idtree: new module
authorRusty Russell <rusty@rustcorp.com.au>
Thu, 20 May 2010 12:30:32 +0000 (22:00 +0930)
committerRusty Russell <rusty@rustcorp.com.au>
Thu, 20 May 2010 12:30:32 +0000 (22:00 +0930)
ccan/idtree/_info [new file with mode: 0644]
ccan/idtree/idtree.c [new file with mode: 0644]
ccan/idtree/idtree.h [new file with mode: 0644]
ccan/idtree/test/run.c [new file with mode: 0644]

diff --git a/ccan/idtree/_info b/ccan/idtree/_info
new file mode 100644 (file)
index 0000000..058b32b
--- /dev/null
@@ -0,0 +1,53 @@
+#include <stdio.h>
+#include <string.h>
+#include "config.h"
+
+/**
+ * idtree - id allocation tree
+ *
+ * There are often cases where you want to provide an integer handle for
+ * some data, and easily map it back to another structure.
+ *
+ * idtree is an efficient implementation of an int->void * mapping, with
+ * assignment of the lowest available id number.  It is from the Linux kernel
+ * via the Samba project.
+ *
+ * Example:
+ *     #include <ccan/idtree/idtree.h>
+ *     #include <ccan/talloc/talloc.h>
+ *     #include <stdlib.h>
+ *     #include <stdio.h>
+ *
+ *     // Silly example which puts args in the idtree and retreives them
+ *     int main(int argc, char *argv[])
+ *     {
+ *             struct idtree *idtree = idtree_new(NULL);
+ *             unsigned int i;
+ *     
+ *             // This will return consecutive id numbers.
+ *             for (i = 0; i < argc; i++) {
+ *                     printf("idtree_add('%s') -> id %i\n",
+ *                            argv[i], idtree_add(idtree, argv[i], -1));
+ *             }
+ *             for (i = 0; i < argc; i++) {
+ *                     printf("id %i -> '%s'\n", i, idtree_lookup(idtree, i));
+ *             }
+ *             return 0;
+ *     }
+ *
+ * Licence: GPL (2 or any later version)
+ * Maintainer: Rusty Russell <rusty@rustcorp.com.au>
+ * Author: Jim Houston <jim.houston@ccur.com>
+ */
+int main(int argc, char *argv[])
+{
+       if (argc != 2)
+               return 1;
+
+       if (strcmp(argv[1], "depends") == 0) {
+               printf("ccan/talloc\n");
+               return 0;
+       }
+
+       return 1;
+}
diff --git a/ccan/idtree/idtree.c b/ccan/idtree/idtree.c
new file mode 100644 (file)
index 0000000..bf83c31
--- /dev/null
@@ -0,0 +1,344 @@
+/*
+   Based on SAMBA 7ce1356c9f571c55af70bd6b966fe50898c1582d.
+
+   very efficient functions to manage mapping a id (such as a fnum) to
+   a pointer. This is used for fnum and search id allocation.
+
+   Copyright (C) Andrew Tridgell 2004
+
+   This code is derived from lib/idr.c in the 2.6 Linux kernel, which was
+   written by Jim Houston jim.houston@ccur.com, and is
+   Copyright (C) 2002 by Concurrent Computer Corporation
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include <ccan/idtree/idtree.h>
+#include <ccan/talloc/talloc.h>
+#include <stdint.h>
+#include <string.h>
+
+#define IDTREE_BITS 5
+#define IDTREE_FULL 0xfffffffful
+#if 0 /* unused */
+#define TOP_LEVEL_FULL (IDTREE_FULL >> 30)
+#endif
+#define IDTREE_SIZE (1 << IDTREE_BITS)
+#define IDTREE_MASK ((1 << IDTREE_BITS)-1)
+#define MAX_ID_SHIFT (sizeof(int)*8 - 1)
+#define MAX_ID_BIT (1U << MAX_ID_SHIFT)
+#define MAX_ID_MASK (MAX_ID_BIT - 1)
+#define MAX_LEVEL (MAX_ID_SHIFT + IDTREE_BITS - 1) / IDTREE_BITS
+#define IDTREE_FREE_MAX MAX_LEVEL + MAX_LEVEL
+
+#define set_bit(bit, v) (v) |= (1<<(bit))
+#define clear_bit(bit, v) (v) &= ~(1<<(bit))
+#define test_bit(bit, v) ((v) & (1<<(bit)))
+
+struct idtree_layer {
+       uint32_t                 bitmap;
+       struct idtree_layer     *ary[IDTREE_SIZE];
+       int                      count;
+};
+
+struct idtree {
+       struct idtree_layer *top;
+       struct idtree_layer *id_free;
+       int               layers;
+       int               id_free_cnt;
+};
+
+static struct idtree_layer *alloc_layer(struct idtree *idp)
+{
+       struct idtree_layer *p;
+
+       if (!(p = idp->id_free))
+               return NULL;
+       idp->id_free = p->ary[0];
+       idp->id_free_cnt--;
+       p->ary[0] = NULL;
+       return p;
+}
+
+static int find_next_bit(uint32_t bm, int maxid, int n)
+{
+       while (n<maxid && !test_bit(n, bm)) n++;
+       return n;
+}
+
+static void free_layer(struct idtree *idp, struct idtree_layer *p)
+{
+       p->ary[0] = idp->id_free;
+       idp->id_free = p;
+       idp->id_free_cnt++;
+}
+
+static int idtree_pre_get(struct idtree *idp)
+{
+       while (idp->id_free_cnt < IDTREE_FREE_MAX) {
+               struct idtree_layer *pn = talloc_zero(idp, struct idtree_layer);
+               if(pn == NULL)
+                       return (0);
+               free_layer(idp, pn);
+       }
+       return 1;
+}
+
+static int sub_alloc(struct idtree *idp, const void *ptr, int *starting_id)
+{
+       int n, m, sh;
+       struct idtree_layer *p, *pn;
+       struct idtree_layer *pa[MAX_LEVEL];
+       int l, id, oid;
+       uint32_t bm;
+
+       memset(pa, 0, sizeof(pa));
+
+       id = *starting_id;
+restart:
+       p = idp->top;
+       l = idp->layers;
+       pa[l--] = NULL;
+       while (1) {
+               /*
+                * We run around this while until we reach the leaf node...
+                */
+               n = (id >> (IDTREE_BITS*l)) & IDTREE_MASK;
+               bm = ~p->bitmap;
+               m = find_next_bit(bm, IDTREE_SIZE, n);
+               if (m == IDTREE_SIZE) {
+                       /* no space available go back to previous layer. */
+                       l++;
+                       oid = id;
+                       id = (id | ((1 << (IDTREE_BITS*l))-1)) + 1;
+
+                       /* if already at the top layer, we need to grow */
+                       if (!(p = pa[l])) {
+                               *starting_id = id;
+                               return -2;
+                       }
+
+                       /* If we need to go up one layer, continue the
+                        * loop; otherwise, restart from the top.
+                        */
+                       sh = IDTREE_BITS * (l + 1);
+                       if (oid >> sh == id >> sh)
+                       continue;
+                       else
+                               goto restart;
+               }
+               if (m != n) {
+                       sh = IDTREE_BITS*l;
+                       id = ((id >> sh) ^ n ^ m) << sh;
+               }
+               if ((id >= MAX_ID_BIT) || (id < 0))
+                       return -1;
+               if (l == 0)
+                       break;
+               /*
+                * Create the layer below if it is missing.
+                */
+               if (!p->ary[m]) {
+                       if (!(pn = alloc_layer(idp)))
+                               return -1;
+                       p->ary[m] = pn;
+                       p->count++;
+               }
+               pa[l--] = p;
+               p = p->ary[m];
+       }
+       /*
+        * We have reached the leaf node, plant the
+        * users pointer and return the raw id.
+        */
+       p->ary[m] = (struct idtree_layer *)ptr;
+       set_bit(m, p->bitmap);
+       p->count++;
+       /*
+        * If this layer is full mark the bit in the layer above
+        * to show that this part of the radix tree is full.
+        * This may complete the layer above and require walking
+        * up the radix tree.
+        */
+       n = id;
+       while (p->bitmap == IDTREE_FULL) {
+               if (!(p = pa[++l]))
+                       break;
+               n = n >> IDTREE_BITS;
+               set_bit((n & IDTREE_MASK), p->bitmap);
+       }
+       return(id);
+}
+
+static int idtree_get_new_above_int(struct idtree *idp,
+                                   const void *ptr, int starting_id)
+{
+       struct idtree_layer *p, *pn;
+       int layers, v, id;
+
+       idtree_pre_get(idp);
+
+       id = starting_id;
+build_up:
+       p = idp->top;
+       layers = idp->layers;
+       if (!p) {
+               if (!(p = alloc_layer(idp)))
+                       return -1;
+               layers = 1;
+       }
+       /*
+        * Add a new layer to the top of the tree if the requested
+        * id is larger than the currently allocated space.
+        */
+       while ((layers < MAX_LEVEL) && (id >= (1 << (layers*IDTREE_BITS)))) {
+               layers++;
+               if (!p->count)
+                       continue;
+               if (!(pn = alloc_layer(idp))) {
+                       /*
+                        * The allocation failed.  If we built part of
+                        * the structure tear it down.
+                        */
+                       for (pn = p; p && p != idp->top; pn = p) {
+                               p = p->ary[0];
+                               pn->ary[0] = NULL;
+                               pn->bitmap = pn->count = 0;
+                               free_layer(idp, pn);
+                       }
+                       return -1;
+               }
+               pn->ary[0] = p;
+               pn->count = 1;
+               if (p->bitmap == IDTREE_FULL)
+                       set_bit(0, pn->bitmap);
+               p = pn;
+       }
+       idp->top = p;
+       idp->layers = layers;
+       v = sub_alloc(idp, ptr, &id);
+       if (v == -2)
+               goto build_up;
+       return(v);
+}
+
+static int sub_remove(struct idtree *idp, int shift, int id)
+{
+       struct idtree_layer *p = idp->top;
+       struct idtree_layer **pa[MAX_LEVEL];
+       struct idtree_layer ***paa = &pa[0];
+       int n;
+
+       *paa = NULL;
+       *++paa = &idp->top;
+
+       while ((shift > 0) && p) {
+               n = (id >> shift) & IDTREE_MASK;
+               clear_bit(n, p->bitmap);
+               *++paa = &p->ary[n];
+               p = p->ary[n];
+               shift -= IDTREE_BITS;
+       }
+       n = id & IDTREE_MASK;
+       if (p != NULL && test_bit(n, p->bitmap)) {
+               clear_bit(n, p->bitmap);
+               p->ary[n] = NULL;
+               while(*paa && ! --((**paa)->count)){
+                       free_layer(idp, **paa);
+                       **paa-- = NULL;
+               }
+               if ( ! *paa )
+                       idp->layers = 0;
+               return 0;
+       }
+       return -1;
+}
+
+void *idtree_lookup(const struct idtree *idp, int id)
+{
+       int n;
+       struct idtree_layer *p;
+
+       n = idp->layers * IDTREE_BITS;
+       p = idp->top;
+       /*
+        * This tests to see if bits outside the current tree are
+        * present.  If so, tain't one of ours!
+        */
+       if ((id & ~(~0 << MAX_ID_SHIFT)) >> (n + IDTREE_BITS))
+            return NULL;
+
+       /* Mask off upper bits we don't use for the search. */
+       id &= MAX_ID_MASK;
+
+       while (n >= IDTREE_BITS && p) {
+               n -= IDTREE_BITS;
+               p = p->ary[(id >> n) & IDTREE_MASK];
+       }
+       return((void *)p);
+}
+
+bool idtree_remove(struct idtree *idp, int id)
+{
+       struct idtree_layer *p;
+
+       /* Mask off upper bits we don't use for the search. */
+       id &= MAX_ID_MASK;
+
+       if (sub_remove(idp, (idp->layers - 1) * IDTREE_BITS, id) == -1) {
+               return false;
+       }
+
+       if ( idp->top && idp->top->count == 1 &&
+            (idp->layers > 1) &&
+            idp->top->ary[0]) {
+               /* We can drop a layer */
+               p = idp->top->ary[0];
+               idp->top->bitmap = idp->top->count = 0;
+               free_layer(idp, idp->top);
+               idp->top = p;
+               --idp->layers;
+       }
+       while (idp->id_free_cnt >= IDTREE_FREE_MAX) {
+               p = alloc_layer(idp);
+               talloc_free(p);
+       }
+       return true;
+}
+
+struct idtree *idtree_new(void *mem_ctx)
+{
+       return talloc_zero(mem_ctx, struct idtree);
+}
+
+int idtree_add(struct idtree *idp, const void *ptr, int limit)
+{
+       int ret = idtree_get_new_above_int(idp, ptr, 0);
+       if (ret > limit) {
+               idtree_remove(idp, ret);
+               return -1;
+       }
+       return ret;
+}
+
+int idtree_add_above(struct idtree *idp, const void *ptr,
+                    int starting_id, int limit)
+{
+       int ret = idtree_get_new_above_int(idp, ptr, starting_id);
+       if (ret > limit) {
+               idtree_remove(idp, ret);
+               return -1;
+       }
+       return ret;
+}
diff --git a/ccan/idtree/idtree.h b/ccan/idtree/idtree.h
new file mode 100644 (file)
index 0000000..a8f8719
--- /dev/null
@@ -0,0 +1,53 @@
+#ifndef CCAN_IDTREE_H
+#define CCAN_IDTREE_H
+#include <stdbool.h>
+
+/**
+ * idtree_new - create an idr_context
+ * @mem_ctx: talloc parent to allocate from (may be NULL).
+ *
+ * Allocate an empty id tree.  You can free it with talloc_free().
+ */
+struct idtree *idtree_new(void *mem_ctx);
+
+/**
+ * idtree_add - get lowest available id, and assign a pointer to it.
+ * @idtree: the tree to allocate from
+ * @ptr: the non-NULL pointer to associate with the id
+ * @limit: the maximum id to allocate (ie. INT_MAX means no limit).
+ *
+ * This returns a non-negative id number, or -1 if all are taken.
+ */
+int idtree_add(struct idtree *idtree, const void *ptr, int limit);
+
+/**
+ * idtree_add_above - get lowest available id, starting at a given value.
+ * @idtree: the tree to allocate from
+ * @ptr: the non-NULL pointer to associate with the id
+ * @starting_id: the minimum id value to consider.
+ * @limit: the maximum id to allocate (ie. INT_MAX means no limit).
+ *
+ * This returns a non-negative id number, or -1 if all are taken.
+ */
+int idtree_add_above(struct idtree *idtree, const void *ptr,
+                    int starting_id, int limit);
+
+/**
+ * idtree_lookup - look up a given id
+ * @idtree: the tree to look in
+ * @id: the id to look up
+ *
+ * Returns NULL if the value is not found, otherwise the pointer value
+ * set with the idtree_add()/idtree_add_above().
+ */
+void *idtree_lookup(const struct idtree *idtree, int id);
+
+/**
+ * idtree_remove - remove a given id.
+ * @idtree: the tree to remove from
+ * @id: the id to remove.
+ *
+ * Returns false if the id was not in the tree.
+ */
+bool idtree_remove(struct idtree *idtree, int id);
+#endif /* CCAN_IDTREE_H */
diff --git a/ccan/idtree/test/run.c b/ccan/idtree/test/run.c
new file mode 100644 (file)
index 0000000..bd12f4c
--- /dev/null
@@ -0,0 +1,47 @@
+#include <ccan/idtree/idtree.c>
+#include <ccan/tap/tap.h>
+#include <limits.h>
+
+#define ALLOC_MAX 32
+
+int main(int argc, char *argv[])
+{
+       unsigned int i;
+       const char allocated[ALLOC_MAX] = { 0 };
+       struct idtree *idtree;
+       void *ctx;
+
+       plan_tests(ALLOC_MAX * 5 + 2);
+       ctx = talloc_named_const(NULL, 1, "test root");
+       idtree = idtree_new(ctx);
+       ok1(talloc_find_parent_byname(idtree, "test root") == ctx);
+
+       for (i = 0; i < ALLOC_MAX; i++) {
+               int id = idtree_add(idtree, &allocated[i], ALLOC_MAX-1);
+               ok1(id == i);
+               ok1(idtree_lookup(idtree, i) == &allocated[i]);
+       }
+       ok1(idtree_add(idtree, &allocated[i], ALLOC_MAX-1) == -1);
+
+       /* Remove every second one. */
+       for (i = 0; i < ALLOC_MAX; i += 2)
+               ok1(idtree_remove(idtree, i));
+
+       for (i = 0; i < ALLOC_MAX; i++) {
+               if (i % 2 == 0)
+                       ok1(!idtree_lookup(idtree, i));
+               else
+                       ok1(idtree_lookup(idtree, i) == &allocated[i]);
+       }
+
+       /* Now, finally, reallocate. */
+       for (i = 0; i < ALLOC_MAX/2; i++) {
+               ok1(idtree_add(idtree, &allocated[i*2], INT_MAX) == i * 2);
+       }
+       
+       for (i = 0; i < ALLOC_MAX; i++) {
+               ok1(idtree_lookup(idtree, i) == &allocated[i]);
+       }
+       talloc_free(ctx);
+       exit(exit_status());
+}