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 #include "glheader.h"
  38 #include "imports.h"
  39 #include "glapi/glthread.h"
  40 #include "hash.h"
  41 #include "hash_table.h"
  42
  43 /**
  44  * Magic GLuint object name that gets stored outside of the struct hash_table.
  45  *
  46  * The hash table needs a particular pointer to be the marker for a key that
  47  * was deleted from the table, along with NULL for the "never allocated in the
  48  * table" marker.  Legacy GL allows any GLuint to be used as a GL object name,
  49  * and we use a 1:1 mapping from GLuints to key pointers, so we need to be
  50  * able to track a GLuint that happens to match the deleted key outside of
  51  * struct hash_table.  We tell the hash table to use "1" as the deleted key
  52  * value, so that we test the deleted-key-in-the-table path as best we can.
  53  */
  54 #define DELETED_KEY_VALUE 1
  55
  56 /**
  57  * The hash table data structure.
  58  */
  59 struct _mesa_HashTable {
  60    struct hash_table *ht;
  61    GLuint MaxKey;                        /**< highest key inserted so far */
  62    _glthread_Mutex Mutex;                /**< mutual exclusion lock */
  63    _glthread_Mutex WalkMutex;            /**< for _mesa_HashWalk() */
  64    GLboolean InDeleteAll;                /**< Debug check */
  65    /** Value that would be in the table for DELETED_KEY_VALUE. */
  66    void *deleted_key_data;
  67 };
  68
  69 /** @{
  70  * Mapping from our use of GLuint as both the key and the hash value to the
  71  * hash_table.h API
  72  *
  73  * There exist many integer hash functions, designed to avoid collisions when
  74  * the integers are spread across key space with some patterns.  In GL, the
  75  * pattern (in the case of glGen*()ed object IDs) is that the keys are unique
  76  * contiguous integers starting from 1.  Because of that, we just use the key
  77  * as the hash value, to minimize the cost of the hash function.  If objects
  78  * are never deleted, we will never see a collision in the table, because the
  79  * table resizes itself when it approaches full, and thus key % table_size ==
  80  * key.
  81  *
  82  * The case where we could have collisions for genned objects would be
  83  * something like: glGenBuffers(&a, 100); glDeleteBuffers(&a + 50, 50);
  84  * glGenBuffers(&b, 100), because objects 1-50 and 101-200 are allocated at
  85  * the end of that sequence, instead of 1-150.  So far it doesn't appear to be
  86  * a problem.
  87  */
  88 static bool
  89 uint_key_compare(const void *a, const void *b)
  90 {
  91    return a == b;
  92 }
  93
  94 static uint32_t
  95 uint_hash(GLuint id)
  96 {
  97    return id;
  98 }
  99
 100 static void *
 101 uint_key(GLuint id)
 102 {
 103    return (void *)(uintptr_t) id;
 104 }
 105 /** @} */
 106
 107 /**
 108  * Create a new hash table.
 109  *
 110  * \return pointer to a new, empty hash table.
 111  */
 112 struct _mesa_HashTable *
 113 _mesa_NewHashTable(void)
 114 {
 115    struct _mesa_HashTable *table = CALLOC_STRUCT(_mesa_HashTable);
 116
 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    if (table) {
 120       _glthread_INIT_MUTEX(table->Mutex);
 121       _glthread_INIT_MUTEX(table->WalkMutex);
 122    }
 123    return table;
 124 }
 125
 126
 127
 128 /**
 129  * Delete a hash table.
 130  * Frees each entry on the hash table and then the hash table structure itself.
 131  * Note that the caller should have already traversed the table and deleted
 132  * the objects in the table (i.e. We don't free the entries' data pointer).
 133  *
 134  * \param table the hash table to delete.
 135  */
 136 void
 137 _mesa_DeleteHashTable(struct _mesa_HashTable *table)
 138 {
 139    assert(table);
 140
 141    if (_mesa_hash_table_next_entry(table->ht, NULL) != NULL) {
 142       _mesa_problem(NULL, "In _mesa_DeleteHashTable, found non-freed data");
 143    }
 144
 145    _mesa_hash_table_destroy(table->ht, NULL);
 146
 147    _glthread_DESTROY_MUTEX(table->Mutex);
 148    _glthread_DESTROY_MUTEX(table->WalkMutex);
 149    free(table);
 150 }
 151
 152
 153
 154 /**
 155  * Lookup an entry in the hash table, without locking.
 156  * \sa _mesa_HashLookup
 157  */
 158 static inline void *
 159 _mesa_HashLookup_unlocked(struct _mesa_HashTable *table, GLuint key)
 160 {
 161    const struct hash_entry *entry;
 162
 163    assert(table);
 164    assert(key);
 165
 166    if (key == DELETED_KEY_VALUE)
 167       return table->deleted_key_data;
 168
 169    entry = _mesa_hash_table_search(table->ht, uint_hash(key), uint_key(key));
 170    if (!entry)
 171       return NULL;
 172
 173    return entry->data;
 174 }
 175
 176
 177 /**
 178  * Lookup an entry in the hash table.
 179  *
 180  * \param table the hash table.
 181  * \param key the key.
 182  *
 183  * \return pointer to user's data or NULL if key not in table
 184  */
 185 void *
 186 _mesa_HashLookup(struct _mesa_HashTable *table, GLuint key)
 187 {
 188    void *res;
 189    assert(table);
 190    _glthread_LOCK_MUTEX(table->Mutex);
 191    res = _mesa_HashLookup_unlocked(table, key);
 192    _glthread_UNLOCK_MUTEX(table->Mutex);
 193    return res;
 194 }
 195
 196
 197 /**
 198  * Insert a key/pointer pair into the hash table.
 199  * If an entry with this key already exists we'll replace the existing entry.
 200  *
 201  * \param table the hash table.
 202  * \param key the key (not zero).
 203  * \param data pointer to user data.
 204  */
 205 void
 206 _mesa_HashInsert(struct _mesa_HashTable *table, GLuint key, void *data)
 207 {
 208    uint32_t hash = uint_hash(key);
 209    struct hash_entry *entry;
 210
 211    assert(table);
 212    assert(key);
 213
 214    _glthread_LOCK_MUTEX(table->Mutex);
 215
 216    if (key > table->MaxKey)
 217       table->MaxKey = key;
 218
 219    if (key == DELETED_KEY_VALUE) {
 220       table->deleted_key_data = data;
 221    } else {
 222       entry = _mesa_hash_table_search(table->ht, hash, uint_key(key));
 223       if (entry) {
 224          entry->data = data;
 225       } else {
 226          _mesa_hash_table_insert(table->ht, hash, uint_key(key), data);
 227       }
 228    }
 229
 230    _glthread_UNLOCK_MUTEX(table->Mutex);
 231 }
 232
 233
 234
 235 /**
 236  * Remove an entry from the hash table.
 237  *
 238  * \param table the hash table.
 239  * \param key key of entry to remove.
 240  *
 241  * While holding the hash table's lock, searches the entry with the matching
 242  * key and unlinks it.
 243  */
 244 void
 245 _mesa_HashRemove(struct _mesa_HashTable *table, GLuint key)
 246 {
 247    struct hash_entry *entry;
 248
 249    assert(table);
 250    assert(key);
 251
 252    /* have to check this outside of mutex lock */
 253    if (table->InDeleteAll) {
 254       _mesa_problem(NULL, "_mesa_HashRemove illegally called from "
 255                     "_mesa_HashDeleteAll callback function");
 256       return;
 257    }
 258
 259    _glthread_LOCK_MUTEX(table->Mutex);
 260    if (key == DELETED_KEY_VALUE) {
 261       table->deleted_key_data = NULL;
 262    } else {
 263       entry = _mesa_hash_table_search(table->ht, uint_hash(key), uint_key(key));
 264       _mesa_hash_table_remove(table->ht, entry);
 265    }
 266    _glthread_UNLOCK_MUTEX(table->Mutex);
 267 }
 268
 269
 270
 271 /**
 272  * Delete all entries in a hash table, but don't delete the table itself.
 273  * Invoke the given callback function for each table entry.
 274  *
 275  * \param table  the hash table to delete
 276  * \param callback  the callback function
 277  * \param userData  arbitrary pointer to pass along to the callback
 278  *                  (this is typically a struct gl_context pointer)
 279  */
 280 void
 281 _mesa_HashDeleteAll(struct _mesa_HashTable *table,
 282                     void (*callback)(GLuint key, void *data, void *userData),
 283                     void *userData)
 284 {
 285    struct hash_entry *entry;
 286
 287    ASSERT(table);
 288    ASSERT(callback);
 289    _glthread_LOCK_MUTEX(table->Mutex);
 290    table->InDeleteAll = GL_TRUE;
 291    hash_table_foreach(table->ht, entry) {
 292       callback((uintptr_t)entry->key, entry->data, userData);
 293       _mesa_hash_table_remove(table->ht, entry);
 294    }
 295    if (table->deleted_key_data) {
 296       callback(DELETED_KEY_VALUE, table->deleted_key_data, userData);
 297       table->deleted_key_data = NULL;
 298    }
 299    table->InDeleteAll = GL_FALSE;
 300    _glthread_UNLOCK_MUTEX(table->Mutex);
 301 }
 302
 303
 304 /**
 305  * Walk over all entries in a hash table, calling callback function for each.
 306  * Note: we use a separate mutex in this function to avoid a recursive
 307  * locking deadlock (in case the callback calls _mesa_HashRemove()) and to
 308  * prevent multiple threads/contexts from getting tangled up.
 309  * A lock-less version of this function could be used when the table will
 310  * not be modified.
 311  * \param table  the hash table to walk
 312  * \param callback  the callback function
 313  * \param userData  arbitrary pointer to pass along to the callback
 314  *                  (this is typically a struct gl_context pointer)
 315  */
 316 void
 317 _mesa_HashWalk(const struct _mesa_HashTable *table,
 318                void (*callback)(GLuint key, void *data, void *userData),
 319                void *userData)
 320 {
 321    /* cast-away const */
 322    struct _mesa_HashTable *table2 = (struct _mesa_HashTable *) table;
 323    struct hash_entry *entry;
 324
 325    ASSERT(table);
 326    ASSERT(callback);
 327    _glthread_LOCK_MUTEX(table2->WalkMutex);
 328    hash_table_foreach(table->ht, entry) {
 329       callback((uintptr_t)entry->key, entry->data, userData);
 330    }
 331    if (table->deleted_key_data)
 332       callback(DELETED_KEY_VALUE, table->deleted_key_data, userData);
 333    _glthread_UNLOCK_MUTEX(table2->WalkMutex);
 334 }
 335
 336 static void
 337 debug_print_entry(GLuint key, void *data, void *userData)
 338 {
 339    _mesa_debug(NULL, "%u %p\n", key, data);
 340 }
 341
 342 /**
 343  * Dump contents of hash table for debugging.
 344  *
 345  * \param table the hash table.
 346  */
 347 void
 348 _mesa_HashPrint(const struct _mesa_HashTable *table)
 349 {
 350    if (table->deleted_key_data)
 351       debug_print_entry(DELETED_KEY_VALUE, table->deleted_key_data, NULL);
 352    _mesa_HashWalk(table, debug_print_entry, NULL);
 353 }
 354
 355
 356 /**
 357  * Find a block of adjacent unused hash keys.
 358  *
 359  * \param table the hash table.
 360  * \param numKeys number of keys needed.
 361  *
 362  * \return Starting key of free block or 0 if failure.
 363  *
 364  * If there are enough free keys between the maximum key existing in the table
 365  * (_mesa_HashTable::MaxKey) and the maximum key possible, then simply return
 366  * the adjacent key. Otherwise do a full search for a free key block in the
 367  * allowable key range.
 368  */
 369 GLuint
 370 _mesa_HashFindFreeKeyBlock(struct _mesa_HashTable *table, GLuint numKeys)
 371 {
 372    const GLuint maxKey = ~((GLuint) 0) - 1;
 373    _glthread_LOCK_MUTEX(table->Mutex);
 374    if (maxKey - numKeys > table->MaxKey) {
 375       /* the quick solution */
 376       _glthread_UNLOCK_MUTEX(table->Mutex);
 377       return table->MaxKey + 1;
 378    }
 379    else {
 380       /* the slow solution */
 381       GLuint freeCount = 0;
 382       GLuint freeStart = 1;
 383       GLuint key;
 384       for (key = 1; key != maxKey; key++) {
 385          if (_mesa_HashLookup_unlocked(table, key)) {
 386             /* darn, this key is already in use */
 387             freeCount = 0;
 388             freeStart = key+1;
 389          }
 390          else {
 391             /* this key not in use, check if we've found enough */
 392             freeCount++;
 393             if (freeCount == numKeys) {
 394                _glthread_UNLOCK_MUTEX(table->Mutex);
 395                return freeStart;
 396             }
 397          }
 398       }
 399       /* cannot allocate a block of numKeys consecutive keys */
 400       _glthread_UNLOCK_MUTEX(table->Mutex);
 401       return 0;
 402    }
 403 }
 404
 405
 406 /**
 407  * Return the number of entries in the hash table.
 408  */
 409 GLuint
 410 _mesa_HashNumEntries(const struct _mesa_HashTable *table)
 411 {
 412    struct hash_entry *entry;
 413    GLuint count = 0;
 414
 415    if (table->deleted_key_data)
 416       count++;
 417
 418    hash_table_foreach(table->ht, entry)
 419       count++;
 420
 421    return count;
 422 }