#include "system.h"
#include "pointer-set.h"
-/* A pointer sets is represented as a simple open-addressing hash
+/* A pointer set is represented as a simple open-addressing hash
table. Simplifications: The hash code is based on the value of the
pointer, not what it points to. The number of buckets is always a
power of 2. Null pointers are a reserved value. Deletion is not
- supported. There is no mechanism for user control of hash
- function, equality comparison, initial size, or resizing policy.
-*/
+ supported (yet). There is no mechanism for user control of hash
+ function, equality comparison, initial size, or resizing policy. */
struct pointer_set_t
{
}
}
-/* Subroutine of pointer_set_insert. Inserts P into an empty
- element of SLOTS, an array of length N_SLOTS. Returns nonzero
- if P was already present in N_SLOTS. */
-static int
+/* Subroutine of pointer_set_insert. Return the insertion slot for P into
+ an empty element of SLOTS, an array of length N_SLOTS. */
+static inline size_t
insert_aux (void *p, void **slots, size_t n_slots, size_t log_slots)
{
size_t n = hash1 (p, n_slots, log_slots);
while (true)
{
- if (slots[n] == p)
- return 1;
- else if (slots[n] == 0)
- {
- slots[n] = p;
- return 0;
- }
+ if (slots[n] == p || slots[n] == 0)
+ return n;
else
{
++n;
int
pointer_set_insert (struct pointer_set_t *pset, void *p)
{
- if (insert_aux (p, pset->slots, pset->n_slots, pset->log_slots))
- return 1;
-
- /* We've inserted a new element. Expand the table if necessary to keep
- the load factor small. */
- ++pset->n_elements;
+ size_t n;
+
+ /* For simplicity, expand the set even if P is already there. This can be
+ superfluous but can happen at most once. */
if (pset->n_elements > pset->n_slots / 4)
{
size_t new_log_slots = pset->log_slots + 1;
size_t i;
for (i = 0; i < pset->n_slots; ++i)
- {
- if (pset->slots[i])
- insert_aux (pset->slots[i], new_slots, new_n_slots, new_log_slots);
+ {
+ void *value = pset->slots[i];
+ n = insert_aux (value, new_slots, new_n_slots, new_log_slots);
+ new_slots[n] = value;
}
XDELETEVEC (pset->slots);
pset->slots = new_slots;
}
+ n = insert_aux (p, pset->slots, pset->n_slots, pset->log_slots);
+ if (pset->slots[n])
+ return 1;
+
+ pset->slots[n] = p;
+ ++pset->n_elements;
return 0;
}
+
+/* Pass each pointer in PSET to the function in FN, together with the fixed
+ parameter DATA. If FN returns false, the iteration stops. */
+
+void pointer_set_traverse (struct pointer_set_t *pset,
+ bool (*fn) (void *, void *), void *data)
+{
+ size_t i;
+ for (i = 0; i < pset->n_slots; ++i)
+ if (pset->slots[i] && !fn (pset->slots[i], data))
+ break;
+}
+
+\f
+/* A pointer map is represented the same way as a pointer_set, so
+ the hash code is based on the address of the key, rather than
+ its contents. Null keys are a reserved value. Deletion is not
+ supported (yet). There is no mechanism for user control of hash
+ function, equality comparison, initial size, or resizing policy. */
+
+struct pointer_map_t
+{
+ size_t log_slots;
+ size_t n_slots; /* n_slots = 2^log_slots */
+ size_t n_elements;
+
+ void **keys;
+ void **values;
+};
+
+/* Allocate an empty pointer map. */
+struct pointer_map_t *
+pointer_map_create (void)
+{
+ struct pointer_map_t *result = XNEW (struct pointer_map_t);
+
+ result->n_elements = 0;
+ result->log_slots = 8;
+ result->n_slots = (size_t) 1 << result->log_slots;
+
+ result->keys = XCNEWVEC (void *, result->n_slots);
+ result->values = XCNEWVEC (void *, result->n_slots);
+ return result;
+}
+
+/* Reclaims all memory associated with PMAP. */
+void pointer_map_destroy (struct pointer_map_t *pmap)
+{
+ XDELETEVEC (pmap->keys);
+ XDELETEVEC (pmap->values);
+ XDELETE (pmap);
+}
+
+/* Returns a pointer to the value to which P maps, if PMAP contains P. P
+ must be nonnull. Return NULL if PMAP does not contain P.
+
+ Collisions are resolved by linear probing. */
+void **
+pointer_map_contains (struct pointer_map_t *pmap, void *p)
+{
+ size_t n = hash1 (p, pmap->n_slots, pmap->log_slots);
+
+ while (true)
+ {
+ if (pmap->keys[n] == p)
+ return &pmap->values[n];
+ else if (pmap->keys[n] == 0)
+ return NULL;
+ else
+ {
+ ++n;
+ if (n == pmap->n_slots)
+ n = 0;
+ }
+ }
+}
+
+/* Inserts P into PMAP if it wasn't already there. Returns a pointer
+ to the value. P must be nonnull. */
+void **
+pointer_map_insert (struct pointer_map_t *pmap, void *p)
+{
+ size_t n;
+
+ /* For simplicity, expand the map even if P is already there. This can be
+ superfluous but can happen at most once. */
+ if (pmap->n_elements > pmap->n_slots / 4)
+ {
+ size_t new_log_slots = pmap->log_slots + 1;
+ size_t new_n_slots = pmap->n_slots * 2;
+ void **new_keys = XCNEWVEC (void *, new_n_slots);
+ void **new_values = XCNEWVEC (void *, new_n_slots);
+ size_t i;
+
+ for (i = 0; i < pmap->n_slots; ++i)
+ if (pmap->keys[i])
+ {
+ void *key = pmap->keys[i];
+ n = insert_aux (key, new_keys, new_n_slots, new_log_slots);
+ new_keys[n] = key;
+ new_values[n] = pmap->values[i];
+ }
+
+ XDELETEVEC (pmap->keys);
+ XDELETEVEC (pmap->values);
+ pmap->n_slots = new_n_slots;
+ pmap->log_slots = new_log_slots;
+ pmap->keys = new_keys;
+ pmap->values = new_values;
+ }
+
+ n = insert_aux (p, pmap->keys, pmap->n_slots, pmap->log_slots);
+ if (!pmap->keys[n])
+ {
+ ++pmap->n_elements;
+ pmap->keys[n] = p;
+ }
+
+ return &pmap->values[n];
+}
+
+/* Pass each pointer in PMAP to the function in FN, together with the pointer
+ to the value and the fixed parameter DATA. If FN returns false, the
+ iteration stops. */
+
+void pointer_map_traverse (struct pointer_map_t *pmap,
+ bool (*fn) (void *, void **, void *), void *data)
+{
+ size_t i;
+ for (i = 0; i < pmap->n_slots; ++i)
+ if (pmap->keys[i] && !fn (pmap->keys[i], &pmap->values[i], data))
+ break;
+}
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