2 * Copyright (c) 1990, 1993, 1994
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5 * This code is derived from software contributed to Berkeley by
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37 #if defined(LIBC_SCCS) && !defined(lint)
38 static char sccsid[] = "@(#)bt_overflow.c 8.5 (Berkeley) 7/16/94";
39 #endif /* LIBC_SCCS and not lint */
41 #include <sys/param.h>
53 * Big key and data entries are stored on linked lists of pages. The initial
54 * reference is byte string stored with the key or data and is the page number
55 * and size. The actual record is stored in a chain of pages linked by the
56 * nextpg field of the PAGE header.
58 * The first page of the chain has a special property. If the record is used
59 * by an internal page, it cannot be deleted and the P_PRESERVE bit will be set
63 * A single DBT is written to each chain, so a lot of space on the last page
64 * is wasted. This is a fairly major bug for some data sets.
68 * __OVFL_GET -- Get an overflow key/data item.
72 * p: pointer to { pgno_t, u_int32_t }
73 * buf: storage address
77 * RET_ERROR, RET_SUCCESS
80 __ovfl_get(t, p, ssz, buf, bufsz)
92 memmove(&pg, p, sizeof(pgno_t));
93 memmove(&sz, (char *)p + sizeof(pgno_t), sizeof(u_int32_t));
97 if (pg == P_INVALID || sz == 0)
100 /* Make the buffer bigger as necessary. */
102 *buf = (char *)(*buf == NULL ? malloc(sz) : reallocf(*buf, sz));
109 * Step through the linked list of pages, copying the data on each one
110 * into the buffer. Never copy more than the data's length.
112 plen = t->bt_psize - BTDATAOFF;
113 for (p = *buf;; p = (char *)p + nb, pg = h->nextpg) {
114 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
118 memmove(p, (char *)h + BTDATAOFF, nb);
119 mpool_put(t->bt_mp, h, 0);
124 return (RET_SUCCESS);
128 * __OVFL_PUT -- Store an overflow key/data item.
133 * pgno: storage page number
136 * RET_ERROR, RET_SUCCESS
139 __ovfl_put(t, dbt, pg)
151 * Allocate pages and copy the key/data record into them. Store the
152 * number of the first page in the chain.
154 plen = t->bt_psize - BTDATAOFF;
155 for (last = NULL, p = dbt->data, sz = dbt->size;;
156 p = (char *)p + plen, last = h) {
157 if ((h = __bt_new(t, &npg)) == NULL)
161 h->nextpg = h->prevpg = P_INVALID;
162 h->flags = P_OVERFLOW;
163 h->lower = h->upper = 0;
166 memmove((char *)h + BTDATAOFF, p, nb);
169 last->nextpg = h->pgno;
170 mpool_put(t->bt_mp, last, MPOOL_DIRTY);
174 if ((sz -= nb) == 0) {
175 mpool_put(t->bt_mp, h, MPOOL_DIRTY);
179 return (RET_SUCCESS);
183 * __OVFL_DELETE -- Delete an overflow chain.
187 * p: pointer to { pgno_t, u_int32_t }
190 * RET_ERROR, RET_SUCCESS
202 memmove(&pg, p, sizeof(pgno_t));
203 memmove(&sz, (char *)p + sizeof(pgno_t), sizeof(u_int32_t));
206 if (pg == P_INVALID || sz == 0)
209 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
212 /* Don't delete chains used by internal pages. */
213 if (h->flags & P_PRESERVE) {
214 mpool_put(t->bt_mp, h, 0);
215 return (RET_SUCCESS);
218 /* Step through the chain, calling the free routine for each page. */
219 for (plen = t->bt_psize - BTDATAOFF;; sz -= plen) {
224 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
227 return (RET_SUCCESS);