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mesa5.zip
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MesaDLL
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hash.cpp
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2002-10-24
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/* $Id: hash.c,v 1.14 2002/10/24 23:57:21 brianp Exp $ */
/*
* Mesa 3-D graphics library
* Version: 4.1
*
* Copyright (C) 1999-2002 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 "glthread.h"
#include "hash.h"
#include "context.h"
/**
* \file hash.c
* \brief Generic hash table. Used for display lists and texture objects.
* The hash functions are thread-safe.
* \author Brian Paul
* \note key=0 is illegal
*/
#define TABLE_SIZE 1023 /**< Size of lookup table/array */
/**
* An entry in the hash table. This struct is private to this file.
*/
struct HashEntry {
GLuint Key; /**< the entry's key */
void *Data; /**< the entry's data */
struct HashEntry *Next; /**< pointer to next entry */
};
/**
* The hashtable data structure. This is an opaque types (it's not
* defined in the .h file).
*/
struct _mesa_HashTable {
struct HashEntry *Table[TABLE_SIZE]; /**< the lookup table */
GLuint MaxKey; /**< highest key inserted so far */
_glthread_Mutex Mutex; /**< mutual exclusion lock */
};
/**
* 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);
}
return table;
}
/**
* Delete a hash table.
* \param table - the hash table to delete
*/
void _mesa_DeleteHashTable(struct _mesa_HashTable *table)
{
GLuint i;
assert(table);
for (i=0;i<TABLE_SIZE;i++) {
struct HashEntry *entry = table->Table[i];
while (entry) {
struct HashEntry *next = entry->Next;
FREE(entry);
entry = next;
}
}
FREE(table);
}
/**
* 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(const struct _mesa_HashTable *table, GLuint key)
{
GLuint pos;
const struct HashEntry *entry;
assert(table);
assert(key);
pos = key & (TABLE_SIZE-1);
entry = table->Table[pos];
while (entry) {
if (entry->Key == key) {
return entry->Data;
}
entry = entry->Next;
}
return NULL;
}
/**
* Insert 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 = key & (TABLE_SIZE-1);
entry = table->Table[pos];
while (entry) {
if (entry->Key == key) {
/* replace entry's data */
entry->Data = data;
_glthread_UNLOCK_MUTEX(table->Mutex);
return;
}
entry = entry->Next;
}
/* 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);
}
/**
* Remove an entry from the hash table.
* \param table - the hash table
* \param key - key of entry to remove
*/
void _mesa_HashRemove(struct _mesa_HashTable *table, GLuint key)
{
GLuint pos;
struct HashEntry *entry, *prev;
assert(table);
assert(key);
_glthread_LOCK_MUTEX(table->Mutex);
pos = key & (TABLE_SIZE-1);
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);
}
/**
* Get the key of the "first" entry in the hash table.
* This is used in the course of deleting all display lists when
* a context is destroyed.
* \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;
}
/**
* Dump contents of hash table for debugging.
* \param table - the hash table
*/
void _mesa_HashPrint(const struct _mesa_HashTable *table)
{
GLuint i;
assert(table);
for (i=0;i<TABLE_SIZE;i++) {
const struct HashEntry *entry = table->Table[i];
while (entry) {
_mesa_debug(NULL, "%u %p\n", entry->Key, entry->Data);
entry = entry->Next;
}
}
}
/**
* Find a block of 'numKeys' 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
*/
GLuint _mesa_HashFindFreeKeyBlock(struct _mesa_HashTable *table, GLuint numKeys)
{
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;
}
}
#ifdef HASH_TEST_HARNESS
int main(int argc, char *argv[])
{
int a, b, c;
struct HashTable *t;
_mesa_printf("&a = %p\n", &a);
_mesa_printf("&b = %p\n", &b);
t = _mesa_NewHashTable();
_mesa_HashInsert(t, 501, &a);
_mesa_HashInsert(t, 10, &c);
_mesa_HashInsert(t, 0xfffffff8, &b);
_mesa_HashPrint(t);
_mesa_printf("Find 501: %p\n", _mesa_HashLookup(t,501));
_mesa_printf("Find 1313: %p\n", _mesa_HashLookup(t,1313));
_mesa_printf("Find block of 100: %d\n", _mesa_HashFindFreeKeyBlock(t, 100));
_mesa_DeleteHashTable(t);
return 0;
}
#endif