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  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
  33  * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
  34  * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
  35  * OTHER DEALINGS IN THE SOFTWARE.
  36  */
  37
  38 #include "glheader.h"
  39 #include "imports.h"
  40 #include "glapi/glthread.h"
  41 #include "hash.h"
  42 #include "hash_table.h"
  43
  44 /**
  45  * Magic GLuint object name that gets stored outside of the struct hash_table.
  46  *
  47  * The hash table needs a particular pointer to be the marker for a key that
  48  * was deleted from the table, along with NULL for the "never allocated in the
  49  * table" marker.  Legacy GL allows any GLuint to be used as a GL object name,
  50  * and we use a 1:1 mapping from GLuints to key pointers, so we need to be
  51  * able to track a GLuint that happens to match the deleted key outside of
  52  * struct hash_table.  We tell the hash table to use "1" as the deleted key
  53  * value, so that we test the deleted-key-in-the-table path as best we can.
  54  */
  55 #define DELETED_KEY_VALUE 1
  56
  57 /**
  58  * The hash table data structure.
  59  */
  60 struct _mesa_HashTable {
  61    struct hash_table *ht;
  62    GLuint MaxKey;                        /**< highest key inserted so far */
  63    _glthread_Mutex Mutex;                /**< mutual exclusion lock */
  64    _glthread_Mutex WalkMutex;            /**< for _mesa_HashWalk() */
  65    GLboolean InDeleteAll;                /**< Debug check */
  66    /** Value that would be in the table for DELETED_KEY_VALUE. */
  67    void *deleted_key_data;
  68 };
  69
  70 /** @{
  71  * Mapping from our use of GLuint as both the key and the hash value to the
  72  * hash_table.h API
  73  *
  74  * There exist many integer hash functions, designed to avoid collisions when
  75  * the integers are spread across key space with some patterns.  In GL, the
  76  * pattern (in the case of glGen*()ed object IDs) is that the keys are unique
  77  * contiguous integers starting from 1.  Because of that, we just use the key
  78  * as the hash value, to minimize the cost of the hash function.  If objects
  79  * are never deleted, we will never see a collision in the table, because the
  80  * table resizes itself when it approaches full, and thus key % table_size ==
  81  * key.
  82  *
  83  * The case where we could have collisions for genned objects would be
  84  * something like: glGenBuffers(&a, 100); glDeleteBuffers(&a + 50, 50);
  85  * glGenBuffers(&b, 100), because objects 1-50 and 101-200 are allocated at
  86  * the end of that sequence, instead of 1-150.  So far it doesn't appear to be
  87  * a problem.
  88  */
  89 static bool
  90 uint_key_compare(const void *a, const void *b)
  91 {
  92    return a == b;
  93 }
  94
  95 static uint32_t
  96 uint_hash(GLuint id)
  97 {
  98    return id;
  99 }
 100
 101 static void *
 102 uint_key(GLuint id)
 103 {
 104    return (void *)(uintptr_t) id;
 105 }
 106 /** @} */
 107
 108 /**
 109  * Create a new hash table.
 110  *
 111  * \return pointer to a new, empty hash table.
 112  */
 113 struct _mesa_HashTable *
 114 _mesa_NewHashTable(void)
 115 {
 116    struct _mesa_HashTable *table = CALLOC_STRUCT(_mesa_HashTable);
 117
 118    if (table) {
 119       table->ht = _mesa_hash_table_create(NULL, uint_key_compare);
 120       _mesa_hash_table_set_deleted_key(table->ht, uint_key(DELETED_KEY_VALUE));
 121       _glthread_INIT_MUTEX(table->Mutex);
 122       _glthread_INIT_MUTEX(table->WalkMutex);
 123    }
 124    return table;
 125 }
 126
 127
 128
 129 /**
 130  * Delete a hash table.
 131  * Frees each entry on the hash table and then the hash table structure itself.
 132  * Note that the caller should have already traversed the table and deleted
 133  * the objects in the table (i.e. We don't free the entries' data pointer).
 134  *
 135  * \param table the hash table to delete.
 136  */
 137 void
 138 _mesa_DeleteHashTable(struct _mesa_HashTable *table)
 139 {
 140    assert(table);
 141
 142    if (_mesa_hash_table_next_entry(table->ht, NULL) != NULL) {
 143       _mesa_problem(NULL, "In _mesa_DeleteHashTable, found non-freed data");
 144    }
 145
 146    _mesa_hash_table_destroy(table->ht, NULL);
 147
 148    _glthread_DESTROY_MUTEX(table->Mutex);
 149    _glthread_DESTROY_MUTEX(table->WalkMutex);
 150    free(table);
 151 }
 152
 153
 154
 155 /**
 156  * Lookup an entry in the hash table, without locking.
 157  * \sa _mesa_HashLookup
 158  */
 159 static inline void *
 160 _mesa_HashLookup_unlocked(struct _mesa_HashTable *table, GLuint key)
 161 {
 162    const struct hash_entry *entry;
 163
 164    assert(table);
 165    assert(key);
 166
 167    if (key == DELETED_KEY_VALUE)
 168       return table->deleted_key_data;
 169
 170    entry = _mesa_hash_table_search(table->ht, uint_hash(key), uint_key(key));
 171    if (!entry)
 172       return NULL;
 173
 174    return entry->data;
 175 }
 176
 177
 178 /**
 179  * Lookup an entry in the hash table.
 180  *
 181  * \param table the hash table.
 182  * \param key the key.
 183  *
 184  * \return pointer to user's data or NULL if key not in table
 185  */
 186 void *
 187 _mesa_HashLookup(struct _mesa_HashTable *table, GLuint key)
 188 {
 189    void *res;
 190    assert(table);
 191    _glthread_LOCK_MUTEX(table->Mutex);
 192    res = _mesa_HashLookup_unlocked(table, key);
 193    _glthread_UNLOCK_MUTEX(table->Mutex);
 194    return res;
 195 }
 196
 197
 198 /**
 199  * Insert a key/pointer pair into the hash table.
 200  * If an entry with this key already exists we'll replace the existing entry.
 201  *
 202  * \param table the hash table.
 203  * \param key the key (not zero).
 204  * \param data pointer to user data.
 205  */
 206 void
 207 _mesa_HashInsert(struct _mesa_HashTable *table, GLuint key, void *data)
 208 {
 209    uint32_t hash = uint_hash(key);
 210    struct hash_entry *entry;
 211
 212    assert(table);
 213    assert(key);
 214
 215    _glthread_LOCK_MUTEX(table->Mutex);
 216
 217    if (key > table->MaxKey)
 218       table->MaxKey = key;
 219
 220    if (key == DELETED_KEY_VALUE) {
 221       table->deleted_key_data = data;
 222    } else {
 223       entry = _mesa_hash_table_search(table->ht, hash, uint_key(key));
 224       if (entry) {
 225          entry->data = data;
 226       } else {
 227          _mesa_hash_table_insert(table->ht, hash, uint_key(key), data);
 228       }
 229    }
 230
 231    _glthread_UNLOCK_MUTEX(table->Mutex);
 232 }
 233
 234
 235
 236 /**
 237  * Remove an entry from the hash table.
 238  *
 239  * \param table the hash table.
 240  * \param key key of entry to remove.
 241  *
 242  * While holding the hash table's lock, searches the entry with the matching
 243  * key and unlinks it.
 244  */
 245 void
 246 _mesa_HashRemove(struct _mesa_HashTable *table, GLuint key)
 247 {
 248    struct hash_entry *entry;
 249
 250    assert(table);
 251    assert(key);
 252
 253    /* have to check this outside of mutex lock */
 254    if (table->InDeleteAll) {
 255       _mesa_problem(NULL, "_mesa_HashRemove illegally called from "
 256                     "_mesa_HashDeleteAll callback function");
 257       return;
 258    }
 259
 260    _glthread_LOCK_MUTEX(table->Mutex);
 261    if (key == DELETED_KEY_VALUE) {
 262       table->deleted_key_data = NULL;
 263    } else {
 264       entry = _mesa_hash_table_search(table->ht, uint_hash(key), uint_key(key));
 265       _mesa_hash_table_remove(table->ht, entry);
 266    }
 267    _glthread_UNLOCK_MUTEX(table->Mutex);
 268 }
 269
 270
 271
 272 /**
 273  * Delete all entries in a hash table, but don't delete the table itself.
 274  * Invoke the given callback function for each table entry.
 275  *
 276  * \param table  the hash table to delete
 277  * \param callback  the callback function
 278  * \param userData  arbitrary pointer to pass along to the callback
 279  *                  (this is typically a struct gl_context pointer)
 280  */
 281 void
 282 _mesa_HashDeleteAll(struct _mesa_HashTable *table,
 283                     void (*callback)(GLuint key, void *data, void *userData),
 284                     void *userData)
 285 {
 286    struct hash_entry *entry;
 287
 288    ASSERT(table);
 289    ASSERT(callback);
 290    _glthread_LOCK_MUTEX(table->Mutex);
 291    table->InDeleteAll = GL_TRUE;
 292    hash_table_foreach(table->ht, entry) {
 293       callback((uintptr_t)entry->key, entry->data, userData);
 294       _mesa_hash_table_remove(table->ht, entry);
 295    }
 296    if (table->deleted_key_data) {
 297       callback(DELETED_KEY_VALUE, table->deleted_key_data, userData);
 298       table->deleted_key_data = NULL;
 299    }
 300    table->InDeleteAll = GL_FALSE;
 301    _glthread_UNLOCK_MUTEX(table->Mutex);
 302 }
 303
 304
 305 /**
 306  * Walk over all entries in a hash table, calling callback function for each.
 307  * Note: we use a separate mutex in this function to avoid a recursive
 308  * locking deadlock (in case the callback calls _mesa_HashRemove()) and to
 309  * prevent multiple threads/contexts from getting tangled up.
 310  * A lock-less version of this function could be used when the table will
 311  * not be modified.
 312  * \param table  the hash table to walk
 313  * \param callback  the callback function
 314  * \param userData  arbitrary pointer to pass along to the callback
 315  *                  (this is typically a struct gl_context pointer)
 316  */
 317 void
 318 _mesa_HashWalk(const struct _mesa_HashTable *table,
 319                void (*callback)(GLuint key, void *data, void *userData),
 320                void *userData)
 321 {
 322    /* cast-away const */
 323    struct _mesa_HashTable *table2 = (struct _mesa_HashTable *) table;
 324    struct hash_entry *entry;
 325
 326    ASSERT(table);
 327    ASSERT(callback);
 328    _glthread_LOCK_MUTEX(table2->WalkMutex);
 329    hash_table_foreach(table->ht, entry) {
 330       callback((uintptr_t)entry->key, entry->data, userData);
 331    }
 332    if (table->deleted_key_data)
 333       callback(DELETED_KEY_VALUE, table->deleted_key_data, userData);
 334    _glthread_UNLOCK_MUTEX(table2->WalkMutex);
 335 }
 336
 337 static void
 338 debug_print_entry(GLuint key, void *data, void *userData)
 339 {
 340    _mesa_debug(NULL, "%u %p\n", key, data);
 341 }
 342
 343 /**
 344  * Dump contents of hash table for debugging.
 345  *
 346  * \param table the hash table.
 347  */
 348 void
 349 _mesa_HashPrint(const struct _mesa_HashTable *table)
 350 {
 351    if (table->deleted_key_data)
 352       debug_print_entry(DELETED_KEY_VALUE, table->deleted_key_data, NULL);
 353    _mesa_HashWalk(table, debug_print_entry, NULL);
 354 }
 355
 356
 357 /**
 358  * Find a block of adjacent unused hash keys.
 359  *
 360  * \param table the hash table.
 361  * \param numKeys number of keys needed.
 362  *
 363  * \return Starting key of free block or 0 if failure.
 364  *
 365  * If there are enough free keys between the maximum key existing in the table
 366  * (_mesa_HashTable::MaxKey) and the maximum key possible, then simply return
 367  * the adjacent key. Otherwise do a full search for a free key block in the
 368  * allowable key range.
 369  */
 370 GLuint
 371 _mesa_HashFindFreeKeyBlock(struct _mesa_HashTable *table, GLuint numKeys)
 372 {
 373    const GLuint maxKey = ~((GLuint) 0) - 1;
 374    _glthread_LOCK_MUTEX(table->Mutex);
 375    if (maxKey - numKeys > table->MaxKey) {
 376       /* the quick solution */
 377       _glthread_UNLOCK_MUTEX(table->Mutex);
 378       return table->MaxKey + 1;
 379    }
 380    else {
 381       /* the slow solution */
 382       GLuint freeCount = 0;
 383       GLuint freeStart = 1;
 384       GLuint key;
 385       for (key = 1; key != maxKey; key++) {
 386          if (_mesa_HashLookup_unlocked(table, key)) {
 387             /* darn, this key is already in use */
 388             freeCount = 0;
 389             freeStart = key+1;
 390          }
 391          else {
 392             /* this key not in use, check if we've found enough */
 393             freeCount++;
 394             if (freeCount == numKeys) {
 395                _glthread_UNLOCK_MUTEX(table->Mutex);
 396                return freeStart;
 397             }
 398          }
 399       }
 400       /* cannot allocate a block of numKeys consecutive keys */
 401       _glthread_UNLOCK_MUTEX(table->Mutex);
 402       return 0;
 403    }
 404 }
 405
 406
 407 /**
 408  * Return the number of entries in the hash table.
 409  */
 410 GLuint
 411 _mesa_HashNumEntries(const struct _mesa_HashTable *table)
 412 {
 413    struct hash_entry *entry;
 414    GLuint count = 0;
 415
 416    if (table->deleted_key_data)
 417       count++;
 418
 419    hash_table_foreach(table->ht, entry)
 420       count++;
 421
 422    return count;
 423 }