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 void *
 100 uint_key(GLuint id)
 101 {
 102    return (void *)(uintptr_t) id;
 103 }
 104 /** @} */
 105
 106 /**
 107  * Create a new hash table.
 108  *
 109  * \return pointer to a new, empty hash table.
 110  */
 111 struct _mesa_HashTable *
 112 _mesa_NewHashTable(void)
 113 {
 114    struct _mesa_HashTable *table = CALLOC_STRUCT(_mesa_HashTable);
 115
 116    if (table) {
 117       table->ht = _mesa_hash_table_create(NULL, uint_key_compare);
 118       if (table->ht == NULL) {
 119          free(table);
 120          _mesa_error_no_memory(__func__);
 121          return NULL;
 122       }
 123
 124       _mesa_hash_table_set_deleted_key(table->ht, uint_key(DELETED_KEY_VALUE));
 125       mtx_init(&table->Mutex, mtx_plain);
 126       mtx_init(&table->WalkMutex, mtx_plain);
 127    }
 128    else {
 129       _mesa_error_no_memory(__func__);
 130    }
 131
 132    return table;
 133 }
 134
 135
 136
 137 /**
 138  * Delete a hash table.
 139  * Frees each entry on the hash table and then the hash table structure itself.
 140  * Note that the caller should have already traversed the table and deleted
 141  * the objects in the table (i.e. We don't free the entries' data pointer).
 142  *
 143  * \param table the hash table to delete.
 144  */
 145 void
 146 _mesa_DeleteHashTable(struct _mesa_HashTable *table)
 147 {
 148    assert(table);
 149
 150    if (_mesa_hash_table_next_entry(table->ht, NULL) != NULL) {
 151       _mesa_problem(NULL, "In _mesa_DeleteHashTable, found non-freed data");
 152    }
 153
 154    _mesa_hash_table_destroy(table->ht, NULL);
 155
 156    mtx_destroy(&table->Mutex);
 157    mtx_destroy(&table->WalkMutex);
 158    free(table);
 159 }
 160
 161
 162
 163 /**
 164  * Lookup an entry in the hash table, without locking.
 165  * \sa _mesa_HashLookup
 166  */
 167 static inline void *
 168 _mesa_HashLookup_unlocked(struct _mesa_HashTable *table, GLuint key)
 169 {
 170    const struct hash_entry *entry;
 171
 172    assert(table);
 173    assert(key);
 174
 175    if (key == DELETED_KEY_VALUE)
 176       return table->deleted_key_data;
 177
 178    entry = _mesa_hash_table_search(table->ht, uint_hash(key), uint_key(key));
 179    if (!entry)
 180       return NULL;
 181
 182    return entry->data;
 183 }
 184
 185
 186 /**
 187  * Lookup an entry in the hash table.
 188  *
 189  * \param table the hash table.
 190  * \param key the key.
 191  *
 192  * \return pointer to user's data or NULL if key not in table
 193  */
 194 void *
 195 _mesa_HashLookup(struct _mesa_HashTable *table, GLuint key)
 196 {
 197    void *res;
 198    assert(table);
 199    mtx_lock(&table->Mutex);
 200    res = _mesa_HashLookup_unlocked(table, key);
 201    mtx_unlock(&table->Mutex);
 202    return res;
 203 }
 204
 205
 206 /**
 207  * Lookup an entry in the hash table without locking the mutex.
 208  *
 209  * The hash table mutex must be locked manually by calling
 210  * _mesa_HashLockMutex() before calling this function.
 211  *
 212  * \param table the hash table.
 213  * \param key the key.
 214  *
 215  * \return pointer to user's data or NULL if key not in table
 216  */
 217 void *
 218 _mesa_HashLookupLocked(struct _mesa_HashTable *table, GLuint key)
 219 {
 220    return _mesa_HashLookup_unlocked(table, key);
 221 }
 222
 223
 224 /**
 225  * Lock the hash table mutex.
 226  *
 227  * This function should be used when multiple objects need
 228  * to be looked up in the hash table, to avoid having to lock
 229  * and unlock the mutex each time.
 230  *
 231  * \param table the hash table.
 232  */
 233 void
 234 _mesa_HashLockMutex(struct _mesa_HashTable *table)
 235 {
 236    assert(table);
 237    mtx_lock(&table->Mutex);
 238 }
 239
 240
 241 /**
 242  * Unlock the hash table mutex.
 243  *
 244  * \param table the hash table.
 245  */
 246 void
 247 _mesa_HashUnlockMutex(struct _mesa_HashTable *table)
 248 {
 249    assert(table);
 250    mtx_unlock(&table->Mutex);
 251 }
 252
 253
 254 static inline void
 255 _mesa_HashInsert_unlocked(struct _mesa_HashTable *table, GLuint key, void *data)
 256 {
 257    uint32_t hash = uint_hash(key);
 258    struct hash_entry *entry;
 259
 260    assert(table);
 261    assert(key);
 262
 263    if (key > table->MaxKey)
 264       table->MaxKey = key;
 265
 266    if (key == DELETED_KEY_VALUE) {
 267       table->deleted_key_data = data;
 268    } else {
 269       entry = _mesa_hash_table_search(table->ht, hash, uint_key(key));
 270       if (entry) {
 271          entry->data = data;
 272       } else {
 273          _mesa_hash_table_insert(table->ht, hash, uint_key(key), data);
 274       }
 275    }
 276 }
 277
 278
 279 /**
 280  * Insert a key/pointer pair into the hash table without locking the mutex.
 281  * If an entry with this key already exists we'll replace the existing entry.
 282  *
 283  * The hash table mutex must be locked manually by calling
 284  * _mesa_HashLockMutex() before calling this function.
 285  *
 286  * \param table the hash table.
 287  * \param key the key (not zero).
 288  * \param data pointer to user data.
 289  */
 290 void
 291 _mesa_HashInsertLocked(struct _mesa_HashTable *table, GLuint key, void *data)
 292 {
 293    _mesa_HashInsert_unlocked(table, key, data);
 294 }
 295
 296
 297 /**
 298  * Insert a key/pointer pair into the hash table.
 299  * If an entry with this key already exists we'll replace the existing entry.
 300  *
 301  * \param table the hash table.
 302  * \param key the key (not zero).
 303  * \param data pointer to user data.
 304  */
 305 void
 306 _mesa_HashInsert(struct _mesa_HashTable *table, GLuint key, void *data)
 307 {
 308    assert(table);
 309    mtx_lock(&table->Mutex);
 310    _mesa_HashInsert_unlocked(table, key, data);
 311    mtx_unlock(&table->Mutex);
 312 }
 313
 314
 315 /**
 316  * Remove an entry from the hash table.
 317  *
 318  * \param table the hash table.
 319  * \param key key of entry to remove.
 320  *
 321  * While holding the hash table's lock, searches the entry with the matching
 322  * key and unlinks it.
 323  */
 324 void
 325 _mesa_HashRemove(struct _mesa_HashTable *table, GLuint key)
 326 {
 327    struct hash_entry *entry;
 328
 329    assert(table);
 330    assert(key);
 331
 332    /* have to check this outside of mutex lock */
 333    if (table->InDeleteAll) {
 334       _mesa_problem(NULL, "_mesa_HashRemove illegally called from "
 335                     "_mesa_HashDeleteAll callback function");
 336       return;
 337    }
 338
 339    mtx_lock(&table->Mutex);
 340    if (key == DELETED_KEY_VALUE) {
 341       table->deleted_key_data = NULL;
 342    } else {
 343       entry = _mesa_hash_table_search(table->ht, uint_hash(key), uint_key(key));
 344       _mesa_hash_table_remove(table->ht, entry);
 345    }
 346    mtx_unlock(&table->Mutex);
 347 }
 348
 349
 350
 351 /**
 352  * Delete all entries in a hash table, but don't delete the table itself.
 353  * Invoke the given callback function for each table entry.
 354  *
 355  * \param table  the hash table to delete
 356  * \param callback  the callback function
 357  * \param userData  arbitrary pointer to pass along to the callback
 358  *                  (this is typically a struct gl_context pointer)
 359  */
 360 void
 361 _mesa_HashDeleteAll(struct _mesa_HashTable *table,
 362                     void (*callback)(GLuint key, void *data, void *userData),
 363                     void *userData)
 364 {
 365    struct hash_entry *entry;
 366
 367    ASSERT(table);
 368    ASSERT(callback);
 369    mtx_lock(&table->Mutex);
 370    table->InDeleteAll = GL_TRUE;
 371    hash_table_foreach(table->ht, entry) {
 372       callback((uintptr_t)entry->key, entry->data, userData);
 373       _mesa_hash_table_remove(table->ht, entry);
 374    }
 375    if (table->deleted_key_data) {
 376       callback(DELETED_KEY_VALUE, table->deleted_key_data, userData);
 377       table->deleted_key_data = NULL;
 378    }
 379    table->InDeleteAll = GL_FALSE;
 380    mtx_unlock(&table->Mutex);
 381 }
 382
 383
 384 /**
 385  * Clone all entries in a hash table, into a new table.
 386  *
 387  * \param table  the hash table to clone
 388  */
 389 struct _mesa_HashTable *
 390 _mesa_HashClone(const struct _mesa_HashTable *table)
 391 {
 392    /* cast-away const */
 393    struct _mesa_HashTable *table2 = (struct _mesa_HashTable *) table;
 394    struct hash_entry *entry;
 395    struct _mesa_HashTable *clonetable;
 396
 397    ASSERT(table);
 398    mtx_lock(&table2->Mutex);
 399
 400    clonetable = _mesa_NewHashTable();
 401    assert(clonetable);
 402    hash_table_foreach(table->ht, entry) {
 403       _mesa_HashInsert(clonetable, (GLint)(uintptr_t)entry->key, entry->data);
 404    }
 405
 406    mtx_unlock(&table2->Mutex);
 407
 408    return clonetable;
 409 }
 410
 411
 412 /**
 413  * Walk over all entries in a hash table, calling callback function for each.
 414  * Note: we use a separate mutex in this function to avoid a recursive
 415  * locking deadlock (in case the callback calls _mesa_HashRemove()) and to
 416  * prevent multiple threads/contexts from getting tangled up.
 417  * A lock-less version of this function could be used when the table will
 418  * not be modified.
 419  * \param table  the hash table to walk
 420  * \param callback  the callback function
 421  * \param userData  arbitrary pointer to pass along to the callback
 422  *                  (this is typically a struct gl_context pointer)
 423  */
 424 void
 425 _mesa_HashWalk(const struct _mesa_HashTable *table,
 426                void (*callback)(GLuint key, void *data, void *userData),
 427                void *userData)
 428 {
 429    /* cast-away const */
 430    struct _mesa_HashTable *table2 = (struct _mesa_HashTable *) table;
 431    struct hash_entry *entry;
 432
 433    ASSERT(table);
 434    ASSERT(callback);
 435    mtx_lock(&table2->WalkMutex);
 436    hash_table_foreach(table->ht, entry) {
 437       callback((uintptr_t)entry->key, entry->data, userData);
 438    }
 439    if (table->deleted_key_data)
 440       callback(DELETED_KEY_VALUE, table->deleted_key_data, userData);
 441    mtx_unlock(&table2->WalkMutex);
 442 }
 443
 444 static void
 445 debug_print_entry(GLuint key, void *data, void *userData)
 446 {
 447    _mesa_debug(NULL, "%u %p\n", key, data);
 448 }
 449
 450 /**
 451  * Dump contents of hash table for debugging.
 452  *
 453  * \param table the hash table.
 454  */
 455 void
 456 _mesa_HashPrint(const struct _mesa_HashTable *table)
 457 {
 458    if (table->deleted_key_data)
 459       debug_print_entry(DELETED_KEY_VALUE, table->deleted_key_data, NULL);
 460    _mesa_HashWalk(table, debug_print_entry, NULL);
 461 }
 462
 463
 464 /**
 465  * Find a block of adjacent unused hash keys.
 466  *
 467  * \param table the hash table.
 468  * \param numKeys number of keys needed.
 469  *
 470  * \return Starting key of free block or 0 if failure.
 471  *
 472  * If there are enough free keys between the maximum key existing in the table
 473  * (_mesa_HashTable::MaxKey) and the maximum key possible, then simply return
 474  * the adjacent key. Otherwise do a full search for a free key block in the
 475  * allowable key range.
 476  */
 477 GLuint
 478 _mesa_HashFindFreeKeyBlock(struct _mesa_HashTable *table, GLuint numKeys)
 479 {
 480    const GLuint maxKey = ~((GLuint) 0) - 1;
 481    mtx_lock(&table->Mutex);
 482    if (maxKey - numKeys > table->MaxKey) {
 483       /* the quick solution */
 484       mtx_unlock(&table->Mutex);
 485       return table->MaxKey + 1;
 486    }
 487    else {
 488       /* the slow solution */
 489       GLuint freeCount = 0;
 490       GLuint freeStart = 1;
 491       GLuint key;
 492       for (key = 1; key != maxKey; key++) {
 493          if (_mesa_HashLookup_unlocked(table, key)) {
 494             /* darn, this key is already in use */
 495             freeCount = 0;
 496             freeStart = key+1;
 497          }
 498          else {
 499             /* this key not in use, check if we've found enough */
 500             freeCount++;
 501             if (freeCount == numKeys) {
 502                mtx_unlock(&table->Mutex);
 503                return freeStart;
 504             }
 505          }
 506       }
 507       /* cannot allocate a block of numKeys consecutive keys */
 508       mtx_unlock(&table->Mutex);
 509       return 0;
 510    }
 511 }
 512
 513
 514 /**
 515  * Return the number of entries in the hash table.
 516  */
 517 GLuint
 518 _mesa_HashNumEntries(const struct _mesa_HashTable *table)
 519 {
 520    struct hash_entry *entry;
 521    GLuint count = 0;
 522
 523    if (table->deleted_key_data)
 524       count++;
 525
 526    hash_table_foreach(table->ht, entry)
 527       count++;
 528
 529    return count;
 530 }