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          free(entry);
 112          entry = next;
 113       }
 114    }
 115    _glthread_DESTROY_MUTEX(table->Mutex);
 116    _glthread_DESTROY_MUTEX(table->WalkMutex);
 117    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(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    _glthread_LOCK_MUTEX(table->Mutex);
 141    entry = table->Table[pos];
 142    while (entry) {
 143       if (entry->Key == key) {
 144          _glthread_UNLOCK_MUTEX(table->Mutex);
 145          return entry->Data;
 146       }
 147       entry = entry->Next;
 148    }
 149    _glthread_UNLOCK_MUTEX(table->Mutex);
 150    return NULL;
 151 }
 152
 153
 154
 155 /**
 156  * Insert a key/pointer pair into the hash table.
 157  * If an entry with this key already exists we'll replace the existing entry.
 158  *
 159  * \param table the hash table.
 160  * \param key the key (not zero).
 161  * \param data pointer to user data.
 162  */
 163 void
 164 _mesa_HashInsert(struct _mesa_HashTable *table, GLuint key, void *data)
 165 {
 166    /* search for existing entry with this key */
 167    GLuint pos;
 168    struct HashEntry *entry;
 169
 170    assert(table);
 171    assert(key);
 172
 173    _glthread_LOCK_MUTEX(table->Mutex);
 174
 175    if (key > table->MaxKey)
 176       table->MaxKey = key;
 177
 178    pos = HASH_FUNC(key);
 179
 180    /* check if replacing an existing entry with same key */
 181    for (entry = table->Table[pos]; entry; entry = entry->Next) {
 182       if (entry->Key == key) {
 183          /* replace entry's data */
 184 #if 0 /* not sure this check is always valid */
 185          if (entry->Data) {
 186             _mesa_problem(NULL, "Memory leak detected in _mesa_HashInsert");
 187          }
 188 #endif
 189          entry->Data = data;
 190          _glthread_UNLOCK_MUTEX(table->Mutex);
 191          return;
 192       }
 193    }
 194
 195    /* alloc and insert new table entry */
 196    entry = MALLOC_STRUCT(HashEntry);
 197    if (entry) {
 198       entry->Key = key;
 199       entry->Data = data;
 200       entry->Next = table->Table[pos];
 201       table->Table[pos] = entry;
 202    }
 203
 204    _glthread_UNLOCK_MUTEX(table->Mutex);
 205 }
 206
 207
 208
 209 /**
 210  * Remove an entry from the hash table.
 211  *
 212  * \param table the hash table.
 213  * \param key key of entry to remove.
 214  *
 215  * While holding the hash table's lock, searches the entry with the matching
 216  * key and unlinks it.
 217  */
 218 void
 219 _mesa_HashRemove(struct _mesa_HashTable *table, GLuint key)
 220 {
 221    GLuint pos;
 222    struct HashEntry *entry, *prev;
 223
 224    assert(table);
 225    assert(key);
 226
 227    /* have to check this outside of mutex lock */
 228    if (table->InDeleteAll) {
 229       _mesa_problem(NULL, "_mesa_HashRemove illegally called from "
 230                     "_mesa_HashDeleteAll callback function");
 231       return;
 232    }
 233
 234    _glthread_LOCK_MUTEX(table->Mutex);
 235
 236    pos = HASH_FUNC(key);
 237    prev = NULL;
 238    entry = table->Table[pos];
 239    while (entry) {
 240       if (entry->Key == key) {
 241          /* found it! */
 242          if (prev) {
 243             prev->Next = entry->Next;
 244          }
 245          else {
 246             table->Table[pos] = entry->Next;
 247          }
 248          free(entry);
 249          _glthread_UNLOCK_MUTEX(table->Mutex);
 250          return;
 251       }
 252       prev = entry;
 253       entry = entry->Next;
 254    }
 255
 256    _glthread_UNLOCK_MUTEX(table->Mutex);
 257 }
 258
 259
 260
 261 /**
 262  * Delete all entries in a hash table, but don't delete the table itself.
 263  * Invoke the given callback function for each table entry.
 264  *
 265  * \param table  the hash table to delete
 266  * \param callback  the callback function
 267  * \param userData  arbitrary pointer to pass along to the callback
 268  *                  (this is typically a GLcontext pointer)
 269  */
 270 void
 271 _mesa_HashDeleteAll(struct _mesa_HashTable *table,
 272                     void (*callback)(GLuint key, void *data, void *userData),
 273                     void *userData)
 274 {
 275    GLuint pos;
 276    ASSERT(table);
 277    ASSERT(callback);
 278    _glthread_LOCK_MUTEX(table->Mutex);
 279    table->InDeleteAll = GL_TRUE;
 280    for (pos = 0; pos < TABLE_SIZE; pos++) {
 281       struct HashEntry *entry, *next;
 282       for (entry = table->Table[pos]; entry; entry = next) {
 283          callback(entry->Key, entry->Data, userData);
 284          next = entry->Next;
 285          free(entry);
 286       }
 287       table->Table[pos] = NULL;
 288    }
 289    table->InDeleteAll = GL_FALSE;
 290    _glthread_UNLOCK_MUTEX(table->Mutex);
 291 }
 292
 293
 294 /**
 295  * Walk over all entries in a hash table, calling callback function for each.
 296  * Note: we use a separate mutex in this function to avoid a recursive
 297  * locking deadlock (in case the callback calls _mesa_HashRemove()) and to
 298  * prevent multiple threads/contexts from getting tangled up.
 299  * A lock-less version of this function could be used when the table will
 300  * not be modified.
 301  * \param table  the hash table to walk
 302  * \param callback  the callback function
 303  * \param userData  arbitrary pointer to pass along to the callback
 304  *                  (this is typically a GLcontext pointer)
 305  */
 306 void
 307 _mesa_HashWalk(const struct _mesa_HashTable *table,
 308                void (*callback)(GLuint key, void *data, void *userData),
 309                void *userData)
 310 {
 311    /* cast-away const */
 312    struct _mesa_HashTable *table2 = (struct _mesa_HashTable *) table;
 313    GLuint pos;
 314    ASSERT(table);
 315    ASSERT(callback);
 316    _glthread_LOCK_MUTEX(table2->WalkMutex);
 317    for (pos = 0; pos < TABLE_SIZE; pos++) {
 318       struct HashEntry *entry, *next;
 319       for (entry = table->Table[pos]; entry; entry = next) {
 320          /* save 'next' pointer now in case the callback deletes the entry */
 321          next = entry->Next;
 322          callback(entry->Key, entry->Data, userData);
 323       }
 324    }
 325    _glthread_UNLOCK_MUTEX(table2->WalkMutex);
 326 }
 327
 328
 329 /**
 330  * Return the key of the "first" entry in the hash table.
 331  * While holding the lock, walks through all table positions until finding
 332  * the first entry of the first non-empty one.
 333  *
 334  * \param table  the hash table
 335  * \return key for the "first" entry in the hash table.
 336  */
 337 GLuint
 338 _mesa_HashFirstEntry(struct _mesa_HashTable *table)
 339 {
 340    GLuint pos;
 341    assert(table);
 342    _glthread_LOCK_MUTEX(table->Mutex);
 343    for (pos = 0; pos < TABLE_SIZE; pos++) {
 344       if (table->Table[pos]) {
 345          _glthread_UNLOCK_MUTEX(table->Mutex);
 346          return table->Table[pos]->Key;
 347       }
 348    }
 349    _glthread_UNLOCK_MUTEX(table->Mutex);
 350    return 0;
 351 }
 352
 353
 354 /**
 355  * Given a hash table key, return the next key.  This is used to walk
 356  * over all entries in the table.  Note that the keys returned during
 357  * walking won't be in any particular order.
 358  * \return next hash key or 0 if end of table.
 359  */
 360 GLuint
 361 _mesa_HashNextEntry(const struct _mesa_HashTable *table, GLuint key)
 362 {
 363    const struct HashEntry *entry;
 364    GLuint pos;
 365
 366    assert(table);
 367    assert(key);
 368
 369    /* Find the entry with given key */
 370    pos = HASH_FUNC(key);
 371    for (entry = table->Table[pos]; entry ; entry = entry->Next) {
 372       if (entry->Key == key) {
 373          break;
 374       }
 375    }
 376
 377    if (!entry) {
 378       /* the given key was not found, so we can't find the next entry */
 379       return 0;
 380    }
 381
 382    if (entry->Next) {
 383       /* return next in linked list */
 384       return entry->Next->Key;
 385    }
 386    else {
 387       /* look for next non-empty table slot */
 388       pos++;
 389       while (pos < TABLE_SIZE) {
 390          if (table->Table[pos]) {
 391             return table->Table[pos]->Key;
 392          }
 393          pos++;
 394       }
 395       return 0;
 396    }
 397 }
 398
 399
 400 /**
 401  * Dump contents of hash table for debugging.
 402  *
 403  * \param table the hash table.
 404  */
 405 void
 406 _mesa_HashPrint(const struct _mesa_HashTable *table)
 407 {
 408    GLuint pos;
 409    assert(table);
 410    for (pos = 0; pos < TABLE_SIZE; pos++) {
 411       const struct HashEntry *entry = table->Table[pos];
 412       while (entry) {
 413          _mesa_debug(NULL, "%u %p\n", entry->Key, entry->Data);
 414          entry = entry->Next;
 415       }
 416    }
 417 }
 418
 419
 420
 421 /**
 422  * Find a block of adjacent unused hash keys.
 423  *
 424  * \param table the hash table.
 425  * \param numKeys number of keys needed.
 426  *
 427  * \return Starting key of free block or 0 if failure.
 428  *
 429  * If there are enough free keys between the maximum key existing in the table
 430  * (_mesa_HashTable::MaxKey) and the maximum key possible, then simply return
 431  * the adjacent key. Otherwise do a full search for a free key block in the
 432  * allowable key range.
 433  */
 434 GLuint
 435 _mesa_HashFindFreeKeyBlock(struct _mesa_HashTable *table, GLuint numKeys)
 436 {
 437    const GLuint maxKey = ~((GLuint) 0);
 438    _glthread_LOCK_MUTEX(table->Mutex);
 439    if (maxKey - numKeys > table->MaxKey) {
 440       /* the quick solution */
 441       _glthread_UNLOCK_MUTEX(table->Mutex);
 442       return table->MaxKey + 1;
 443    }
 444    else {
 445       /* the slow solution */
 446       GLuint freeCount = 0;
 447       GLuint freeStart = 1;
 448       GLuint key;
 449       for (key = 1; key != maxKey; key++) {
 450          if (_mesa_HashLookup(table, key)) {
 451             /* darn, this key is already in use */
 452             freeCount = 0;
 453             freeStart = key+1;
 454          }
 455          else {
 456             /* this key not in use, check if we've found enough */
 457             freeCount++;
 458             if (freeCount == numKeys) {
 459                _glthread_UNLOCK_MUTEX(table->Mutex);
 460                return freeStart;
 461             }
 462          }
 463       }
 464       /* cannot allocate a block of numKeys consecutive keys */
 465       _glthread_UNLOCK_MUTEX(table->Mutex);
 466       return 0;
 467    }
 468 }
 469
 470
 471 #if 0 /* debug only */
 472
 473 /**
 474  * Test walking over all the entries in a hash table.
 475  */
 476 static void
 477 test_hash_walking(void)
 478 {
 479    struct _mesa_HashTable *t = _mesa_NewHashTable();
 480    const GLuint limit = 50000;
 481    GLuint i;
 482
 483    /* create some entries */
 484    for (i = 0; i < limit; i++) {
 485       GLuint dummy;
 486       GLuint k = (rand() % (limit * 10)) + 1;
 487       while (_mesa_HashLookup(t, k)) {
 488          /* id already in use, try another */
 489          k = (rand() % (limit * 10)) + 1;
 490       }
 491       _mesa_HashInsert(t, k, &dummy);
 492    }
 493
 494    /* walk over all entries */
 495    {
 496       GLuint k = _mesa_HashFirstEntry(t);
 497       GLuint count = 0;
 498       while (k) {
 499          GLuint knext = _mesa_HashNextEntry(t, k);
 500          assert(knext != k);
 501          _mesa_HashRemove(t, k);
 502          count++;
 503          k = knext;
 504       }
 505       assert(count == limit);
 506       k = _mesa_HashFirstEntry(t);
 507       assert(k==0);
 508    }
 509
 510    _mesa_DeleteHashTable(t);
 511 }
 512
 513
 514 void
 515 _mesa_test_hash_functions(void)
 516 {
 517    int a, b, c;
 518    struct _mesa_HashTable *t;
 519
 520    t = _mesa_NewHashTable();
 521    _mesa_HashInsert(t, 501, &a);
 522    _mesa_HashInsert(t, 10, &c);
 523    _mesa_HashInsert(t, 0xfffffff8, &b);
 524    /*_mesa_HashPrint(t);*/
 525
 526    assert(_mesa_HashLookup(t,501));
 527    assert(!_mesa_HashLookup(t,1313));
 528    assert(_mesa_HashFindFreeKeyBlock(t, 100));
 529
 530    _mesa_DeleteHashTable(t);
 531
 532    test_hash_walking();
 533 }
 534
 535 #endif