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