libdb2/hash/hash.c

/*
 * Copyright (c) 2001, 2011, Oracle and/or its affiliates. All rights reserved.
 */
/*-
 * 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 <paths.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

/* Solaris Kerberos */
#include <libintl.h>

#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(file, flags, mode, info, dflags)
    const char *file;
    int flags, mode, dflags;
    const HASHINFO *info;   /* Special directives for create */
{
    struct stat statbuf;
    DB *dbp;
    DBT mpool_key;
    HTAB *hashp;
    int32_t bpages, csize, new_table, save_errno, specified_file;

    if ((flags & O_ACCMODE) == O_WRONLY) {
        errno = EINVAL;
        return (NULL);
    }
    if (!(hashp = (HTAB *)calloc(1, sizeof(HTAB))))
        return (NULL);
    hashp->fp = -1;

    /* set this now, before file goes away... */
    specified_file = (file != NULL);
    if (!file) {
        file = tmpnam(NULL);
        /* store the file name so that we can unlink it later */
        hashp->fname = file;
#ifdef DEBUG
        fprintf(stderr, "Using file name %s.\n", file);
#endif
    }
    /*
     * 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 = specified_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:
        /* Solaris Kerberos */
    if (!specified_file)
        free((void*)(hashp->fname));
    free(hashp);
    errno = save_errno;
    return (NULL);
}

static int32_t
hash_close(dbp)
    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(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;
{
    struct stat statbuf;
    int32_t nelem;

    nelem = 1;
    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(hashp, nelem)
    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(hashp, page_size)
    HTAB *hashp;
    u_int32_t page_size;
{
    u_int32_t num_copied, i;
    u_int8_t *hdr_dest;

    num_copied = 0;
    i = 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)) {
        /* Solaris Kerberos: Make sure to print a newline */
        fprintf(stderr, dgettext(TEXT_DOMAIN,
            "hash: could not retrieve header\n"));
        return (0);
    }
#if DB_BYTE_ORDER == DB_LITTLE_ENDIAN
    swap_header(hashp);
#endif
    return (num_copied);
}

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

    num_copied = i = 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))
        /* Solaris Kerberos: Make sure to print a newline */
        (void)fprintf(stderr, dgettext(TEXT_DOMAIN,
            "hash: could not write hash header\n"));
    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(hashp)
    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);
        /* destroy the temporary name */
        tmpnam(NULL);
    }
    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(dbp, flags)
    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(hashp)
    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(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->local_errno = errno = EINVAL;
        return (ERROR);
    }
    return (hash_access(hashp, HASH_GET, key, data));
}

static int32_t
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->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(dbp, key, flag)
    const DB *dbp;
    const DBT *key;
    u_int32_t flag;     /* Ignored */
{
    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(hashp, action, key, val)
    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(dbp)
    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(dbp, cursorp, key, val, flags)
    const DB *dbp;
    CURSOR *cursorp;
    DBT *key, *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(dbp, cursor, flags)
    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(dbp, key, val, flag)
    const DB *dbp;
    DBT *key, *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(hashp)
    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,dgettext(TEXT_DOMAIN,
             "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(hashp, k, len)
    HTAB *hashp;
    int8_t *k;
    int32_t len;
{
    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(srcp, destp)
    HASHHDR *srcp, *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(hashp)
    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 */