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 REGENTS 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.
 */

#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)hash.c  8.9 (Berkeley) 6/16/94";
#endif /* LIBC_SCCS and not lint */

#include <sys/param.h>
#include <sys/stat.h>

#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#ifdef DEBUG
#include <assert.h>
#endif

#include "../include/db.h"
#include "hash.h"
#include "page.h"
#include "extern.h"

static int   alloc_segs __P((HTAB *, int));
static int   flush_meta __P((HTAB *));
static int   hash_access __P((HTAB *, ACTION, DBT *, DBT *));
static int   hash_close __P((DB *));
static int   hash_delete __P((const DB *, const DBT *, u_int32_t));
static int   hash_fd __P((const DB *));
static int   hash_get __P((const DB *, const DBT *, DBT *, u_int32_t));
static int   hash_put __P((const DB *, DBT *, const DBT *, u_int32_t));
static void *hash_realloc __P((SEGMENT **, int, int));
static int   hash_seq __P((const DB *, DBT *, DBT *, u_int32_t));
static int   hash_sync __P((const DB *, u_int32_t));
static int   hdestroy __P((HTAB *));
static HTAB *init_hash __P((HTAB *, const char *, const HASHINFO *));
static int   init_htab __P((HTAB *, int));
#if BYTE_ORDER == LITTLE_ENDIAN
static void  swap_header __P((HTAB *));
static void  swap_header_copy __P((HASHHDR *, HASHHDR *));
#endif

/* Fast arithmetic, relying on powers of 2, */
#define MOD(x, y)    ((x) & ((y) - 1))

#define RETURN_ERROR(ERR, LOC)   { save_errno = ERR; goto LOC; }

/* Return values */
#define  SUCCESS   (0)
#define  ERROR (-1)
#define  ABNORMAL (1)

#ifdef HASH_STATISTICS
int hash_accesses, hash_collisions, hash_expansions, hash_overflows;
#endif

/************************** INTERFACE ROUTINES ***************************/
/* OPEN/CLOSE */

extern DB *
__hash_open(file, flags, mode, info, dflags)
   const char *file;
   int flags, mode, dflags;
   const HASHINFO *info;   /* Special directives for create */
{
   HTAB *hashp;
   struct stat statbuf;
   DB *dbp;
   int bpages, hdrsize, new_table, nsegs, save_errno;

   if ((flags & O_ACCMODE) == O_WRONLY) {
      errno = EINVAL;
      return (NULL);
   }

   if (!(hashp = (HTAB *)calloc(1, sizeof(HTAB))))
      return (NULL);
   hashp->fp = -1;

   /*
    * Even if user wants write only, we need to be able to read
    * the actual file, so we need to open it read/write. But, the
    * field in the hashp structure needs to be accurate so that
    * we can check accesses.
    */
   hashp->flags = flags;

   new_table = 0;
   if (!file || (flags & O_TRUNC) ||
       (stat(file, &statbuf) && (errno == ENOENT))) {
      if (errno == ENOENT)
         errno = 0; /* Just in case someone looks at errno */
      new_table = 1;
   }
   if (file) {
      if ((hashp->fp = open(file, flags, mode)) == -1)
         RETURN_ERROR(errno, error0);
      (void)fcntl(hashp->fp, F_SETFD, 1);
   }
   if (new_table) {
      if (!(hashp = init_hash(hashp, file, info)))
         RETURN_ERROR(errno, error1);
   } else {
      /* Table already exists */
      if (info && info->hash)
         hashp->hash = info->hash;
      else
         hashp->hash = __default_hash;

      hdrsize = read(hashp->fp, &hashp->hdr, sizeof(HASHHDR));
#if BYTE_ORDER == LITTLE_ENDIAN
      swap_header(hashp);
#endif
      if (hdrsize == -1)
         RETURN_ERROR(errno, error1);
      if (hdrsize != sizeof(HASHHDR))
         RETURN_ERROR(EFTYPE, error1);
      /* Verify file type, versions and hash function */
      if (hashp->MAGIC != HASHMAGIC)
         RETURN_ERROR(EFTYPE, error1);
#define  OLDHASHVERSION 1
      if (hashp->VERSION != HASHVERSION &&
          hashp->VERSION != OLDHASHVERSION)
         RETURN_ERROR(EFTYPE, error1);
      if (hashp->hash(CHARKEY, sizeof(CHARKEY))
          != (u_int32_t) hashp->H_CHARKEY)
         RETURN_ERROR(EFTYPE, error1);
      /*
       * Figure out how many segments we need.  Max_Bucket is the
       * maximum bucket number, so the number of buckets is
       * max_bucket + 1.
       */
      nsegs = (hashp->MAX_BUCKET + 1 + hashp->SGSIZE - 1) /
          hashp->SGSIZE;
      hashp->nsegs = 0;
      if (alloc_segs(hashp, nsegs))
         /*
          * If alloc_segs fails, table will have been destroyed
          * and errno will have been set.
          */
         return (NULL);
      /* Read in bitmaps */
      bpages = (hashp->SPARES[hashp->OVFL_POINT] +
          (hashp->BSIZE << BYTE_SHIFT) - 1) >>
          (hashp->BSHIFT + BYTE_SHIFT);

      hashp->nmaps = bpages;
      (void)memset(&hashp->mapp[0], 0, bpages * sizeof(u_int32_t *));
   }

   /* Initialize Buffer Manager */
   if (info && info->cachesize)
      __buf_init(hashp, info->cachesize);
   else
      __buf_init(hashp, DEF_BUFSIZE);

   hashp->new_file = new_table;
   hashp->save_file = file && (hashp->flags & O_ACCMODE) != O_RDONLY;
   hashp->cbucket = -1;
   if (!(dbp = (DB *)malloc(sizeof(DB)))) {
      save_errno = errno;
      hdestroy(hashp);
      errno = save_errno;
      return (NULL);
   }
   dbp->internal = hashp;
   dbp->close = hash_close;
   dbp->del = hash_delete;
   dbp->fd = hash_fd;
   dbp->get = hash_get;
   dbp->put = hash_put;
   dbp->seq = hash_seq;
   dbp->sync = hash_sync;
   dbp->type = DB_HASH;

#ifdef DEBUG
   (void)fprintf(stderr,
"%s\n%s%x\n%s%d\n%s%d\n%s%d\n%s%d\n%s%d\n%s%d\n%s%d\n%s%d\n%s%d\n%s%x\n%s%x\n%s%d\n%s%d\n",
       "init_htab:",
       "TABLE POINTER   ", hashp,
       "BUCKET SIZE     ", hashp->BSIZE,
       "BUCKET SHIFT    ", hashp->BSHIFT,
       "DIRECTORY SIZE  ", hashp->DSIZE,
       "SEGMENT SIZE    ", hashp->SGSIZE,
       "SEGMENT SHIFT   ", hashp->SSHIFT,
       "FILL FACTOR     ", hashp->FFACTOR,
       "MAX BUCKET      ", hashp->MAX_BUCKET,
       "OVFL POINT        ", hashp->OVFL_POINT,
       "LAST FREED      ", hashp->LAST_FREED,
       "HIGH MASK       ", hashp->HIGH_MASK,
       "LOW  MASK       ", hashp->LOW_MASK,
       "NSEGS           ", hashp->nsegs,
       "NKEYS           ", hashp->NKEYS);
#endif
#ifdef HASH_STATISTICS
   hash_overflows = hash_accesses = hash_collisions = hash_expansions = 0;
#endif
   return (dbp);

error1:
   if (hashp != NULL)
      (void)close(hashp->fp);

error0:
   free(hashp);
   errno = save_errno;
   return (NULL);
}

static int
hash_close(dbp)
   DB *dbp;
{
   HTAB *hashp;
   int retval;

   if (!dbp)
      return (ERROR);

   hashp = (HTAB *)dbp->internal;
   retval = hdestroy(hashp);
   free(dbp);
   return (retval);
}

static int
hash_fd(dbp)
   const DB *dbp;
{
   HTAB *hashp;

   if (!dbp)
      return (ERROR);

   hashp = (HTAB *)dbp->internal;
   if (hashp->fp == -1) {
      errno = ENOENT;
      return (-1);
   }
   return (hashp->fp);
}

/************************** LOCAL CREATION ROUTINES **********************/
static HTAB *
init_hash(hashp, file, info)
   HTAB *hashp;
   const char *file;
   const HASHINFO *info;
{
#ifdef _STATBUF_ST_BLKSIZE
   struct stat statbuf;
#endif
   int nelem;

   nelem = 1;
   hashp->NKEYS = 0;
   hashp->LORDER = BYTE_ORDER;
   hashp->BSIZE = DEF_BUCKET_SIZE;
   hashp->BSHIFT = DEF_BUCKET_SHIFT;
   hashp->SGSIZE = DEF_SEGSIZE;
   hashp->SSHIFT = DEF_SEGSIZE_SHIFT;
   hashp->DSIZE = DEF_DIRSIZE;
   hashp->FFACTOR = DEF_FFACTOR;
   hashp->hash = __default_hash;
   memset(hashp->SPARES, 0, sizeof(hashp->SPARES));
   memset(hashp->BITMAPS, 0, sizeof (hashp->BITMAPS));

   /* Fix bucket size to be optimal for file system */
#ifdef _STATBUF_ST_BLKSIZE
   if (file != NULL) {
      if (stat(file, &statbuf))
         return (NULL);
      hashp->BSIZE = statbuf.st_blksize;
      hashp->BSHIFT = __hash_log2(hashp->BSIZE);
   }
#endif

   if (info) {
      if (info->bsize) {
         /* Round pagesize up to power of 2 */
         hashp->BSHIFT = __hash_log2(info->bsize);
         hashp->BSIZE = 1 << hashp->BSHIFT;
         if (hashp->BSIZE > MAX_BSIZE) {
            errno = EINVAL;
            return (NULL);
         }
      }
      if (info->ffactor)
         hashp->FFACTOR = info->ffactor;
      if (info->hash)
         hashp->hash = info->hash;
      if (info->nelem)
         nelem = info->nelem;
      if (info->lorder) {
         if (info->lorder != BIG_ENDIAN &&
             info->lorder != LITTLE_ENDIAN) {
            errno = EINVAL;
            return (NULL);
         }
         hashp->LORDER = info->lorder;
      }
   }
   /* init_htab should destroy the table and set errno if it fails */
   if (init_htab(hashp, nelem))
      return (NULL);
   else
      return (hashp);
}
/*
 * This calls alloc_segs which may run out of memory.  Alloc_segs will destroy
 * the table and set errno, so we just pass the error information along.
 *
 * Returns 0 on No Error
 */
static int
init_htab(hashp, nelem)
   HTAB *hashp;
   int nelem;
{
   register int nbuckets, nsegs;
   int l2;

   /*
    * Divide number of elements by the fill factor and determine a
    * desired number of buckets.  Allocate space for the next greater
    * power of two number of buckets.
    */
   nelem = (nelem - 1) / hashp->FFACTOR + 1;

   l2 = __hash_log2(MAX(nelem, 2));
   nbuckets = 1 << l2;

   hashp->SPARES[l2] = l2 + 1;
   hashp->SPARES[l2 + 1] = l2 + 1;
   hashp->OVFL_POINT = l2;
   hashp->LAST_FREED = 2;

   /* First bitmap page is at: splitpoint l2 page offset 1 */
   if (__ibitmap(hashp, OADDR_OF(l2, 1), l2 + 1, 0))
      return (-1);

   hashp->MAX_BUCKET = hashp->LOW_MASK = nbuckets - 1;
   hashp->HIGH_MASK = (nbuckets << 1) - 1;
   hashp->HDRPAGES = ((MAX(sizeof(HASHHDR), MINHDRSIZE) - 1) >>
       hashp->BSHIFT) + 1;

   nsegs = (nbuckets - 1) / hashp->SGSIZE + 1;
   nsegs = 1 << __hash_log2(nsegs);

   if (nsegs > hashp->DSIZE)
      hashp->DSIZE = nsegs;
   return (alloc_segs(hashp, nsegs));
}

/********************** DESTROY/CLOSE ROUTINES ************************/

/*
 * Flushes any changes to the file if necessary and destroys the hashp
 * structure, freeing all allocated space.
 */
static int
hdestroy(hashp)
   HTAB *hashp;
{
   int i, save_errno;

   save_errno = 0;

#ifdef HASH_STATISTICS
   (void)fprintf(stderr, "hdestroy: accesses %ld collisions %ld\n",
       hash_accesses, hash_collisions);
   (void)fprintf(stderr, "hdestroy: expansions %ld\n",
       hash_expansions);
   (void)fprintf(stderr, "hdestroy: overflows %ld\n",
       hash_overflows);
   (void)fprintf(stderr, "keys %ld maxp %d segmentcount %d\n",
       hashp->NKEYS, hashp->MAX_BUCKET, hashp->nsegs);

   for (i = 0; i < NCACHED; i++)
      (void)fprintf(stderr,
          "spares[%d] = %d\n", i, hashp->SPARES[i]);
#endif
   /*
    * Call on buffer manager to free buffers, and if required,
    * write them to disk.
    */
   if (__buf_free(hashp, 1, hashp->save_file))
      save_errno = errno;
   if (hashp->dir) {
      free(*hashp->dir);   /* Free initial segments */
      /* Free extra segments */
      while (hashp->exsegs--)
         free(hashp->dir[--hashp->nsegs]);
      free(hashp->dir);
   }
   if (flush_meta(hashp) && !save_errno)
      save_errno = errno;
   /* Free Bigmaps */
   for (i = 0; i < hashp->nmaps; i++)
      if (hashp->mapp[i])
         free(hashp->mapp[i]);

   if (hashp->fp != -1)
      (void)close(hashp->fp);

   free(hashp);

   if (save_errno) {
      errno = save_errno;
      return (ERROR);
   }
   return (SUCCESS);
}
/*
 * Write modified pages to disk
 *
 * Returns:
 *  0 == OK
 * -1 ERROR
 */
static int
hash_sync(dbp, flags)
   const DB *dbp;
   u_int32_t flags;
{
   HTAB *hashp;

   if (flags != 0) {
      errno = EINVAL;
      return (ERROR);
   }

   if (!dbp)
      return (ERROR);

   hashp = (HTAB *)dbp->internal;
   if (!hashp->save_file)
      return (0);
   if (__buf_free(hashp, 0, 1) || flush_meta(hashp))
      return (ERROR);
   hashp->new_file = 0;
   return (0);
}

/*
 * Returns:
 *  0 == OK
 * -1 indicates that errno should be set
 */
static int
flush_meta(hashp)
   HTAB *hashp;
{
   HASHHDR *whdrp;
#if BYTE_ORDER == LITTLE_ENDIAN
   HASHHDR whdr;
#endif
   int fp, i, wsize;

   if (!hashp->save_file)
      return (0);
   hashp->MAGIC = HASHMAGIC;
   hashp->VERSION = HASHVERSION;
   hashp->H_CHARKEY = hashp->hash(CHARKEY, sizeof(CHARKEY));

   fp = hashp->fp;
   whdrp = &hashp->hdr;
#if BYTE_ORDER == LITTLE_ENDIAN
   whdrp = &whdr;
   swap_header_copy(&hashp->hdr, whdrp);
#endif
   if ((lseek(fp, (off_t)0, SEEK_SET) == -1) ||
       ((wsize = write(fp, whdrp, sizeof(HASHHDR))) == -1))
      return (-1);
   else
      if (wsize != sizeof(HASHHDR)) {
         errno = EFTYPE;
         hashp->errnum = errno;
         return (-1);
      }
   for (i = 0; i < NCACHED; i++)
      if (hashp->mapp[i])
         if (__put_page(hashp, (char *)hashp->mapp[i],
            hashp->BITMAPS[i], 0, 1))
            return (-1);
   return (0);
}

/*******************************SEARCH ROUTINES *****************************/
/*
 * All the access routines return
 *
 * Returns:
 *  0 on SUCCESS
 *  1 to indicate an external ERROR (i.e. key not found, etc)
 * -1 to indicate an internal ERROR (i.e. out of memory, etc)
 */
static int
hash_get(dbp, key, data, flag)
   const DB *dbp;
   const DBT *key;
   DBT *data;
   u_int32_t flag;
{
   HTAB *hashp;

   hashp = (HTAB *)dbp->internal;
   if (flag) {
      hashp->errnum = errno = EINVAL;
      return (ERROR);
   }
   return (hash_access(hashp, HASH_GET, (DBT *)key, data));
}

static int
hash_put(dbp, key, data, flag)
   const DB *dbp;
   DBT *key;
   const DBT *data;
   u_int32_t flag;
{
   HTAB *hashp;

   hashp = (HTAB *)dbp->internal;
   if (flag && flag != R_NOOVERWRITE) {
      hashp->errnum = errno = EINVAL;
      return (ERROR);
   }
   if ((hashp->flags & O_ACCMODE) == O_RDONLY) {
      hashp->errnum = errno = EPERM;
      return (ERROR);
   }
   return (hash_access(hashp, flag == R_NOOVERWRITE ?
       HASH_PUTNEW : HASH_PUT, (DBT *)key, (DBT *)data));
}

static int
hash_delete(dbp, key, flag)
   const DB *dbp;
   const DBT *key;
   u_int32_t flag;      /* Ignored */
{
   HTAB *hashp;

   hashp = (HTAB *)dbp->internal;
   if (flag && flag != R_CURSOR) {
      hashp->errnum = errno = EINVAL;
      return (ERROR);
   }
   if ((hashp->flags & O_ACCMODE) == O_RDONLY) {
      hashp->errnum = errno = EPERM;
      return (ERROR);
   }
   return (hash_access(hashp, HASH_DELETE, (DBT *)key, NULL));
}

/*
 * Assume that hashp has been set in wrapper routine.
 */
static int
hash_access(hashp, action, key, val)
   HTAB *hashp;
   ACTION action;
   DBT *key, *val;
{
   register BUFHEAD *rbufp;
   BUFHEAD *bufp, *save_bufp;
   register u_int16_t *bp;
   register int n, ndx, off, size;
   register char *kp;
   u_int16_t pageno;

#ifdef HASH_STATISTICS
   hash_accesses++;
#endif

   off = hashp->BSIZE;
   size = key->size;
   kp = (char *)key->data;
   rbufp = __get_buf(hashp, __call_hash(hashp, kp, size), NULL, 0);
   if (!rbufp)
      return (ERROR);
   save_bufp = rbufp;

   /* Pin the bucket chain */
   rbufp->flags |= BUF_PIN;
   for (bp = (u_int16_t *)rbufp->page, n = *bp++, ndx = 1; ndx < n;)
      if (bp[1] >= REAL_KEY) {
         /* Real key/data pair */
         if (size == off - *bp &&
             memcmp(kp, rbufp->page + *bp, size) == 0)
            goto found;
         off = bp[1];
#ifdef HASH_STATISTICS
         hash_collisions++;
#endif
         bp += 2;
         ndx += 2;
      } else if (bp[1] == OVFLPAGE) {
         rbufp = __get_buf(hashp, *bp, rbufp, 0);
         if (!rbufp) {
            save_bufp->flags &= ~BUF_PIN;
            return (ERROR);
         }
         /* FOR LOOP INIT */
         bp = (u_int16_t *)rbufp->page;
         n = *bp++;
         ndx = 1;
         off = hashp->BSIZE;
      } else if (bp[1] < REAL_KEY) {
         if ((ndx =
             __find_bigpair(hashp, rbufp, ndx, kp, size)) > 0)
            goto found;
         if (ndx == -2) {
            bufp = rbufp;
            if (!(pageno =
                __find_last_page(hashp, &bufp))) {
               ndx = 0;
               rbufp = bufp;
               break;   /* FOR */
            }
            rbufp = __get_buf(hashp, pageno, bufp, 0);
            if (!rbufp) {
               save_bufp->flags &= ~BUF_PIN;
               return (ERROR);
            }
            /* FOR LOOP INIT */
            bp = (u_int16_t *)rbufp->page;
            n = *bp++;
            ndx = 1;
            off = hashp->BSIZE;
         } else {
            save_bufp->flags &= ~BUF_PIN;
            return (ERROR);
         }
      }

   /* Not found */
   switch (action) {
   case HASH_PUT:
   case HASH_PUTNEW:
      if (__addel(hashp, rbufp, key, val)) {
         save_bufp->flags &= ~BUF_PIN;
         return (ERROR);
      } else {
         save_bufp->flags &= ~BUF_PIN;
         return (SUCCESS);
      }
   case HASH_GET:
   case HASH_DELETE:
   default:
      save_bufp->flags &= ~BUF_PIN;
      return (ABNORMAL);
   }

found:
   switch (action) {
   case HASH_PUTNEW:
      save_bufp->flags &= ~BUF_PIN;
      return (ABNORMAL);
   case HASH_GET:
      bp = (u_int16_t *)rbufp->page;
      if (bp[ndx + 1] < REAL_KEY) {
         if (__big_return(hashp, rbufp, ndx, val, 0))
            return (ERROR);
      } else {
         val->data = (u_char *)rbufp->page + (int)bp[ndx + 1];
         val->size = bp[ndx] - bp[ndx + 1];
      }
      break;
   case HASH_PUT:
      if ((__delpair(hashp, rbufp, ndx)) ||
          (__addel(hashp, rbufp, key, val))) {
         save_bufp->flags &= ~BUF_PIN;
         return (ERROR);
      }
      break;
   case HASH_DELETE:
      if (__delpair(hashp, rbufp, ndx))
         return (ERROR);
      break;
   default:
      abort();
   }
   save_bufp->flags &= ~BUF_PIN;
   return (SUCCESS);
}

static int
hash_seq(dbp, key, data, flag)
   const DB *dbp;
   DBT *key, *data;
   u_int32_t flag;
{
   register u_int32_t bucket;
   register BUFHEAD *bufp = NULL;
   HTAB *hashp;
   u_int16_t *bp, ndx;

   hashp = (HTAB *)dbp->internal;
   if (flag && flag != R_FIRST && flag != R_NEXT) {
      hashp->errnum = errno = EINVAL;
      return (ERROR);
   }
#ifdef HASH_STATISTICS
   hash_accesses++;
#endif
   if ((hashp->cbucket < 0) || (flag == R_FIRST)) {
      hashp->cbucket = 0;
      hashp->cndx = 1;
      hashp->cpage = NULL;
   }

   for (bp = NULL; !bp || !bp[0]; ) {
      if (!(bufp = hashp->cpage)) {
         for (bucket = hashp->cbucket;
             bucket <= (u_int32_t) hashp->MAX_BUCKET;
             bucket++, hashp->cndx = 1) {
            bufp = __get_buf(hashp, bucket, NULL, 0);
            if (!bufp)
               return (ERROR);
            hashp->cpage = bufp;
            bp = (u_int16_t *)bufp->page;
            if (bp[0])
               break;
         }
         hashp->cbucket = bucket;
         if (hashp->cbucket > hashp->MAX_BUCKET) {
            hashp->cbucket = -1;
            return (ABNORMAL);
         }
      } else
         bp = (u_int16_t *)hashp->cpage->page;

#ifdef DEBUG
      assert(bp);
      assert(bufp);
#endif
      while (bp[hashp->cndx + 1] == OVFLPAGE) {
         bufp = hashp->cpage =
             __get_buf(hashp, bp[hashp->cndx], bufp, 0);
         if (!bufp)
            return (ERROR);
         bp = (u_int16_t *)(bufp->page);
         hashp->cndx = 1;
      }
      if (!bp[0]) {
         hashp->cpage = NULL;
         ++hashp->cbucket;
      }
   }
   ndx = hashp->cndx;
   if (bp[ndx + 1] < REAL_KEY) {
      if (__big_keydata(hashp, bufp, key, data, 1))
         return (ERROR);
   } else {
      key->data = (u_char *)hashp->cpage->page + bp[ndx];
      key->size = (ndx > 1 ? bp[ndx - 1] : hashp->BSIZE) - bp[ndx];
      data->data = (u_char *)hashp->cpage->page + bp[ndx + 1];
      data->size = bp[ndx] - bp[ndx + 1];
      ndx += 2;
      if (ndx > bp[0]) {
         hashp->cpage = NULL;
         hashp->cbucket++;
         hashp->cndx = 1;
      } else
         hashp->cndx = ndx;
   }
   return (SUCCESS);
}

/********************************* UTILITIES ************************/

/*
 * Returns:
 *  0 ==> OK
 * -1 ==> Error
 */
extern int
__expand_table(hashp)
   HTAB *hashp;
{
   u_int32_t old_bucket, new_bucket;
   int dirsize, new_segnum, spare_ndx;

#ifdef HASH_STATISTICS
   hash_expansions++;
#endif
   new_bucket = ++hashp->MAX_BUCKET;
   old_bucket = (hashp->MAX_BUCKET & hashp->LOW_MASK);

   new_segnum = new_bucket >> hashp->SSHIFT;

   /* Check if we need a new segment */
   if (new_segnum >= hashp->nsegs) {
      /* Check if we need to expand directory */
      if (new_segnum >= hashp->DSIZE) {
         /* Reallocate directory */
         dirsize = hashp->DSIZE * sizeof(SEGMENT *);
         if (!hash_realloc(&hashp->dir, dirsize, dirsize << 1))
            return (-1);
         hashp->DSIZE = dirsize << 1;
      }
      if ((hashp->dir[new_segnum] =
          (SEGMENT)calloc(hashp->SGSIZE, sizeof(SEGMENT))) == NULL)
         return (-1);
      hashp->exsegs++;
      hashp->nsegs++;
   }
   /*
    * If the split point is increasing (MAX_BUCKET's log base 2
    * * increases), we need to copy the current contents of the spare
    * split bucket to the next bucket.
    */
   spare_ndx = __hash_log2(hashp->MAX_BUCKET + 1);
   if (spare_ndx > hashp->OVFL_POINT) {
      hashp->SPARES[spare_ndx] = hashp->SPARES[hashp->OVFL_POINT];
      hashp->OVFL_POINT = spare_ndx;
   }

   if (new_bucket > (u_int32_t) hashp->HIGH_MASK) {
      /* Starting a new doubling */
      hashp->LOW_MASK = hashp->HIGH_MASK;
      hashp->HIGH_MASK = new_bucket | hashp->LOW_MASK;
   }
   /* Relocate records to the new bucket */
   return (__split_page(hashp, old_bucket, new_bucket));
}

/*
 * If realloc guarantees that the pointer is not destroyed if the realloc
 * fails, then this routine can go away.
 */
static void *
hash_realloc(p_ptr, oldsize, newsize)
   SEGMENT **p_ptr;
   int oldsize, newsize;
{
   register void *p;

   if ((p = malloc(newsize))) {
      memmove(p, *p_ptr, oldsize);
      memset((char *)p + oldsize, 0, newsize - oldsize);
      free(*p_ptr);
      *p_ptr = p;
   }
   return (p);
}

extern u_int32_t
__call_hash(hashp, k, len)
   HTAB *hashp;
   char *k;
   int len;
{
   int n, bucket;

   n = hashp->hash(k, len);
   bucket = n & hashp->HIGH_MASK;
   if (bucket > hashp->MAX_BUCKET)
      bucket = bucket & hashp->LOW_MASK;
   return (bucket);
}

/*
 * Allocate segment table.  On error, destroy the table and set errno.
 *
 * Returns 0 on success
 */
static int
alloc_segs(hashp, nsegs)
   HTAB *hashp;
   int nsegs;
{
   register int i;
   register SEGMENT store;

   int save_errno;

   if ((hashp->dir =
       (SEGMENT *)calloc(hashp->DSIZE, sizeof(SEGMENT *))) == NULL) {
      save_errno = errno;
      (void)hdestroy(hashp);
      errno = save_errno;
      return (-1);
   }
   /* Allocate segments */
   if ((store =
       (SEGMENT)calloc(nsegs << hashp->SSHIFT, sizeof(SEGMENT))) == NULL) {
      save_errno = errno;
      (void)hdestroy(hashp);
      errno = save_errno;
      return (-1);
   }
   for (i = 0; i < nsegs; i++, hashp->nsegs++)
      hashp->dir[i] = &store[i << hashp->SSHIFT];
   return (0);
}

#if BYTE_ORDER == LITTLE_ENDIAN
/*
 * Hashp->hdr needs to be byteswapped.
 */
static void
swap_header_copy(srcp, destp)
   HASHHDR *srcp, *destp;
{
   int i;

   P_32_COPY(srcp->magic, destp->magic);
   P_32_COPY(srcp->version, destp->version);
   P_32_COPY(srcp->lorder, destp->lorder);
   P_32_COPY(srcp->bsize, destp->bsize);
   P_32_COPY(srcp->bshift, destp->bshift);
   P_32_COPY(srcp->dsize, destp->dsize);
   P_32_COPY(srcp->ssize, destp->ssize);
   P_32_COPY(srcp->sshift, destp->sshift);
   P_32_COPY(srcp->ovfl_point, destp->ovfl_point);
   P_32_COPY(srcp->last_freed, destp->last_freed);
   P_32_COPY(srcp->max_bucket, destp->max_bucket);
   P_32_COPY(srcp->high_mask, destp->high_mask);
   P_32_COPY(srcp->low_mask, destp->low_mask);
   P_32_COPY(srcp->ffactor, destp->ffactor);
   P_32_COPY(srcp->nkeys, destp->nkeys);
   P_32_COPY(srcp->hdrpages, destp->hdrpages);
   P_32_COPY(srcp->h_charkey, destp->h_charkey);
   for (i = 0; i < NCACHED; i++) {
      P_32_COPY(srcp->spares[i], destp->spares[i]);
      P_16_COPY(srcp->bitmaps[i], destp->bitmaps[i]);
   }
}

static void
swap_header(hashp)
   HTAB *hashp;
{
   HASHHDR *hdrp;
   int i;

   hdrp = &hashp->hdr;

   M_32_SWAP(hdrp->magic);
   M_32_SWAP(hdrp->version);
   M_32_SWAP(hdrp->lorder);
   M_32_SWAP(hdrp->bsize);
   M_32_SWAP(hdrp->bshift);
   M_32_SWAP(hdrp->dsize);
   M_32_SWAP(hdrp->ssize);
   M_32_SWAP(hdrp->sshift);
   M_32_SWAP(hdrp->ovfl_point);
   M_32_SWAP(hdrp->last_freed);
   M_32_SWAP(hdrp->max_bucket);
   M_32_SWAP(hdrp->high_mask);
   M_32_SWAP(hdrp->low_mask);
   M_32_SWAP(hdrp->ffactor);
   M_32_SWAP(hdrp->nkeys);
   M_32_SWAP(hdrp->hdrpages);
   M_32_SWAP(hdrp->h_charkey);
   for (i = 0; i < NCACHED; i++) {
      M_32_SWAP(hdrp->spares[i]);
      M_16_SWAP(hdrp->bitmaps[i]);
   }
}
#endif