2 Unix SMB/CIFS implementation.
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.
7 Copyright (C) Andrew Tridgell 2004
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
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.
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.
23 You should have received a copy of the GNU General Public License
24 along with this program; if not, write to the Free Software
25 Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
29 see the section marked "public interface" below for documentation
39 #define IDR_FULL 0xfffffffful
40 #define TOP_LEVEL_FULL (IDR_FULL >> 30)
41 #define IDR_SIZE (1 << IDR_BITS)
42 #define IDR_MASK ((1 << IDR_BITS)-1)
43 #define MAX_ID_SHIFT (sizeof(int)*8 - 1)
44 #define MAX_ID_BIT (1U << MAX_ID_SHIFT)
45 #define MAX_ID_MASK (MAX_ID_BIT - 1)
46 #define MAX_LEVEL (MAX_ID_SHIFT + IDR_BITS - 1) / IDR_BITS
47 #define IDR_FREE_MAX MAX_LEVEL + MAX_LEVEL
49 #define set_bit(bit, v) (v) |= (1<<(bit))
50 #define clear_bit(bit, v) (v) &= ~(1<<(bit))
51 #define test_bit(bit, v) ((v) & (1<<(bit)))
55 struct idr_layer *ary[IDR_SIZE];
60 struct idr_layer *top;
61 struct idr_layer *id_free;
66 static struct idr_layer *alloc_layer(struct idr_context *idp)
70 if (!(p = idp->id_free))
72 idp->id_free = p->ary[0];
78 static int find_next_bit(uint32_t bm, int maxid, int n)
80 while (n<maxid && !test_bit(n, bm)) n++;
84 static void free_layer(struct idr_context *idp, struct idr_layer *p)
86 p->ary[0] = idp->id_free;
91 static int idr_pre_get(struct idr_context *idp)
93 while (idp->id_free_cnt < IDR_FREE_MAX) {
94 struct idr_layer *new = talloc_zero(idp, struct idr_layer);
102 static int sub_alloc(struct idr_context *idp, void *ptr, int *starting_id)
105 struct idr_layer *p, *new;
106 struct idr_layer *pa[MAX_LEVEL];
116 * We run around this while until we reach the leaf node...
118 n = (id >> (IDR_BITS*l)) & IDR_MASK;
120 m = find_next_bit(bm, IDR_SIZE, n);
122 /* no space available go back to previous layer. */
124 id = (id | ((1 << (IDR_BITS*l))-1)) + 1;
133 id = ((id >> sh) ^ n ^ m) << sh;
135 if ((id >= MAX_ID_BIT) || (id < 0))
140 * Create the layer below if it is missing.
143 if (!(new = alloc_layer(idp)))
152 * We have reached the leaf node, plant the
153 * users pointer and return the raw id.
155 p->ary[m] = (struct idr_layer *)ptr;
156 set_bit(m, p->bitmap);
159 * If this layer is full mark the bit in the layer above
160 * to show that this part of the radix tree is full.
161 * This may complete the layer above and require walking
165 while (p->bitmap == IDR_FULL) {
169 set_bit((n & IDR_MASK), p->bitmap);
174 static int idr_get_new_above_int(struct idr_context *idp, void *ptr, int starting_id)
176 struct idr_layer *p, *new;
184 layers = idp->layers;
186 if (!(p = alloc_layer(idp)))
191 * Add a new layer to the top of the tree if the requested
192 * id is larger than the currently allocated space.
194 while ((layers < MAX_LEVEL) && (id >= (1 << (layers*IDR_BITS)))) {
198 if (!(new = alloc_layer(idp))) {
200 * The allocation failed. If we built part of
201 * the structure tear it down.
203 for (new = p; p && p != idp->top; new = p) {
206 new->bitmap = new->count = 0;
207 free_layer(idp, new);
213 if (p->bitmap == IDR_FULL)
214 set_bit(0, new->bitmap);
218 idp->layers = layers;
219 v = sub_alloc(idp, ptr, &id);
225 static int sub_remove(struct idr_context *idp, int shift, int id)
227 struct idr_layer *p = idp->top;
228 struct idr_layer **pa[MAX_LEVEL];
229 struct idr_layer ***paa = &pa[0];
235 while ((shift > 0) && p) {
236 n = (id >> shift) & IDR_MASK;
237 clear_bit(n, p->bitmap);
243 if (p != NULL && test_bit(n, p->bitmap)) {
244 clear_bit(n, p->bitmap);
246 while(*paa && ! --((**paa)->count)){
247 free_layer(idp, **paa);
257 static void *_idr_find(struct idr_context *idp, int id)
262 n = idp->layers * IDR_BITS;
265 * This tests to see if bits outside the current tree are
266 * present. If so, tain't one of ours!
268 if ((id & ~(~0 << MAX_ID_SHIFT)) >> (n + IDR_BITS))
271 /* Mask off upper bits we don't use for the search. */
276 p = p->ary[(id >> n) & IDR_MASK];
281 static int _idr_remove(struct idr_context *idp, int id)
285 /* Mask off upper bits we don't use for the search. */
288 if (sub_remove(idp, (idp->layers - 1) * IDR_BITS, id) == -1) {
292 if ( idp->top && idp->top->count == 1 &&
295 /* We can drop a layer */
296 p = idp->top->ary[0];
297 idp->top->bitmap = idp->top->count = 0;
298 free_layer(idp, idp->top);
302 while (idp->id_free_cnt >= IDR_FREE_MAX) {
303 p = alloc_layer(idp);
309 /************************************************************************
310 this is the public interface
311 **************************************************************************/
314 initialise a idr tree. The context return value must be passed to
315 all subsequent idr calls. To destroy the idr tree use talloc_free()
318 struct idr_context *idr_init(TALLOC_CTX *mem_ctx)
320 return talloc_zero(mem_ctx, struct idr_context);
324 allocate the next available id, and assign 'ptr' into its slot.
325 you can retrieve later this pointer using idr_find()
327 int idr_get_new(struct idr_context *idp, void *ptr, int limit)
329 int ret = idr_get_new_above_int(idp, ptr, 0);
331 idr_remove(idp, ret);
338 allocate a new id, giving the first available value greater than or
339 equal to the given starting id
341 int idr_get_new_above(struct idr_context *idp, void *ptr, int starting_id, int limit)
343 int ret = idr_get_new_above_int(idp, ptr, starting_id);
345 idr_remove(idp, ret);
352 allocate a new id randomly in the given range
354 int idr_get_new_random(struct idr_context *idp, void *ptr, int limit)
358 /* first try a random starting point in the whole range, and if that fails,
359 then start randomly in the bottom half of the range. This can only
360 fail if the range is over half full */
361 id = idr_get_new_above(idp, ptr, 1+(generate_random() % limit), limit);
363 id = idr_get_new_above(idp, ptr, 1+(generate_random()%(limit/2)), limit);
370 find a pointer value previously set with idr_get_new given an id
372 void *idr_find(struct idr_context *idp, int id)
374 return _idr_find(idp, id);
378 remove an id from the idr tree
380 int idr_remove(struct idr_context *idp, int id)
383 ret = _idr_remove((struct idr_context *)idp, id);
385 DEBUG(0,("WARNING: attempt to remove unset id %d in idtree\n", id));