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  * Version:  6.5.1
  16  *
  17  * Copyright (C) 1999-2006  Brian Paul   All Rights Reserved.
  18  *
  19  * Permission is hereby granted, free of charge, to any person obtaining a
  20  * copy of this software and associated documentation files (the "Software"),
  21  * to deal in the Software without restriction, including without limitation
  22  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
  23  * and/or sell copies of the Software, and to permit persons to whom the
  24  * Software is furnished to do so, subject to the following conditions:
  25  *
  26  * The above copyright notice and this permission notice shall be included
  27  * in all copies or substantial portions of the Software.
  28  *
  29  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
  30  * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  31  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  32  * BRIAN PAUL BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
  33  * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  34  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  35  */
  36
  37
  38 #include "glheader.h"
  39 #include "imports.h"
  40 #include "glapi/glthread.h"
  41 #include "hash.h"
  42
  43
  44 #define TABLE_SIZE 1023  /**< Size of lookup table/array */
  45
  46 #define HASH_FUNC(K)  ((K) % TABLE_SIZE)
  47
  48
  49 /**
  50  * An entry in the hash table.
  51  */
  52 struct HashEntry {
  53    GLuint Key;             /**< the entry's key */
  54    void *Data;             /**< the entry's data */
  55    struct HashEntry *Next; /**< pointer to next entry */
  56 };
  57
  58
  59 /**
  60  * The hash table data structure.
  61  */
  62 struct _mesa_HashTable {
  63    struct HashEntry *Table[TABLE_SIZE];  /**< the lookup table */
  64    GLuint MaxKey;                        /**< highest key inserted so far */
  65    _glthread_Mutex Mutex;                /**< mutual exclusion lock */
  66    _glthread_Mutex WalkMutex;            /**< for _mesa_HashWalk() */
  67    GLboolean InDeleteAll;                /**< Debug check */
  68 };
  69
  70
  71
  72 /**
  73  * Create a new hash table.
  74  *
  75  * \return pointer to a new, empty hash table.
  76  */
  77 struct _mesa_HashTable *
  78 _mesa_NewHashTable(void)
  79 {
  80    struct _mesa_HashTable *table = CALLOC_STRUCT(_mesa_HashTable);
  81    if (table) {
  82       _glthread_INIT_MUTEX(table->Mutex);
  83       _glthread_INIT_MUTEX(table->WalkMutex);
  84    }
  85    return table;
  86 }
  87
  88
  89
  90 /**
  91  * Delete a hash table.
  92  * Frees each entry on the hash table and then the hash table structure itself.
  93  * Note that the caller should have already traversed the table and deleted
  94  * the objects in the table (i.e. We don't free the entries' data pointer).
  95  *
  96  * \param table the hash table to delete.
  97  */
  98 void
  99 _mesa_DeleteHashTable(struct _mesa_HashTable *table)
 100 {
 101    GLuint pos;
 102    assert(table);
 103    for (pos = 0; pos < TABLE_SIZE; pos++) {
 104       struct HashEntry *entry = table->Table[pos];
 105       while (entry) {
 106          struct HashEntry *next = entry->Next;
 107          if (entry->Data) {
 108             _mesa_problem(NULL,
 109                           "In _mesa_DeleteHashTable, found non-freed data");
 110          }
 111          _mesa_free(entry);
 112          entry = next;
 113       }
 114    }
 115    _glthread_DESTROY_MUTEX(table->Mutex);
 116    _glthread_DESTROY_MUTEX(table->WalkMutex);
 117    _mesa_free(table);
 118 }
 119
 120
 121
 122 /**
 123  * Lookup an entry in the hash table.
 124  *
 125  * \param table the hash table.
 126  * \param key the key.
 127  *
 128  * \return pointer to user's data or NULL if key not in table
 129  */
 130 void *
 131 _mesa_HashLookup(const struct _mesa_HashTable *table, GLuint key)
 132 {
 133    GLuint pos;
 134    const struct HashEntry *entry;
 135
 136    assert(table);
 137    assert(key);
 138
 139    pos = HASH_FUNC(key);
 140    entry = table->Table[pos];
 141    while (entry) {
 142       if (entry->Key == key) {
 143          return entry->Data;
 144       }
 145       entry = entry->Next;
 146    }
 147    return NULL;
 148 }
 149
 150
 151
 152 /**
 153  * Insert a key/pointer pair into the hash table.
 154  * If an entry with this key already exists we'll replace the existing entry.
 155  *
 156  * \param table the hash table.
 157  * \param key the key (not zero).
 158  * \param data pointer to user data.
 159  */
 160 void
 161 _mesa_HashInsert(struct _mesa_HashTable *table, GLuint key, void *data)
 162 {
 163    /* search for existing entry with this key */
 164    GLuint pos;
 165    struct HashEntry *entry;
 166
 167    assert(table);
 168    assert(key);
 169
 170    _glthread_LOCK_MUTEX(table->Mutex);
 171
 172    if (key > table->MaxKey)
 173       table->MaxKey = key;
 174
 175    pos = HASH_FUNC(key);
 176
 177    /* check if replacing an existing entry with same key */
 178    for (entry = table->Table[pos]; entry; entry = entry->Next) {
 179       if (entry->Key == key) {
 180          /* replace entry's data */
 181 #if 0 /* not sure this check is always valid */
 182          if (entry->Data) {
 183             _mesa_problem(NULL, "Memory leak detected in _mesa_HashInsert");
 184          }
 185 #endif
 186          entry->Data = data;
 187          _glthread_UNLOCK_MUTEX(table->Mutex);
 188          return;
 189       }
 190    }
 191
 192    /* alloc and insert new table entry */
 193    entry = MALLOC_STRUCT(HashEntry);
 194    entry->Key = key;
 195    entry->Data = data;
 196    entry->Next = table->Table[pos];
 197    table->Table[pos] = entry;
 198
 199    _glthread_UNLOCK_MUTEX(table->Mutex);
 200 }
 201
 202
 203
 204 /**
 205  * Remove an entry from the hash table.
 206  *
 207  * \param table the hash table.
 208  * \param key key of entry to remove.
 209  *
 210  * While holding the hash table's lock, searches the entry with the matching
 211  * key and unlinks it.
 212  */
 213 void
 214 _mesa_HashRemove(struct _mesa_HashTable *table, GLuint key)
 215 {
 216    GLuint pos;
 217    struct HashEntry *entry, *prev;
 218
 219    assert(table);
 220    assert(key);
 221
 222    /* have to check this outside of mutex lock */
 223    if (table->InDeleteAll) {
 224       _mesa_problem(NULL, "_mesa_HashRemove illegally called from "
 225                     "_mesa_HashDeleteAll callback function");
 226       return;
 227    }
 228
 229    _glthread_LOCK_MUTEX(table->Mutex);
 230
 231    pos = HASH_FUNC(key);
 232    prev = NULL;
 233    entry = table->Table[pos];
 234    while (entry) {
 235       if (entry->Key == key) {
 236          /* found it! */
 237          if (prev) {
 238             prev->Next = entry->Next;
 239          }
 240          else {
 241             table->Table[pos] = entry->Next;
 242          }
 243          _mesa_free(entry);
 244          _glthread_UNLOCK_MUTEX(table->Mutex);
 245          return;
 246       }
 247       prev = entry;
 248       entry = entry->Next;
 249    }
 250
 251    _glthread_UNLOCK_MUTEX(table->Mutex);
 252 }
 253
 254
 255
 256 /**
 257  * Delete all entries in a hash table, but don't delete the table itself.
 258  * Invoke the given callback function for each table entry.
 259  *
 260  * \param table  the hash table to delete
 261  * \param callback  the callback function
 262  * \param userData  arbitrary pointer to pass along to the callback
 263  *                  (this is typically a GLcontext pointer)
 264  */
 265 void
 266 _mesa_HashDeleteAll(struct _mesa_HashTable *table,
 267                     void (*callback)(GLuint key, void *data, void *userData),
 268                     void *userData)
 269 {
 270    GLuint pos;
 271    ASSERT(table);
 272    ASSERT(callback);
 273    _glthread_LOCK_MUTEX(table->Mutex);
 274    table->InDeleteAll = GL_TRUE;
 275    for (pos = 0; pos < TABLE_SIZE; pos++) {
 276       struct HashEntry *entry, *next;
 277       for (entry = table->Table[pos]; entry; entry = next) {
 278          callback(entry->Key, entry->Data, userData);
 279          next = entry->Next;
 280          _mesa_free(entry);
 281       }
 282       table->Table[pos] = NULL;
 283    }
 284    table->InDeleteAll = GL_FALSE;
 285    _glthread_UNLOCK_MUTEX(table->Mutex);
 286 }
 287
 288
 289 /**
 290  * Walk over all entries in a hash table, calling callback function for each.
 291  * Note: we use a separate mutex in this function to avoid a recursive
 292  * locking deadlock (in case the callback calls _mesa_HashRemove()) and to
 293  * prevent multiple threads/contexts from getting tangled up.
 294  * A lock-less version of this function could be used when the table will
 295  * not be modified.
 296  * \param table  the hash table to walk
 297  * \param callback  the callback function
 298  * \param userData  arbitrary pointer to pass along to the callback
 299  *                  (this is typically a GLcontext pointer)
 300  */
 301 void
 302 _mesa_HashWalk(const struct _mesa_HashTable *table,
 303                void (*callback)(GLuint key, void *data, void *userData),
 304                void *userData)
 305 {
 306    /* cast-away const */
 307    struct _mesa_HashTable *table2 = (struct _mesa_HashTable *) table;
 308    GLuint pos;
 309    ASSERT(table);
 310    ASSERT(callback);
 311    _glthread_LOCK_MUTEX(table2->WalkMutex);
 312    for (pos = 0; pos < TABLE_SIZE; pos++) {
 313       struct HashEntry *entry, *next;
 314       for (entry = table->Table[pos]; entry; entry = next) {
 315          /* save 'next' pointer now in case the callback deletes the entry */
 316          next = entry->Next;
 317          callback(entry->Key, entry->Data, userData);
 318       }
 319    }
 320    _glthread_UNLOCK_MUTEX(table2->WalkMutex);
 321 }
 322
 323
 324 /**
 325  * Return the key of the "first" entry in the hash table.
 326  * While holding the lock, walks through all table positions until finding
 327  * the first entry of the first non-empty one.
 328  *
 329  * \param table  the hash table
 330  * \return key for the "first" entry in the hash table.
 331  */
 332 GLuint
 333 _mesa_HashFirstEntry(struct _mesa_HashTable *table)
 334 {
 335    GLuint pos;
 336    assert(table);
 337    _glthread_LOCK_MUTEX(table->Mutex);
 338    for (pos = 0; pos < TABLE_SIZE; pos++) {
 339       if (table->Table[pos]) {
 340          _glthread_UNLOCK_MUTEX(table->Mutex);
 341          return table->Table[pos]->Key;
 342       }
 343    }
 344    _glthread_UNLOCK_MUTEX(table->Mutex);
 345    return 0;
 346 }
 347
 348
 349 /**
 350  * Given a hash table key, return the next key.  This is used to walk
 351  * over all entries in the table.  Note that the keys returned during
 352  * walking won't be in any particular order.
 353  * \return next hash key or 0 if end of table.
 354  */
 355 GLuint
 356 _mesa_HashNextEntry(const struct _mesa_HashTable *table, GLuint key)
 357 {
 358    const struct HashEntry *entry;
 359    GLuint pos;
 360
 361    assert(table);
 362    assert(key);
 363
 364    /* Find the entry with given key */
 365    pos = HASH_FUNC(key);
 366    for (entry = table->Table[pos]; entry ; entry = entry->Next) {
 367       if (entry->Key == key) {
 368          break;
 369       }
 370    }
 371
 372    if (!entry) {
 373       /* the given key was not found, so we can't find the next entry */
 374       return 0;
 375    }
 376
 377    if (entry->Next) {
 378       /* return next in linked list */
 379       return entry->Next->Key;
 380    }
 381    else {
 382       /* look for next non-empty table slot */
 383       pos++;
 384       while (pos < TABLE_SIZE) {
 385          if (table->Table[pos]) {
 386             return table->Table[pos]->Key;
 387          }
 388          pos++;
 389       }
 390       return 0;
 391    }
 392 }
 393
 394
 395 /**
 396  * Dump contents of hash table for debugging.
 397  *
 398  * \param table the hash table.
 399  */
 400 void
 401 _mesa_HashPrint(const struct _mesa_HashTable *table)
 402 {
 403    GLuint pos;
 404    assert(table);
 405    for (pos = 0; pos < TABLE_SIZE; pos++) {
 406       const struct HashEntry *entry = table->Table[pos];
 407       while (entry) {
 408          _mesa_debug(NULL, "%u %p\n", entry->Key, entry->Data);
 409          entry = entry->Next;
 410       }
 411    }
 412 }
 413
 414
 415
 416 /**
 417  * Find a block of adjacent unused hash keys.
 418  *
 419  * \param table the hash table.
 420  * \param numKeys number of keys needed.
 421  *
 422  * \return Starting key of free block or 0 if failure.
 423  *
 424  * If there are enough free keys between the maximum key existing in the table
 425  * (_mesa_HashTable::MaxKey) and the maximum key possible, then simply return
 426  * the adjacent key. Otherwise do a full search for a free key block in the
 427  * allowable key range.
 428  */
 429 GLuint
 430 _mesa_HashFindFreeKeyBlock(struct _mesa_HashTable *table, GLuint numKeys)
 431 {
 432    const GLuint maxKey = ~((GLuint) 0);
 433    _glthread_LOCK_MUTEX(table->Mutex);
 434    if (maxKey - numKeys > table->MaxKey) {
 435       /* the quick solution */
 436       _glthread_UNLOCK_MUTEX(table->Mutex);
 437       return table->MaxKey + 1;
 438    }
 439    else {
 440       /* the slow solution */
 441       GLuint freeCount = 0;
 442       GLuint freeStart = 1;
 443       GLuint key;
 444       for (key = 1; key != maxKey; key++) {
 445          if (_mesa_HashLookup(table, key)) {
 446             /* darn, this key is already in use */
 447             freeCount = 0;
 448             freeStart = key+1;
 449          }
 450          else {
 451             /* this key not in use, check if we've found enough */
 452             freeCount++;
 453             if (freeCount == numKeys) {
 454                _glthread_UNLOCK_MUTEX(table->Mutex);
 455                return freeStart;
 456             }
 457          }
 458       }
 459       /* cannot allocate a block of numKeys consecutive keys */
 460       _glthread_UNLOCK_MUTEX(table->Mutex);
 461       return 0;
 462    }
 463 }
 464
 465
 466 #if 0 /* debug only */
 467
 468 /**
 469  * Test walking over all the entries in a hash table.
 470  */
 471 static void
 472 test_hash_walking(void)
 473 {
 474    struct _mesa_HashTable *t = _mesa_NewHashTable();
 475    const GLuint limit = 50000;
 476    GLuint i;
 477
 478    /* create some entries */
 479    for (i = 0; i < limit; i++) {
 480       GLuint dummy;
 481       GLuint k = (rand() % (limit * 10)) + 1;
 482       while (_mesa_HashLookup(t, k)) {
 483          /* id already in use, try another */
 484          k = (rand() % (limit * 10)) + 1;
 485       }
 486       _mesa_HashInsert(t, k, &dummy);
 487    }
 488
 489    /* walk over all entries */
 490    {
 491       GLuint k = _mesa_HashFirstEntry(t);
 492       GLuint count = 0;
 493       while (k) {
 494          GLuint knext = _mesa_HashNextEntry(t, k);
 495          assert(knext != k);
 496          _mesa_HashRemove(t, k);
 497          count++;
 498          k = knext;
 499       }
 500       assert(count == limit);
 501       k = _mesa_HashFirstEntry(t);
 502       assert(k==0);
 503    }
 504
 505    _mesa_DeleteHashTable(t);
 506 }
 507
 508
 509 void
 510 _mesa_test_hash_functions(void)
 511 {
 512    int a, b, c;
 513    struct _mesa_HashTable *t;
 514
 515    t = _mesa_NewHashTable();
 516    _mesa_HashInsert(t, 501, &a);
 517    _mesa_HashInsert(t, 10, &c);
 518    _mesa_HashInsert(t, 0xfffffff8, &b);
 519    /*_mesa_HashPrint(t);*/
 520
 521    assert(_mesa_HashLookup(t,501));
 522    assert(!_mesa_HashLookup(t,1313));
 523    assert(_mesa_HashFindFreeKeyBlock(t, 100));
 524
 525    _mesa_DeleteHashTable(t);
 526
 527    test_hash_walking();
 528 }
 529
 530 #endif