db_ret.c

/*-
 * See the file LICENSE for redistribution information.
 *
 * Copyright (c) 1996-2005
 *      Sleepycat Software.  All rights reserved.
 *
 * $Id: db_ret.c,v 12.1 2005/06/16 20:21:14 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_am.h"

/*
 * __db_ret --
 *      Build return DBT.
 *
 * PUBLIC: int __db_ret __P((DB *,
 * PUBLIC:    PAGE *, u_int32_t, DBT *, void **, u_int32_t *));
 */
int
__db_ret(dbp, h, indx, dbt, memp, memsize)
        DB *dbp;
        PAGE *h;
        u_int32_t indx;
        DBT *dbt;
        void **memp;
        u_int32_t *memsize;
{
        BKEYDATA *bk;
        HOFFPAGE ho;
        BOVERFLOW *bo;
        u_int32_t len;
        u_int8_t *hk;
        void *data;

        switch (TYPE(h)) {
        case P_HASH:
                hk = P_ENTRY(dbp, h, indx);
                if (HPAGE_PTYPE(hk) == H_OFFPAGE) {
                        memcpy(&ho, hk, sizeof(HOFFPAGE));
                        return (__db_goff(dbp, dbt,
                            ho.tlen, ho.pgno, memp, memsize));
                }
                len = LEN_HKEYDATA(dbp, h, dbp->pgsize, indx);
                data = HKEYDATA_DATA(hk);
                break;
        case P_LBTREE:
        case P_LDUP:
        case P_LRECNO:
                bk = GET_BKEYDATA(dbp, h, indx);
                if (B_TYPE(bk->type) == B_OVERFLOW) {
                        bo = (BOVERFLOW *)bk;
                        return (__db_goff(dbp, dbt,
                            bo->tlen, bo->pgno, memp, memsize));
                }
                len = bk->len;
                data = bk->data;
                break;
        default:
                return (__db_pgfmt(dbp->dbenv, h->pgno));
        }

        return (__db_retcopy(dbp->dbenv, dbt, data, len, memp, memsize));
}

/*
 * __db_retcopy --
 *      Copy the returned data into the user's DBT, handling special flags.
 *
 * PUBLIC: int __db_retcopy __P((DB_ENV *, DBT *,
 * PUBLIC:    void *, u_int32_t, void **, u_int32_t *));
 */
int
__db_retcopy(dbenv, dbt, data, len, memp, memsize)
        DB_ENV *dbenv;
        DBT *dbt;
        void *data;
        u_int32_t len;
        void **memp;
        u_int32_t *memsize;
{
        int ret;

        ret = 0;

        /* If returning a partial record, reset the length. */
        if (F_ISSET(dbt, DB_DBT_PARTIAL)) {
                data = (u_int8_t *)data + dbt->doff;
                if (len > dbt->doff) {
                        len -= dbt->doff;
                        if (len > dbt->dlen)
                                len = dbt->dlen;
                } else
                        len = 0;
        }

        /*
         * Allocate memory to be owned by the application: DB_DBT_MALLOC,
         * DB_DBT_REALLOC.
         *
         * !!!
         * We always allocate memory, even if we're copying out 0 bytes. This
         * guarantees consistency, i.e., the application can always free memory
         * without concern as to how many bytes of the record were requested.
         *
         * Use the memory specified by the application: DB_DBT_USERMEM.
         *
         * !!!
         * If the length we're going to copy is 0, the application-supplied
         * memory pointer is allowed to be NULL.
         */
        if (F_ISSET(dbt, DB_DBT_MALLOC)) {
                ret = __os_umalloc(dbenv, len, &dbt->data);
        } else if (F_ISSET(dbt, DB_DBT_REALLOC)) {
                if (dbt->data == NULL || dbt->size == 0 || dbt->size < len)
                        ret = __os_urealloc(dbenv, len, &dbt->data);
        } else if (F_ISSET(dbt, DB_DBT_USERMEM)) {
                if (len != 0 && (dbt->data == NULL || dbt->ulen < len))
                        ret = DB_BUFFER_SMALL;
        } else if (memp == NULL || memsize == NULL) {
                ret = EINVAL;
        } else {
                if (len != 0 && (*memsize == 0 || *memsize < len)) {
                        if ((ret = __os_realloc(dbenv, len, memp)) == 0)
                                *memsize = len;
                        else
                                *memsize = 0;
                }
                if (ret == 0)
                        dbt->data = *memp;
        }

        if (ret == 0 && len != 0)
                memcpy(dbt->data, data, len);

        /*
         * Return the length of the returned record in the DBT size field.
         * This satisfies the requirement that if we're using user memory
         * and insufficient memory was provided, return the amount necessary
         * in the size field.
         */
        dbt->size = len;

        return (ret);
}

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