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