hash.c

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


struct HashEntry {
   GLuint Key;             
   void *Data;             
   struct HashEntry *Next; 
};


struct _mesa_HashTable {
   struct HashEntry *Table[TABLE_SIZE];  
   GLuint MaxKey;                        
   _glthread_Mutex Mutex;                
   GLboolean InDeleteAll;                
};



struct _mesa_HashTable *
_mesa_NewHashTable(void)
{
   struct _mesa_HashTable *table = CALLOC_STRUCT(_mesa_HashTable);
   if (table) {
      _glthread_INIT_MUTEX(table->Mutex);
   }
   return table;
}



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");
         }
     _mesa_free(entry);
     entry = next;
      }
   }
   _glthread_DESTROY_MUTEX(table->Mutex);
   _mesa_free(table);
}



void *
_mesa_HashLookup(const 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;
}



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);
   entry->Key = key;
   entry->Data = data;
   entry->Next = table->Table[pos];
   table->Table[pos] = entry;

   _glthread_UNLOCK_MUTEX(table->Mutex);
}



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;
         }
         _mesa_free(entry);
         _glthread_UNLOCK_MUTEX(table->Mutex);
     return;
      }
      prev = entry;
      entry = entry->Next;
   }

   _glthread_UNLOCK_MUTEX(table->Mutex);
}



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;
         _mesa_free(entry);
      }
      table->Table[pos] = NULL;
   }
   table->InDeleteAll = GL_FALSE;
   _glthread_UNLOCK_MUTEX(table->Mutex);
}


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->Mutex);
   for (pos = 0; pos < TABLE_SIZE; pos++) {
      struct HashEntry *entry;
      for (entry = table->Table[pos]; entry; entry = entry->Next) {
         callback(entry->Key, entry->Data, userData);
      }
   }
   _glthread_UNLOCK_MUTEX(table2->Mutex);
}


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;
}


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;
   }
}


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;
      }
   }
}



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(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 */

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