src/main/java/com/bazaarvoice/jackson/rison/RisonGenerator.java
private int _prependOrWrite(char[] buffer, int ptr, char esc)
            throws IOException, JsonGenerationException
    {
        if (ptr > 0) { // fits, just prepend
            buffer[--ptr] = esc;
        } else { // won't fit, write
            _writer.write(esc);
        }
        return ptr;
    }
private int _prependOrWrite(char[] buffer, int ptr, char esc)
            throws IOException, JsonGenerationException
    {
        if (ptr > 0) { // fits, just prepend
            buffer[--ptr] = esc;
        } else { // won't fit, write
            _writer.write(esc);
        }
        return ptr;
    }
Method called to try to either prepend character escape at front of
given buffer; or if not possible, to write it out directly.

@return Pointer to start of prepended entity (if prepended); or 'ptr'
if not.