1 files changed, 44 insertions, 0 deletions
diff --git a/hash.c b/hash.c
index b51cbdddce..57357269c4 100644
--- a/hash.c
+++ b/hash.c
@@ -1519,6 +1519,49 @@ rb_hash_eql(hash1, hash2)
     return hash_equal(hash1, hash2, Qtrue);
 }
 
+
+rb_hash_hash_i(key, value, hp)
+    VALUE key, value;
+    long *hp;
+{
+    long h = *hp;
+    VALUE n;
+
+    h = (h << 1) | (h<0 ? 1 : 0);
+    n = rb_hash(key);
+    h ^= NUM2LONG(n);
+    h = (h << 1) | (h<0 ? 1 : 0);
+    n = rb_hash(value);
+    h ^= NUM2LONG(n);
+    
+    *hp = h;
+    return ST_CONTINUE;
+}
+
+/*
+ *  call-seq:
+ *     hash.hash   -> fixnum
+ *
+ *  Compute a hash-code for this hash. Two hashes with the same content
+ *  will have the same hash code (and will compare using <code>eql?</code>).
+ */
+
+static VALUE
+rb_hash_hash(hash)
+    VALUE hash;
+{
+    long h;
+    VALUE n;
+
+    h = RHASH(hash)->tbl->num_entries;
+    rb_hash_foreach(hash, rb_hash_hash_i, (VALUE)&h);
+    h = (h << 1) | (h<0 ? 1 : 0);
+    n = rb_hash(RHASH(hash)->ifnone);
+    h ^= NUM2LONG(n);
+
+    return LONG2FIX(h);
+}
+
 static int
 rb_hash_invert_i(key, value, hash)
     VALUE key, value;
@@ -2454,6 +2497,7 @@ Init_Hash()
 
     rb_define_method(rb_cHash,"==", rb_hash_equal, 1);
     rb_define_method(rb_cHash,"eql?", rb_hash_eql, 1);
+    rb_define_method(rb_cHash,"hash", rb_hash_hash, 0);
     rb_define_method(rb_cHash,"[]", rb_hash_aref, 1);
     rb_define_method(rb_cHash,"fetch", rb_hash_fetch, -1);
     rb_define_method(rb_cHash,"[]=", rb_hash_aset, 2);