1 /*- 2 * Copyright (c) 1990 The Regents of the University of California. 3 * All rights reserved. 4 * 5 * This code is derived from software contributed to Berkeley by 6 * Margo Seltzer. 7 * 8 * %sccs.include.redist.c% 9 * 10 * @(#)hash.h 5.4 (Berkeley) 03/12/91 11 */ 12 13 /* Operations */ 14 typedef enum { HASH_GET, HASH_PUT, HASH_PUTNEW, HASH_DELETE, 15 HASH_FIRST, HASH_NEXT } ACTION; 16 17 /* Buffer Management structures */ 18 typedef struct _bufhead BUFHEAD; 19 20 struct _bufhead { 21 BUFHEAD *prev; /* LRU links */ 22 BUFHEAD *next; /* LRU links */ 23 BUFHEAD *ovfl; /* Overflow page buffer header */ 24 u_int addr; /* Address of this page */ 25 char *page; /* Actual page data */ 26 char flags; 27 #define BUF_MOD 0x0001 28 #define BUF_DISK 0x0002 29 #define BUF_BUCKET 0x0004 30 #define BUF_PIN 0x0008 31 }; 32 33 34 #define IS_BUCKET(X) (X & BUF_BUCKET) 35 36 typedef BUFHEAD **SEGMENT; 37 38 /* Hash Table Information */ 39 typedef struct hashhdr { /* Disk resident portion */ 40 int magic; /* Magic NO for hash tables */ 41 int version; /* Version ID */ 42 long lorder; /* Byte Order */ 43 int bsize; /* Bucket/Page Size */ 44 int bshift; /* Bucket shift */ 45 int dsize; /* Directory Size */ 46 int ssize; /* Segment Size */ 47 int sshift; /* Segment shift */ 48 int max_bucket; /* ID of Maximum bucket in use */ 49 int high_mask; /* Mask to modulo into entire table */ 50 int low_mask; /* Mask to modulo into lower half of table */ 51 int ffactor; /* Fill factor */ 52 int nkeys; /* Number of keys in hash table */ 53 int hdrpages; /* Size of table header */ 54 int h_charkey; /* value of hash(CHARKEY) */ 55 # define NCACHED 32 /* number of bit maps and spare points*/ 56 int spares[NCACHED]; /* spare pages for overflow */ 57 u_short bitmaps[NCACHED]; /* address of overflow page bitmaps */ 58 } HASHHDR; 59 60 typedef struct htab { /* Memory resident data structure */ 61 HASHHDR hdr; /* Header */ 62 int nsegs; /* Number of allocated segments */ 63 int exsegs; /* Number of extra allocated segments */ 64 int (*hash)(); /* Hash Function */ 65 int flags; /* Flag values */ 66 int fp; /* File pointer */ 67 char *tmp_buf; /* Temporary Buffer for BIG data */ 68 char *tmp_key; /* Temporary Buffer for BIG keys */ 69 BUFHEAD *cpage; /* Current page */ 70 int cbucket; /* Current bucket */ 71 int cndx; /* Index of next item on cpage */ 72 int errno; /* Error Number -- for DBM compatability */ 73 int new_file; /* Indicates whether fd is backing store or no */ 74 int save_file; /* Indicates whether we need to flush file at exit */ 75 u_long *mapp[NCACHED]; /* Pointers to page maps */ 76 int nmaps; /* Initial number of bitmaps */ 77 int nbufs; /* Number of buffers left to allocate */ 78 BUFHEAD bufhead; /* Header of buffer lru list */ 79 SEGMENT *dir; /* Hash Bucket directory */ 80 } HTAB; 81 82 83 /* 84 * Constants 85 */ 86 #define MAX_BSIZE 65536 /* 2^16 */ 87 #define MIN_BUFFERS 6 88 #define MINHDRSIZE 512 89 #define DEF_BUFSIZE 65536 /* 64 K */ 90 #define DEF_BUCKET_SIZE 256 91 #define DEF_BUCKET_SHIFT 8 /* log2(BUCKET) */ 92 #define DEF_SEGSIZE 256 93 #define DEF_SEGSIZE_SHIFT 8 /* log2(SEGSIZE) */ 94 #define DEF_DIRSIZE 256 95 #define DEF_FFACTOR 5 96 #define SPLTMAX 8 97 #define CHARKEY "%$sniglet^&" 98 #define NUMKEY 1038583 99 #define VERSION_NO 3 100 #define BYTE_SHIFT 3 101 #define INT_TO_BYTE 2 102 #define INT_BYTE_SHIFT 5 103 #define ALL_SET ((unsigned)0xFFFFFFFF) 104 #define ALL_CLEAR 0 105 106 107 #define PTROF(X) ((BUFHEAD *)((unsigned)(X)&~0x3)) 108 #define ISMOD(X) ((unsigned)(X)&0x1) 109 #define DOMOD(X) (X = (char *)( (unsigned)X | 0x1)) 110 #define ISDISK(X) ((unsigned)(X)&0x2) 111 #define DODISK(X) (X = (char *)( (unsigned)X | 0x2)) 112 113 #define BITS_PER_MAP 32 114 115 /* Given the address of the beginning of a big map, clear/set the nth bit */ 116 117 #define CLRBIT(A,N) ((A)[N/BITS_PER_MAP] &= ~(1<<(N%BITS_PER_MAP))) 118 #define SETBIT(A,N) ((A)[N/BITS_PER_MAP] |= (1<<(N%BITS_PER_MAP))) 119 #define ISSET(A,N) ((A)[N/BITS_PER_MAP] & (1<<(N%BITS_PER_MAP))) 120 121 /* Overflow management */ 122 /* 123 Overflow page numbers are allocated per split point. 124 At each doubling of the table, we can allocate extra 125 pages. So, an overflow page number has the top 5 bits 126 indicate which split point and the lower 11 bits indicate 127 which page at that split point is indicated (pages within 128 split points are numberered starting with 1). 129 130 131 */ 132 133 #define SPLITSHIFT 11 134 #define SPLITMASK 0x7FF 135 #define SPLITNUM(N) (((unsigned)N) >> SPLITSHIFT) 136 #define OPAGENUM(N) (N & SPLITMASK) 137 #define OADDR_OF(S,O) ((unsigned)((unsigned)S << SPLITSHIFT) + O) 138 139 #define BUCKET_TO_PAGE(B) \ 140 B + hashp->HDRPAGES + (B ? hashp->SPARES[__log2(B+1)-1] : 0) 141 #define OADDR_TO_PAGE(B) \ 142 BUCKET_TO_PAGE ( (1 << SPLITNUM(B)) -1 ) + OPAGENUM(B); 143 144 /* 145 page.h contains a detailed description of the page format. 146 147 Normally, keys and data are accessed from offset tables in the 148 top of each page which point to the beginning of the key and 149 data. There are four flag values which may be stored in these 150 offset tables which indicate the following: 151 152 OVFLPAGE Rather than a key data pair, this pair contains 153 the address of an overflow page. The format of 154 the pair is: 155 OVERFLOW_PAGE_NUMBER OVFLPAGE 156 157 PARTIAL_KEY This must be the first key/data pair on a page 158 and implies that page contains only a partial key. 159 That is, the key is too big to fit on a single page 160 so it starts on this page and continues on the next. 161 The format of the page is: 162 KEY_OFF PARTIAL_KEY OVFL_PAGENO OVFLPAGE 163 164 KEY_OFF -- offset of the beginning of the key 165 PARTIAL_KEY -- 1 166 OVFL_PAGENO - page number of the next overflow page 167 OVFLPAGE -- 0 168 FULL_KEY This must be the first key/data pair on the page. It 169 is used in two cases. 170 171 Case 1: 172 There is a complete key on the page but no data 173 (because it wouldn't fit). The next page contains 174 the data. 175 176 Page format it: 177 KEY_OFF FULL_KEY OVFL_PAGENO OVFL_PAGE 178 179 KEY_OFF -- offset of the beginning of the key 180 FULL_KEY -- 2 181 OVFL_PAGENO - page number of the next overflow page 182 OVFLPAGE -- 0 183 184 Case 2: 185 This page contains no key, but part of a large 186 data field, which is continued on the next page. 187 188 Page format it: 189 DATA_OFF FULL_KEY OVFL_PAGENO OVFL_PAGE 190 191 KEY_OFF -- offset of the beginning of the data on 192 this page 193 FULL_KEY -- 2 194 OVFL_PAGENO - page number of the next overflow page 195 OVFLPAGE -- 0 196 197 FULL_KEY_DATA This must be the first key/data pair on the page. 198 There are two cases: 199 200 Case 1: 201 This page contains a key and the beginning of the 202 data field, but the data field is continued on the 203 next page. 204 205 Page format is: 206 KEY_OFF FULL_KEY_DATA OVFL_PAGENO DATA_OFF 207 208 KEY_OFF -- offset of the beginning of the key 209 FULL_KEY_DATA -- 3 210 OVFL_PAGENO - page number of the next overflow page 211 DATA_OFF -- offset of the beginning of the data 212 213 Case 2: 214 This page contains the last page of a big data pair. 215 There is no key, only the tail end of the data 216 on this page. 217 218 Page format is: 219 DATA_OFF FULL_KEY_DATA <OVFL_PAGENO> <OVFLPAGE> 220 221 DATA_OFF -- offset of the beginning of the data on 222 this page 223 FULL_KEY_DATA -- 3 224 OVFL_PAGENO - page number of the next overflow page 225 OVFLPAGE -- 0 226 227 OVFL_PAGENO and OVFLPAGE are optional (they are 228 not present if there is no next page). 229 */ 230 231 #define OVFLPAGE 0 232 #define PARTIAL_KEY 1 233 #define FULL_KEY 2 234 #define FULL_KEY_DATA 3 235 #define REAL_KEY 4 236 /* Short hands for accessing structure */ 237 #define BSIZE hdr.bsize 238 #define BSHIFT hdr.bshift 239 #define DSIZE hdr.dsize 240 #define SGSIZE hdr.ssize 241 #define SSHIFT hdr.sshift 242 #define LORDER hdr.lorder 243 #define MAX_BUCKET hdr.max_bucket 244 #define FFACTOR hdr.ffactor 245 #define HIGH_MASK hdr.high_mask 246 #define LOW_MASK hdr.low_mask 247 #define NKEYS hdr.nkeys 248 #define HDRPAGES hdr.hdrpages 249 #define SPARES hdr.spares 250 #define BITMAPS hdr.bitmaps 251 #define VERSION hdr.version 252 #define MAGIC hdr.magic 253 #define NEXT_FREE hdr.next_free 254 #define H_CHARKEY hdr.h_charkey 255