src/mesa/main/hash.c

   1 /**
   2  * \file hash.c
   3  * Generic hash table.
   4  *
   5  * Used for display lists, texture objects, vertex/fragment programs,
   6  * buffer objects, etc.  The hash functions are thread-safe.
   7  *
   8  * \note key=0 is illegal.
   9  *
  10  * \author Brian Paul
  11  */
  12
  13 /*
  14  * Mesa 3-D graphics library
  15  *
  16  * Copyright (C) 1999-2006  Brian Paul   All Rights Reserved.
  17  *
  18  * Permission is hereby granted, free of charge, to any person obtaining a
  19  * copy of this software and associated documentation files (the "Software"),
  20  * to deal in the Software without restriction, including without limitation
  21  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
  22  * and/or sell copies of the Software, and to permit persons to whom the
  23  * Software is furnished to do so, subject to the following conditions:
  24  *
  25  * The above copyright notice and this permission notice shall be included
  26  * in all copies or substantial portions of the Software.
  27  *
  28  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
  29  * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  30  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  31  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
  32  * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
  33  * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
  34  * OTHER DEALINGS IN THE SOFTWARE.
  35  */
  36
  37 #include "glheader.h"
  38 #include "imports.h"
  39 #include "hash.h"
  40 #include "util/hash_table.h"
  41
  42 /**
  43  * Magic GLuint object name that gets stored outside of the struct hash_table.
  44  *
  45  * The hash table needs a particular pointer to be the marker for a key that
  46  * was deleted from the table, along with NULL for the "never allocated in the
  47  * table" marker.  Legacy GL allows any GLuint to be used as a GL object name,
  48  * and we use a 1:1 mapping from GLuints to key pointers, so we need to be
  49  * able to track a GLuint that happens to match the deleted key outside of
  50  * struct hash_table.  We tell the hash table to use "1" as the deleted key
  51  * value, so that we test the deleted-key-in-the-table path as best we can.
  52  */
  53 #define DELETED_KEY_VALUE 1
  54
  55 /**
  56  * The hash table data structure.
  57  */
  58 struct _mesa_HashTable {
  59    struct hash_table *ht;
  60    GLuint MaxKey;                        /**< highest key inserted so far */
  61    mtx_t Mutex;                /**< mutual exclusion lock */
  62    mtx_t WalkMutex;            /**< for _mesa_HashWalk() */
  63    GLboolean InDeleteAll;                /**< Debug check */
  64    /** Value that would be in the table for DELETED_KEY_VALUE. */
  65    void *deleted_key_data;
  66 };
  67
  68 /** @{
  69  * Mapping from our use of GLuint as both the key and the hash value to the
  70  * hash_table.h API
  71  *
  72  * There exist many integer hash functions, designed to avoid collisions when
  73  * the integers are spread across key space with some patterns.  In GL, the
  74  * pattern (in the case of glGen*()ed object IDs) is that the keys are unique
  75  * contiguous integers starting from 1.  Because of that, we just use the key
  76  * as the hash value, to minimize the cost of the hash function.  If objects
  77  * are never deleted, we will never see a collision in the table, because the
  78  * table resizes itself when it approaches full, and thus key % table_size ==
  79  * key.
  80  *
  81  * The case where we could have collisions for genned objects would be
  82  * something like: glGenBuffers(&a, 100); glDeleteBuffers(&a + 50, 50);
  83  * glGenBuffers(&b, 100), because objects 1-50 and 101-200 are allocated at
  84  * the end of that sequence, instead of 1-150.  So far it doesn't appear to be
  85  * a problem.
  86  */
  87 static bool
  88 uint_key_compare(const void *a, const void *b)
  89 {
  90    return a == b;
  91 }
  92
  93 static uint32_t
  94 uint_hash(GLuint id)
  95 {
  96    return id;
  97 }
  98
  99 static uint32_t
 100 uint_key_hash(const void *key)
 101 {
 102    return uint_hash((uintptr_t)key);
 103 }
 104
 105 static void *
 106 uint_key(GLuint id)
 107 {
 108    return (void *)(uintptr_t) id;
 109 }
 110 /** @} */
 111
 112 /**
 113  * Create a new hash table.
 114  *
 115  * \return pointer to a new, empty hash table.
 116  */
 117 struct _mesa_HashTable *
 118 _mesa_NewHashTable(void)
 119 {
 120    struct _mesa_HashTable *table = CALLOC_STRUCT(_mesa_HashTable);
 121
 122    if (table) {
 123       table->ht = _mesa_hash_table_create(NULL, uint_key_hash,
 124                                           uint_key_compare);
 125       if (table->ht == NULL) {
 126          free(table);
 127          _mesa_error_no_memory(__func__);
 128          return NULL;
 129       }
 130
 131       _mesa_hash_table_set_deleted_key(table->ht, uint_key(DELETED_KEY_VALUE));
 132       mtx_init(&table->Mutex, mtx_plain);
 133       mtx_init(&table->WalkMutex, mtx_plain);
 134    }
 135    else {
 136       _mesa_error_no_memory(__func__);
 137    }
 138
 139    return table;
 140 }
 141
 142
 143
 144 /**
 145  * Delete a hash table.
 146  * Frees each entry on the hash table and then the hash table structure itself.
 147  * Note that the caller should have already traversed the table and deleted
 148  * the objects in the table (i.e. We don't free the entries' data pointer).
 149  *
 150  * \param table the hash table to delete.
 151  */
 152 void
 153 _mesa_DeleteHashTable(struct _mesa_HashTable *table)
 154 {
 155    assert(table);
 156
 157    if (_mesa_hash_table_next_entry(table->ht, NULL) != NULL) {
 158       _mesa_problem(NULL, "In _mesa_DeleteHashTable, found non-freed data");
 159    }
 160
 161    _mesa_hash_table_destroy(table->ht, NULL);
 162
 163    mtx_destroy(&table->Mutex);
 164    mtx_destroy(&table->WalkMutex);
 165    free(table);
 166 }
 167
 168
 169
 170 /**
 171  * Lookup an entry in the hash table, without locking.
 172  * \sa _mesa_HashLookup
 173  */
 174 static inline void *
 175 _mesa_HashLookup_unlocked(struct _mesa_HashTable *table, GLuint key)
 176 {
 177    const struct hash_entry *entry;
 178
 179    assert(table);
 180    assert(key);
 181
 182    if (key == DELETED_KEY_VALUE)
 183       return table->deleted_key_data;
 184
 185    entry = _mesa_hash_table_search(table->ht, uint_key(key));
 186    if (!entry)
 187       return NULL;
 188
 189    return entry->data;
 190 }
 191
 192
 193 /**
 194  * Lookup an entry in the hash table.
 195  *
 196  * \param table the hash table.
 197  * \param key the key.
 198  *
 199  * \return pointer to user's data or NULL if key not in table
 200  */
 201 void *
 202 _mesa_HashLookup(struct _mesa_HashTable *table, GLuint key)
 203 {
 204    void *res;
 205    assert(table);
 206    mtx_lock(&table->Mutex);
 207    res = _mesa_HashLookup_unlocked(table, key);
 208    mtx_unlock(&table->Mutex);
 209    return res;
 210 }
 211
 212
 213 /**
 214  * Lookup an entry in the hash table without locking the mutex.
 215  *
 216  * The hash table mutex must be locked manually by calling
 217  * _mesa_HashLockMutex() before calling this function.
 218  *
 219  * \param table the hash table.
 220  * \param key the key.
 221  *
 222  * \return pointer to user's data or NULL if key not in table
 223  */
 224 void *
 225 _mesa_HashLookupLocked(struct _mesa_HashTable *table, GLuint key)
 226 {
 227    return _mesa_HashLookup_unlocked(table, key);
 228 }
 229
 230
 231 /**
 232  * Lock the hash table mutex.
 233  *
 234  * This function should be used when multiple objects need
 235  * to be looked up in the hash table, to avoid having to lock
 236  * and unlock the mutex each time.
 237  *
 238  * \param table the hash table.
 239  */
 240 void
 241 _mesa_HashLockMutex(struct _mesa_HashTable *table)
 242 {
 243    assert(table);
 244    mtx_lock(&table->Mutex);
 245 }
 246
 247
 248 /**
 249  * Unlock the hash table mutex.
 250  *
 251  * \param table the hash table.
 252  */
 253 void
 254 _mesa_HashUnlockMutex(struct _mesa_HashTable *table)
 255 {
 256    assert(table);
 257    mtx_unlock(&table->Mutex);
 258 }
 259
 260
 261 static inline void
 262 _mesa_HashInsert_unlocked(struct _mesa_HashTable *table, GLuint key, void *data)
 263 {
 264    uint32_t hash = uint_hash(key);
 265    struct hash_entry *entry;
 266
 267    assert(table);
 268    assert(key);
 269
 270    if (key > table->MaxKey)
 271       table->MaxKey = key;
 272
 273    if (key == DELETED_KEY_VALUE) {
 274       table->deleted_key_data = data;
 275    } else {
 276       entry = _mesa_hash_table_search_pre_hashed(table->ht, hash, uint_key(key));
 277       if (entry) {
 278          entry->data = data;
 279       } else {
 280          _mesa_hash_table_insert_pre_hashed(table->ht, hash, uint_key(key), data);
 281       }
 282    }
 283 }
 284
 285
 286 /**
 287  * Insert a key/pointer pair into the hash table without locking the mutex.
 288  * If an entry with this key already exists we'll replace the existing entry.
 289  *
 290  * The hash table mutex must be locked manually by calling
 291  * _mesa_HashLockMutex() before calling this function.
 292  *
 293  * \param table the hash table.
 294  * \param key the key (not zero).
 295  * \param data pointer to user data.
 296  */
 297 void
 298 _mesa_HashInsertLocked(struct _mesa_HashTable *table, GLuint key, void *data)
 299 {
 300    _mesa_HashInsert_unlocked(table, key, data);
 301 }
 302
 303
 304 /**
 305  * Insert a key/pointer pair into the hash table.
 306  * If an entry with this key already exists we'll replace the existing entry.
 307  *
 308  * \param table the hash table.
 309  * \param key the key (not zero).
 310  * \param data pointer to user data.
 311  */
 312 void
 313 _mesa_HashInsert(struct _mesa_HashTable *table, GLuint key, void *data)
 314 {
 315    assert(table);
 316    mtx_lock(&table->Mutex);
 317    _mesa_HashInsert_unlocked(table, key, data);
 318    mtx_unlock(&table->Mutex);
 319 }
 320
 321
 322 /**
 323  * Remove an entry from the hash table.
 324  *
 325  * \param table the hash table.
 326  * \param key key of entry to remove.
 327  *
 328  * While holding the hash table's lock, searches the entry with the matching
 329  * key and unlinks it.
 330  */
 331 void
 332 _mesa_HashRemove(struct _mesa_HashTable *table, GLuint key)
 333 {
 334    struct hash_entry *entry;
 335
 336    assert(table);
 337    assert(key);
 338
 339    /* have to check this outside of mutex lock */
 340    if (table->InDeleteAll) {
 341       _mesa_problem(NULL, "_mesa_HashRemove illegally called from "
 342                     "_mesa_HashDeleteAll callback function");
 343       return;
 344    }
 345
 346    mtx_lock(&table->Mutex);
 347    if (key == DELETED_KEY_VALUE) {
 348       table->deleted_key_data = NULL;
 349    } else {
 350       entry = _mesa_hash_table_search(table->ht, uint_key(key));
 351       _mesa_hash_table_remove(table->ht, entry);
 352    }
 353    mtx_unlock(&table->Mutex);
 354 }
 355
 356
 357
 358 /**
 359  * Delete all entries in a hash table, but don't delete the table itself.
 360  * Invoke the given callback function for each table entry.
 361  *
 362  * \param table  the hash table to delete
 363  * \param callback  the callback function
 364  * \param userData  arbitrary pointer to pass along to the callback
 365  *                  (this is typically a struct gl_context pointer)
 366  */
 367 void
 368 _mesa_HashDeleteAll(struct _mesa_HashTable *table,
 369                     void (*callback)(GLuint key, void *data, void *userData),
 370                     void *userData)
 371 {
 372    struct hash_entry *entry;
 373
 374    assert(table);
 375    assert(callback);
 376    mtx_lock(&table->Mutex);
 377    table->InDeleteAll = GL_TRUE;
 378    hash_table_foreach(table->ht, entry) {
 379       callback((uintptr_t)entry->key, entry->data, userData);
 380       _mesa_hash_table_remove(table->ht, entry);
 381    }
 382    if (table->deleted_key_data) {
 383       callback(DELETED_KEY_VALUE, table->deleted_key_data, userData);
 384       table->deleted_key_data = NULL;
 385    }
 386    table->InDeleteAll = GL_FALSE;
 387    mtx_unlock(&table->Mutex);
 388 }
 389
 390
 391 /**
 392  * Walk over all entries in a hash table, calling callback function for each.
 393  * Note: we use a separate mutex in this function to avoid a recursive
 394  * locking deadlock (in case the callback calls _mesa_HashRemove()) and to
 395  * prevent multiple threads/contexts from getting tangled up.
 396  * A lock-less version of this function could be used when the table will
 397  * not be modified.
 398  * \param table  the hash table to walk
 399  * \param callback  the callback function
 400  * \param userData  arbitrary pointer to pass along to the callback
 401  *                  (this is typically a struct gl_context pointer)
 402  */
 403 void
 404 _mesa_HashWalk(const struct _mesa_HashTable *table,
 405                void (*callback)(GLuint key, void *data, void *userData),
 406                void *userData)
 407 {
 408    /* cast-away const */
 409    struct _mesa_HashTable *table2 = (struct _mesa_HashTable *) table;
 410    struct hash_entry *entry;
 411
 412    assert(table);
 413    assert(callback);
 414    mtx_lock(&table2->WalkMutex);
 415    hash_table_foreach(table->ht, entry) {
 416       callback((uintptr_t)entry->key, entry->data, userData);
 417    }
 418    if (table->deleted_key_data)
 419       callback(DELETED_KEY_VALUE, table->deleted_key_data, userData);
 420    mtx_unlock(&table2->WalkMutex);
 421 }
 422
 423 static void
 424 debug_print_entry(GLuint key, void *data, void *userData)
 425 {
 426    _mesa_debug(NULL, "%u %p\n", key, data);
 427 }
 428
 429 /**
 430  * Dump contents of hash table for debugging.
 431  *
 432  * \param table the hash table.
 433  */
 434 void
 435 _mesa_HashPrint(const struct _mesa_HashTable *table)
 436 {
 437    if (table->deleted_key_data)
 438       debug_print_entry(DELETED_KEY_VALUE, table->deleted_key_data, NULL);
 439    _mesa_HashWalk(table, debug_print_entry, NULL);
 440 }
 441
 442
 443 /**
 444  * Find a block of adjacent unused hash keys.
 445  *
 446  * \param table the hash table.
 447  * \param numKeys number of keys needed.
 448  *
 449  * \return Starting key of free block or 0 if failure.
 450  *
 451  * If there are enough free keys between the maximum key existing in the table
 452  * (_mesa_HashTable::MaxKey) and the maximum key possible, then simply return
 453  * the adjacent key. Otherwise do a full search for a free key block in the
 454  * allowable key range.
 455  */
 456 GLuint
 457 _mesa_HashFindFreeKeyBlock(struct _mesa_HashTable *table, GLuint numKeys)
 458 {
 459    const GLuint maxKey = ~((GLuint) 0) - 1;
 460    mtx_lock(&table->Mutex);
 461    if (maxKey - numKeys > table->MaxKey) {
 462       /* the quick solution */
 463       mtx_unlock(&table->Mutex);
 464       return table->MaxKey + 1;
 465    }
 466    else {
 467       /* the slow solution */
 468       GLuint freeCount = 0;
 469       GLuint freeStart = 1;
 470       GLuint key;
 471       for (key = 1; key != maxKey; key++) {
 472          if (_mesa_HashLookup_unlocked(table, key)) {
 473             /* darn, this key is already in use */
 474             freeCount = 0;
 475             freeStart = key+1;
 476          }
 477          else {
 478             /* this key not in use, check if we've found enough */
 479             freeCount++;
 480             if (freeCount == numKeys) {
 481                mtx_unlock(&table->Mutex);
 482                return freeStart;
 483             }
 484          }
 485       }
 486       /* cannot allocate a block of numKeys consecutive keys */
 487       mtx_unlock(&table->Mutex);
 488       return 0;
 489    }
 490 }
 491
 492
 493 /**
 494  * Return the number of entries in the hash table.
 495  */
 496 GLuint
 497 _mesa_HashNumEntries(const struct _mesa_HashTable *table)
 498 {
 499    struct hash_entry *entry;
 500    GLuint count = 0;
 501
 502    if (table->deleted_key_data)
 503       count++;
 504
 505    hash_table_foreach(table->ht, entry)
 506       count++;
 507
 508    return count;
 509 }