db/db/db_ret.c

/*-
 * See the file LICENSE for redistribution information.
 *
 * Copyright (c) 1996, 1997, 1998
 *  Sleepycat Software.  All rights reserved.
 */

#include "config.h"

#ifndef lint
static const char sccsid[] = "@(#)db_ret.c  10.16 (Sleepycat) 10/4/98";
#endif /* not lint */

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

#include <errno.h>
#include <string.h>
#endif

#include "db_int.h"
#include "db_page.h"
#include "btree.h"
#include "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(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(h, dbp->pgsize, indx);
        data = HKEYDATA_DATA(hk);
        break;
    case P_DUPLICATE:
    case P_LBTREE:
    case P_LRECNO:
        bk = GET_BKEYDATA(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, h->pgno));
    }

    return (__db_retcopy(dbt, data, len, memp, memsize,
        F_ISSET(dbt, DB_DBT_INTERNAL) ? NULL : dbp->db_malloc));
}

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

    /* 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;
    }

    /*
     * 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;

    /*
     * Allocate memory to be owned by the application: DB_DBT_MALLOC.
     *
     * !!!
     * 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)) {
        if ((ret = __os_malloc(len, db_malloc, &dbt->data)) != 0)
            return (ret);
    } else if (F_ISSET(dbt, DB_DBT_USERMEM)) {
        if (len != 0 && (dbt->data == NULL || dbt->ulen < len))
            return (ENOMEM);
    } else if (memp == NULL || memsize == NULL) {
        return (EINVAL);
    } else {
        if (len != 0 && (*memsize == 0 || *memsize < len)) {
            if ((ret = __os_realloc(memp, len)) != 0) {
                *memsize = 0;
                return (ret);
            }
            *memsize = len;
        }
        dbt->data = *memp;
    }

    if (len != 0)
        memcpy(dbt->data, data, len);
    return (0);
}