Question

I need some help converting a java byte array to a 7-Bit ASCII string. However I am getting 8-bit sequences and need to escape any unreadable character to it’s escaped sequence. Is there a simple solution for this or do I need to build my own?

Seeing that the range of readable characters in 7-bit ASCII is continuous right now I am thinking of the following:

for( int i = 0; i < buffer.length; i++ ) {
   int codePoint = ( (int) buffer[ i ] ) & 255;
   if( 0x20 <= codePoint && codePoint <= 0x7e ) {
      res = res + String( (char) codePoint );
   } else {
     String c = Integer.toHexString( codePoint );
     if( c.length() < 2 ) {
       c = "0" + c;
     }
     res = res + "\\0x" + c;
   }
}

However this seems like an awful lot of work for such a simple conversion. Is there a better way?

Also I might need to do the same to data that has been converted from the byte array to strings. Is there a simpler solution in this case?

Answer 1

  public static String escape(byte[] data) {
    StringBuilder cbuf = new StringBuilder();
    for (byte b : data) {
      if (b >= 0x20 && b <= 0x7e) {
        cbuf.append((char) b);
      } else {
        cbuf.append(String.format("\\0x%02x", b & 0xFF));
      }
    }
    return cbuf.toString();
  }

You can use the format method to pare back the verbiage.

Note that this method is only safe because the ASCII range matches the lower range of the UTF-16 encoding used by Java Strings.