db_dup.c

/*-
 * See the file LICENSE for redistribution information.
 *
 * Copyright (c) 1996-2005
 *      Sleepycat Software.  All rights reserved.
 *
 * $Id: db_dup.c,v 12.2 2005/06/16 20:21:10 bostic Exp $
 */

#include "db_config.h"

#ifndef NO_SYSTEM_INCLUDES
#include <sys/types.h>

#include <string.h>
#endif

#include "db_int.h"
#include "dbinc/db_page.h"
#include "dbinc/db_shash.h"
#include "dbinc/mp.h"
#include "dbinc/db_am.h"

/*
 * __db_ditem --
 *      Remove an item from a page.
 *
 * PUBLIC:  int __db_ditem __P((DBC *, PAGE *, u_int32_t, u_int32_t));
 */
int
__db_ditem(dbc, pagep, indx, nbytes)
        DBC *dbc;
        PAGE *pagep;
        u_int32_t indx, nbytes;
{
        DB *dbp;
        DBT ldbt;
        db_indx_t cnt, *inp, offset;
        int ret;
        u_int8_t *from;

        dbp = dbc->dbp;
        if (DBC_LOGGING(dbc)) {
                ldbt.data = P_ENTRY(dbp, pagep, indx);
                ldbt.size = nbytes;
                if ((ret = __db_addrem_log(dbp, dbc->txn,
                    &LSN(pagep), 0, DB_REM_DUP, PGNO(pagep),
                    (u_int32_t)indx, nbytes, &ldbt, NULL, &LSN(pagep))) != 0)
                        return (ret);
        } else
                LSN_NOT_LOGGED(LSN(pagep));

        /*
         * If there's only a single item on the page, we don't have to
         * work hard.
         */
        if (NUM_ENT(pagep) == 1) {
                NUM_ENT(pagep) = 0;
                HOFFSET(pagep) = dbp->pgsize;
                return (0);
        }

        inp = P_INP(dbp, pagep);
        /*
         * Pack the remaining key/data items at the end of the page.  Use
         * memmove(3), the regions may overlap.
         */
        from = (u_int8_t *)pagep + HOFFSET(pagep);
        DB_ASSERT(inp[indx] >= HOFFSET(pagep));
        memmove(from + nbytes, from, inp[indx] - HOFFSET(pagep));
        HOFFSET(pagep) += nbytes;

        /* Adjust the indices' offsets. */
        offset = inp[indx];
        for (cnt = 0; cnt < NUM_ENT(pagep); ++cnt)
                if (inp[cnt] < offset)
                        inp[cnt] += nbytes;

        /* Shift the indices down. */
        --NUM_ENT(pagep);
        if (indx != NUM_ENT(pagep))
                memmove(&inp[indx], &inp[indx + 1],
                    sizeof(db_indx_t) * (NUM_ENT(pagep) - indx));

        return (0);
}

/*
 * __db_pitem --
 *      Put an item on a page.
 *
 * PUBLIC: int __db_pitem
 * PUBLIC:     __P((DBC *, PAGE *, u_int32_t, u_int32_t, DBT *, DBT *));
 */
int
__db_pitem(dbc, pagep, indx, nbytes, hdr, data)
        DBC *dbc;
        PAGE *pagep;
        u_int32_t indx;
        u_int32_t nbytes;
        DBT *hdr, *data;
{
        DB *dbp;
        BKEYDATA bk;
        DBT thdr;
        db_indx_t *inp;
        int ret;
        u_int8_t *p;

        dbp = dbc->dbp;
        if (nbytes > P_FREESPACE(dbp, pagep)) {
                DB_ASSERT(nbytes <= P_FREESPACE(dbp, pagep));
                return (EINVAL);
        }
        /*
         * Put a single item onto a page.  The logic figuring out where to
         * insert and whether it fits is handled in the caller.  All we do
         * here is manage the page shuffling.  We cheat a little bit in that
         * we don't want to copy the dbt on a normal put twice.  If hdr is
         * NULL, we create a BKEYDATA structure on the page, otherwise, just
         * copy the caller's information onto the page.
         *
         * This routine is also used to put entries onto the page where the
         * entry is pre-built, e.g., during recovery.  In this case, the hdr
         * will point to the entry, and the data argument will be NULL.
         *
         * !!!
         * There's a tremendous potential for off-by-one errors here, since
         * the passed in header sizes must be adjusted for the structure's
         * placeholder for the trailing variable-length data field.
         */
        if (DBC_LOGGING(dbc)) {
                if ((ret = __db_addrem_log(dbp, dbc->txn,
                    &LSN(pagep), 0, DB_ADD_DUP, PGNO(pagep),
                    (u_int32_t)indx, nbytes, hdr, data, &LSN(pagep))) != 0)
                        return (ret);
        } else
                LSN_NOT_LOGGED(LSN(pagep));

        if (hdr == NULL) {
                B_TSET(bk.type, B_KEYDATA, 0);
                bk.len = data == NULL ? 0 : data->size;

                thdr.data = &bk;
                thdr.size = SSZA(BKEYDATA, data);
                hdr = &thdr;
        }
        inp = P_INP(dbp, pagep);

        /* Adjust the index table, then put the item on the page. */
        if (indx != NUM_ENT(pagep))
                memmove(&inp[indx + 1], &inp[indx],
                    sizeof(db_indx_t) * (NUM_ENT(pagep) - indx));
        HOFFSET(pagep) -= nbytes;
        inp[indx] = HOFFSET(pagep);
        ++NUM_ENT(pagep);

        p = P_ENTRY(dbp, pagep, indx);
        memcpy(p, hdr->data, hdr->size);
        if (data != NULL)
                memcpy(p + hdr->size, data->data, data->size);

        return (0);
}

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