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