unroff/src/table.c

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2023-02-13 08:45:50 -05:00
/* $Revision: 1.8 $
*/
/* Simple hash tables.
*
* table_new(size) -- returns a new hash table
* table_delete(t) -- frees a table and its entries
* table_store(t,key,keylen,obj,flags)
* -- stores Scheme object and flags under key
* table_lookup(t,key,keylen) -- returns object stored under key, or 0
* table_remove(t,key,keylen) -- removes entry stored under key
*/
#include "unroff.h"
Table *table_new(int size) {
Table *p;
int i;
assert(size > 0);
p = safe_malloc(sizeof *p);
p->data = safe_malloc(size * sizeof(Elem *));
for (i = 0; i < size; i++)
p->data[i] = 0;
p->size = size;
return p;
}
void table_delete(Table *tp) {
int i;
Elem *p, *q;
for (i = 0; i < tp->size; i++)
for (p = tp->data[i]; p; p = q) {
deregister_object(p->obj);
free(p->data);
q = p->next;
free(p);
}
free(tp->data);
free(tp);
}
/* This function ensures that no collisions can occur in tables of
* size 256^N if all keys are of length <= N (for small values of N).
*/
static unsigned long hash(char *key, int size) {
unsigned long i, j;
assert(size > 0);
for (i = j = 0; j < size; j++)
i = i * 256 + (unsigned char)key[j];
return i;
}
void table_store(Table *tp, char *key, int size, Object obj,
unsigned long flags) {
int i = hash(key, size) % tp->size;
Elem *p;
for (p = tp->data[i]; p; p = p->next) {
if (size == p->size && memcmp(key, p->data, size) == 0) break;
}
if (p) {
deregister_object(p->obj);
} else {
p = safe_malloc(sizeof *p);
p->data = safe_malloc(size);
memcpy(p->data, key, size);
p->size = size;
p->next = tp->data[i];
tp->data[i] = p;
}
p->obj = register_object(obj);
p->flags = flags;
}
void table_remove(Table *tp, char *key, int size) {
int i = hash(key, size) % tp->size;
Elem *p, **pp;
for (pp = &tp->data[i]; (p = *pp); pp = &p->next )
if (size == p->size && memcmp(key, p->data, size) == 0) break;
if (p) {
*pp = p->next;
deregister_object(p->obj);
free(p->data);
free(p);
}
}
Elem *table_lookup(Table *tp, char *key, int size) {
int i = hash(key, size) % tp->size;
Elem *p;
for (p = tp->data[i]; p; p = p->next) {
if (size == p->size && memcmp(key, p->data, size) == 0) return p;
}
return 0;
}