source: vendor/current/lib/util/idtree.c

Last change on this file was 988, checked in by Silvan Scherrer, 9 years ago

Samba Server: update vendor to version 4.4.3
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Line 
1/*
2 Unix SMB/CIFS implementation.
3
4 very efficient functions to manage mapping a id (such as a fnum) to
5 a pointer. This is used for fnum and search id allocation.
6
7 Copyright (C) Andrew Tridgell 2004
8
9 This code is derived from lib/idr.c in the 2.6 Linux kernel, which was
10 written by Jim Houston jim.houston@ccur.com, and is
11 Copyright (C) 2002 by Concurrent Computer Corporation
12
13 This program is free software; you can redistribute it and/or modify
14 it under the terms of the GNU General Public License as published by
15 the Free Software Foundation; either version 2 of the License, or
16 (at your option) any later version.
17
18 This program is distributed in the hope that it will be useful,
19 but WITHOUT ANY WARRANTY; without even the implied warranty of
20 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
21 GNU General Public License for more details.
22
23 You should have received a copy of the GNU General Public License
24 along with this program. If not, see <http://www.gnu.org/licenses/>.
25*/
26
27/*
28 see the section marked "public interface" below for documentation
29*/
30
31/**
32 * @file
33 */
34
35#include "replace.h"
36#include <talloc.h>
37#include "debug.h"
38#include "idtree.h"
39
40#define IDR_BITS 5
41#define IDR_FULL 0xfffffffful
42#if 0 /* unused */
43#define TOP_LEVEL_FULL (IDR_FULL >> 30)
44#endif
45#define IDR_SIZE (1 << IDR_BITS)
46#define IDR_MASK ((1 << IDR_BITS)-1)
47#define MAX_ID_SHIFT (sizeof(int)*8 - 1)
48#define MAX_ID_BIT (1U << MAX_ID_SHIFT)
49#define MAX_ID_MASK (MAX_ID_BIT - 1)
50#define MAX_LEVEL (MAX_ID_SHIFT + IDR_BITS - 1) / IDR_BITS
51#define IDR_FREE_MAX MAX_LEVEL + MAX_LEVEL
52
53#define set_bit(bit, v) (v) |= (1<<(bit))
54#define clear_bit(bit, v) (v) &= ~(1<<(bit))
55#define test_bit(bit, v) ((v) & (1<<(bit)))
56
57struct idr_layer {
58 uint32_t bitmap;
59 struct idr_layer *ary[IDR_SIZE];
60 int count;
61};
62
63struct idr_context {
64 struct idr_layer *top;
65 struct idr_layer *id_free;
66 int layers;
67 int id_free_cnt;
68};
69
70static struct idr_layer *alloc_layer(struct idr_context *idp)
71{
72 struct idr_layer *p;
73
74 if (!(p = idp->id_free))
75 return NULL;
76 idp->id_free = p->ary[0];
77 idp->id_free_cnt--;
78 p->ary[0] = NULL;
79 return p;
80}
81
82static int find_next_bit(uint32_t bm, int maxid, int n)
83{
84 while (n<maxid && !test_bit(n, bm)) n++;
85 return n;
86}
87
88static void free_layer(struct idr_context *idp, struct idr_layer *p)
89{
90 p->ary[0] = idp->id_free;
91 idp->id_free = p;
92 idp->id_free_cnt++;
93}
94
95static int idr_pre_get(struct idr_context *idp)
96{
97 while (idp->id_free_cnt < IDR_FREE_MAX) {
98 struct idr_layer *pn = talloc_zero(idp, struct idr_layer);
99 if(pn == NULL)
100 return (0);
101 free_layer(idp, pn);
102 }
103 return 1;
104}
105
106static int sub_alloc(struct idr_context *idp, void *ptr, int *starting_id)
107{
108 int n, m, sh;
109 struct idr_layer *p, *pn;
110 struct idr_layer *pa[MAX_LEVEL+1];
111 unsigned int l, id, oid;
112 uint32_t bm;
113
114 memset(pa, 0, sizeof(pa));
115
116 id = *starting_id;
117restart:
118 p = idp->top;
119 l = idp->layers;
120 pa[l--] = NULL;
121 while (1) {
122 /*
123 * We run around this while until we reach the leaf node...
124 */
125 n = (id >> (IDR_BITS*l)) & IDR_MASK;
126 bm = ~p->bitmap;
127 m = find_next_bit(bm, IDR_SIZE, n);
128 if (m == IDR_SIZE) {
129 /* no space available go back to previous layer. */
130 l++;
131 oid = id;
132 id = (id | ((1 << (IDR_BITS*l))-1)) + 1;
133
134 /* if already at the top layer, we need to grow */
135 if (!(p = pa[l])) {
136 *starting_id = id;
137 return -2;
138 }
139
140 /* If we need to go up one layer, continue the
141 * loop; otherwise, restart from the top.
142 */
143 sh = IDR_BITS * (l + 1);
144 if (oid >> sh == id >> sh)
145 continue;
146 else
147 goto restart;
148 }
149 if (m != n) {
150 sh = IDR_BITS*l;
151 id = ((id >> sh) ^ n ^ m) << sh;
152 }
153 if ((id >= MAX_ID_BIT) || (id < 0))
154 return -1;
155 if (l == 0)
156 break;
157 /*
158 * Create the layer below if it is missing.
159 */
160 if (!p->ary[m]) {
161 if (!(pn = alloc_layer(idp)))
162 return -1;
163 p->ary[m] = pn;
164 p->count++;
165 }
166 pa[l--] = p;
167 p = p->ary[m];
168 }
169 /*
170 * We have reached the leaf node, plant the
171 * users pointer and return the raw id.
172 */
173 p->ary[m] = (struct idr_layer *)ptr;
174 set_bit(m, p->bitmap);
175 p->count++;
176 /*
177 * If this layer is full mark the bit in the layer above
178 * to show that this part of the radix tree is full.
179 * This may complete the layer above and require walking
180 * up the radix tree.
181 */
182 n = id;
183 while (p->bitmap == IDR_FULL) {
184 if (l >= MAX_LEVEL) {
185 break;
186 }
187 p = pa[++l];
188 if (p == NULL) {
189 break;
190 }
191 n = n >> IDR_BITS;
192 set_bit((n & IDR_MASK), p->bitmap);
193 }
194 return(id);
195}
196
197static int idr_get_new_above_int(struct idr_context *idp, void *ptr, int starting_id)
198{
199 struct idr_layer *p, *pn;
200 int layers, v, id;
201
202 idr_pre_get(idp);
203
204 id = starting_id;
205build_up:
206 p = idp->top;
207 layers = idp->layers;
208 if (!p) {
209 if (!(p = alloc_layer(idp)))
210 return -1;
211 layers = 1;
212 }
213 /*
214 * Add a new layer to the top of the tree if the requested
215 * id is larger than the currently allocated space.
216 */
217 while ((layers < MAX_LEVEL) && (id >= (1 << (layers*IDR_BITS)))) {
218 layers++;
219 if (!p->count)
220 continue;
221 if (!(pn = alloc_layer(idp))) {
222 /*
223 * The allocation failed. If we built part of
224 * the structure tear it down.
225 */
226 for (pn = p; p && p != idp->top; pn = p) {
227 p = p->ary[0];
228 pn->ary[0] = NULL;
229 pn->bitmap = pn->count = 0;
230 free_layer(idp, pn);
231 }
232 return -1;
233 }
234 pn->ary[0] = p;
235 pn->count = 1;
236 if (p->bitmap == IDR_FULL)
237 set_bit(0, pn->bitmap);
238 p = pn;
239 }
240 idp->top = p;
241 idp->layers = layers;
242 v = sub_alloc(idp, ptr, &id);
243 if (v == -2)
244 goto build_up;
245 return(v);
246}
247
248static int sub_remove(struct idr_context *idp, int shift, int id)
249{
250 struct idr_layer *p = idp->top;
251 struct idr_layer **pa[1+MAX_LEVEL];
252 struct idr_layer ***paa = &pa[0];
253 int n;
254
255 *paa = NULL;
256 *++paa = &idp->top;
257
258 while ((shift > 0) && p) {
259 n = (id >> shift) & IDR_MASK;
260 clear_bit(n, p->bitmap);
261 *++paa = &p->ary[n];
262 p = p->ary[n];
263 shift -= IDR_BITS;
264 }
265 n = id & IDR_MASK;
266 if (p != NULL && test_bit(n, p->bitmap)) {
267 clear_bit(n, p->bitmap);
268 p->ary[n] = NULL;
269 while(*paa && ! --((**paa)->count)){
270 free_layer(idp, **paa);
271 **paa-- = NULL;
272 }
273 if ( ! *paa )
274 idp->layers = 0;
275 return 0;
276 }
277 return -1;
278}
279
280static void *_idr_find(struct idr_context *idp, int id)
281{
282 int n;
283 struct idr_layer *p;
284
285 n = idp->layers * IDR_BITS;
286 p = idp->top;
287 /*
288 * This tests to see if bits outside the current tree are
289 * present. If so, tain't one of ours!
290 */
291 if (n + IDR_BITS < 31 &&
292 ((id & ~(~0 << MAX_ID_SHIFT)) >> (n + IDR_BITS))) {
293 return NULL;
294 }
295
296 /* Mask off upper bits we don't use for the search. */
297 id &= MAX_ID_MASK;
298
299 while (n >= IDR_BITS && p) {
300 n -= IDR_BITS;
301 p = p->ary[(id >> n) & IDR_MASK];
302 }
303 return((void *)p);
304}
305
306static int _idr_remove(struct idr_context *idp, int id)
307{
308 struct idr_layer *p;
309
310 /* Mask off upper bits we don't use for the search. */
311 id &= MAX_ID_MASK;
312
313 if (sub_remove(idp, (idp->layers - 1) * IDR_BITS, id) == -1) {
314 return -1;
315 }
316
317 if ( idp->top && idp->top->count == 1 &&
318 (idp->layers > 1) &&
319 idp->top->ary[0]) {
320 /* We can drop a layer */
321 p = idp->top->ary[0];
322 idp->top->bitmap = idp->top->count = 0;
323 free_layer(idp, idp->top);
324 idp->top = p;
325 --idp->layers;
326 }
327 while (idp->id_free_cnt >= IDR_FREE_MAX) {
328 p = alloc_layer(idp);
329 talloc_free(p);
330 }
331 return 0;
332}
333
334/************************************************************************
335 this is the public interface
336**************************************************************************/
337
338/**
339 initialise a idr tree. The context return value must be passed to
340 all subsequent idr calls. To destroy the idr tree use talloc_free()
341 on this context
342 */
343_PUBLIC_ struct idr_context *idr_init(TALLOC_CTX *mem_ctx)
344{
345 return talloc_zero(mem_ctx, struct idr_context);
346}
347
348/**
349 allocate the next available id, and assign 'ptr' into its slot.
350 you can retrieve later this pointer using idr_find()
351*/
352_PUBLIC_ int idr_get_new(struct idr_context *idp, void *ptr, int limit)
353{
354 int ret = idr_get_new_above_int(idp, ptr, 0);
355 if (ret > limit) {
356 idr_remove(idp, ret);
357 return -1;
358 }
359 return ret;
360}
361
362/**
363 allocate a new id, giving the first available value greater than or
364 equal to the given starting id
365*/
366_PUBLIC_ int idr_get_new_above(struct idr_context *idp, void *ptr, int starting_id, int limit)
367{
368 int ret = idr_get_new_above_int(idp, ptr, starting_id);
369 if (ret > limit) {
370 idr_remove(idp, ret);
371 return -1;
372 }
373 return ret;
374}
375
376/**
377 find a pointer value previously set with idr_get_new given an id
378*/
379_PUBLIC_ void *idr_find(struct idr_context *idp, int id)
380{
381 return _idr_find(idp, id);
382}
383
384/**
385 remove an id from the idr tree
386*/
387_PUBLIC_ int idr_remove(struct idr_context *idp, int id)
388{
389 int ret;
390 ret = _idr_remove((struct idr_context *)idp, id);
391 if (ret != 0) {
392 DEBUG(0,("WARNING: attempt to remove unset id %d in idtree\n", id));
393 }
394 return ret;
395}
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