db2/db/db_ret.c

   1 /*-
   2  * See the file LICENSE for redistribution information.
   3  *
   4  * Copyright (c) 1996, 1997
   5  *      Sleepycat Software.  All rights reserved.
   6  */
   7
   8 #include "config.h"
   9
  10 #ifndef lint
  11 static const char sccsid[] = "@(#)db_ret.c      10.10 (Sleepycat) 11/28/97";
  12 #endif /* not lint */
  13
  14 #ifndef NO_SYSTEM_INCLUDES
  15 #include <sys/types.h>
  16
  17 #include <errno.h>
  18 #include <stdio.h>
  19 #include <stdlib.h>
  20 #include <string.h>
  21 #endif
  22
  23 #include "db_int.h"
  24 #include "db_page.h"
  25 #include "btree.h"
  26 #include "hash.h"
  27 #include "db_am.h"
  28
  29 /*
  30  * __db_ret --
  31  *      Build return DBT.
  32  *
  33  * PUBLIC: int __db_ret __P((DB *,
  34  * PUBLIC:    PAGE *, u_int32_t, DBT *, void **, u_int32_t *));
  35  */
  36 int
  37 __db_ret(dbp, h, indx, dbt, memp, memsize)
  38         DB *dbp;
  39         PAGE *h;
  40         u_int32_t indx;
  41         DBT *dbt;
  42         void **memp;
  43         u_int32_t *memsize;
  44 {
  45         BKEYDATA *bk;
  46         HOFFPAGE ho;
  47         BOVERFLOW *bo;
  48         u_int32_t len;
  49         u_int8_t *hk;
  50         void *data;
  51
  52         switch (TYPE(h)) {
  53         case P_HASH:
  54                 hk = P_ENTRY(h, indx);
  55                 if (HPAGE_PTYPE(hk) == H_OFFPAGE) {
  56                         memcpy(&ho, hk, sizeof(HOFFPAGE));
  57                         return (__db_goff(dbp, dbt,
  58                             ho.tlen, ho.pgno, memp, memsize));
  59                 }
  60                 len = LEN_HKEYDATA(h, dbp->pgsize, indx);
  61                 data = HKEYDATA_DATA(hk);
  62                 break;
  63         case P_DUPLICATE:
  64         case P_LBTREE:
  65         case P_LRECNO:
  66                 bk = GET_BKEYDATA(h, indx);
  67                 if (B_TYPE(bk->type) == B_OVERFLOW) {
  68                         bo = (BOVERFLOW *)bk;
  69                         return (__db_goff(dbp, dbt,
  70                             bo->tlen, bo->pgno, memp, memsize));
  71                 }
  72                 len = bk->len;
  73                 data = bk->data;
  74                 break;
  75         default:
  76                 return (__db_pgfmt(dbp, h->pgno));
  77         }
  78
  79         return (__db_retcopy(dbt, data, len, memp, memsize,
  80             F_ISSET(dbt, DB_DBT_INTERNAL) ? NULL : dbp->db_malloc));
  81 }
  82
  83 /*
  84  * __db_retcopy --
  85  *      Copy the returned data into the user's DBT, handling special flags.
  86  *
  87  * PUBLIC: int __db_retcopy __P((DBT *,
  88  * PUBLIC:    void *, u_int32_t, void **, u_int32_t *, void *(*)(size_t)));
  89  */
  90 int
  91 __db_retcopy(dbt, data, len, memp, memsize, db_malloc)
  92         DBT *dbt;
  93         void *data;
  94         u_int32_t len;
  95         void **memp;
  96         u_int32_t *memsize;
  97         void *(*db_malloc) __P((size_t));
  98 {
  99         /* If returning a partial record, reset the length. */
 100         if (F_ISSET(dbt, DB_DBT_PARTIAL)) {
 101                 data = (u_int8_t *)data + dbt->doff;
 102                 if (len > dbt->doff) {
 103                         len -= dbt->doff;
 104                         if (len > dbt->dlen)
 105                                 len = dbt->dlen;
 106                 } else
 107                         len = 0;
 108         }
 109
 110         /*
 111          * Return the length of the returned record in the DBT size field.
 112          * This satisfies the requirement that if we're using user memory
 113          * and insufficient memory was provided, return the amount necessary
 114          * in the size field.
 115          */
 116         dbt->size = len;
 117
 118         /*
 119          * Allocate memory to be owned by the application: DB_DBT_MALLOC.
 120          *
 121          * !!!
 122          * We always allocate memory, even if we're copying out 0 bytes. This
 123          * guarantees consistency, i.e., the application can always free memory
 124          * without concern as to how many bytes of the record were requested.
 125          *
 126          * XXX
 127          * Never allocate 0 bytes, it's known to make malloc/realloc unhappy.
 128          *
 129          * Use the memory specified by the application: DB_DBT_USERMEM.
 130          *
 131          * !!!
 132          * If the length we're going to copy is 0, the application-supplied
 133          * memory pointer is allowed to be NULL.
 134          */
 135         if (F_ISSET(dbt, DB_DBT_MALLOC)) {
 136                 dbt->data = db_malloc == NULL ?
 137                     (void *)__db_malloc(len) :
 138                     (void *)db_malloc(len + 1);
 139                 if (dbt->data == NULL)
 140                         return (ENOMEM);
 141         } else if (F_ISSET(dbt, DB_DBT_USERMEM)) {
 142                 if (len != 0 && (dbt->data == NULL || dbt->ulen < len))
 143                         return (ENOMEM);
 144         } else if (memp == NULL || memsize == NULL) {
 145                 return (EINVAL);
 146         } else {
 147                 if (len != 0 && (*memsize == 0 || *memsize < len)) {
 148                         *memp = *memp == NULL ?
 149                             (void *)__db_malloc(len) :
 150                             (void *)__db_realloc(*memp, len);
 151                         if (*memp == NULL) {
 152                                 *memsize = 0;
 153                                 return (ENOMEM);
 154                         }
 155                         *memsize = len;
 156                 }
 157                 dbt->data = *memp;
 158         }
 159
 160         if (len != 0)
 161                 memcpy(dbt->data, data, len);
 162         return (0);
 163 }