no code changes, only comments to make sense of what is going on

git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@271895 13f79535-47bb-0310-9956-ffa450edef68

src/main/org/apache/tools/ant/ProjectHelper.java

@@ -438,25 +438,36 @@ public class ProjectHelper {
      *                           <code>${</code> without a closing 
      *                           <code>}</code>
      */
-    public static void parsePropertyString(String value, Vector fragments, Vector propertyRefs) 
+    public static void parsePropertyString(String value, Vector fragments, Vector propertyRefs)
         throws BuildException {
         int prev = 0;
         int pos;
+        //search for the next instance of $ from the 'prev' position
         while ((pos = value.indexOf("$", prev)) >= 0) {
+
+            //if there was any text before this, add it as a fragment
+            //TODO, this check could me modified to go if pos>prev;
+            //seems like this current version could stick empty strings
+            //into the list
             if (pos > 0) {
                 fragments.addElement(value.substring(prev, pos));
             }
-
-            if (pos == (value.length() - 1)) {
+            //if we are at the end of the string, we tack on a $
+            //then move past it
+            if( pos == (value.length() - 1)) {
                 fragments.addElement("$");
                 prev = pos + 1;
-            } else if (value.charAt(pos + 1) != '{' ) {
+            }
+            //peek ahead to see if the next char is a property or not
+            else if (value.charAt(pos + 1) != '{' ) {
+                //not a property: insert the char as a literal
                 fragments.addElement(value.substring(pos + 1, pos + 2));
                 prev = pos + 2;
             } else {
+                //property found, extract its name or bail on a typo
                 int endName = value.indexOf('}', pos);
                 if (endName < 0) {
-                    throw new BuildException("Syntax error in property: " 
+                    throw new BuildException("Syntax error in property: "
                                                  + value );
                 }
                 String propertyName = value.substring(pos + 2, endName);
@@ -465,9 +476,11 @@ public class ProjectHelper {
                 prev = endName + 1;
             }
         }
-
+        //no more $ signs found
+        //if there is any tail to the file, append it
         if (prev < value.length()) {
             fragments.addElement(value.substring(prev));
         }
     }
+//end class
 }