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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 EXT extern |
13 | # define EXTCONST extern const |
14 | #else |
15 | # include "EXTERN.h" |
16 | #endif |
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17 | #include "sdbm.h" |
18 | #include "tune.h" |
19 | #include "pair.h" |
20 | |
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21 | #define exhash(item) sdbm_hash((item).dptr, (item).dsize) |
22 | |
23 | /* |
24 | * forward |
25 | */ |
26 | static int seepair proto((char *, int, char *, int)); |
27 | |
28 | /* |
29 | * page format: |
30 | * +------------------------------+ |
31 | * ino | n | keyoff | datoff | keyoff | |
32 | * +------------+--------+--------+ |
33 | * | datoff | - - - ----> | |
34 | * +--------+---------------------+ |
35 | * | F R E E A R E A | |
36 | * +--------------+---------------+ |
37 | * | <---- - - - | data | |
38 | * +--------+-----+----+----------+ |
39 | * | key | data | key | |
40 | * +--------+----------+----------+ |
41 | * |
42 | * calculating the offsets for free area: if the number |
43 | * of entries (ino[0]) is zero, the offset to the END of |
44 | * the free area is the block size. Otherwise, it is the |
45 | * nth (ino[ino[0]]) entry's offset. |
46 | */ |
47 | |
48 | int |
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49 | fitpair(char *pag, int need) |
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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 |
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66 | putpair(char *pag, datum key, datum val) |
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67 | { |
68 | register int n; |
69 | register int off; |
70 | register short *ino = (short *) pag; |
71 | |
72 | off = ((n = ino[0]) > 0) ? ino[n] : PBLKSIZ; |
73 | /* |
74 | * enter the key first |
75 | */ |
76 | off -= key.dsize; |
77 | (void) memcpy(pag + off, key.dptr, key.dsize); |
78 | ino[n + 1] = off; |
79 | /* |
80 | * now the data |
81 | */ |
82 | off -= val.dsize; |
83 | (void) memcpy(pag + off, val.dptr, val.dsize); |
84 | ino[n + 2] = off; |
85 | /* |
86 | * adjust item count |
87 | */ |
88 | ino[0] += 2; |
89 | } |
90 | |
91 | datum |
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92 | getpair(char *pag, datum key) |
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93 | { |
94 | register int i; |
95 | register int n; |
96 | datum val; |
97 | register short *ino = (short *) pag; |
98 | |
99 | if ((n = ino[0]) == 0) |
100 | return nullitem; |
101 | |
102 | if ((i = seepair(pag, n, key.dptr, key.dsize)) == 0) |
103 | return nullitem; |
104 | |
105 | val.dptr = pag + ino[i + 1]; |
106 | val.dsize = ino[i] - ino[i + 1]; |
107 | return val; |
108 | } |
109 | |
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110 | int |
111 | exipair(char *pag, datum key) |
112 | { |
113 | register short *ino = (short *) pag; |
114 | |
115 | if (ino[0] == 0) |
116 | return 0; |
117 | |
118 | return (seepair(pag, ino[0], key.dptr, key.dsize) != 0); |
119 | } |
120 | |
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121 | #ifdef SEEDUPS |
122 | int |
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123 | duppair(char *pag, datum key) |
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124 | { |
125 | register short *ino = (short *) pag; |
126 | return ino[0] > 0 && seepair(pag, ino[0], key.dptr, key.dsize) > 0; |
127 | } |
128 | #endif |
129 | |
130 | datum |
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131 | getnkey(char *pag, int num) |
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132 | { |
133 | datum key; |
134 | register int off; |
135 | register short *ino = (short *) pag; |
136 | |
137 | num = num * 2 - 1; |
138 | if (ino[0] == 0 || num > ino[0]) |
139 | return nullitem; |
140 | |
141 | off = (num > 1) ? ino[num - 1] : PBLKSIZ; |
142 | |
143 | key.dptr = pag + ino[num]; |
144 | key.dsize = off - ino[num]; |
145 | |
146 | return key; |
147 | } |
148 | |
149 | int |
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150 | delpair(char *pag, datum key) |
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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 |
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222 | seepair(char *pag, register int n, register char *key, register int siz) |
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223 | { |
224 | register int i; |
225 | register int off = PBLKSIZ; |
226 | register short *ino = (short *) pag; |
227 | |
228 | for (i = 1; i < n; i += 2) { |
229 | if (siz == off - ino[i] && |
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230 | memEQ(key, pag + ino[i], siz)) |
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231 | return i; |
232 | off = ino[i + 1]; |
233 | } |
234 | return 0; |
235 | } |
236 | |
237 | void |
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238 | splpage(char *pag, char *New, long int sbit) |
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239 | { |
240 | datum key; |
241 | datum val; |
242 | |
243 | register int n; |
244 | register int off = PBLKSIZ; |
245 | char cur[PBLKSIZ]; |
246 | register short *ino = (short *) cur; |
247 | |
248 | (void) memcpy(cur, pag, PBLKSIZ); |
249 | (void) memset(pag, 0, PBLKSIZ); |
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250 | (void) memset(New, 0, PBLKSIZ); |
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251 | |
252 | n = ino[0]; |
253 | for (ino++; n > 0; ino += 2) { |
254 | key.dptr = cur + ino[0]; |
255 | key.dsize = off - ino[0]; |
256 | val.dptr = cur + ino[1]; |
257 | val.dsize = ino[0] - ino[1]; |
258 | /* |
259 | * select the page pointer (by looking at sbit) and insert |
260 | */ |
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261 | (void) putpair((exhash(key) & sbit) ? New : pag, key, val); |
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262 | |
263 | off = ino[1]; |
264 | n -= 2; |
265 | } |
266 | |
267 | debug(("%d split %d/%d\n", ((short *) cur)[0] / 2, |
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268 | ((short *) New)[0] / 2, |
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269 | ((short *) pag)[0] / 2)); |
270 | } |
271 | |
272 | /* |
273 | * check page sanity: |
274 | * number of entries should be something |
275 | * reasonable, and all offsets in the index should be in order. |
276 | * this could be made more rigorous. |
277 | */ |
278 | int |
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279 | chkpage(char *pag) |
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280 | { |
281 | register int n; |
282 | register int off; |
283 | register short *ino = (short *) pag; |
284 | |
285 | if ((n = ino[0]) < 0 || n > PBLKSIZ / sizeof(short)) |
286 | return 0; |
287 | |
288 | if (n > 0) { |
289 | off = PBLKSIZ; |
290 | for (ino++; n > 0; ino += 2) { |
291 | if (ino[0] > off || ino[1] > off || |
292 | ino[1] > ino[0]) |
293 | return 0; |
294 | off = ino[1]; |
295 | n -= 2; |
296 | } |
297 | } |
298 | return 1; |
299 | } |