/*-
 * 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      8.12 (Berkeley) 11/7/95";
#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 "db-int.h"
#include "hash.h"
#include "page.h"
#include "extern.h"

static int32_t flush_meta __P((HTAB *));
static int32_t hash_access __P((HTAB *, ACTION, const DBT *, DBT *));
static int32_t hash_close __P((DB *));
static int32_t hash_delete __P((const DB *, const DBT *, u_int32_t));
static int32_t hash_fd __P((const DB *));
static int32_t hash_get __P((const DB *, const DBT *, DBT *, u_int32_t));
static int32_t hash_put __P((const DB *, DBT *, const DBT *, u_int32_t));
static int32_t hash_seq __P((const DB *, DBT *, DBT *, u_int32_t));
static int32_t hash_sync __P((const DB *, u_int32_t));
static int32_t hdestroy __P((HTAB *));
static int32_t cursor_get __P((const DB *, CURSOR *, DBT *, DBT *, \
        u_int32_t));
static int32_t cursor_delete __P((const DB *, CURSOR *, u_int32_t));
static HTAB *init_hash __P((HTAB *, const char *, const HASHINFO *));
static int32_t init_htab __P((HTAB *, int32_t));
#if DB_BYTE_ORDER == DB_LITTLE_ENDIAN
static void swap_header __P((HTAB *));
static void swap_header_copy __P((HASHHDR *, HASHHDR *));
#endif
static u_int32_t hget_header __P((HTAB *, u_int32_t));
static void hput_header __P((HTAB *));

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

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

#ifdef HASH_STATISTICS
u_int32_t hash_accesses, hash_collisions, hash_expansions, hash_overflows,
        hash_bigpages;
#endif

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

extern DB *
__kdb2_hash_open(const char *file, int flags, int mode, const HASHINFO *info,
                 int dflags)
{
        struct stat statbuf;
        DB *dbp;
        DBT mpool_key;
        HTAB *hashp;
        int32_t bpages, csize, new_table, save_errno;

        if (!file || (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;
        hashp->save_file = hashp->flags & O_RDWR;

        new_table = 0;
        if (!file || (flags & O_TRUNC) ||
            (stat(file, &statbuf) && (errno == ENOENT))) {
                if (errno == ENOENT)
                        errno = 0;      /* In case someone looks at errno. */
                new_table = 1;
        }
        if (file) {
                if ((hashp->fp = open(file, flags|O_BINARY, mode)) == -1)
                        RETURN_ERROR(errno, error0);
                (void)fcntl(hashp->fp, F_SETFD, 1);
        }

        /* Process arguments to set up hash table header. */
        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;

                /* copy metadata from page into header */
                if (hget_header(hashp,
                    (info && info->bsize ? info->bsize : DEF_BUCKET_SIZE)) !=
                    sizeof(HASHHDR))
                        RETURN_ERROR(EFTYPE, error1);

                /* Verify file type, versions and hash function */
                if (hashp->hdr.magic != HASHMAGIC)
                        RETURN_ERROR(EFTYPE, error1);
#define OLDHASHVERSION  1
                if (hashp->hdr.version != HASHVERSION &&
                    hashp->hdr.version != OLDHASHVERSION)
                        RETURN_ERROR(EFTYPE, error1);
                if (hashp->hash(CHARKEY, sizeof(CHARKEY))
                    != hashp->hdr.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.
                 */

                /* Read in bitmaps */
                bpages = (hashp->hdr.spares[hashp->hdr.ovfl_point] +
                    (hashp->hdr.bsize << BYTE_SHIFT) - 1) >>
                    (hashp->hdr.bshift + BYTE_SHIFT);

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

        /* start up mpool */
        mpool_key.data = (u_int8_t *)file;
        mpool_key.size = strlen(file);

        if (info && info->cachesize)
                csize = info->cachesize / hashp->hdr.bsize;
        else
                csize = DEF_CACHESIZE / hashp->hdr.bsize;
        hashp->mp = mpool_open(&mpool_key, hashp->fp, hashp->hdr.bsize, csize);

        if (!hashp->mp)
                RETURN_ERROR(errno, error1);
        mpool_filter(hashp->mp, __pgin_routine, __pgout_routine, hashp);

        /*
         * For a new table, set up the bitmaps.
         */
        if (new_table &&
           init_htab(hashp, info && info->nelem ? info->nelem : 1))
                goto error2;

        /* initialize the cursor queue */
        TAILQ_INIT(&hashp->curs_queue);
        hashp->seq_cursor = NULL;


        /* get a chunk of memory for our split buffer */
        hashp->split_buf = (PAGE16 *)malloc(hashp->hdr.bsize);
        if (!hashp->split_buf)
                goto error2;

        hashp->new_file = new_table;

        if (!(dbp = (DB *)malloc(sizeof(DB))))
                goto error2;

        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%lx\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   ", (void *)hashp,
            "BUCKET SIZE     ", hashp->hdr.bsize,
            "BUCKET SHIFT    ", hashp->hdr.bshift,
            "FILL FACTOR     ", hashp->hdr.ffactor,
            "MAX BUCKET      ", hashp->hdr.max_bucket,
            "OVFL POINT      ", hashp->hdr.ovfl_point,
            "LAST FREED      ", hashp->hdr.last_freed,
            "HIGH MASK       ", hashp->hdr.high_mask,
            "LOW  MASK       ", hashp->hdr.low_mask,
            "NKEYS           ", hashp->hdr.nkeys);
#endif
#ifdef HASH_STATISTICS
        hash_overflows = hash_accesses = hash_collisions = hash_expansions = 0;
        hash_bigpages = 0;
#endif
        return (dbp);

error2:
        save_errno = errno;
        hdestroy(hashp);
        errno = save_errno;
        return (NULL);

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

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

static int32_t
hash_close(DB *dbp)
{
        HTAB *hashp;
        int32_t retval;

        if (!dbp)
                return (ERROR);

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

static int32_t
hash_fd(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(HTAB *hashp, const char *file, const HASHINFO *info)
{
        struct stat statbuf;

        hashp->hdr.nkeys = 0;
        hashp->hdr.lorder = DB_BYTE_ORDER;
        hashp->hdr.bsize = DEF_BUCKET_SIZE;
        hashp->hdr.bshift = DEF_BUCKET_SHIFT;
        hashp->hdr.ffactor = DEF_FFACTOR;
        hashp->hash = __default_hash;
        memset(hashp->hdr.spares, 0, sizeof(hashp->hdr.spares));
        memset(hashp->hdr.bitmaps, 0, sizeof(hashp->hdr.bitmaps));

        /* Fix bucket size to be optimal for file system */
        if (file != NULL) {
                if (stat(file, &statbuf))
                        return (NULL);
                hashp->hdr.bsize = statbuf.st_blksize;
                if (hashp->hdr.bsize > MAX_BSIZE)
                    hashp->hdr.bsize = MAX_BSIZE;
                hashp->hdr.bshift = __log2(hashp->hdr.bsize);
        }
        if (info) {
                if (info->bsize) {
                        /* Round pagesize up to power of 2 */
                        hashp->hdr.bshift = __log2(info->bsize);
                        hashp->hdr.bsize = 1 << hashp->hdr.bshift;
                        if (hashp->hdr.bsize > MAX_BSIZE) {
                                errno = EINVAL;
                                return (NULL);
                        }
                }
                if (info->ffactor)
                        hashp->hdr.ffactor = info->ffactor;
                if (info->hash)
                        hashp->hash = info->hash;
                if (info->lorder) {
                        if ((info->lorder != DB_BIG_ENDIAN) &&
                            (info->lorder != DB_LITTLE_ENDIAN)) {
                                errno = EINVAL;
                                return (NULL);
                        }
                        hashp->hdr.lorder = info->lorder;
                }
        }
        return (hashp);
}

/*
 * Returns 0 on No Error
 */
static int32_t
init_htab(HTAB *hashp, int32_t nelem)
{
        int32_t l2, nbuckets;

        /*
         * 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->hdr.ffactor + 1;

        l2 = __log2(MAX(nelem, 2));
        nbuckets = 1 << l2;

        hashp->hdr.spares[l2] = l2 + 1;
        hashp->hdr.spares[l2 + 1] = l2 + 1;
        hashp->hdr.ovfl_point = l2;
        hashp->hdr.last_freed = 2;

        hashp->hdr.max_bucket = hashp->hdr.low_mask = nbuckets - 1;
        hashp->hdr.high_mask = (nbuckets << 1) - 1;

        /*
         * The number of header pages is the size of the header divided by
         * the amount of freespace on header pages (the page size - the
         * size of 1 integer where the length of the header info on that
         * page is stored) plus another page if it didn't divide evenly.
         */
        hashp->hdr.hdrpages =
            (sizeof(HASHHDR) / (hashp->hdr.bsize - HEADER_OVERHEAD)) +
            (((sizeof(HASHHDR) % (hashp->hdr.bsize - HEADER_OVERHEAD)) == 0)
            ? 0 : 1);

        /* Create pages for these buckets */
        /*
        for (i = 0; i <= hashp->hdr.max_bucket; i++) {
                if (__new_page(hashp, (u_int32_t)i, A_BUCKET) != 0)
                        return (-1);
        }
        */

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

        return (0);
}

/*
 * Functions to get/put hash header.  We access the file directly.
 */
static u_int32_t
hget_header(HTAB *hashp, u_int32_t page_size)
{
        u_int32_t num_copied;
        u_int8_t *hdr_dest;

        num_copied = 0;

        hdr_dest = (u_int8_t *)&hashp->hdr;

        /*
         * XXX
         * This should not be printing to stderr on a "normal" error case.
         */
        lseek(hashp->fp, 0, SEEK_SET);
        num_copied = read(hashp->fp, hdr_dest, sizeof(HASHHDR));
        if (num_copied != sizeof(HASHHDR)) {
                fprintf(stderr, "hash: could not retrieve header");
                return (0);
        }
#if DB_BYTE_ORDER == DB_LITTLE_ENDIAN
        swap_header(hashp);
#endif
        return (num_copied);
}

static void
hput_header(HTAB *hashp)
{
        HASHHDR *whdrp;
#if DB_BYTE_ORDER == DB_LITTLE_ENDIAN
        HASHHDR whdr;
#endif
        u_int32_t num_copied;

        num_copied = 0;

        whdrp = &hashp->hdr;
#if DB_BYTE_ORDER == DB_LITTLE_ENDIAN
        whdrp = &whdr;
        swap_header_copy(&hashp->hdr, whdrp);
#endif

        lseek(hashp->fp, 0, SEEK_SET);
        num_copied = write(hashp->fp, whdrp, sizeof(HASHHDR));
        if (num_copied != sizeof(HASHHDR))
                (void)fprintf(stderr, "hash: could not write hash header");
        return;
}

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

/*
 * Flushes any changes to the file if necessary and destroys the hashp
 * structure, freeing all allocated space.
 */
static int32_t
hdestroy(HTAB *hashp)
{
        int32_t save_errno;

        save_errno = 0;

#ifdef HASH_STATISTICS
        { int i;
        (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,
            "hdestroy: big key/data pages %ld\n", hash_bigpages);
        (void)fprintf(stderr,
            "keys %ld maxp %d\n", hashp->hdr.nkeys, hashp->hdr.max_bucket);

        for (i = 0; i < NCACHED; i++)
                (void)fprintf(stderr,
                    "spares[%d] = %d\n", i, hashp->hdr.spares[i]);
        }
#endif

        if (flush_meta(hashp) && !save_errno)
                save_errno = errno;

        /* Free the split page */
        if (hashp->split_buf)
                free(hashp->split_buf);

        /* Free the big key and big data returns */
        if (hashp->bigkey_buf)
                free(hashp->bigkey_buf);
        if (hashp->bigdata_buf)
                free(hashp->bigdata_buf);

        /* XXX This should really iterate over the cursor queue, but
           it's not clear how to do that, and the only cursor a hash
           table ever creates is the one used by hash_seq().  Passing
           NULL as the first arg is also a kludge, but I know that
           it's never used, so I do it.  The intent is to plug the
           memory leak.  Correctness can come later. */

        if (hashp->seq_cursor)
                hashp->seq_cursor->delete(NULL, hashp->seq_cursor, 0);

        /* shut down mpool */
        mpool_sync(hashp->mp);
        mpool_close(hashp->mp);

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

        /*
         * *** This may cause problems if hashp->fname is set in any case
         * other than the case that we are generating a temporary file name.
         * Note that the new version of mpool should support temporary
         * files within mpool itself.
         */
        if (hashp->fname && !hashp->save_file) {
#ifdef DEBUG
                fprintf(stderr, "Unlinking file %s.\n", hashp->fname);
#endif
                /* we need to chmod the file to allow it to be deleted... */
                chmod(hashp->fname, 0700);
                unlink(hashp->fname);
        }
        free(hashp);

        if (save_errno) {
                errno = save_errno;
                return (ERROR);
        }
        return (SUCCESS);
}

/*
 * Write modified pages to disk
 *
 * Returns:
 *       0 == OK
 *      -1 ERROR
 */
static int32_t
hash_sync(const DB *dbp, u_int32_t flags)
{
        HTAB *hashp;

        hashp = (HTAB *)dbp->internal;

        /*
         * XXX
         * Check success/failure conditions.
         */
        return (flush_meta(hashp) || mpool_sync(hashp->mp));
}

/*
 * Returns:
 *       0 == OK
 *      -1 indicates that errno should be set
 */
static int32_t
flush_meta(HTAB *hashp)
{
        int32_t i;

        if (!hashp->save_file)
                return (0);
        hashp->hdr.magic = HASHMAGIC;
        hashp->hdr.version = HASHVERSION;
        hashp->hdr.h_charkey = hashp->hash(CHARKEY, sizeof(CHARKEY));

        /* write out metadata */
        hput_header(hashp);

        for (i = 0; i < NCACHED; i++)
                if (hashp->mapp[i]) {
                        if (__put_page(hashp,
                            (PAGE16 *)hashp->mapp[i], A_BITMAP, 1))
                                return (-1);
                        hashp->mapp[i] = NULL;
                }
        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)
 */

/* *** make sure this is true! */

static int32_t
hash_get(const DB *dbp, const DBT *key, DBT *data, u_int32_t flag)
{
        HTAB *hashp;

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

static int32_t
hash_put(const DB *dbp, DBT *key, const DBT *data, u_int32_t flag)
{
        HTAB *hashp;

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

static int32_t
hash_delete(const DB *dbp, const DBT *key, u_int32_t flag)
{
        HTAB *hashp;

        hashp = (HTAB *)dbp->internal;
        if (flag) {
                hashp->local_errno = errno = EINVAL;
                return (ERROR);
        }
        if ((hashp->flags & O_ACCMODE) == O_RDONLY) {
                hashp->local_errno = errno = EPERM;
                return (ERROR);
        }

        return (hash_access(hashp, HASH_DELETE, key, NULL));
}

/*
 * Assume that hashp has been set in wrapper routine.
 */
static int32_t
hash_access(HTAB *hashp, ACTION action, const DBT *key, DBT *val)
{
        DBT page_key, page_val;
        CURSOR cursor;
        ITEM_INFO item_info;
        u_int32_t bucket;
        u_int32_t num_items;

#ifdef HASH_STATISTICS
        hash_accesses++;
#endif

        num_items = 0;

        /*
         * Set up item_info so that we're looking for space to add an item
         * as we cycle through the pages looking for the key.
         */
        if (action == HASH_PUT || action == HASH_PUTNEW) {
                if (ISBIG(key->size + val->size, hashp))
                        item_info.seek_size = PAIR_OVERHEAD;
                else
                        item_info.seek_size = key->size + val->size;
        } else
                item_info.seek_size = 0;
        item_info.seek_found_page = 0;

        bucket = __call_hash(hashp, (int8_t *)key->data, key->size);

        cursor.pagep = NULL;
        __get_item_reset(hashp, &cursor);

        cursor.bucket = bucket;
        while (1) {
                __get_item_next(hashp, &cursor, &page_key, &page_val, &item_info);
                if (item_info.status == ITEM_ERROR)
                        return (ABNORMAL);
                if (item_info.status == ITEM_NO_MORE)
                        break;
                num_items++;
                if (item_info.key_off == BIGPAIR) {
                        /*
                         * !!!
                         * 0 is a valid index.
                         */
                        if (__find_bigpair(hashp, &cursor, (int8_t *)key->data,
                            key->size) > 0)
                                goto found;
                } else if (key->size == page_key.size &&
                    !memcmp(key->data, page_key.data, key->size))
                        goto found;
        }
#ifdef HASH_STATISTICS
        hash_collisions++;
#endif
        __get_item_done(hashp, &cursor);

        /*
         * At this point, item_info will list either the last page in
         * the chain, or the last page in the chain plus a pgno for where
         * to find the first page in the chain with space for the
         * item we wish to add.
         */

        /* Not found */
        switch (action) {
        case HASH_PUT:
        case HASH_PUTNEW:
                if (__addel(hashp, &item_info, key, val, num_items, 0))
                        return (ERROR);
                break;
        case HASH_GET:
        case HASH_DELETE:
        default:
                return (ABNORMAL);
        }

        if (item_info.caused_expand)
                __expand_table(hashp);
        return (SUCCESS);

found:  __get_item_done(hashp, &cursor);

        switch (action) {
        case HASH_PUTNEW:
                /* mpool_put(hashp->mp, pagep, 0); */
                return (ABNORMAL);
        case HASH_GET:
                if (item_info.key_off == BIGPAIR) {
                        if (__big_return(hashp, &item_info, val, 0))
                                return (ERROR);
                } else {
                        val->data = page_val.data;
                        val->size = page_val.size;
                }
                /* *** data may not be available! */
                break;
        case HASH_PUT:
                if (__delpair(hashp, &cursor, &item_info) ||
                    __addel(hashp, &item_info, key, val, UNKNOWN, 0))
                        return (ERROR);
                __get_item_done(hashp, &cursor);
                if (item_info.caused_expand)
                        __expand_table(hashp);
                break;
        case HASH_DELETE:
                if (__delpair(hashp, &cursor, &item_info))
                        return (ERROR);
                break;
        default:
                abort();
        }
        return (SUCCESS);
}

/* ****************** CURSORS ********************************** */
CURSOR *
__cursor_creat(const DB *dbp)
{
        CURSOR *new_curs;
        HTAB *hashp;

        new_curs = (CURSOR *)malloc(sizeof(struct cursor_t));
        if (!new_curs)
                return NULL;
        new_curs->internal =
            (struct item_info *)malloc(sizeof(struct item_info));
        if (!new_curs->internal) {
                free(new_curs);
                return NULL;
        }
        new_curs->get = cursor_get;
        new_curs->delete = cursor_delete;

        new_curs->bucket = 0;
        new_curs->pgno = INVALID_PGNO;
        new_curs->ndx = 0;
        new_curs->pgndx = 0;
        new_curs->pagep = NULL;

        /* place onto queue of cursors */
        hashp = (HTAB *)dbp->internal;
        TAILQ_INSERT_TAIL(&hashp->curs_queue, new_curs, queue);

        return new_curs;
}

static int32_t
cursor_get(const DB *dbp, CURSOR *cursorp, DBT *key, DBT *val, u_int32_t flags)
{
        HTAB *hashp;
        ITEM_INFO item_info;

        hashp = (HTAB *)dbp->internal;

        if (flags && flags != R_FIRST && flags != R_NEXT) {
                hashp->local_errno = errno = EINVAL;
                return (ERROR);
        }
#ifdef HASH_STATISTICS
        hash_accesses++;
#endif

        item_info.seek_size = 0;

        if (flags == R_FIRST)
                __get_item_first(hashp, cursorp, key, val, &item_info);
        else
                __get_item_next(hashp, cursorp, key, val, &item_info);

        /*
         * This needs to be changed around.  As is, get_item_next advances
         * the pointers on the page but this function actually advances
         * bucket pointers.  This works, since the only other place we
         * use get_item_next is in hash_access which only deals with one
         * bucket at a time.  However, there is the problem that certain other
         * functions (such as find_bigpair and delpair) depend on the
         * pgndx member of the cursor.  Right now, they are using pngdx - 1
         * since indices refer to the __next__ item that is to be fetched
         * from the page.  This is ugly, as you may have noticed, whoever
         * you are.  The best solution would be to depend on item_infos to
         * deal with _current_ information, and have the cursors only
         * deal with _next_ information.  In that scheme, get_item_next
         * would also advance buckets.  Version 3...
         */


        /*
         * Must always enter this loop to do error handling and
         * check for big key/data pair.
         */
        while (1) {
                if (item_info.status == ITEM_OK) {
                        if (item_info.key_off == BIGPAIR &&
                            __big_keydata(hashp, cursorp->pagep, key, val,
                            item_info.pgndx))
                                return (ABNORMAL);

                        break;
                } else if (item_info.status != ITEM_NO_MORE)
                        return (ABNORMAL);

                __put_page(hashp, cursorp->pagep, A_RAW, 0);
                cursorp->ndx = cursorp->pgndx = 0;
                cursorp->bucket++;
                cursorp->pgno = INVALID_PGNO;
                cursorp->pagep = NULL;
                if (cursorp->bucket > hashp->hdr.max_bucket)
                        return (ABNORMAL);
                __get_item_next(hashp, cursorp, key, val, &item_info);
        }

        __get_item_done(hashp, cursorp);
        return (0);
}

static int32_t
cursor_delete(const DB *dbp, CURSOR *cursor, u_int32_t flags)
{
        /* XXX this is empirically determined, so it might not be completely
           correct, but it seems to work.  At the very least it fixes
           a memory leak */

        free(cursor->internal);
        free(cursor);

        return (0);
}

static int32_t
hash_seq(const DB *dbp, DBT *key, DBT *val, u_int32_t flag)
{
        HTAB *hashp;

        /*
         * Seq just uses the default cursor to go sequecing through the
         * database.  Note that the default cursor is the first in the list.
         */

        hashp = (HTAB *)dbp->internal;
        if (!hashp->seq_cursor)
                hashp->seq_cursor = __cursor_creat(dbp);

        return (hashp->seq_cursor->get(dbp, hashp->seq_cursor, key, val, flag));
}

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

/*
 * Returns:
 *       0 ==> OK
 *      -1 ==> Error
 */
int32_t
__expand_table(HTAB *hashp)
{
        u_int32_t old_bucket, new_bucket;
        int32_t spare_ndx;

#ifdef HASH_STATISTICS
        hash_expansions++;
#endif
        new_bucket = ++hashp->hdr.max_bucket;
        old_bucket = (hashp->hdr.max_bucket & hashp->hdr.low_mask);

        /* Get a page for this new bucket */
        if (__new_page(hashp, new_bucket, A_BUCKET) != 0)
                return (-1);

        /*
         * If the split point is increasing (hdr.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 = __log2(hashp->hdr.max_bucket + 1);
        if (spare_ndx > hashp->hdr.ovfl_point) {
                hashp->hdr.spares[spare_ndx] = hashp->hdr.spares[hashp->hdr.ovfl_point];
                hashp->hdr.ovfl_point = spare_ndx;
        }
        if (new_bucket > hashp->hdr.high_mask) {
                /* Starting a new doubling */
                hashp->hdr.low_mask = hashp->hdr.high_mask;
                hashp->hdr.high_mask = new_bucket | hashp->hdr.low_mask;
        }
        if (BUCKET_TO_PAGE(new_bucket) > MAX_PAGES(hashp)) {
                fprintf(stderr, "hash: Cannot allocate new bucket.  Pages exhausted.\n");
                return (-1);
        }
        /* Relocate records to the new bucket */
        return (__split_page(hashp, old_bucket, new_bucket));
}

u_int32_t
__call_hash(HTAB *hashp, int8_t *k, int32_t len)
{
        u_int32_t n, bucket;

        n = hashp->hash(k, len);
        bucket = n & hashp->hdr.high_mask;
        if (bucket > hashp->hdr.max_bucket)
                bucket = bucket & hashp->hdr.low_mask;
        return (bucket);
}

#if DB_BYTE_ORDER == DB_LITTLE_ENDIAN
/*
 * Hashp->hdr needs to be byteswapped.
 */
static void
swap_header_copy(HASHHDR *srcp, HASHHDR *destp)
{
        int32_t 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->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(HTAB *hashp)
{
        HASHHDR *hdrp;
        int32_t 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->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 /* DB_BYTE_ORDER == DB_LITTLE_ENDIAN */