From 1bd5c48c3a7842006d8ba66af02b618fb2ef000c Mon Sep 17 00:00:00 2001
From: "brendan%mozilla.org" <brendan%mozilla.org>
Date: Thu, 24 Feb 2005 05:24:26 +0000
Subject: [PATCH] Implement specialized Deutsch-Schorr-Waite under js_MarkXML
 to avoid stack overflow (280844, r=igor, sr=shaver).

---
 js/src/jsxml.c | 151 +++++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 127 insertions(+), 24 deletions(-)

diff --git a/js/src/jsxml.c b/js/src/jsxml.c
index f635765645c4..b83c21c90b8d 100644
--- a/js/src/jsxml.c
+++ b/js/src/jsxml.c
@@ -6920,40 +6920,143 @@ js_NewXML(JSContext *cx, JSXMLClass xml_class)
     return xml;
 }
 
+/*
+ * Code factored from js_MarkXML for use by xml_DeutschScorrWaite, see below.
+ * All things marked here cannot lead to overlong lists (mark stack overflow).
+ */
+static void
+xml_mark_tail(JSContext *cx, JSXML *xml, void *arg)
+{
+    XMLArrayTrim(&xml->xml_kids);
+
+    if (xml->xml_class == JSXML_CLASS_LIST) {
+        if (xml->xml_target)
+            js_MarkXML(cx, xml->xml_target, arg);
+        if (xml->xml_targetprop)
+            js_MarkXMLQName(cx, xml->xml_targetprop, arg);
+    } else {
+        namespace_mark_vector(cx,
+                              (JSXMLNamespace **) xml->xml_namespaces.vector,
+                              xml->xml_namespaces.length,
+                              arg);
+        XMLArrayTrim(&xml->xml_namespaces);
+
+        xml_mark_vector(cx,
+                        (JSXML **) xml->xml_attrs.vector,
+                        xml->xml_attrs.length,
+                        arg);
+        XMLArrayTrim(&xml->xml_attrs);
+    }
+}
+
+static void
+xml_DeutschSchorrWaite(JSContext *cx, JSXML *xml, void *arg)
+{
+    JSXML *top, *kid;
+    uint8 *flagp;
+    uint32 i, n;
+#ifdef JS_GCMETER
+    JSRuntime *rt = cx->runtime;
+# define GCMETER(x)     x
+#else
+# define GCMETER(x)     /* nothing */
+#endif
+
+    top = NULL;
+    flagp = js_GetGCThingFlags(xml);
+
+down:
+    GCMETER(if (++rt->gcStats.dswdepth > rt->gcStats.maxdswdepth)
+                rt->gcStats.maxdswdepth = rt->gcStats.dswdepth);
+
+    *flagp |= GCF_MARK;
+
+    i = 0;
+    for (;;) {
+        /*
+         * Let (i == n) index xml->parent, not any child in xml->xml_kids.
+         * Use JSXML_LENGTH here and below in case xml is a leaf node whose
+         * parent we are marking non-recursively.  In the case where parent
+         * is being marked, the "kid/down" sense is backwards -- humor me.
+         */
+        for (n = JSXML_LENGTH(xml); i <= n; i++) {
+            if (i < n) {
+                kid = XMLARRAY_MEMBER(&xml->xml_kids, i, JSXML);
+            } else {
+                kid = xml->parent;
+                if (!kid)
+                    continue;
+            }
+
+            flagp = js_GetGCThingFlags(kid);
+            if (*flagp & GCF_MARK)
+                continue;
+
+            /*
+             * Don't descend if a for..in loop is enumerating xml's kids, i.e.
+             * if xml has kids and its xml_kids.cursors member is non-null.
+             */
+            if (JSXML_HAS_KIDS(kid) &&
+                (JSXML_HAS_VALUE(xml) || !xml->xml_kids.cursors)) {
+                if (i < n)
+                    XMLARRAY_SET_MEMBER(&xml->xml_kids, i, top);
+                else
+                    xml->parent = top;
+                if (JSXML_HAS_KIDS(xml))
+                    xml->xml_kids.cursors = (JSXMLArrayCursor *) i;
+                top = xml;
+                xml = kid;
+                goto down;
+            }
+
+            js_MarkXML(cx, kid, arg);
+        }
+
+        /* If we are back at the root (or we never left it), we're done. */
+        GCMETER(rt->gcStats.dswdepth--);
+        xml->xml_kids.cursors = NULL;
+        if (!top)
+            return;
+
+        /* Time to go back up the spanning tree. */
+        GCMETER(rt->gcStats.dswup++);
+        i = JSXML_HAS_KIDS(top) ? JS_PTR_TO_INT32(top->xml_kids.cursors) : 0;
+        if (i < JSXML_LENGTH(top)) {
+            kid = XMLARRAY_MEMBER(&top->xml_kids, i, JSXML);
+            XMLARRAY_SET_MEMBER(&top->xml_kids, i, xml);
+        } else {
+            JS_ASSERT(i == JSXML_LENGTH(top));
+            kid = top->parent;
+            top->parent = xml;
+        }
+        xml = top;
+        top = kid;
+        i++;
+    }
+#undef GCMETER
+}
+
 void
 js_MarkXML(JSContext *cx, JSXML *xml, void *arg)
 {
+    int stackDummy;
+
     JS_MarkGCThing(cx, xml->object, js_object_str, arg);
-    JS_MarkGCThing(cx, xml->parent, js_xml_parent_str, arg);
     JS_MarkGCThing(cx, xml->name, js_name_str, arg);
-
-    if (JSXML_HAS_VALUE(xml)) {
-        JS_MarkGCThing(cx, xml->xml_value, "value", arg);
+    if (!JS_CHECK_STACK_SIZE(cx, stackDummy)) {
+        xml_DeutschSchorrWaite(cx, xml, arg);
     } else {
-        xml_mark_vector(cx,
-                        (JSXML **) xml->xml_kids.vector,
-                        xml->xml_kids.length,
-                        arg);
-        XMLArrayTrim(&xml->xml_kids);
+        JS_MarkGCThing(cx, xml->parent, js_xml_parent_str, arg);
 
-        if (xml->xml_class == JSXML_CLASS_LIST) {
-            if (xml->xml_target)
-                js_MarkXML(cx, xml->xml_target, arg);
-            if (xml->xml_targetprop)
-                js_MarkXMLQName(cx, xml->xml_targetprop, arg);
+        if (JSXML_HAS_VALUE(xml)) {
+            JS_MarkGCThing(cx, xml->xml_value, "value", arg);
         } else {
-            namespace_mark_vector(cx,
-                                  (JSXMLNamespace **)
-                                  xml->xml_namespaces.vector,
-                                  xml->xml_namespaces.length,
-                                  arg);
-            XMLArrayTrim(&xml->xml_namespaces);
-
             xml_mark_vector(cx,
-                            (JSXML **) xml->xml_attrs.vector,
-                            xml->xml_attrs.length,
+                            (JSXML **) xml->xml_kids.vector,
+                            xml->xml_kids.length,
                             arg);
-            XMLArrayTrim(&xml->xml_attrs);
+
+            xml_mark_tail(cx, xml, arg);
         }
     }
 }