From 218d1f5e1e2377b237c294e871bd3bfd6abf6633 Mon Sep 17 00:00:00 2001
From: nobu <nobu@b2dd03c8-39d4-4d8f-98ff-823fe69b080e>
Date: Tue, 3 Dec 2013 13:32:24 +0000
Subject: hash.c: same hash value for similar constructs

* hash.c (rb_hash_recursive): make similar (recursive) constructs
  return same hash value.  execute recursively, and rewind to the
  topmost frame with an object which .eql? to the recursive
  object, if recursion is detected.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@43981 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
---
 hash.c | 69 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 67 insertions(+), 2 deletions(-)

(limited to 'hash.c')

diff --git a/hash.c b/hash.c
index 7d27c543d7..a69d99a821 100644
--- a/hash.c
+++ b/hash.c
@@ -48,7 +48,7 @@ rb_hash_freeze(VALUE hash)
 VALUE rb_cHash;
 
 static VALUE envtbl;
-static ID id_hash, id_yield, id_default;
+static ID id_hash, id_yield, id_default, id_recursive_hash;
 
 VALUE
 rb_hash_set_ifnone(VALUE hash, VALUE ifnone)
@@ -76,6 +76,71 @@ rb_any_cmp(VALUE a, VALUE b)
     return !rb_eql(a, b);
 }
 
+struct hash_recursive_args {
+    VALUE (*func)(VALUE, VALUE, int);
+    VALUE obj;
+    VALUE arg;
+};
+
+static VALUE
+call_hash(RB_BLOCK_CALL_FUNC_ARGLIST(tag, data))
+{
+    struct hash_recursive_args *p = (struct hash_recursive_args *)tag;
+    return p->func(p->obj, p->arg, 0);
+}
+
+static VALUE
+rb_hash_recursive(VALUE (*func)(VALUE, VALUE, int), VALUE obj, VALUE arg)
+{
+    VALUE hval;
+    VALUE thread = rb_thread_current();
+    VALUE recursion_list = rb_thread_local_aref(thread, id_recursive_hash);
+    struct hash_recursive_args args;
+    long len = 0;
+    int state;
+
+    if (!NIL_P(recursion_list) && (len = RARRAY_LEN(recursion_list)) > 0) {
+	VALUE outer;
+	struct hash_recursive_args *outerp;
+	const VALUE *ptr = RARRAY_CONST_PTR(recursion_list);
+	long i = 0;
+	do {
+	    outerp = (struct hash_recursive_args *)(ptr[i] & ~FIXNUM_FLAG);
+	    if (outerp->obj == obj) {
+		len = i;
+		for (i = 0; i < len; ++i) {
+		    outer = RARRAY_AREF(recursion_list, i) & ~FIXNUM_FLAG;
+		    outerp = (struct hash_recursive_args *)outer;
+		    if (rb_eql(obj, outerp->obj)) {
+			rb_throw_obj(outer, outer);
+		    }
+		}
+		outer = RARRAY_AREF(recursion_list, len) & ~FIXNUM_FLAG;
+		outerp = (struct hash_recursive_args *)outer;
+		rb_throw_obj(outer, outer);
+	    }
+	} while (++i < len);
+    }
+    else {
+	recursion_list = rb_ary_new();
+	rb_thread_local_aset(thread, id_recursive_hash, recursion_list);
+    }
+    args.func = func;
+    args.obj = obj;
+    args.arg = arg;
+    rb_ary_push(recursion_list, (VALUE)&args | FIXNUM_FLAG);
+    hval = rb_catch_protect((VALUE)&args, call_hash, (VALUE)&args, &state);
+    if (RARRAY_LEN(recursion_list) >= len) {
+	rb_ary_set_len(recursion_list, len);
+	if (len == 0) rb_thread_local_aset(thread, id_recursive_hash, Qnil);
+    }
+    if (state) rb_jump_tag(state);
+    if (hval == (VALUE)&args) {
+	hval = (*func)(obj, arg, 1);
+    }
+    return hval;
+}
+
 static VALUE
 hash_recursive(VALUE obj, VALUE arg, int recurse)
 {
@@ -89,7 +154,7 @@ hash_recursive(VALUE obj, VALUE arg, int recurse)
 VALUE
 rb_hash(VALUE obj)
 {
-    VALUE hval = rb_exec_recursive_paired(hash_recursive, obj, obj, 0);
+    VALUE hval = rb_hash_recursive(hash_recursive, obj, 0);
   retry:
     switch (TYPE(hval)) {
       case T_FIXNUM:
-- 
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