Commit | Line | Data |
463ee0b2 |
1 | /* |
2 | * sdbm - ndbm work-alike hashed database library |
3 | * based on Per-Aake Larson's Dynamic Hashing algorithms. BIT 18 (1978). |
4 | * author: oz@nexus.yorku.ca |
5 | * status: public domain. |
6 | * |
7 | * page-level routines |
8 | */ |
9 | |
10 | #ifndef lint |
11 | static char rcsid[] = "$Id: pair.c,v 1.10 90/12/13 13:00:35 oz Exp $"; |
12 | #endif |
13 | |
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14 | #include "config.h" |
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15 | #include "sdbm.h" |
16 | #include "tune.h" |
17 | #include "pair.h" |
18 | |
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19 | #define exhash(item) sdbm_hash((item).dptr, (item).dsize) |
20 | |
21 | /* |
22 | * forward |
23 | */ |
24 | static int seepair proto((char *, int, char *, int)); |
25 | |
26 | /* |
27 | * page format: |
28 | * +------------------------------+ |
29 | * ino | n | keyoff | datoff | keyoff | |
30 | * +------------+--------+--------+ |
31 | * | datoff | - - - ----> | |
32 | * +--------+---------------------+ |
33 | * | F R E E A R E A | |
34 | * +--------------+---------------+ |
35 | * | <---- - - - | data | |
36 | * +--------+-----+----+----------+ |
37 | * | key | data | key | |
38 | * +--------+----------+----------+ |
39 | * |
40 | * calculating the offsets for free area: if the number |
41 | * of entries (ino[0]) is zero, the offset to the END of |
42 | * the free area is the block size. Otherwise, it is the |
43 | * nth (ino[ino[0]]) entry's offset. |
44 | */ |
45 | |
46 | int |
47 | fitpair(pag, need) |
48 | char *pag; |
49 | int need; |
50 | { |
51 | register int n; |
52 | register int off; |
53 | register int free; |
54 | register short *ino = (short *) pag; |
55 | |
56 | off = ((n = ino[0]) > 0) ? ino[n] : PBLKSIZ; |
57 | free = off - (n + 1) * sizeof(short); |
58 | need += 2 * sizeof(short); |
59 | |
60 | debug(("free %d need %d\n", free, need)); |
61 | |
62 | return need <= free; |
63 | } |
64 | |
65 | void |
66 | putpair(pag, key, val) |
67 | char *pag; |
68 | datum key; |
69 | datum val; |
70 | { |
71 | register int n; |
72 | register int off; |
73 | register short *ino = (short *) pag; |
74 | |
75 | off = ((n = ino[0]) > 0) ? ino[n] : PBLKSIZ; |
76 | /* |
77 | * enter the key first |
78 | */ |
79 | off -= key.dsize; |
80 | (void) memcpy(pag + off, key.dptr, key.dsize); |
81 | ino[n + 1] = off; |
82 | /* |
83 | * now the data |
84 | */ |
85 | off -= val.dsize; |
86 | (void) memcpy(pag + off, val.dptr, val.dsize); |
87 | ino[n + 2] = off; |
88 | /* |
89 | * adjust item count |
90 | */ |
91 | ino[0] += 2; |
92 | } |
93 | |
94 | datum |
95 | getpair(pag, key) |
96 | char *pag; |
97 | datum key; |
98 | { |
99 | register int i; |
100 | register int n; |
101 | datum val; |
102 | register short *ino = (short *) pag; |
103 | |
104 | if ((n = ino[0]) == 0) |
105 | return nullitem; |
106 | |
107 | if ((i = seepair(pag, n, key.dptr, key.dsize)) == 0) |
108 | return nullitem; |
109 | |
110 | val.dptr = pag + ino[i + 1]; |
111 | val.dsize = ino[i] - ino[i + 1]; |
112 | return val; |
113 | } |
114 | |
115 | #ifdef SEEDUPS |
116 | int |
117 | duppair(pag, key) |
118 | char *pag; |
119 | datum key; |
120 | { |
121 | register short *ino = (short *) pag; |
122 | return ino[0] > 0 && seepair(pag, ino[0], key.dptr, key.dsize) > 0; |
123 | } |
124 | #endif |
125 | |
126 | datum |
127 | getnkey(pag, num) |
128 | char *pag; |
129 | int num; |
130 | { |
131 | datum key; |
132 | register int off; |
133 | register short *ino = (short *) pag; |
134 | |
135 | num = num * 2 - 1; |
136 | if (ino[0] == 0 || num > ino[0]) |
137 | return nullitem; |
138 | |
139 | off = (num > 1) ? ino[num - 1] : PBLKSIZ; |
140 | |
141 | key.dptr = pag + ino[num]; |
142 | key.dsize = off - ino[num]; |
143 | |
144 | return key; |
145 | } |
146 | |
147 | int |
148 | delpair(pag, key) |
149 | char *pag; |
150 | datum key; |
151 | { |
152 | register int n; |
153 | register int i; |
154 | register short *ino = (short *) pag; |
155 | |
156 | if ((n = ino[0]) == 0) |
157 | return 0; |
158 | |
159 | if ((i = seepair(pag, n, key.dptr, key.dsize)) == 0) |
160 | return 0; |
161 | /* |
162 | * found the key. if it is the last entry |
163 | * [i.e. i == n - 1] we just adjust the entry count. |
164 | * hard case: move all data down onto the deleted pair, |
165 | * shift offsets onto deleted offsets, and adjust them. |
166 | * [note: 0 < i < n] |
167 | */ |
168 | if (i < n - 1) { |
169 | register int m; |
170 | register char *dst = pag + (i == 1 ? PBLKSIZ : ino[i - 1]); |
171 | register char *src = pag + ino[i + 1]; |
172 | register int zoo = dst - src; |
173 | |
174 | debug(("free-up %d ", zoo)); |
175 | /* |
176 | * shift data/keys down |
177 | */ |
178 | m = ino[i + 1] - ino[n]; |
179 | #ifdef DUFF |
180 | #define MOVB *--dst = *--src |
181 | |
182 | if (m > 0) { |
183 | register int loop = (m + 8 - 1) >> 3; |
184 | |
185 | switch (m & (8 - 1)) { |
186 | case 0: do { |
187 | MOVB; case 7: MOVB; |
188 | case 6: MOVB; case 5: MOVB; |
189 | case 4: MOVB; case 3: MOVB; |
190 | case 2: MOVB; case 1: MOVB; |
191 | } while (--loop); |
192 | } |
193 | } |
194 | #else |
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195 | #ifdef HAS_MEMMOVE |
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196 | dst -= m; |
197 | src -= m; |
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198 | memmove(dst, src, m); |
199 | #else |
200 | while (m--) |
201 | *--dst = *--src; |
202 | #endif |
203 | #endif |
204 | /* |
205 | * adjust offset index up |
206 | */ |
207 | while (i < n - 1) { |
208 | ino[i] = ino[i + 2] + zoo; |
209 | i++; |
210 | } |
211 | } |
212 | ino[0] -= 2; |
213 | return 1; |
214 | } |
215 | |
216 | /* |
217 | * search for the key in the page. |
218 | * return offset index in the range 0 < i < n. |
219 | * return 0 if not found. |
220 | */ |
221 | static int |
222 | seepair(pag, n, key, siz) |
223 | char *pag; |
224 | register int n; |
225 | register char *key; |
226 | register int siz; |
227 | { |
228 | register int i; |
229 | register int off = PBLKSIZ; |
230 | register short *ino = (short *) pag; |
231 | |
232 | for (i = 1; i < n; i += 2) { |
233 | if (siz == off - ino[i] && |
234 | memcmp(key, pag + ino[i], siz) == 0) |
235 | return i; |
236 | off = ino[i + 1]; |
237 | } |
238 | return 0; |
239 | } |
240 | |
241 | void |
242 | splpage(pag, new, sbit) |
243 | char *pag; |
244 | char *new; |
245 | long sbit; |
246 | { |
247 | datum key; |
248 | datum val; |
249 | |
250 | register int n; |
251 | register int off = PBLKSIZ; |
252 | char cur[PBLKSIZ]; |
253 | register short *ino = (short *) cur; |
254 | |
255 | (void) memcpy(cur, pag, PBLKSIZ); |
256 | (void) memset(pag, 0, PBLKSIZ); |
257 | (void) memset(new, 0, PBLKSIZ); |
258 | |
259 | n = ino[0]; |
260 | for (ino++; n > 0; ino += 2) { |
261 | key.dptr = cur + ino[0]; |
262 | key.dsize = off - ino[0]; |
263 | val.dptr = cur + ino[1]; |
264 | val.dsize = ino[0] - ino[1]; |
265 | /* |
266 | * select the page pointer (by looking at sbit) and insert |
267 | */ |
268 | (void) putpair((exhash(key) & sbit) ? new : pag, key, val); |
269 | |
270 | off = ino[1]; |
271 | n -= 2; |
272 | } |
273 | |
274 | debug(("%d split %d/%d\n", ((short *) cur)[0] / 2, |
275 | ((short *) new)[0] / 2, |
276 | ((short *) pag)[0] / 2)); |
277 | } |
278 | |
279 | /* |
280 | * check page sanity: |
281 | * number of entries should be something |
282 | * reasonable, and all offsets in the index should be in order. |
283 | * this could be made more rigorous. |
284 | */ |
285 | int |
286 | chkpage(pag) |
287 | char *pag; |
288 | { |
289 | register int n; |
290 | register int off; |
291 | register short *ino = (short *) pag; |
292 | |
293 | if ((n = ino[0]) < 0 || n > PBLKSIZ / sizeof(short)) |
294 | return 0; |
295 | |
296 | if (n > 0) { |
297 | off = PBLKSIZ; |
298 | for (ino++; n > 0; ino += 2) { |
299 | if (ino[0] > off || ino[1] > off || |
300 | ino[1] > ino[0]) |
301 | return 0; |
302 | off = ino[1]; |
303 | n -= 2; |
304 | } |
305 | } |
306 | return 1; |
307 | } |