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34 * @(#)hash.h 8.3 (Berkeley) 5/31/94
40 HASH_GET, HASH_PUT, HASH_PUTNEW, HASH_DELETE, HASH_FIRST, HASH_NEXT
43 /* Buffer Management structures */
44 typedef struct _bufhead BUFHEAD;
47 BUFHEAD *prev; /* LRU links */
48 BUFHEAD *next; /* LRU links */
49 BUFHEAD *ovfl; /* Overflow page buffer header */
50 u_int32_t addr; /* Address of this page */
51 char *page; /* Actual page data */
53 #define BUF_MOD 0x0001
54 #define BUF_DISK 0x0002
55 #define BUF_BUCKET 0x0004
56 #define BUF_PIN 0x0008
59 #define IS_BUCKET(X) ((X) & BUF_BUCKET)
61 typedef BUFHEAD **SEGMENT;
63 /* Hash Table Information */
64 typedef struct hashhdr { /* Disk resident portion */
65 int32_t magic; /* Magic NO for hash tables */
66 int32_t version; /* Version ID */
67 u_int32_t lorder; /* Byte Order */
68 int32_t bsize; /* Bucket/Page Size */
69 int32_t bshift; /* Bucket shift */
70 int32_t dsize; /* Directory Size */
71 int32_t ssize; /* Segment Size */
72 int32_t sshift; /* Segment shift */
73 int32_t ovfl_point; /* Where overflow pages are being
75 int32_t last_freed; /* Last overflow page freed */
76 u_int32_t max_bucket; /* ID of Maximum bucket in use */
77 u_int32_t high_mask; /* Mask to modulo into entire table */
78 u_int32_t low_mask; /* Mask to modulo into lower half of
80 u_int32_t ffactor; /* Fill factor */
81 int32_t nkeys; /* Number of keys in hash table */
82 int32_t hdrpages; /* Size of table header */
83 int32_t h_charkey; /* value of hash(CHARKEY) */
84 #define NCACHED 32 /* number of bit maps and spare
86 int32_t spares[NCACHED];/* spare pages for overflow */
87 u_int16_t bitmaps[NCACHED]; /* address of overflow page
91 typedef struct htab { /* Memory resident data structure */
92 HASHHDR hdr; /* Header */
93 int nsegs; /* Number of allocated segments */
94 int exsegs; /* Number of extra allocated
96 u_int32_t /* Hash function */
97 (*hash)(const void *, size_t);
98 int flags; /* Flag values */
99 int fp; /* File pointer */
100 char *tmp_buf; /* Temporary Buffer for BIG data */
101 char *tmp_key; /* Temporary Buffer for BIG keys */
102 BUFHEAD *cpage; /* Current page */
103 int cbucket; /* Current bucket */
104 int cndx; /* Index of next item on cpage */
105 int error; /* Error Number -- for DBM
107 int new_file; /* Indicates if fd is backing store
109 int save_file; /* Indicates whether we need to flush
112 u_int32_t *mapp[NCACHED]; /* Pointers to page maps */
113 int nmaps; /* Initial number of bitmaps */
114 int nbufs; /* Number of buffers left to
116 BUFHEAD bufhead; /* Header of buffer lru list */
117 SEGMENT *dir; /* Hash Bucket directory */
123 #define MAX_BSIZE 32768 /* 2^15 but should be 65536 */
124 #define MIN_BUFFERS 6
125 #define MINHDRSIZE 512
126 #define DEF_BUFSIZE 65536 /* 64 K */
127 #define DEF_BUCKET_SIZE 4096
128 #define DEF_BUCKET_SHIFT 12 /* log2(BUCKET) */
129 #define DEF_SEGSIZE 256
130 #define DEF_SEGSIZE_SHIFT 8 /* log2(SEGSIZE) */
131 #define DEF_DIRSIZE 256
132 #define DEF_FFACTOR 65536
133 #define MIN_FFACTOR 4
135 #define CHARKEY "%$sniglet^&"
136 #define NUMKEY 1038583
138 #define INT_TO_BYTE 2
139 #define INT_BYTE_SHIFT 5
140 #define ALL_SET ((u_int32_t)0xFFFFFFFF)
143 #define PTROF(X) ((BUFHEAD *)((intptr_t)(X)&~0x3))
144 #define ISMOD(X) ((u_int32_t)(intptr_t)(X)&0x1)
145 #define DOMOD(X) ((X) = (char *)((intptr_t)(X)|0x1))
146 #define ISDISK(X) ((u_int32_t)(intptr_t)(X)&0x2)
147 #define DODISK(X) ((X) = (char *)((intptr_t)(X)|0x2))
149 #define BITS_PER_MAP 32
151 /* Given the address of the beginning of a big map, clear/set the nth bit */
152 #define CLRBIT(A, N) ((A)[(N)/BITS_PER_MAP] &= ~(1<<((N)%BITS_PER_MAP)))
153 #define SETBIT(A, N) ((A)[(N)/BITS_PER_MAP] |= (1<<((N)%BITS_PER_MAP)))
154 #define ISSET(A, N) ((A)[(N)/BITS_PER_MAP] & (1<<((N)%BITS_PER_MAP)))
156 /* Overflow management */
158 * Overflow page numbers are allocated per split point. At each doubling of
159 * the table, we can allocate extra pages. So, an overflow page number has
160 * the top 5 bits indicate which split point and the lower 11 bits indicate
161 * which page at that split point is indicated (pages within split points are
162 * numberered starting with 1).
165 #define SPLITSHIFT 11
166 #define SPLITMASK 0x7FF
167 #define SPLITNUM(N) (((u_int32_t)(N)) >> SPLITSHIFT)
168 #define OPAGENUM(N) ((N) & SPLITMASK)
169 #define OADDR_OF(S,O) ((u_int32_t)((u_int32_t)(S) << SPLITSHIFT) + (O))
171 #define BUCKET_TO_PAGE(B) \
172 (B) + hashp->HDRPAGES + ((B) ? hashp->SPARES[__log2((B)+1)-1] : 0)
173 #define OADDR_TO_PAGE(B) \
174 BUCKET_TO_PAGE ( (1 << SPLITNUM((B))) -1 ) + OPAGENUM((B));
177 * page.h contains a detailed description of the page format.
179 * Normally, keys and data are accessed from offset tables in the top of
180 * each page which point to the beginning of the key and data. There are
181 * four flag values which may be stored in these offset tables which indicate
185 * OVFLPAGE Rather than a key data pair, this pair contains
186 * the address of an overflow page. The format of
188 * OVERFLOW_PAGE_NUMBER OVFLPAGE
190 * PARTIAL_KEY This must be the first key/data pair on a page
191 * and implies that page contains only a partial key.
192 * That is, the key is too big to fit on a single page
193 * so it starts on this page and continues on the next.
194 * The format of the page is:
195 * KEY_OFF PARTIAL_KEY OVFL_PAGENO OVFLPAGE
197 * KEY_OFF -- offset of the beginning of the key
199 * OVFL_PAGENO - page number of the next overflow page
202 * FULL_KEY This must be the first key/data pair on the page. It
203 * is used in two cases.
206 * There is a complete key on the page but no data
207 * (because it wouldn't fit). The next page contains
211 * KEY_OFF FULL_KEY OVFL_PAGENO OVFL_PAGE
213 * KEY_OFF -- offset of the beginning of the key
215 * OVFL_PAGENO - page number of the next overflow page
219 * This page contains no key, but part of a large
220 * data field, which is continued on the next page.
223 * DATA_OFF FULL_KEY OVFL_PAGENO OVFL_PAGE
225 * KEY_OFF -- offset of the beginning of the data on
228 * OVFL_PAGENO - page number of the next overflow page
232 * This must be the first key/data pair on the page.
233 * There are two cases:
236 * This page contains a key and the beginning of the
237 * data field, but the data field is continued on the
241 * KEY_OFF FULL_KEY_DATA OVFL_PAGENO DATA_OFF
243 * KEY_OFF -- offset of the beginning of the key
245 * OVFL_PAGENO - page number of the next overflow page
246 * DATA_OFF -- offset of the beginning of the data
249 * This page contains the last page of a big data pair.
250 * There is no key, only the tail end of the data
254 * DATA_OFF FULL_KEY_DATA <OVFL_PAGENO> <OVFLPAGE>
256 * DATA_OFF -- offset of the beginning of the data on
259 * OVFL_PAGENO - page number of the next overflow page
262 * OVFL_PAGENO and OVFLPAGE are optional (they are
263 * not present if there is no next page).
267 #define PARTIAL_KEY 1
269 #define FULL_KEY_DATA 3
272 /* Short hands for accessing structure */
273 #define BSIZE hdr.bsize
274 #define BSHIFT hdr.bshift
275 #define DSIZE hdr.dsize
276 #define SGSIZE hdr.ssize
277 #define SSHIFT hdr.sshift
278 #define LORDER hdr.lorder
279 #define OVFL_POINT hdr.ovfl_point
280 #define LAST_FREED hdr.last_freed
281 #define MAX_BUCKET hdr.max_bucket
282 #define FFACTOR hdr.ffactor
283 #define HIGH_MASK hdr.high_mask
284 #define LOW_MASK hdr.low_mask
285 #define NKEYS hdr.nkeys
286 #define HDRPAGES hdr.hdrpages
287 #define SPARES hdr.spares
288 #define BITMAPS hdr.bitmaps
289 #define VERSION hdr.version
290 #define MAGIC hdr.magic
291 #define NEXT_FREE hdr.next_free
292 #define H_CHARKEY hdr.h_charkey