public static String getTextTransferEncoding()

in geronimo-mail_2.1_spec/src/main/java/org/apache/geronimo/mail/util/ASCIIUtil.java [85:147]
44 lines of code
10 McCabe index (conditional complexity)

    public static String getTextTransferEncoding(final InputStream content) throws IOException {

        // for efficiency, we'll read in blocks.
        final BufferedInputStream in = new BufferedInputStream(content, 4096);

        int span = 0;            // span of characters without a line break.
        boolean containsLongLines = false;
        int asciiChars = 0;
        int nonAsciiChars = 0;

        while (true) {
            final int ch = in.read();
            // if we hit an EOF here, go decide what type we've actually found.
            if (ch == -1) {
                break;
            }

            // we found a linebreak.  Reset the line length counters on either one.  We don't
            // really need to validate here.
            if (ch == '\n' || ch == '\r') {
                // hit a line end, reset our line length counter
                span = 0;
            }
            else {
                span++;
                // the text has long lines, we can't transfer this as unencoded text.
                if (span > 998) {
                    containsLongLines = true;
                }

                // non-ascii character, we have to transfer this in binary.
                if (!isAscii(ch)) {
                    nonAsciiChars++;
                }
                else {
                    asciiChars++;
                }
            }
        }

        // looking good so far, only valid chars here.
        if (nonAsciiChars == 0) {
            // does this contain long text lines?  We need to use a Q-P encoding which will
            // be only slightly longer, but handles folding the longer lines.
            if (containsLongLines) {
                return "quoted-printable";
            }
            else {
                // ideal!  Easiest one to handle.
                return "7bit";
            }
        }
        else {
            // mostly characters requiring encoding?  Base64 is our best bet.
            if (nonAsciiChars > asciiChars) {
                return "base64";
            }
            else {
                // Q-P encoding will use fewer bytes than the full Base64.
                return "quoted-printable";
            }
        }
    }