* Implement res.pushBuffer(StringBuffer) and res.popBuffer() to get

StringBuffers in and out of the res buffer stack. This is needed for
  efficiently implementing the method described in
  http://dev.helma.org/wiki/Handler+for+rendered+skins/

src/helma/framework/ResponseBean.java

@@ -471,7 +471,7 @@ public class ResponseBean implements Serializable {
      * writes will be redirected to this buffer.
      */
     public void push() {
-        res.pushStringBuffer();
+        res.pushBuffer(null);
     }
 
     /**
@@ -481,23 +481,40 @@ public class ResponseBean implements Serializable {
      * @return ...
      */
     public String pop() {
-        return res.popStringBuffer();
+        return res.popString();
     }
 
     /**
      * Old version for push() kept for compatibility
+     * @deprecated
      */
     public void pushStringBuffer() {
-        res.pushStringBuffer();
+        res.pushBuffer(null);
     }
 
     /**
      * Old version for pop() kept for compatibility
-     *
+     * @deprecated
      * @return ...
      */
     public String popStringBuffer() {
-        return res.popStringBuffer();
+        return res.popString();
+    }
+
+    /**
+     * Push a string buffer on the response object. All further
+     * writes will be redirected to this buffer.
+     * @param buffer the string buffer
+     */
+    public void pushBuffer(StringBuffer buffer) {
+        res.pushBuffer(buffer);
+    }
+
+   /**
+    * Pops the current response buffer without converting it to a string
+    */
+   public StringBuffer popBuffer() {
+        return res.popBuffer();
     }
 
    /**

src/helma/framework/ResponseTrans.java

@@ -199,10 +199,13 @@ public final class ResponseTrans extends Writer implements Serializable {
     }
 
     /**
-     * This is called before a skin is rendered as string (renderSkinAsString) to redirect the output
-     * to a new string buffer.
+     * This is called before a skin is rendered as string
+     * (renderSkinAsString) to redirect the output to a new
+     * string buffer.
+     * @param buf the StringBuffer to use, or null
+     * @return the new StringBuffer instance
      */
-    public synchronized void pushStringBuffer() {
+    public synchronized StringBuffer pushBuffer(StringBuffer buf) {
         if (buffers == null) {
             buffers = new Stack();
         }
@@ -211,33 +214,40 @@ public final class ResponseTrans extends Writer implements Serializable {
             buffers.push(buffer);
         }
 
-        if (cachedBuffer != null) {
+        if (buf != null) {
+            buffer = buf;
+        } else if (cachedBuffer != null) {
             buffer = cachedBuffer;
             cachedBuffer = null;
         } else {
             buffer = new StringBuffer(64);
         }
+        return buffer;
     }
 
     /**
      * Returns the content of the current string buffer and switches back to the previos one.
      */
-    public synchronized String popStringBuffer() {
+    public synchronized String popString() {
+        StringBuffer buf = popBuffer();
+        String str = buf.toString();
+        // store stringbuffer for later reuse
+        buf.setLength(0);
+        cachedBuffer = buf;
+        return str;
+    }
+
+    public synchronized StringBuffer popBuffer() {
         if (buffer == null) {
             throw new RuntimeException("Can't pop string buffer: buffer is null");
         } else if (buffers == null) {
             throw new RuntimeException("Can't pop string buffer: buffer stack is empty");
         }
-
-        String str = buffer.toString();
-
-        buffer.setLength(0);
-        cachedBuffer = buffer;
-
+        // get local reference
+        StringBuffer buf = buffer;
         // restore the previous buffer, which may be null
         buffer = buffers.empty() ? null : (StringBuffer) buffers.pop();
-
-        return str;
+        return buf;
     }
 
     /**

src/helma/framework/core/Skin.java

@@ -226,11 +226,11 @@ public final class Skin {
                 throws RedirectException, UnsupportedEncodingException {
         String result = "";
         ResponseTrans res = reval.getResponse();
-        res.pushStringBuffer();
+        res.pushBuffer(null);
         try {
             render(reval, thisObject, paramObject);
         } finally {
-            result = res.popStringBuffer();
+            result = res.popString();
         }
         return result;
     }
@@ -657,14 +657,12 @@ public final class Skin {
                 } else {
                     if (handler == HANDLER_RESPONSE) {
                         // some special handling for response handler
-                        if ("message".equals(propName)) {
+                        if ("message".equals(propName))
                             value = reval.getResponse().getMessage();
-                        } else if ("error".equals(propName)) {
+                        else if ("error".equals(propName))
                             value = reval.getResponse().getError();
-                        }
-                        if (value != null) {
+                        if (value != null)
                             return filter(reval, value, thisObject, handlerCache);
-                        }
                     }
                     // display error message unless silent failmode is on
                     if ((handlerObject == null || !engine.hasProperty(handlerObject, propName))
@@ -1018,8 +1016,11 @@ public final class Skin {
     }
 }
 
+/**
+ * Exception type for unhandled macros
+ */
 class MacroUnhandledException extends Exception {
     MacroUnhandledException(String name) {
         super(name);
     }
-}
+}