Fixes #39. Fix errors in FileReader/FileWriter found by MobileSpec.

Address several failures reported by MobileSpec test suite for the
FileReader and FileWriter API.

 - Change the encoding of writes with the FileWriter API to use
   UTF-8 instead of the BlackBerry default of ISO-8859-1

 - Truncate the file to the seek position before writing new
   data in order to match behavior on other platforms.  Return the
   length of the file as the seek position plus data written.

 - Provide stubs for FileReader.readAsBinaryString and
   FileReader.readAsArrayBuffer.

framework/ext/src/com/phonegap/file/FileManager.java

@@ -383,7 +383,10 @@ protected static PluginResult writeFile(String filePath, String data, int positi
         int bytesWritten = 0;
         try {
             // write file data
-            bytesWritten = FileUtils.writeFile(filePath, data.getBytes(), position);
+            // The default String encoding on BB is ISO-8859-1 which causes
+            // issues with extended characters.  Force to UTF-8 to provide
+            // greater character support and match other platforms.
+            bytesWritten = FileUtils.writeFile(filePath, data.getBytes("UTF-8"), position);
             result = new PluginResult(PluginResult.Status.OK, bytesWritten);
         }
         catch (SecurityException e) {

framework/ext/src/com/phonegap/file/FileUtils.java

@@ -125,6 +125,11 @@ public static int writeFile(String filePath, byte[] data, int position)
                     Connector.READ_WRITE);
             if (!fconn.exists()) {
                 fconn.create();
+            } else {
+                // Originally, this did an overwrite in place and did not
+                // truncate.  The truncate was added to match behavior on
+                // other platforms.
+                fconn.truncate(position);
             }
             os = fconn.openOutputStream(position);
             os.write(data);

javascript/file.js

@@ -341,6 +341,34 @@ var FileReader = FileReader || (function() {
         );
     };
 
+    /**
+     * Read file and return data as a binary data.
+     *
+     * @param file          {File} File object containing file properties
+     */
+    FileReader.prototype.readAsBinaryString = function(file) {
+        // TODO - Can't return binary data to browser.
+        if (typeof file.fullPath === "undefined") {
+            this.fileName = file;
+        } else {
+            this.fileName = file.fullPath;
+        }
+    };
+
+    /**
+     * Read file and return data as a binary data.
+     *
+     * @param file          {File} File object containing file properties
+     */
+    FileReader.prototype.readAsArrayBuffer = function(file) {
+        // TODO - Can't return binary data to browser.
+        if (typeof file.fullPath === "undefined") {
+            this.fileName = file;
+        } else {
+            this.fileName = file.fullPath;
+        }
+    };
+
     return FileReader;
 }());
 
@@ -551,11 +579,12 @@ var FileWriter = FileWriter || (function() {
                     return;
                 }
 
-                // new length is maximum of old length, or position plus bytes written
-                me.length = Math.max(me.length, me.position + result);
                 // position always increases by bytes written because file would be extended
                 me.position += result;
 
+                // new length is now where writing finished
+                me.length = me.position;
+
                 // success procedure
                 if (typeof me.onwrite == "function") {
                     event = {"type":"write", "target":me};