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/**

 * \file hash.c

 * Generic hash table.

 *

 * Used for display lists, texture objects, vertex/fragment programs,

 * buffer objects, etc.  The hash functions are thread-safe.

 *

 * \note key=0 is illegal.

 *

 * \author Brian Paul

 */

/*

 * Mesa 3-D graphics library

 * Version:  6.5.1

 *

 * Copyright (C) 1999-2006  Brian Paul   All Rights Reserved.

 *

 * Permission is hereby granted, free of charge, to any person obtaining a

 * copy of this software and associated documentation files (the "Software"),

 * to deal in the Software without restriction, including without limitation

 * the rights to use, copy, modify, merge, publish, distribute, sublicense,

 * and/or sell copies of the Software, and to permit persons to whom the

 * Software is furnished to do so, subject to the following conditions:

 *

 * The above copyright notice and this permission notice shall be included

 * in all copies or substantial portions of the Software.

 *

 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS

 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL

 * BRIAN PAUL BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN

 * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN

 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

 */

#include "glheader.h"

#include "imports.h"

#include "glapi/glthread.h"

#include "hash.h"

#define TABLE_SIZE 1023  /**< Size of lookup table/array */

#define HASH_FUNC(K)  ((K) % TABLE_SIZE)

/**

 * An entry in the hash table.

 */

struct HashEntry {

   GLuint Key;             /**< the entry's key */

   void *Data;             /**< the entry's data */

   struct HashEntry *Next; /**< pointer to next entry */

};

/**

 * The hash table data structure.

 */

struct _mesa_HashTable {

   struct HashEntry *Table[TABLE_SIZE];  /**< the lookup table */

   GLuint MaxKey;                        /**< highest key inserted so far */

   _glthread_Mutex Mutex;                /**< mutual exclusion lock */

   _glthread_Mutex WalkMutex;            /**< for _mesa_HashWalk() */

   GLboolean InDeleteAll;                /**< Debug check */

};

/**

 * Create a new hash table.

 *

 * \return pointer to a new, empty hash table.

 */

struct _mesa_HashTable *

_mesa_NewHashTable(void)

{

   struct _mesa_HashTable *table = CALLOC_STRUCT(_mesa_HashTable);

   if (table) {

      _glthread_INIT_MUTEX(table->Mutex);

      _glthread_INIT_MUTEX(table->WalkMutex);

   }

   return table;

}

/**

 * Delete a hash table.

 * Frees each entry on the hash table and then the hash table structure itself.

 * Note that the caller should have already traversed the table and deleted

 * the objects in the table (i.e. We don't free the entries' data pointer).

 *

 * \param table the hash table to delete.

 */

void

_mesa_DeleteHashTable(struct _mesa_HashTable *table)

{

   GLuint pos;

   assert(table);

   for (pos = 0; pos < TABLE_SIZE; pos++) {

      struct HashEntry *entry = table->Table[pos];

      while (entry) {

	 struct HashEntry *next = entry->Next;

         if (entry->Data) {

            _mesa_problem(NULL,

                          "In _mesa_DeleteHashTable, found non-freed data");

         }

	 free(entry);

	 entry = next;

      }

   }

   _glthread_DESTROY_MUTEX(table->Mutex);

   _glthread_DESTROY_MUTEX(table->WalkMutex);

   free(table);

}

/**

 * Lookup an entry in the hash table, without locking.

 * \sa _mesa_HashLookup

 */

static INLINE void *

_mesa_HashLookup_unlocked(struct _mesa_HashTable *table, GLuint key)

{

   GLuint pos;

   const struct HashEntry *entry;

   assert(table);

   assert(key);

   pos = HASH_FUNC(key);

   entry = table->Table[pos];

   while (entry) {

      if (entry->Key == key) {

         return entry->Data;

      }

      entry = entry->Next;

   }

   return NULL;

}

/**

 * Lookup an entry in the hash table.

 *

 * \param table the hash table.

 * \param key the key.

 *

 * \return pointer to user's data or NULL if key not in table

 */

void *

_mesa_HashLookup(struct _mesa_HashTable *table, GLuint key)

{

   void *res;

   assert(table);

   _glthread_LOCK_MUTEX(table->Mutex);

   res = _mesa_HashLookup_unlocked(table, key);

   _glthread_UNLOCK_MUTEX(table->Mutex);

   return res;

}

/**

 * Insert a key/pointer pair into the hash table.

 * If an entry with this key already exists we'll replace the existing entry.

 *

 * \param table the hash table.

 * \param key the key (not zero).

 * \param data pointer to user data.

 */

void

_mesa_HashInsert(struct _mesa_HashTable *table, GLuint key, void *data)

{

   /* search for existing entry with this key */

   GLuint pos;

   struct HashEntry *entry;

   assert(table);

   assert(key);

   _glthread_LOCK_MUTEX(table->Mutex);

   if (key > table->MaxKey)

      table->MaxKey = key;

   pos = HASH_FUNC(key);

   /* check if replacing an existing entry with same key */

   for (entry = table->Table[pos]; entry; entry = entry->Next) {

      if (entry->Key == key) {

         /* replace entry's data */

#if 0 /* not sure this check is always valid */

         if (entry->Data) {

            _mesa_problem(NULL, "Memory leak detected in _mesa_HashInsert");

         }

#endif

	 entry->Data = data;

         _glthread_UNLOCK_MUTEX(table->Mutex);

	 return;

      }

   }

   /* alloc and insert new table entry */

   entry = MALLOC_STRUCT(HashEntry);

   if (entry) {

      entry->Key = key;

      entry->Data = data;

      entry->Next = table->Table[pos];

      table->Table[pos] = entry;

   }

   _glthread_UNLOCK_MUTEX(table->Mutex);

}

/**

 * Remove an entry from the hash table.

 *

 * \param table the hash table.

 * \param key key of entry to remove.

 *

 * While holding the hash table's lock, searches the entry with the matching

 * key and unlinks it.

 */

void

_mesa_HashRemove(struct _mesa_HashTable *table, GLuint key)

{

   GLuint pos;

   struct HashEntry *entry, *prev;

   assert(table);

   assert(key);

   /* have to check this outside of mutex lock */

   if (table->InDeleteAll) {

      _mesa_problem(NULL, "_mesa_HashRemove illegally called from "

                    "_mesa_HashDeleteAll callback function");

      return;

   }

   _glthread_LOCK_MUTEX(table->Mutex);

   pos = HASH_FUNC(key);

   prev = NULL;

   entry = table->Table[pos];

   while (entry) {

      if (entry->Key == key) {

         /* found it! */

         if (prev) {

            prev->Next = entry->Next;

         }

         else {

            table->Table[pos] = entry->Next;

         }

         free(entry);

         _glthread_UNLOCK_MUTEX(table->Mutex);

	 return;

      }

      prev = entry;

      entry = entry->Next;

   }

   _glthread_UNLOCK_MUTEX(table->Mutex);

}

/**

 * Delete all entries in a hash table, but don't delete the table itself.

 * Invoke the given callback function for each table entry.

 *

 * \param table  the hash table to delete

 * \param callback  the callback function

 * \param userData  arbitrary pointer to pass along to the callback

 *                  (this is typically a struct gl_context pointer)

 */

void

_mesa_HashDeleteAll(struct _mesa_HashTable *table,

                    void (*callback)(GLuint key, void *data, void *userData),

                    void *userData)

{

   GLuint pos;

   ASSERT(table);

   ASSERT(callback);

   _glthread_LOCK_MUTEX(table->Mutex);

   table->InDeleteAll = GL_TRUE;

   for (pos = 0; pos < TABLE_SIZE; pos++) {

      struct HashEntry *entry, *next;

      for (entry = table->Table[pos]; entry; entry = next) {

         callback(entry->Key, entry->Data, userData);

         next = entry->Next;

         free(entry);

      }

      table->Table[pos] = NULL;

   }

   table->InDeleteAll = GL_FALSE;

   _glthread_UNLOCK_MUTEX(table->Mutex);

}

/**

 * Walk over all entries in a hash table, calling callback function for each.

 * Note: we use a separate mutex in this function to avoid a recursive

 * locking deadlock (in case the callback calls _mesa_HashRemove()) and to

 * prevent multiple threads/contexts from getting tangled up.

 * A lock-less version of this function could be used when the table will

 * not be modified.

 * \param table  the hash table to walk

 * \param callback  the callback function

 * \param userData  arbitrary pointer to pass along to the callback

 *                  (this is typically a struct gl_context pointer)

 */

void

_mesa_HashWalk(const struct _mesa_HashTable *table,

               void (*callback)(GLuint key, void *data, void *userData),

               void *userData)

{

   /* cast-away const */

   struct _mesa_HashTable *table2 = (struct _mesa_HashTable *) table;

   GLuint pos;

   ASSERT(table);

   ASSERT(callback);

   _glthread_LOCK_MUTEX(table2->WalkMutex);

   for (pos = 0; pos < TABLE_SIZE; pos++) {

      struct HashEntry *entry, *next;

      for (entry = table->Table[pos]; entry; entry = next) {

         /* save 'next' pointer now in case the callback deletes the entry */

         next = entry->Next;

         callback(entry->Key, entry->Data, userData);

      }

   }

   _glthread_UNLOCK_MUTEX(table2->WalkMutex);

}

/**

 * Return the key of the "first" entry in the hash table.

 * While holding the lock, walks through all table positions until finding

 * the first entry of the first non-empty one.

 *

 * \param table  the hash table

 * \return key for the "first" entry in the hash table.

 */

GLuint

_mesa_HashFirstEntry(struct _mesa_HashTable *table)

{

   GLuint pos;

   assert(table);

   _glthread_LOCK_MUTEX(table->Mutex);

   for (pos = 0; pos < TABLE_SIZE; pos++) {

      if (table->Table[pos]) {

         _glthread_UNLOCK_MUTEX(table->Mutex);

         return table->Table[pos]->Key;

      }

   }

   _glthread_UNLOCK_MUTEX(table->Mutex);

   return 0;

}

/**

 * Given a hash table key, return the next key.  This is used to walk

 * over all entries in the table.  Note that the keys returned during

 * walking won't be in any particular order.

 * \return next hash key or 0 if end of table.

 */

GLuint

_mesa_HashNextEntry(const struct _mesa_HashTable *table, GLuint key)

{

   const struct HashEntry *entry;

   GLuint pos;

   assert(table);

   assert(key);

   /* Find the entry with given key */

   pos = HASH_FUNC(key);

   for (entry = table->Table[pos]; entry ; entry = entry->Next) {

      if (entry->Key == key) {

         break;

      }

   }

   if (!entry) {

      /* the given key was not found, so we can't find the next entry */

      return 0;

   }

   if (entry->Next) {

      /* return next in linked list */

      return entry->Next->Key;

   }

   else {

      /* look for next non-empty table slot */

      pos++;

      while (pos < TABLE_SIZE) {

         if (table->Table[pos]) {

            return table->Table[pos]->Key;

         }

         pos++;

      }

      return 0;

   }

}

/**

 * Dump contents of hash table for debugging.

 *

 * \param table the hash table.

 */

void

_mesa_HashPrint(const struct _mesa_HashTable *table)

{

   GLuint pos;

   assert(table);

   for (pos = 0; pos < TABLE_SIZE; pos++) {

      const struct HashEntry *entry = table->Table[pos];

      while (entry) {

	 _mesa_debug(NULL, "%u %p\n", entry->Key, entry->Data);

	 entry = entry->Next;

      }

   }

}

/**

 * Find a block of adjacent unused hash keys.

 *

 * \param table the hash table.

 * \param numKeys number of keys needed.

 *

 * \return Starting key of free block or 0 if failure.

 *

 * If there are enough free keys between the maximum key existing in the table

 * (_mesa_HashTable::MaxKey) and the maximum key possible, then simply return

 * the adjacent key. Otherwise do a full search for a free key block in the

 * allowable key range.

 */

GLuint

_mesa_HashFindFreeKeyBlock(struct _mesa_HashTable *table, GLuint numKeys)

{

   const GLuint maxKey = ~((GLuint) 0);

   _glthread_LOCK_MUTEX(table->Mutex);

   if (maxKey - numKeys > table->MaxKey) {

      /* the quick solution */

      _glthread_UNLOCK_MUTEX(table->Mutex);

      return table->MaxKey + 1;

   }

   else {

      /* the slow solution */

      GLuint freeCount = 0;

      GLuint freeStart = 1;

      GLuint key;

      for (key = 1; key != maxKey; key++) {

	 if (_mesa_HashLookup_unlocked(table, key)) {

	    /* darn, this key is already in use */

	    freeCount = 0;

	    freeStart = key+1;

	 }

	 else {

	    /* this key not in use, check if we've found enough */

	    freeCount++;

	    if (freeCount == numKeys) {

               _glthread_UNLOCK_MUTEX(table->Mutex);

	       return freeStart;

	    }

	 }

      }

      /* cannot allocate a block of numKeys consecutive keys */

      _glthread_UNLOCK_MUTEX(table->Mutex);

      return 0;

   }

}

#if 0 /* debug only */

/**

 * Test walking over all the entries in a hash table.

 */

static void

test_hash_walking(void)

{

   struct _mesa_HashTable *t = _mesa_NewHashTable();

   const GLuint limit = 50000;

   GLuint i;

   /* create some entries */

   for (i = 0; i < limit; i++) {

      GLuint dummy;

      GLuint k = (rand() % (limit * 10)) + 1;

      while (_mesa_HashLookup(t, k)) {

         /* id already in use, try another */

         k = (rand() % (limit * 10)) + 1;

      }

      _mesa_HashInsert(t, k, &dummy);

   }

   /* walk over all entries */

   {

      GLuint k = _mesa_HashFirstEntry(t);

      GLuint count = 0;

      while (k) {

         GLuint knext = _mesa_HashNextEntry(t, k);

         assert(knext != k);

         _mesa_HashRemove(t, k);

         count++;

         k = knext;

      }

      assert(count == limit);

      k = _mesa_HashFirstEntry(t);

      assert(k==0);

   }

   _mesa_DeleteHashTable(t);

}

void

_mesa_test_hash_functions(void)

{

   int a, b, c;

   struct _mesa_HashTable *t;

   t = _mesa_NewHashTable();

   _mesa_HashInsert(t, 501, &a);

   _mesa_HashInsert(t, 10, &c);

   _mesa_HashInsert(t, 0xfffffff8, &b);

   /*_mesa_HashPrint(t);*/

   assert(_mesa_HashLookup(t,501));

   assert(!_mesa_HashLookup(t,1313));

   assert(_mesa_HashFindFreeKeyBlock(t, 100));

   _mesa_DeleteHashTable(t);

   test_hash_walking();

}

#endif