/**
* \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
*
* 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
* THE AUTHORS OR COPYRIGHT HOLDERS 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"
#include "hash_table.h"
/**
* Magic GLuint object name that gets stored outside of the struct hash_table.
*
* The hash table needs a particular pointer to be the marker for a key that
* was deleted from the table, along with NULL for the "never allocated in the
* table" marker. Legacy GL allows any GLuint to be used as a GL object name,
* and we use a 1:1 mapping from GLuints to key pointers, so we need to be
* able to track a GLuint that happens to match the deleted key outside of
* struct hash_table. We tell the hash table to use "1" as the deleted key
* value, so that we test the deleted-key-in-the-table path as best we can.
*/
#define DELETED_KEY_VALUE 1
/**
* The hash table data structure.
*/
struct _mesa_HashTable {
struct hash_table *ht;
GLuint MaxKey; /**< highest key inserted so far */
_glthread_Mutex Mutex; /**< mutual exclusion lock */
_glthread_Mutex WalkMutex; /**< for _mesa_HashWalk() */
GLboolean InDeleteAll; /**< Debug check */
/** Value that would be in the table for DELETED_KEY_VALUE. */
void *deleted_key_data;
};
/** @{
* Mapping from our use of GLuint as both the key and the hash value to the
* hash_table.h API
*
* There exist many integer hash functions, designed to avoid collisions when
* the integers are spread across key space with some patterns. In GL, the
* pattern (in the case of glGen*()ed object IDs) is that the keys are unique
* contiguous integers starting from 1. Because of that, we just use the key
* as the hash value, to minimize the cost of the hash function. If objects
* are never deleted, we will never see a collision in the table, because the
* table resizes itself when it approaches full, and thus key % table_size ==
* key.
*
* The case where we could have collisions for genned objects would be
* something like: glGenBuffers(&a, 100); glDeleteBuffers(&a + 50, 50);
* glGenBuffers(&b, 100), because objects 1-50 and 101-200 are allocated at
* the end of that sequence, instead of 1-150. So far it doesn't appear to be
* a problem.
*/
static bool
uint_key_compare(const void *a, const void *b)
{
return a == b;
}
static uint32_t
uint_hash(GLuint id)
{
return id;
}
static void *
uint_key(GLuint id)
{
return (void *)(uintptr_t) id;
}
/** @} */
/**
* 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) {
table->ht = _mesa_hash_table_create(NULL, uint_key_compare);
_mesa_hash_table_set_deleted_key(table->ht, uint_key(DELETED_KEY_VALUE));
_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)
{
if (_mesa_hash_table_next_entry(table->ht, NULL) != NULL) {
_mesa_problem(NULL, "In _mesa_DeleteHashTable, found non-freed data");
}
_mesa_hash_table_destroy(table->ht, NULL);
_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)
{
const struct hash_entry *entry;
if (key == DELETED_KEY_VALUE)
return table->deleted_key_data;
entry = _mesa_hash_table_search(table->ht, uint_hash(key), uint_key(key));
if (!entry)
return NULL;
return entry->data;
}
/**
* 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)
{
uint32_t hash = uint_hash(key);
struct hash_entry *entry;
_glthread_LOCK_MUTEX(table->Mutex);
if (key > table->MaxKey)
table->MaxKey = key;
if (key == DELETED_KEY_VALUE) {
table->deleted_key_data = data;
} else {
entry = _mesa_hash_table_search(table->ht, hash, uint_key(key));
if (entry) {
entry->data = data;
} else {
_mesa_hash_table_insert(table->ht, hash, uint_key(key), data);
}
}
_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)
{
struct hash_entry *entry;
/* 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);
if (key == DELETED_KEY_VALUE) {
table->deleted_key_data = NULL;
} else {
entry = _mesa_hash_table_search(table->ht, uint_hash(key), uint_key(key));
_mesa_hash_table_remove(table->ht, entry);
}
_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)
{
struct hash_entry *entry;
ASSERT(table);
ASSERT(callback);
_glthread_LOCK_MUTEX(table->Mutex);
table->InDeleteAll = GL_TRUE;
hash_table_foreach(table->ht, entry) {
callback((uintptr_t)entry->key, entry->data, userData);
_mesa_hash_table_remove(table->ht, entry);
}
if (table->deleted_key_data) {
callback(DELETED_KEY_VALUE, table->deleted_key_data, userData);
table->deleted_key_data = 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;
struct hash_entry *entry;
ASSERT(table);
ASSERT(callback);
_glthread_LOCK_MUTEX(table2->WalkMutex);
hash_table_foreach(table->ht, entry) {
callback((uintptr_t)entry->key, entry->data, userData);
}
if (table->deleted_key_data)
callback(DELETED_KEY_VALUE, table->deleted_key_data, userData);
_glthread_UNLOCK_MUTEX(table2->WalkMutex);
}
static void
debug_print_entry(GLuint key, void *data, void *userData)
{
_mesa_debug(NULL, "%u %p\n", key, data);
}
/**
* Dump contents of hash table for debugging.
*
* \param table the hash table.
*/
void
_mesa_HashPrint(const struct _mesa_HashTable *table)
{
if (table->deleted_key_data)
debug_print_entry(DELETED_KEY_VALUE, table->deleted_key_data, NULL);
_mesa_HashWalk(table, debug_print_entry, NULL);
}
/**
* 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) - 1;
_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;
}
}
/**
* Return the number of entries in the hash table.
*/
GLuint
_mesa_HashNumEntries(const struct _mesa_HashTable *table)
{
struct hash_entry *entry;
GLuint count = 0;
if (table->deleted_key_data)
count++;
hash_table_foreach(table->ht, entry)
count++;
return count;
}