fix the Array#hash since its method had returned just size of array

NSArray.m

@@ -1458,32 +1458,29 @@
     return values;
 }
 
-// A very naive hashing function for arrays, which hashes the array's length,
-// then first and last elements (in case the array has more than 4 elements).
-// We cannot rely on the CoreFoundation hashing function for arrays as it's
-// simply returning the number of elements, and can trigger huge performance
-// problems when using same-sized arrays as keys in Hash objects.
-unsigned long
-rb_ary_hash(VALUE ary)
+static unsigned long
+recursive_hash(VALUE ary, VALUE dummy, int recur)
 {
-    const long len = RARRAY_LEN(ary);
-    unsigned long hash = 0;
-    if (len > 0) {
-	VALUE elem = RARRAY_AT(ary, 0);
-	if (elem == ary) {
-	    // recursive array
-	    return (unsigned long)rb_cRubyArray;
-	}
-	hash += rb_hash_code(elem);
-	if (len > 4) {
-	    elem = RARRAY_AT(ary, len - 1);
-	    if (elem == ary) {
-		// recursive array
-		return (unsigned long)rb_cRubyArray;
-	    }
-	    hash = (hash >> 3) ^ rb_hash_code(elem);
+    long i;
+    st_index_t h;
+    VALUE n;
+
+    h = rb_hash_start(RARRAY_LEN(ary));
+    if (recur) {
+	h = rb_hash_uint(h, NUM2LONG(rb_hash(rb_cArray)));
+    }
+    else {
+	for (i=0; i<RARRAY_LEN(ary); i++) {
+	    n = rb_hash(RARRAY_PTR(ary)[i]);
+	    h = rb_hash_uint(h, NUM2LONG(n));
 	}
-	hash += len;
     }
-    return hash;
+    h = rb_hash_end(h);
+    return h;
+}
+
+unsigned long
+rb_ary_hash(VALUE ary)
+{
+    return rb_exec_recursive_outer(recursive_hash, ary, 0);
 }

array.c

@@ -2587,6 +2587,20 @@ rary_eql_fast(rb_ary_t *ary1, rb_ary_t *ary2)
     return rb_exec_recursive(recursive_eql_fast, (VALUE)ary1, (VALUE)ary2);
 }
 
+/*
+ *  call-seq:
+ *     ary.hash   -> fixnum
+ *
+ *  Compute a hash-code for this array. Two arrays with the same content
+ *  will have the same hash code (and will compare using <code>eql?</code>).
+ */
+
+static VALUE
+rary_hash(VALUE ary, SEL sel)
+{
+    return LONG2FIX(rb_ary_hash(ary));
+}
+
 /*
  *  call-seq:
  *     array.include?(obj)   -> true or false
@@ -3790,6 +3804,7 @@ Init_Array(void)
     rb_objc_define_method(rb_cRubyArray, "inspect", rary_inspect, 0);
     rb_objc_define_method(rb_cRubyArray, "==", rary_equal, 1);
     rb_objc_define_method(rb_cRubyArray, "eql?", rary_eql, 1);
+    rb_objc_define_method(rb_cRubyArray, "hash", rary_hash, 0);
     rb_objc_define_method(rb_cRubyArray, "[]", rary_aref, -1);
     rb_objc_define_method(rb_cRubyArray, "[]=", rary_aset, -1);
     rb_objc_define_method(rb_cRubyArray, "at", rary_at, 1);