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