root/include/linux/radix-tree.h

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INCLUDED FROM


DEFINITIONS

This source file includes following definitions.
  1. radix_tree_is_indirect_ptr
  2. radix_tree_deref_slot
  3. radix_tree_deref_slot_protected
  4. radix_tree_deref_retry
  5. radix_tree_exceptional_entry
  6. radix_tree_exception
  7. radix_tree_replace_slot
  8. radix_tree_preload_end
  9. radix_tree_iter_init
  10. radix_tree_chunk_size
  11. radix_tree_next_slot

   1 /*
   2  * Copyright (C) 2001 Momchil Velikov
   3  * Portions Copyright (C) 2001 Christoph Hellwig
   4  * Copyright (C) 2006 Nick Piggin
   5  * Copyright (C) 2012 Konstantin Khlebnikov
   6  *
   7  * This program is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU General Public License as
   9  * published by the Free Software Foundation; either version 2, or (at
  10  * your option) any later version.
  11  * 
  12  * This program is distributed in the hope that it will be useful, but
  13  * WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  * General Public License for more details.
  16  * 
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program; if not, write to the Free Software
  19  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  20  */
  21 #ifndef _LINUX_RADIX_TREE_H
  22 #define _LINUX_RADIX_TREE_H
  23 
  24 #include <linux/preempt.h>
  25 #include <linux/types.h>
  26 #include <linux/bug.h>
  27 #include <linux/kernel.h>
  28 #include <linux/rcupdate.h>
  29 
  30 /*
  31  * An indirect pointer (root->rnode pointing to a radix_tree_node, rather
  32  * than a data item) is signalled by the low bit set in the root->rnode
  33  * pointer.
  34  *
  35  * In this case root->height is > 0, but the indirect pointer tests are
  36  * needed for RCU lookups (because root->height is unreliable). The only
  37  * time callers need worry about this is when doing a lookup_slot under
  38  * RCU.
  39  *
  40  * Indirect pointer in fact is also used to tag the last pointer of a node
  41  * when it is shrunk, before we rcu free the node. See shrink code for
  42  * details.
  43  */
  44 #define RADIX_TREE_INDIRECT_PTR         1
  45 /*
  46  * A common use of the radix tree is to store pointers to struct pages;
  47  * but shmem/tmpfs needs also to store swap entries in the same tree:
  48  * those are marked as exceptional entries to distinguish them.
  49  * EXCEPTIONAL_ENTRY tests the bit, EXCEPTIONAL_SHIFT shifts content past it.
  50  */
  51 #define RADIX_TREE_EXCEPTIONAL_ENTRY    2
  52 #define RADIX_TREE_EXCEPTIONAL_SHIFT    2
  53 
  54 static inline int radix_tree_is_indirect_ptr(void *ptr)
     /* [previous][next][first][last][top][bottom][index][help] [+54 include/linux/radix-tree.h] */
  55 {
  56         return (int)((unsigned long)ptr & RADIX_TREE_INDIRECT_PTR);
  57 }
  58 
  59 /*** radix-tree API starts here ***/
  60 
  61 #define RADIX_TREE_MAX_TAGS 3
  62 
  63 #ifdef __KERNEL__
  64 #define RADIX_TREE_MAP_SHIFT    (CONFIG_BASE_SMALL ? 4 : 6)
  65 #else
  66 #define RADIX_TREE_MAP_SHIFT    3       /* For more stressful testing */
  67 #endif
  68 
  69 #define RADIX_TREE_MAP_SIZE     (1UL << RADIX_TREE_MAP_SHIFT)
  70 #define RADIX_TREE_MAP_MASK     (RADIX_TREE_MAP_SIZE-1)
  71 
  72 #define RADIX_TREE_TAG_LONGS    \
  73         ((RADIX_TREE_MAP_SIZE + BITS_PER_LONG - 1) / BITS_PER_LONG)
  74 
  75 #define RADIX_TREE_INDEX_BITS  (8 /* CHAR_BIT */ * sizeof(unsigned long))
  76 #define RADIX_TREE_MAX_PATH (DIV_ROUND_UP(RADIX_TREE_INDEX_BITS, \
  77                                           RADIX_TREE_MAP_SHIFT))
  78 
  79 /* Height component in node->path */
  80 #define RADIX_TREE_HEIGHT_SHIFT (RADIX_TREE_MAX_PATH + 1)
  81 #define RADIX_TREE_HEIGHT_MASK  ((1UL << RADIX_TREE_HEIGHT_SHIFT) - 1)
  82 
  83 /* Internally used bits of node->count */
  84 #define RADIX_TREE_COUNT_SHIFT  (RADIX_TREE_MAP_SHIFT + 1)
  85 #define RADIX_TREE_COUNT_MASK   ((1UL << RADIX_TREE_COUNT_SHIFT) - 1)
  86 
  87 struct radix_tree_node {
  88         unsigned int    path;   /* Offset in parent & height from the bottom */
  89         unsigned int    count;
  90         union {
  91                 struct {
  92                         /* Used when ascending tree */
  93                         struct radix_tree_node *parent;
  94                         /* For tree user */
  95                         void *private_data;
  96                 };
  97                 /* Used when freeing node */
  98                 struct rcu_head rcu_head;
  99         };
 100         /* For tree user */
 101         struct list_head private_list;
 102         void __rcu      *slots[RADIX_TREE_MAP_SIZE];
 103         unsigned long   tags[RADIX_TREE_MAX_TAGS][RADIX_TREE_TAG_LONGS];
 104 };
 105 
 106 /* root tags are stored in gfp_mask, shifted by __GFP_BITS_SHIFT */
 107 struct radix_tree_root {
 108         unsigned int            height;
 109         gfp_t                   gfp_mask;
 110         struct radix_tree_node  __rcu *rnode;
 111 };
 112 
 113 #define RADIX_TREE_INIT(mask)   {                                       \
 114         .height = 0,                                                    \
 115         .gfp_mask = (mask),                                             \
 116         .rnode = NULL,                                                  \
 117 }
 118 
 119 #define RADIX_TREE(name, mask) \
 120         struct radix_tree_root name = RADIX_TREE_INIT(mask)
 121 
 122 #define INIT_RADIX_TREE(root, mask)                                     \
 123 do {                                                                    \
 124         (root)->height = 0;                                             \
 125         (root)->gfp_mask = (mask);                                      \
 126         (root)->rnode = NULL;                                           \
 127 } while (0)
 128 
 129 /**
 130  * Radix-tree synchronization
 131  *
 132  * The radix-tree API requires that users provide all synchronisation (with
 133  * specific exceptions, noted below).
 134  *
 135  * Synchronization of access to the data items being stored in the tree, and
 136  * management of their lifetimes must be completely managed by API users.
 137  *
 138  * For API usage, in general,
 139  * - any function _modifying_ the tree or tags (inserting or deleting
 140  *   items, setting or clearing tags) must exclude other modifications, and
 141  *   exclude any functions reading the tree.
 142  * - any function _reading_ the tree or tags (looking up items or tags,
 143  *   gang lookups) must exclude modifications to the tree, but may occur
 144  *   concurrently with other readers.
 145  *
 146  * The notable exceptions to this rule are the following functions:
 147  * __radix_tree_lookup
 148  * radix_tree_lookup
 149  * radix_tree_lookup_slot
 150  * radix_tree_tag_get
 151  * radix_tree_gang_lookup
 152  * radix_tree_gang_lookup_slot
 153  * radix_tree_gang_lookup_tag
 154  * radix_tree_gang_lookup_tag_slot
 155  * radix_tree_tagged
 156  *
 157  * The first 7 functions are able to be called locklessly, using RCU. The
 158  * caller must ensure calls to these functions are made within rcu_read_lock()
 159  * regions. Other readers (lock-free or otherwise) and modifications may be
 160  * running concurrently.
 161  *
 162  * It is still required that the caller manage the synchronization and lifetimes
 163  * of the items. So if RCU lock-free lookups are used, typically this would mean
 164  * that the items have their own locks, or are amenable to lock-free access; and
 165  * that the items are freed by RCU (or only freed after having been deleted from
 166  * the radix tree *and* a synchronize_rcu() grace period).
 167  *
 168  * (Note, rcu_assign_pointer and rcu_dereference are not needed to control
 169  * access to data items when inserting into or looking up from the radix tree)
 170  *
 171  * Note that the value returned by radix_tree_tag_get() may not be relied upon
 172  * if only the RCU read lock is held.  Functions to set/clear tags and to
 173  * delete nodes running concurrently with it may affect its result such that
 174  * two consecutive reads in the same locked section may return different
 175  * values.  If reliability is required, modification functions must also be
 176  * excluded from concurrency.
 177  *
 178  * radix_tree_tagged is able to be called without locking or RCU.
 179  */
 180 
 181 /**
 182  * radix_tree_deref_slot        - dereference a slot
 183  * @pslot:      pointer to slot, returned by radix_tree_lookup_slot
 184  * Returns:     item that was stored in that slot with any direct pointer flag
 185  *              removed.
 186  *
 187  * For use with radix_tree_lookup_slot().  Caller must hold tree at least read
 188  * locked across slot lookup and dereference. Not required if write lock is
 189  * held (ie. items cannot be concurrently inserted).
 190  *
 191  * radix_tree_deref_retry must be used to confirm validity of the pointer if
 192  * only the read lock is held.
 193  */
 194 static inline void *radix_tree_deref_slot(void **pslot)
     /* [previous][next][first][last][top][bottom][index][help] [+194 include/linux/radix-tree.h] */
 195 {
 196         return rcu_dereference(*pslot);
 197 }
 198 
 199 /**
 200  * radix_tree_deref_slot_protected      - dereference a slot without RCU lock but with tree lock held
 201  * @pslot:      pointer to slot, returned by radix_tree_lookup_slot
 202  * Returns:     item that was stored in that slot with any direct pointer flag
 203  *              removed.
 204  *
 205  * Similar to radix_tree_deref_slot but only used during migration when a pages
 206  * mapping is being moved. The caller does not hold the RCU read lock but it
 207  * must hold the tree lock to prevent parallel updates.
 208  */
 209 static inline void *radix_tree_deref_slot_protected(void **pslot,
     /* [previous][next][first][last][top][bottom][index][help] [+209 include/linux/radix-tree.h] */
 210                                                         spinlock_t *treelock)
 211 {
 212         return rcu_dereference_protected(*pslot, lockdep_is_held(treelock));
 213 }
 214 
 215 /**
 216  * radix_tree_deref_retry       - check radix_tree_deref_slot
 217  * @arg:        pointer returned by radix_tree_deref_slot
 218  * Returns:     0 if retry is not required, otherwise retry is required
 219  *
 220  * radix_tree_deref_retry must be used with radix_tree_deref_slot.
 221  */
 222 static inline int radix_tree_deref_retry(void *arg)
     /* [previous][next][first][last][top][bottom][index][help] [+222 include/linux/radix-tree.h] */
 223 {
 224         return unlikely((unsigned long)arg & RADIX_TREE_INDIRECT_PTR);
 225 }
 226 
 227 /**
 228  * radix_tree_exceptional_entry - radix_tree_deref_slot gave exceptional entry?
 229  * @arg:        value returned by radix_tree_deref_slot
 230  * Returns:     0 if well-aligned pointer, non-0 if exceptional entry.
 231  */
 232 static inline int radix_tree_exceptional_entry(void *arg)
     /* [previous][next][first][last][top][bottom][index][help] [+232 include/linux/radix-tree.h] */
 233 {
 234         /* Not unlikely because radix_tree_exception often tested first */
 235         return (unsigned long)arg & RADIX_TREE_EXCEPTIONAL_ENTRY;
 236 }
 237 
 238 /**
 239  * radix_tree_exception - radix_tree_deref_slot returned either exception?
 240  * @arg:        value returned by radix_tree_deref_slot
 241  * Returns:     0 if well-aligned pointer, non-0 if either kind of exception.
 242  */
 243 static inline int radix_tree_exception(void *arg)
     /* [previous][next][first][last][top][bottom][index][help] [+243 include/linux/radix-tree.h] */
 244 {
 245         return unlikely((unsigned long)arg &
 246                 (RADIX_TREE_INDIRECT_PTR | RADIX_TREE_EXCEPTIONAL_ENTRY));
 247 }
 248 
 249 /**
 250  * radix_tree_replace_slot      - replace item in a slot
 251  * @pslot:      pointer to slot, returned by radix_tree_lookup_slot
 252  * @item:       new item to store in the slot.
 253  *
 254  * For use with radix_tree_lookup_slot().  Caller must hold tree write locked
 255  * across slot lookup and replacement.
 256  */
 257 static inline void radix_tree_replace_slot(void **pslot, void *item)
     /* [previous][next][first][last][top][bottom][index][help] [+257 include/linux/radix-tree.h] */
 258 {
 259         BUG_ON(radix_tree_is_indirect_ptr(item));
 260         rcu_assign_pointer(*pslot, item);
 261 }
 262 
 263 int __radix_tree_create(struct radix_tree_root *root, unsigned long index,
 264                         struct radix_tree_node **nodep, void ***slotp);
 265 int radix_tree_insert(struct radix_tree_root *, unsigned long, void *);
 266 void *__radix_tree_lookup(struct radix_tree_root *root, unsigned long index,
 267                           struct radix_tree_node **nodep, void ***slotp);
 268 void *radix_tree_lookup(struct radix_tree_root *, unsigned long);
 269 void **radix_tree_lookup_slot(struct radix_tree_root *, unsigned long);
 270 bool __radix_tree_delete_node(struct radix_tree_root *root,
 271                               struct radix_tree_node *node);
 272 void *radix_tree_delete_item(struct radix_tree_root *, unsigned long, void *);
 273 void *radix_tree_delete(struct radix_tree_root *, unsigned long);
 274 unsigned int
 275 radix_tree_gang_lookup(struct radix_tree_root *root, void **results,
 276                         unsigned long first_index, unsigned int max_items);
 277 unsigned int radix_tree_gang_lookup_slot(struct radix_tree_root *root,
 278                         void ***results, unsigned long *indices,
 279                         unsigned long first_index, unsigned int max_items);
 280 int radix_tree_preload(gfp_t gfp_mask);
 281 int radix_tree_maybe_preload(gfp_t gfp_mask);
 282 void radix_tree_init(void);
 283 void *radix_tree_tag_set(struct radix_tree_root *root,
 284                         unsigned long index, unsigned int tag);
 285 void *radix_tree_tag_clear(struct radix_tree_root *root,
 286                         unsigned long index, unsigned int tag);
 287 int radix_tree_tag_get(struct radix_tree_root *root,
 288                         unsigned long index, unsigned int tag);
 289 unsigned int
 290 radix_tree_gang_lookup_tag(struct radix_tree_root *root, void **results,
 291                 unsigned long first_index, unsigned int max_items,
 292                 unsigned int tag);
 293 unsigned int
 294 radix_tree_gang_lookup_tag_slot(struct radix_tree_root *root, void ***results,
 295                 unsigned long first_index, unsigned int max_items,
 296                 unsigned int tag);
 297 unsigned long radix_tree_range_tag_if_tagged(struct radix_tree_root *root,
 298                 unsigned long *first_indexp, unsigned long last_index,
 299                 unsigned long nr_to_tag,
 300                 unsigned int fromtag, unsigned int totag);
 301 int radix_tree_tagged(struct radix_tree_root *root, unsigned int tag);
 302 unsigned long radix_tree_locate_item(struct radix_tree_root *root, void *item);
 303 
 304 static inline void radix_tree_preload_end(void)
     /* [previous][next][first][last][top][bottom][index][help] [+304 include/linux/radix-tree.h] */
 305 {
 306         preempt_enable();
 307 }
 308 
 309 /**
 310  * struct radix_tree_iter - radix tree iterator state
 311  *
 312  * @index:      index of current slot
 313  * @next_index: next-to-last index for this chunk
 314  * @tags:       bit-mask for tag-iterating
 315  *
 316  * This radix tree iterator works in terms of "chunks" of slots.  A chunk is a
 317  * subinterval of slots contained within one radix tree leaf node.  It is
 318  * described by a pointer to its first slot and a struct radix_tree_iter
 319  * which holds the chunk's position in the tree and its size.  For tagged
 320  * iteration radix_tree_iter also holds the slots' bit-mask for one chosen
 321  * radix tree tag.
 322  */
 323 struct radix_tree_iter {
 324         unsigned long   index;
 325         unsigned long   next_index;
 326         unsigned long   tags;
 327 };
 328 
 329 #define RADIX_TREE_ITER_TAG_MASK        0x00FF  /* tag index in lower byte */
 330 #define RADIX_TREE_ITER_TAGGED          0x0100  /* lookup tagged slots */
 331 #define RADIX_TREE_ITER_CONTIG          0x0200  /* stop at first hole */
 332 
 333 /**
 334  * radix_tree_iter_init - initialize radix tree iterator
 335  *
 336  * @iter:       pointer to iterator state
 337  * @start:      iteration starting index
 338  * Returns:     NULL
 339  */
 340 static __always_inline void **
 341 radix_tree_iter_init(struct radix_tree_iter *iter, unsigned long start)
     /* [previous][next][first][last][top][bottom][index][help] [+341 include/linux/radix-tree.h] */
 342 {
 343         /*
 344          * Leave iter->tags uninitialized. radix_tree_next_chunk() will fill it
 345          * in the case of a successful tagged chunk lookup.  If the lookup was
 346          * unsuccessful or non-tagged then nobody cares about ->tags.
 347          *
 348          * Set index to zero to bypass next_index overflow protection.
 349          * See the comment in radix_tree_next_chunk() for details.
 350          */
 351         iter->index = 0;
 352         iter->next_index = start;
 353         return NULL;
 354 }
 355 
 356 /**
 357  * radix_tree_next_chunk - find next chunk of slots for iteration
 358  *
 359  * @root:       radix tree root
 360  * @iter:       iterator state
 361  * @flags:      RADIX_TREE_ITER_* flags and tag index
 362  * Returns:     pointer to chunk first slot, or NULL if there no more left
 363  *
 364  * This function looks up the next chunk in the radix tree starting from
 365  * @iter->next_index.  It returns a pointer to the chunk's first slot.
 366  * Also it fills @iter with data about chunk: position in the tree (index),
 367  * its end (next_index), and constructs a bit mask for tagged iterating (tags).
 368  */
 369 void **radix_tree_next_chunk(struct radix_tree_root *root,
 370                              struct radix_tree_iter *iter, unsigned flags);
 371 
 372 /**
 373  * radix_tree_chunk_size - get current chunk size
 374  *
 375  * @iter:       pointer to radix tree iterator
 376  * Returns:     current chunk size
 377  */
 378 static __always_inline unsigned
 379 radix_tree_chunk_size(struct radix_tree_iter *iter)
     /* [previous][next][first][last][top][bottom][index][help] [+379 include/linux/radix-tree.h] */
 380 {
 381         return iter->next_index - iter->index;
 382 }
 383 
 384 /**
 385  * radix_tree_next_slot - find next slot in chunk
 386  *
 387  * @slot:       pointer to current slot
 388  * @iter:       pointer to interator state
 389  * @flags:      RADIX_TREE_ITER_*, should be constant
 390  * Returns:     pointer to next slot, or NULL if there no more left
 391  *
 392  * This function updates @iter->index in the case of a successful lookup.
 393  * For tagged lookup it also eats @iter->tags.
 394  */
 395 static __always_inline void **
 396 radix_tree_next_slot(void **slot, struct radix_tree_iter *iter, unsigned flags)
     /* [previous][next][first][last][top][bottom][index][help] [+396 include/linux/radix-tree.h] */
 397 {
 398         if (flags & RADIX_TREE_ITER_TAGGED) {
 399                 iter->tags >>= 1;
 400                 if (likely(iter->tags & 1ul)) {
 401                         iter->index++;
 402                         return slot + 1;
 403                 }
 404                 if (!(flags & RADIX_TREE_ITER_CONTIG) && likely(iter->tags)) {
 405                         unsigned offset = __ffs(iter->tags);
 406 
 407                         iter->tags >>= offset;
 408                         iter->index += offset + 1;
 409                         return slot + offset + 1;
 410                 }
 411         } else {
 412                 unsigned size = radix_tree_chunk_size(iter) - 1;
 413 
 414                 while (size--) {
 415                         slot++;
 416                         iter->index++;
 417                         if (likely(*slot))
 418                                 return slot;
 419                         if (flags & RADIX_TREE_ITER_CONTIG) {
 420                                 /* forbid switching to the next chunk */
 421                                 iter->next_index = 0;
 422                                 break;
 423                         }
 424                 }
 425         }
 426         return NULL;
 427 }
 428 
 429 /**
 430  * radix_tree_for_each_chunk - iterate over chunks
 431  *
 432  * @slot:       the void** variable for pointer to chunk first slot
 433  * @root:       the struct radix_tree_root pointer
 434  * @iter:       the struct radix_tree_iter pointer
 435  * @start:      iteration starting index
 436  * @flags:      RADIX_TREE_ITER_* and tag index
 437  *
 438  * Locks can be released and reacquired between iterations.
 439  */
 440 #define radix_tree_for_each_chunk(slot, root, iter, start, flags)       \
 441         for (slot = radix_tree_iter_init(iter, start) ;                 \
 442               (slot = radix_tree_next_chunk(root, iter, flags)) ;)
 443 
 444 /**
 445  * radix_tree_for_each_chunk_slot - iterate over slots in one chunk
 446  *
 447  * @slot:       the void** variable, at the beginning points to chunk first slot
 448  * @iter:       the struct radix_tree_iter pointer
 449  * @flags:      RADIX_TREE_ITER_*, should be constant
 450  *
 451  * This macro is designed to be nested inside radix_tree_for_each_chunk().
 452  * @slot points to the radix tree slot, @iter->index contains its index.
 453  */
 454 #define radix_tree_for_each_chunk_slot(slot, iter, flags)               \
 455         for (; slot ; slot = radix_tree_next_slot(slot, iter, flags))
 456 
 457 /**
 458  * radix_tree_for_each_slot - iterate over non-empty slots
 459  *
 460  * @slot:       the void** variable for pointer to slot
 461  * @root:       the struct radix_tree_root pointer
 462  * @iter:       the struct radix_tree_iter pointer
 463  * @start:      iteration starting index
 464  *
 465  * @slot points to radix tree slot, @iter->index contains its index.
 466  */
 467 #define radix_tree_for_each_slot(slot, root, iter, start)               \
 468         for (slot = radix_tree_iter_init(iter, start) ;                 \
 469              slot || (slot = radix_tree_next_chunk(root, iter, 0)) ;    \
 470              slot = radix_tree_next_slot(slot, iter, 0))
 471 
 472 /**
 473  * radix_tree_for_each_contig - iterate over contiguous slots
 474  *
 475  * @slot:       the void** variable for pointer to slot
 476  * @root:       the struct radix_tree_root pointer
 477  * @iter:       the struct radix_tree_iter pointer
 478  * @start:      iteration starting index
 479  *
 480  * @slot points to radix tree slot, @iter->index contains its index.
 481  */
 482 #define radix_tree_for_each_contig(slot, root, iter, start)             \
 483         for (slot = radix_tree_iter_init(iter, start) ;                 \
 484              slot || (slot = radix_tree_next_chunk(root, iter,          \
 485                                 RADIX_TREE_ITER_CONTIG)) ;              \
 486              slot = radix_tree_next_slot(slot, iter,                    \
 487                                 RADIX_TREE_ITER_CONTIG))
 488 
 489 /**
 490  * radix_tree_for_each_tagged - iterate over tagged slots
 491  *
 492  * @slot:       the void** variable for pointer to slot
 493  * @root:       the struct radix_tree_root pointer
 494  * @iter:       the struct radix_tree_iter pointer
 495  * @start:      iteration starting index
 496  * @tag:        tag index
 497  *
 498  * @slot points to radix tree slot, @iter->index contains its index.
 499  */
 500 #define radix_tree_for_each_tagged(slot, root, iter, start, tag)        \
 501         for (slot = radix_tree_iter_init(iter, start) ;                 \
 502              slot || (slot = radix_tree_next_chunk(root, iter,          \
 503                               RADIX_TREE_ITER_TAGGED | tag)) ;          \
 504              slot = radix_tree_next_slot(slot, iter,                    \
 505                                 RADIX_TREE_ITER_TAGGED))
 506 
 507 #endif /* _LINUX_RADIX_TREE_H */

/* [previous][next][first][last][top][bottom][index][help] [+507 include/linux/radix-tree.h] */