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303 lines
6.3 KiB
C
303 lines
6.3 KiB
C
![]() |
/* $Id: hash.c,v 1.4 1998/02/07 14:25:12 brianp Exp $ */
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/*
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* Mesa 3-D graphics library
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* Version: 2.5
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* Copyright (C) 1995-1997 Brian Paul
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Library General Public
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* License as published by the Free Software Foundation; either
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* version 2 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Library General Public License for more details.
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*
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* You should have received a copy of the GNU Library General Public
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* License along with this library; if not, write to the Free
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* Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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/*
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* $Log: hash.c,v $
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* Revision 1.4 1998/02/07 14:25:12 brianp
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* fixed small Sun compiler warning (John Stone)
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*
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* Revision 1.3 1997/09/22 02:33:07 brianp
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* added HashRemove() and HashFirstEntry()
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*
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* Revision 1.2 1997/09/03 13:13:45 brianp
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* added a few pointer casts
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*
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* Revision 1.1 1997/08/22 01:15:10 brianp
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* Initial revision
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*
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*/
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#ifdef PC_HEADER
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#include "all.h"
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#else
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#include <assert.h>
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#include <stdlib.h>
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#include <stdio.h>
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#include "hash.h"
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#endif
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/*
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* Generic hash table. Only dependency is the GLuint datatype.
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*
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* This is used to implement display list and texture object lookup.
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* NOTE: key=0 is illegal.
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*/
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#define TABLE_SIZE 1001
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struct HashEntry {
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GLuint Key;
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void *Data;
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struct HashEntry *Next;
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};
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struct HashTable {
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struct HashEntry *Table[TABLE_SIZE];
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GLuint MaxKey;
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};
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/*
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* Return pointer to a new, empty hash table.
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*/
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struct HashTable *NewHashTable(void)
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{
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return (struct HashTable *) calloc(sizeof (struct HashTable), 1);
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}
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/*
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* Delete a hash table.
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*/
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void DeleteHashTable(struct HashTable *table)
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{
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GLuint i;
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assert(table);
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for (i=0;i<TABLE_SIZE;i++) {
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struct HashEntry *entry = table->Table[i];
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while (entry) {
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struct HashEntry *next = entry->Next;
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free(entry);
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entry = next;
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}
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}
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free(table);
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}
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/*
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* Lookup an entry in the hash table.
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* Input: table - the hash table
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* key - the key
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* Return: user data pointer or NULL if key not in table
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*/
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void *HashLookup(const struct HashTable *table, GLuint key)
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{
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GLuint pos;
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struct HashEntry *entry;
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assert(table);
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assert(key);
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pos = key % TABLE_SIZE;
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entry = table->Table[pos];
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while (entry) {
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if (entry->Key == key) {
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return entry->Data;
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}
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entry = entry->Next;
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}
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return NULL;
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}
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/*
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* Insert into the hash table. If an entry with this key already exists
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* we'll replace the existing entry.
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* Input: table - the hash table
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* key - the key (not zero)
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* data - pointer to user data
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*/
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void HashInsert(struct HashTable *table, GLuint key, void *data)
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{
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/* search for existing entry with this key */
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GLuint pos;
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struct HashEntry *entry;
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assert(table);
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assert(key);
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if (key > table->MaxKey)
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table->MaxKey = key;
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pos = key % TABLE_SIZE;
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entry = table->Table[pos];
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while (entry) {
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if (entry->Key == key) {
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/* replace entry's data */
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entry->Data = data;
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return;
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}
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entry = entry->Next;
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}
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/* alloc and insert new table entry */
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entry = (struct HashEntry *) calloc(sizeof(struct HashEntry), 1);
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entry->Key = key;
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entry->Data = data;
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entry->Next = table->Table[pos];
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table->Table[pos] = entry;
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}
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/*
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* Remove an entry from the hash table.
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* Input: table - the hash table
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* key - key of entry to remove
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*/
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void HashRemove(struct HashTable *table, GLuint key)
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{
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GLuint pos;
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struct HashEntry *entry, *prev;
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assert(table);
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assert(key);
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pos = key % TABLE_SIZE;
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prev = NULL;
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entry = table->Table[pos];
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while (entry) {
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if (entry->Key == key) {
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/* found it! */
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if (prev) {
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prev->Next = entry->Next;
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}
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else {
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table->Table[pos] = entry->Next;
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}
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free(entry);
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return;
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}
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prev = entry;
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entry = entry->Next;
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}
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}
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/*
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* Return the key of the "first" entry in the hash table.
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* By calling this function until zero is returned we can get
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* the keys of all entries in the table.
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*/
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GLuint HashFirstEntry(const struct HashTable *table)
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{
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GLuint pos;
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assert(table);
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for (pos=0; pos < TABLE_SIZE; pos++) {
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if (table->Table[pos])
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return table->Table[pos]->Key;
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}
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return 0;
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}
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/*
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* Dump contents of hash table for debugging.
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*/
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void HashPrint(const struct HashTable *table)
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{
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GLuint i;
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assert(table);
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for (i=0;i<TABLE_SIZE;i++) {
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struct HashEntry *entry = table->Table[i];
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while (entry) {
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printf("%u %p\n", entry->Key, entry->Data);
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entry = entry->Next;
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}
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}
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}
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/*
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* Find a block of 'numKeys' adjacent unused hash keys.
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* Input: table - the hash table
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* numKeys - number of keys needed
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* Return: startint key of free block or 0 if failure
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*/
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GLuint HashFindFreeKeyBlock(const struct HashTable *table, GLuint numKeys)
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{
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GLuint maxKey = ~((GLuint) 0);
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if (maxKey - numKeys > table->MaxKey) {
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/* the quick solution */
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return table->MaxKey + 1;
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}
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else {
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/* the slow solution */
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GLuint freeCount = 0;
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GLuint freeStart = 0;
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GLuint key;
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for (key=0; key!=maxKey; key++) {
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if (HashLookup(table, key)) {
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/* darn, this key is already in use */
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freeCount = 0;
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freeStart = key+1;
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}
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else {
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/* this key not in use, check if we've found enough */
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freeCount++;
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if (freeCount == numKeys) {
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return freeStart;
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}
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}
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}
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/* cannot allocate a block of numKeys consecutive keys */
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return 0;
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}
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}
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#ifdef HASH_TEST_HARNESS
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int main(int argc, char *argv[])
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{
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int a, b, c;
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struct HashTable *t;
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printf("&a = %p\n", &a);
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printf("&b = %p\n", &b);
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t = NewHashTable();
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HashInsert(t, 501, &a);
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HashInsert(t, 10, &c);
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HashInsert(t, 0xfffffff8, &b);
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HashPrint(t);
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printf("Find 501: %p\n", HashLookup(t,501));
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printf("Find 1313: %p\n", HashLookup(t,1313));
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printf("Find block of 100: %d\n", HashFindFreeKeyBlock(t, 100));
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DeleteHashTable(t);
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return 0;
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}
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#endif
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