hashing: overhaul part 2.

In this commit we feature-complete the seeded hashing
implementation. The *hash-seed* special variable is provided
from which newly created hashes take their seed.  The
make-hash and hash-equal functions get an optional seed
argument. A function called gen-hash-seed is provided for
obtaining a randomized seed.

* hash.c (hash_seed): New macro.
(hash_seed_s): New symbol variable.
(make_seeded_hash): New function, made from make_hash.
(make_hash): Reduced to wrapper around make_seeded_hash.
(hash-equal): Take seed argument.
(gen_hash_seed): New function.
(hash_init): Initialize hash_seed_s and register *hash-seed*
special variable. Re-register make-hash with new optional
parameter, with regard to make_seeded_hash.
Re-register hash-equal with new optional parameter.
Register gen-hash-seed.

* hash.h (make_seeded_hash): Declared.
(hash_equal): Declaration updated.

* txr.1: Documented optional seed arguments of make-hash
and hash-equal. Documented new *hash-seed* variable
and gen-hash-seed function.

1 files changed, 2 insertions, 1 deletions

diff --git a/hash.h b/hash.h
index 61d58424..2b8f70b2 100644
--- a/hash.h
+++ b/hash.h
@@ -28,6 +28,7 @@
 extern val weak_keys_k, weak_vals_k, equal_based_k, eql_based_k, userdata_k;
 
 cnum equal_hash(val obj, int *count, ucnum);
+val make_seeded_hash(val weak_keys, val weak_vals, val equal_based, val seed);
 val make_hash(val weak_keys, val weak_vals, val equal_based);
 val make_similar_hash(val existing);
 val copy_hash(val existing);
@@ -49,7 +50,7 @@ val maphash(val func, val hash);
 val hash_begin(val hash);
 val hash_next(val iter);
 val hash_eql(val obj);
-val hash_equal(val obj);
+val hash_equal(val obj, val seed);
 val hashv(struct args *args);
 val hashl(val args);
 val hash_construct(val hashl_args, val pairs);