/**
* \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;
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");
}
entry = next;
}
}
_glthread_DESTROY_MUTEX(table->Mutex);
_glthread_DESTROY_MUTEX(table->WalkMutex);
}
/**
* 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;
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;
_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;
_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;
/* 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;
}
_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;
}
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;
_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;
/* 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;
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);
_mesa_HashRemove(t, k);
count++;
k = knext;
}
k = _mesa_HashFirstEntry(t);
}
_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