Use FileUtils to validate FAT filenames.

Bug: 18512473
Change-Id: I686c7c3487f789dc0437513fbc6fed54dc62721f

src/com/android/providers/downloads/Helpers.java

@@ -214,7 +214,7 @@ public class Helpers {
 
         // The VFAT file system is assumed as target for downloads.
         // Replace invalid characters according to the specifications of VFAT.
-        filename = replaceInvalidVfatCharacters(filename);
+        filename = FileUtils.buildValidFatFilename(filename);
 
         return filename;
     }
@@ -665,53 +665,4 @@ public class Helpers {
                     (c >= '0' && c <= '9');
         }
     }
-
-    /**
-     * Replace invalid filename characters according to
-     * specifications of the VFAT.
-     * @note Package-private due to testing.
-     */
-    private static String replaceInvalidVfatCharacters(String filename) {
-        final char START_CTRLCODE = 0x00;
-        final char END_CTRLCODE = 0x1f;
-        final char QUOTEDBL = 0x22;
-        final char ASTERISK = 0x2A;
-        final char SLASH = 0x2F;
-        final char COLON = 0x3A;
-        final char LESS = 0x3C;
-        final char GREATER = 0x3E;
-        final char QUESTION = 0x3F;
-        final char BACKSLASH = 0x5C;
-        final char BAR = 0x7C;
-        final char DEL = 0x7F;
-        final char UNDERSCORE = 0x5F;
-
-        StringBuffer sb = new StringBuffer();
-        char ch;
-        boolean isRepetition = false;
-        for (int i = 0; i < filename.length(); i++) {
-            ch = filename.charAt(i);
-            if ((START_CTRLCODE <= ch &&
-                ch <= END_CTRLCODE) ||
-                ch == QUOTEDBL ||
-                ch == ASTERISK ||
-                ch == SLASH ||
-                ch == COLON ||
-                ch == LESS ||
-                ch == GREATER ||
-                ch == QUESTION ||
-                ch == BACKSLASH ||
-                ch == BAR ||
-                ch == DEL){
-                if (!isRepetition) {
-                    sb.append(UNDERSCORE);
-                    isRepetition = true;
-                }
-            } else {
-                sb.append(ch);
-                isRepetition = false;
-            }
-        }
-        return sb.toString();
-    }
 }