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, see <http://www.gnu.org/licenses/>.
28 see the section marked "public interface" below for documentation
38 #define IDR_FULL 0xfffffffful
40 #define TOP_LEVEL_FULL (IDR_FULL >> 30)
42 #define IDR_SIZE (1 << IDR_BITS)
43 #define IDR_MASK ((1 << IDR_BITS)-1)
44 #define MAX_ID_SHIFT (sizeof(int)*8 - 1)
45 #define MAX_ID_BIT (1U << MAX_ID_SHIFT)
46 #define MAX_ID_MASK (MAX_ID_BIT - 1)
47 #define MAX_LEVEL (MAX_ID_SHIFT + IDR_BITS - 1) / IDR_BITS
48 #define IDR_FREE_MAX MAX_LEVEL + MAX_LEVEL
50 #define set_bit(bit, v) (v) |= (1<<(bit))
51 #define clear_bit(bit, v) (v) &= ~(1<<(bit))
52 #define test_bit(bit, v) ((v) & (1<<(bit)))
56 struct idr_layer *ary[IDR_SIZE];
61 struct idr_layer *top;
62 struct idr_layer *id_free;
67 static struct idr_layer *alloc_layer(struct idr_context *idp)
71 if (!(p = idp->id_free))
73 idp->id_free = p->ary[0];
79 static int find_next_bit(uint32_t bm, int maxid, int n)
81 while (n<maxid && !test_bit(n, bm)) n++;
85 static void free_layer(struct idr_context *idp, struct idr_layer *p)
87 p->ary[0] = idp->id_free;
92 static int idr_pre_get(struct idr_context *idp)
94 while (idp->id_free_cnt < IDR_FREE_MAX) {
95 struct idr_layer *new = talloc_zero(idp, struct idr_layer);
103 static int sub_alloc(struct idr_context *idp, void *ptr, int *starting_id)
106 struct idr_layer *p, *new;
107 struct idr_layer *pa[MAX_LEVEL];
108 unsigned int l, id, oid;
111 memset(pa, 0, sizeof(pa));
120 * We run around this while until we reach the leaf node...
122 n = (id >> (IDR_BITS*l)) & IDR_MASK;
124 m = find_next_bit(bm, IDR_SIZE, n);
126 /* no space available go back to previous layer. */
129 id = (id | ((1 << (IDR_BITS*l))-1)) + 1;
131 /* if already at the top layer, we need to grow */
137 /* If we need to go up one layer, continue the
138 * loop; otherwise, restart from the top.
140 sh = IDR_BITS * (l + 1);
141 if (oid >> sh == id >> sh)
148 id = ((id >> sh) ^ n ^ m) << sh;
150 if ((id >= MAX_ID_BIT) || (id < 0))
155 * Create the layer below if it is missing.
158 if (!(new = alloc_layer(idp)))
167 * We have reached the leaf node, plant the
168 * users pointer and return the raw id.
170 p->ary[m] = (struct idr_layer *)ptr;
171 set_bit(m, p->bitmap);
174 * If this layer is full mark the bit in the layer above
175 * to show that this part of the radix tree is full.
176 * This may complete the layer above and require walking
180 while (p->bitmap == IDR_FULL) {
184 set_bit((n & IDR_MASK), p->bitmap);
189 static int idr_get_new_above_int(struct idr_context *idp, void *ptr, int starting_id)
191 struct idr_layer *p, *new;
199 layers = idp->layers;
201 if (!(p = alloc_layer(idp)))
206 * Add a new layer to the top of the tree if the requested
207 * id is larger than the currently allocated space.
209 while ((layers < MAX_LEVEL) && (id >= (1 << (layers*IDR_BITS)))) {
213 if (!(new = alloc_layer(idp))) {
215 * The allocation failed. If we built part of
216 * the structure tear it down.
218 for (new = p; p && p != idp->top; new = p) {
221 new->bitmap = new->count = 0;
222 free_layer(idp, new);
228 if (p->bitmap == IDR_FULL)
229 set_bit(0, new->bitmap);
233 idp->layers = layers;
234 v = sub_alloc(idp, ptr, &id);
240 static int sub_remove(struct idr_context *idp, int shift, int id)
242 struct idr_layer *p = idp->top;
243 struct idr_layer **pa[1+MAX_LEVEL];
244 struct idr_layer ***paa = &pa[0];
250 while ((shift > 0) && p) {
251 n = (id >> shift) & IDR_MASK;
252 clear_bit(n, p->bitmap);
258 if (p != NULL && test_bit(n, p->bitmap)) {
259 clear_bit(n, p->bitmap);
261 while(*paa && ! --((**paa)->count)){
262 free_layer(idp, **paa);
272 static void *_idr_find(struct idr_context *idp, int id)
277 n = idp->layers * IDR_BITS;
280 * This tests to see if bits outside the current tree are
281 * present. If so, tain't one of ours!
283 if (n + IDR_BITS < 31 &&
284 ((id & ~(~0 << MAX_ID_SHIFT)) >> (n + IDR_BITS))) {
288 /* Mask off upper bits we don't use for the search. */
291 while (n >= IDR_BITS && p) {
293 p = p->ary[(id >> n) & IDR_MASK];
298 static int _idr_remove(struct idr_context *idp, int id)
302 /* Mask off upper bits we don't use for the search. */
305 if (sub_remove(idp, (idp->layers - 1) * IDR_BITS, id) == -1) {
309 if ( idp->top && idp->top->count == 1 &&
312 /* We can drop a layer */
313 p = idp->top->ary[0];
314 idp->top->bitmap = idp->top->count = 0;
315 free_layer(idp, idp->top);
319 while (idp->id_free_cnt >= IDR_FREE_MAX) {
320 p = alloc_layer(idp);
326 /************************************************************************
327 this is the public interface
328 **************************************************************************/
331 initialise a idr tree. The context return value must be passed to
332 all subsequent idr calls. To destroy the idr tree use talloc_free()
335 _PUBLIC_ struct idr_context *idr_init(TALLOC_CTX *mem_ctx)
337 return talloc_zero(mem_ctx, struct idr_context);
341 allocate the next available id, and assign 'ptr' into its slot.
342 you can retrieve later this pointer using idr_find()
344 _PUBLIC_ int idr_get_new(struct idr_context *idp, void *ptr, int limit)
346 int ret = idr_get_new_above_int(idp, ptr, 0);
348 idr_remove(idp, ret);
355 allocate a new id, giving the first available value greater than or
356 equal to the given starting id
358 _PUBLIC_ int idr_get_new_above(struct idr_context *idp, void *ptr, int starting_id, int limit)
360 int ret = idr_get_new_above_int(idp, ptr, starting_id);
362 idr_remove(idp, ret);
369 find a pointer value previously set with idr_get_new given an id
371 _PUBLIC_ void *idr_find(struct idr_context *idp, int id)
373 return _idr_find(idp, id);
377 remove an id from the idr tree
379 _PUBLIC_ int idr_remove(struct idr_context *idp, int id)
382 ret = _idr_remove((struct idr_context *)idp, id);
384 DEBUG(0,("WARNING: attempt to remove unset id %d in idtree\n", id));