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36 * @(#)hash.h 8.3 (Berkeley) 5/31/94
37 * $FreeBSD: src/lib/libc/db/hash/hash.h,v 1.4.8.1 2001/03/05 03:50:02 kris Exp $
38 * $DragonFly: src/lib/libc/db/hash/hash.h,v 1.3 2003/11/12 20:21:23 eirikn Exp $
43 HASH_GET, HASH_PUT, HASH_PUTNEW, HASH_DELETE, HASH_FIRST, HASH_NEXT
46 /* Buffer Management structures */
47 typedef struct _bufhead BUFHEAD;
50 BUFHEAD *prev; /* LRU links */
51 BUFHEAD *next; /* LRU links */
52 BUFHEAD *ovfl; /* Overflow page buffer header */
53 u_int32_t addr; /* Address of this page */
54 char *page; /* Actual page data */
56 #define BUF_MOD 0x0001
57 #define BUF_DISK 0x0002
58 #define BUF_BUCKET 0x0004
59 #define BUF_PIN 0x0008
62 #define IS_BUCKET(X) ((X) & BUF_BUCKET)
64 typedef BUFHEAD **SEGMENT;
66 /* Hash Table Information */
67 typedef struct hashhdr { /* Disk resident portion */
68 int magic; /* Magic NO for hash tables */
69 int version; /* Version ID */
70 u_int32_t lorder; /* Byte Order */
71 int bsize; /* Bucket/Page Size */
72 int bshift; /* Bucket shift */
73 int dsize; /* Directory Size */
74 int ssize; /* Segment Size */
75 int sshift; /* Segment shift */
76 int ovfl_point; /* Where overflow pages are being
78 int last_freed; /* Last overflow page freed */
79 int max_bucket; /* ID of Maximum bucket in use */
80 int high_mask; /* Mask to modulo into entire table */
81 int low_mask; /* Mask to modulo into lower half of
83 int ffactor; /* Fill factor */
84 int nkeys; /* Number of keys in hash table */
85 int hdrpages; /* Size of table header */
86 int h_charkey; /* value of hash(CHARKEY) */
87 #define NCACHED 32 /* number of bit maps and spare
89 int spares[NCACHED];/* spare pages for overflow */
90 u_int16_t bitmaps[NCACHED]; /* address of overflow page
94 typedef struct htab { /* Memory resident data structure */
95 HASHHDR hdr; /* Header */
96 int nsegs; /* Number of allocated segments */
97 int exsegs; /* Number of extra allocated
99 u_int32_t /* Hash function */
100 (*hash)(const void *, size_t);
101 int flags; /* Flag values */
102 int fp; /* File pointer */
103 char *tmp_buf; /* Temporary Buffer for BIG data */
104 char *tmp_key; /* Temporary Buffer for BIG keys */
105 BUFHEAD *cpage; /* Current page */
106 int cbucket; /* Current bucket */
107 int cndx; /* Index of next item on cpage */
108 int error; /* Error Number -- for DBM
110 int new_file; /* Indicates if fd is backing store
112 int save_file; /* Indicates whether we need to flush
115 u_int32_t *mapp[NCACHED]; /* Pointers to page maps */
116 int nmaps; /* Initial number of bitmaps */
117 int nbufs; /* Number of buffers left to
119 BUFHEAD bufhead; /* Header of buffer lru list */
120 SEGMENT *dir; /* Hash Bucket directory */
126 #define MAX_BSIZE 65536 /* 2^16 */
127 #define MIN_BUFFERS 6
128 #define MINHDRSIZE 512
129 #define DEF_BUFSIZE 65536 /* 64 K */
130 #define DEF_BUCKET_SIZE 4096
131 #define DEF_BUCKET_SHIFT 12 /* log2(BUCKET) */
132 #define DEF_SEGSIZE 256
133 #define DEF_SEGSIZE_SHIFT 8 /* log2(SEGSIZE) */
134 #define DEF_DIRSIZE 256
135 #define DEF_FFACTOR 65536
136 #define MIN_FFACTOR 4
138 #define CHARKEY "%$sniglet^&"
139 #define NUMKEY 1038583
141 #define INT_TO_BYTE 2
142 #define INT_BYTE_SHIFT 5
143 #define ALL_SET ((u_int32_t)0xFFFFFFFF)
146 #define PTROF(X) ((BUFHEAD *)((ptrdiff_t)(X)&~0x3))
147 #define ISMOD(X) ((u_int32_t)(ptrdiff_t)(X)&0x1)
148 #define DOMOD(X) ((X) = (char *)((ptrdiff_t)(X)|0x1))
149 #define ISDISK(X) ((u_int32_t)(ptrdiff_t)(X)&0x2)
150 #define DODISK(X) ((X) = (char *)((ptrdiff_t)(X)|0x2))
152 #define BITS_PER_MAP 32
154 /* Given the address of the beginning of a big map, clear/set the nth bit */
155 #define CLRBIT(A, N) ((A)[(N)/BITS_PER_MAP] &= ~(1<<((N)%BITS_PER_MAP)))
156 #define SETBIT(A, N) ((A)[(N)/BITS_PER_MAP] |= (1<<((N)%BITS_PER_MAP)))
157 #define ISSET(A, N) ((A)[(N)/BITS_PER_MAP] & (1<<((N)%BITS_PER_MAP)))
159 /* Overflow management */
161 * Overflow page numbers are allocated per split point. At each doubling of
162 * the table, we can allocate extra pages. So, an overflow page number has
163 * the top 5 bits indicate which split point and the lower 11 bits indicate
164 * which page at that split point is indicated (pages within split points are
165 * numberered starting with 1).
168 #define SPLITSHIFT 11
169 #define SPLITMASK 0x7FF
170 #define SPLITNUM(N) (((u_int32_t)(N)) >> SPLITSHIFT)
171 #define OPAGENUM(N) ((N) & SPLITMASK)
172 #define OADDR_OF(S,O) ((u_int32_t)((u_int32_t)(S) << SPLITSHIFT) + (O))
174 #define BUCKET_TO_PAGE(B) \
175 (B) + hashp->HDRPAGES + ((B) ? hashp->SPARES[__log2((B)+1)-1] : 0)
176 #define OADDR_TO_PAGE(B) \
177 BUCKET_TO_PAGE ( (1 << SPLITNUM((B))) -1 ) + OPAGENUM((B));
180 * page.h contains a detailed description of the page format.
182 * Normally, keys and data are accessed from offset tables in the top of
183 * each page which point to the beginning of the key and data. There are
184 * four flag values which may be stored in these offset tables which indicate
188 * OVFLPAGE Rather than a key data pair, this pair contains
189 * the address of an overflow page. The format of
191 * OVERFLOW_PAGE_NUMBER OVFLPAGE
193 * PARTIAL_KEY This must be the first key/data pair on a page
194 * and implies that page contains only a partial key.
195 * That is, the key is too big to fit on a single page
196 * so it starts on this page and continues on the next.
197 * The format of the page is:
198 * KEY_OFF PARTIAL_KEY OVFL_PAGENO OVFLPAGE
200 * KEY_OFF -- offset of the beginning of the key
202 * OVFL_PAGENO - page number of the next overflow page
205 * FULL_KEY This must be the first key/data pair on the page. It
206 * is used in two cases.
209 * There is a complete key on the page but no data
210 * (because it wouldn't fit). The next page contains
214 * KEY_OFF FULL_KEY OVFL_PAGENO OVFL_PAGE
216 * KEY_OFF -- offset of the beginning of the key
218 * OVFL_PAGENO - page number of the next overflow page
222 * This page contains no key, but part of a large
223 * data field, which is continued on the next page.
226 * DATA_OFF FULL_KEY OVFL_PAGENO OVFL_PAGE
228 * KEY_OFF -- offset of the beginning of the data on
231 * OVFL_PAGENO - page number of the next overflow page
235 * This must be the first key/data pair on the page.
236 * There are two cases:
239 * This page contains a key and the beginning of the
240 * data field, but the data field is continued on the
244 * KEY_OFF FULL_KEY_DATA OVFL_PAGENO DATA_OFF
246 * KEY_OFF -- offset of the beginning of the key
248 * OVFL_PAGENO - page number of the next overflow page
249 * DATA_OFF -- offset of the beginning of the data
252 * This page contains the last page of a big data pair.
253 * There is no key, only the tail end of the data
257 * DATA_OFF FULL_KEY_DATA <OVFL_PAGENO> <OVFLPAGE>
259 * DATA_OFF -- offset of the beginning of the data on
262 * OVFL_PAGENO - page number of the next overflow page
265 * OVFL_PAGENO and OVFLPAGE are optional (they are
266 * not present if there is no next page).
270 #define PARTIAL_KEY 1
272 #define FULL_KEY_DATA 3
275 /* Short hands for accessing structure */
276 #define BSIZE hdr.bsize
277 #define BSHIFT hdr.bshift
278 #define DSIZE hdr.dsize
279 #define SGSIZE hdr.ssize
280 #define SSHIFT hdr.sshift
281 #define LORDER hdr.lorder
282 #define OVFL_POINT hdr.ovfl_point
283 #define LAST_FREED hdr.last_freed
284 #define MAX_BUCKET hdr.max_bucket
285 #define FFACTOR hdr.ffactor
286 #define HIGH_MASK hdr.high_mask
287 #define LOW_MASK hdr.low_mask
288 #define NKEYS hdr.nkeys
289 #define HDRPAGES hdr.hdrpages
290 #define SPARES hdr.spares
291 #define BITMAPS hdr.bitmaps
292 #define VERSION hdr.version
293 #define MAGIC hdr.magic
294 #define NEXT_FREE hdr.next_free
295 #define H_CHARKEY hdr.h_charkey