Fixing bug 69468. Finally adding support for string nullness to XPConnect. r=jaggernaut@netscape.com, shaver@mozilla.org, sr=jband@netscape.com

content/xul/content/src/nsXULAttributeValue.cpp

@@ -80,7 +80,8 @@ nsresult nsXULAttributeValue::GetValue( nsAWritableString& aResult )
 }
 
 
-nsresult nsXULAttributeValue::SetValue(const nsAReadableString& aValue, PRBool forceAtom)
+nsresult nsXULAttributeValue::SetValue(const nsAReadableString& aValue,
+                                       PRBool forceAtom)
 {   
     nsCOMPtr<nsIAtom> newAtom;
     
@@ -89,7 +90,10 @@ nsresult nsXULAttributeValue::SetValue(const nsAReadableString& aValue, PRBool f
     // atom table: the style system frequently asks for it, and if the
     // table is "unprimed" we see quite a bit of thrashing as the 'id'
     // value is repeatedly added and then removed from the atom table.
-    if ((aValue.Length() <= kMaxAtomValueLength) || forceAtom)
+
+    PRUint32 len = aValue.Length();
+
+    if (len && ((len <= kMaxAtomValueLength) || forceAtom))
     {
         newAtom = getter_AddRefs( NS_NewAtom(aValue) );
     }
@@ -104,10 +108,14 @@ nsresult nsXULAttributeValue::SetValue(const nsAReadableString& aValue, PRBool f
         mValue = (void*)(PRWord(newAtom.get()) | kAtomType);
     }
     else {
-        PRUnichar* str = ToNewUnicode(aValue);
-        if (! str)
-            return NS_ERROR_OUT_OF_MEMORY;
-  
+        PRUnichar* str = nsnull;
+
+        if (len) {
+            str = ToNewUnicode(aValue);
+            if (! str)
+                return NS_ERROR_OUT_OF_MEMORY;
+        }
+
         mValue = str;
     }
 

dom/public/idl/base/domstubs.idl

@@ -45,15 +45,13 @@
 
 inline PRBool DOMStringIsNull(const nsAReadableString& aString)
 {
-  // Null string code goes here.
-
-  return PR_FALSE;
+  return aString.IsVoid();
 }
 
 inline void SetDOMStringToNull(nsAWritableString& aString)
 {
   aString.Truncate();
-  // Set aString to null here.
+  aString.SetIsVoid(PR_TRUE);
 }
 
 %}

js/src/xpconnect/src/xpcconvert.cpp

@@ -290,11 +290,18 @@ XPCConvert::NativeData2JS(XPCCallContext& ccx, jsval* d, const void* s,
                 if(!p)
                     break;
 
-                JSString *str = XPCStringConvert::ReadableToJSString(cx, *p);
-                if(!str)
-                    return JS_FALSE;
+                if(!p->IsVoid()) {
+                    JSString *str =
+                        XPCStringConvert::ReadableToJSString(cx, *p);
+                    if(!str)
+                        return JS_FALSE;
+
+                    *d = STRING_TO_JSVAL(str);
+                }
+
+                // *d is defaulted to JSVAL_NULL so no need to set it
+                // again if p is a "void" string
 
-                *d = STRING_TO_JSVAL(str);
                 break;
             }
 
@@ -535,7 +542,6 @@ XPCConvert::JSData2Native(XPCCallContext& ccx, void* d, jsval s,
         case nsXPTType::T_DOMSTRING:
         {
             static const NS_NAMED_LITERAL_STRING(sEmptyString, "");
-            static const NS_NAMED_LITERAL_STRING(sNullString, "null");
             static const NS_NAMED_LITERAL_STRING(sVoidString, "undefined");
 
             const PRUnichar* chars;
@@ -548,14 +554,7 @@ XPCConvert::JSData2Native(XPCCallContext& ccx, void* d, jsval s,
                chars  = sVoidString.get();
                length = sVoidString.Length();
             }
-            else if(JSVAL_IS_NULL(s))
-            {
-                // XXX We don't yet have a way to represent a null nsAXXXString
-                // XXX Do we *want* to use "null"?
-               chars  = sNullString.get();
-               length = sNullString.Length();
-            }
-            else
+            else if(!JSVAL_IS_NULL(s))
             {
                 str = JS_ValueToString(cx, s);
                 if(!str)
@@ -577,8 +576,6 @@ XPCConvert::JSData2Native(XPCCallContext& ccx, void* d, jsval s,
                 }
             }
 
-            NS_ASSERTION(chars, "I must be really confused");
-
             if(useAllocator)
             {
                 if(str)
@@ -591,13 +588,22 @@ XPCConvert::JSData2Native(XPCCallContext& ccx, void* d, jsval s,
                     // Ask for the shared buffer handle, which will root the
                     // string.
                     if(isNewString && ! wrapper->GetSharedBufferHandle())
-                            return JS_FALSE;
+                        return JS_FALSE;
+
+                    *((nsAReadableString**)d) = wrapper;
+                }
+                else if(JSVAL_IS_NULL(s))
+                {
+                    XPCReadableJSStringWrapper *wrapper =
+                        new XPCReadableJSStringWrapper();
+                    if(!wrapper)
+                        return JS_FALSE;
 
                     *((nsAReadableString**)d) = wrapper;
                 }
                 else
                 {
-                    nsAReadableString *rs = new nsString(chars, length);
+                    nsAReadableString *rs = new nsAutoString(chars, length);
                     if(!rs)
                         return JS_FALSE;
                     *((nsAReadableString**)d) = rs;
@@ -606,7 +612,11 @@ XPCConvert::JSData2Native(XPCCallContext& ccx, void* d, jsval s,
             else
             {
                 nsAWritableString* ws = *((nsAWritableString**)d);
-                ws->Assign(chars);
+
+                if(JSVAL_IS_NULL(s))
+                    ws->SetIsVoid(PR_TRUE);
+                else
+                    ws->Assign(chars);
             }
             return JS_TRUE;
         }

js/src/xpconnect/src/xpcprivate.h

@@ -2212,11 +2212,16 @@ class XPCReadableJSStringWrapper : public nsDependentString
 public:
     XPCReadableJSStringWrapper(JSString *str) :
         nsDependentString(NS_REINTERPRET_CAST(PRUnichar *,
-                                          JS_GetStringChars(str)),
+                                              JS_GetStringChars(str)),
                       JS_GetStringLength(str)),
         mStr(str), mBufferHandle(0), mHandleIsShared(JS_FALSE)
     { }
 
+    XPCReadableJSStringWrapper() :
+        nsDependentString(nsnull, (PRUint32)0), mStr(nsnull),
+        mBufferHandle(nsnull), mHandleIsShared(JS_FALSE)
+    { }
+
     ~XPCReadableJSStringWrapper();
 
     // buffer-handle accessors
@@ -2230,6 +2235,11 @@ public:
         return BufferHandle(JS_TRUE);
     }
 
+    PRBool IsVoid() const
+    {
+        return mStr == nsnull;
+    }
+
 protected:
     struct WrapperBufferHandle :
         public nsSharedBufferHandleWithAllocator<PRUnichar>
@@ -2267,6 +2277,41 @@ protected:
     JSBool              mHandleIsShared;
 };
 
+// "voidable" nsAString implementation
+class XPCVoidableString : public nsAutoString
+{
+public:
+    XPCVoidableString() :
+        nsAutoString(), mIsVoid(PR_FALSE)
+    { }
+
+    char_type* GetWritableFragment(nsWritableFragment<char_type>& aFragment,
+                                   nsFragmentRequest aRequest,
+                                   PRUint32 aOffset)
+    {
+        mIsVoid = PR_FALSE;
+
+        return nsAutoString::GetWritableFragment(aFragment, aRequest, aOffset);
+    }
+
+    PRBool IsVoid() const
+    {
+        return mIsVoid;
+    }
+
+    void SetIsVoid(PRBool aVoid)
+    {
+        if(aVoid && !mIsVoid) {
+            Truncate();
+        }
+
+        mIsVoid = aVoid;
+    }
+
+protected:
+    PRBool mIsVoid;
+};
+
 // readable string conversions, static methods only
 class XPCStringConvert
 {

js/src/xpconnect/src/xpcstring.cpp

@@ -77,6 +77,11 @@ XPCReadableJSStringWrapper::~XPCReadableJSStringWrapper()
 const nsSharedBufferHandle<PRUnichar>*
 XPCReadableJSStringWrapper::BufferHandle(JSBool shared) const
 {
+    if (!mStr) {
+        // This is a "void" string, no buffer handle available
+        return nsnull;
+    }
+
     XPCReadableJSStringWrapper * mutable_this =
         NS_CONST_CAST(XPCReadableJSStringWrapper *, this);
 

js/src/xpconnect/src/xpcwrappednative.cpp

@@ -1750,7 +1750,7 @@ XPCWrappedNative::CallMethod(XPCCallContext& ccx,
                         // Is an 'out' DOMString. Make a new nsAWritableString
                         // now and then continue in order to skip the call to
                         // JSData2Native
-                        if(!(dp->val.p = new nsString()))
+                        if(!(dp->val.p = new XPCVoidableString()))
                         {
                             JS_ReportOutOfMemory(ccx);
                             goto done;

layout/xul/base/src/outliner/src/nsOutlinerBodyFrame.cpp

@@ -172,8 +172,10 @@ nsOutlinerColumn::nsOutlinerColumn(nsIContent* aColElement, nsIFrame* aFrame)
   // Fetch the ID.
   mColElement->GetAttr(kNameSpaceID_None, nsHTMLAtoms::id, mID);
 
-  // Cache the ID as an atom.
-  mIDAtom = getter_AddRefs(NS_NewAtom(mID));
+  // If we have an ID, cache the ID as an atom.
+  if (!mID.IsEmpty()) {
+    mIDAtom = getter_AddRefs(NS_NewAtom(mID));
+  }
 
   nsCOMPtr<nsIStyleContext> styleContext;
   aFrame->GetStyleContext(getter_AddRefs(styleContext));

layout/xul/base/src/tree/src/nsTreeBodyFrame.cpp

@@ -172,8 +172,10 @@ nsOutlinerColumn::nsOutlinerColumn(nsIContent* aColElement, nsIFrame* aFrame)
   // Fetch the ID.
   mColElement->GetAttr(kNameSpaceID_None, nsHTMLAtoms::id, mID);
 
-  // Cache the ID as an atom.
-  mIDAtom = getter_AddRefs(NS_NewAtom(mID));
+  // If we have an ID, cache the ID as an atom.
+  if (!mID.IsEmpty()) {
+    mIDAtom = getter_AddRefs(NS_NewAtom(mID));
+  }
 
   nsCOMPtr<nsIStyleContext> styleContext;
   aFrame->GetStyleContext(getter_AddRefs(styleContext));

xpcom/ds/nsAtomTable.cpp

@@ -68,7 +68,7 @@ AtomTableGetKey(PLDHashTable *table, PLDHashEntryHdr *entry)
 PR_STATIC_CALLBACK(PLDHashNumber)
 AtomTableHashKey(PLDHashTable *table, const void *key)
 {
-  return nsCRT::HashCode(NS_STATIC_CAST(const PRUnichar*,key));
+  return nsCRT::HashCode(NS_STATIC_CAST(const PRUnichar*, key));
 }
 
 PR_STATIC_CALLBACK(PRBool)
@@ -273,6 +273,12 @@ static AtomTableEntry* GetAtomHashEntry(const nsAString& aString)
 
 NS_COM nsIAtom* NS_NewAtom( const nsAString& aString )
 {
+  if (aString.IsEmpty()) {
+    NS_ERROR("Atom requested for empty string!");
+
+    return nsnull;
+  }
+
   AtomTableEntry *he = GetAtomHashEntry(aString);
   AtomImpl* atom = he->mAtom;