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/* Atoms: Names to numbers HTAtom.c
** =======================
**
** Atoms are names which are given representative pointer values
** so that they can be stored more efficiently, and comparisons
** for equality done more efficiently.
**
** Atoms are kept in a hash table consisting of an array of linked lists.
**
** Authors:
** TBL Tim Berners-Lee, WorldWideWeb project, CERN
** (c) Copyright CERN 1991 - See Copyright.html
**
*/
#include "../config.h"
#define HASH_SIZE 101 /* Tunable */
#include "HTAtom.h"
#include <stdio.h> /* joe@athena, TBL 921019 */
#include "HTUtils.h"
#include "tcp.h"
#ifndef DISABLE_TRACE
extern int www2Trace;
#endif
PRIVATE HTAtom * hash_table[HASH_SIZE];
PRIVATE BOOL initialised = NO;
#ifdef __STDC__
PUBLIC HTAtom * HTAtom_for(char * string)
#else
PUBLIC HTAtom * HTAtom_for(string)
char * string;
#endif
{
int hash;
WWW_CONST char * p;
HTAtom * a;
/* Bug hack. */
if (!string || !*string)
string = strdup ("blargh");
/* First time around, clear hash table
*/
if (!initialised) {
int i;
for (i=0; i<HASH_SIZE; i++)
hash_table[i] = (HTAtom *) 0;
initialised = YES;
}
/* Generate hash function
*/
for(p=string, hash=0; *p; p++) {
hash = (hash * 3 + *p) % HASH_SIZE;
}
/* Search for the string in the list
*/
for (a=hash_table[hash]; a; a=a->next) {
if (0==strcmp(a->name, string)) {
#ifndef DISABLE_TRACE
if (www2Trace) fprintf(stderr,
"HTAtom: Old atom %p for `%s'\n", a, string);
#endif
return a; /* Found: return it */
}
}
/* Generate a new entry
*/
a = (HTAtom *)malloc(sizeof(*a));
if (a == NULL) outofmem(__FILE__, "HTAtom_for");
a->name = (char *)malloc(strlen(string)+1);
if (a->name == NULL) outofmem(__FILE__, "HTAtom_for");
strcpy(a->name, string);
a->next = hash_table[hash]; /* Put onto the head of list */
hash_table[hash] = a;
#ifndef DISABLE_TRACE
if (www2Trace) fprintf(stderr, "HTAtom: New atom %p for `%s'\n", a, string);
#endif
return a;
}
#ifdef __STDC__
PUBLIC HTAtom * HTAtom_exists(char * string)
#else
PUBLIC HTAtom * HTAtom_exists(string)
char * string;
#endif
{
int hash;
WWW_CONST char * p;
HTAtom * a;
if (!initialised) {
return NULL;
}
/* Generate hash function
*/
for(p=string, hash=0; *p; p++) {
hash = (hash * 3 + *p) % HASH_SIZE;
}
/* Search for the string in the list
*/
for (a=hash_table[hash]; a; a=a->next) {
if (0==strcmp(a->name, string)) {
return a; /* Found: return it */
}
}
return NULL;
}