HexUtil Class — netty Architecture

Source Code

buffer/src/main/java/io/netty/buffer/ByteBufUtil.java lines 1513–1700

    private static final class HexUtil {

        private static final char[] BYTE2CHAR = new char[256];
        private static final char[] HEXDUMP_TABLE = new char[256 * 4];
        private static final String[] HEXPADDING = new String[16];
        private static final String[] HEXDUMP_ROWPREFIXES = new String[65536 >>> 4];
        private static final String[] BYTE2HEX = new String[256];
        private static final String[] BYTEPADDING = new String[16];

        static {
            final char[] DIGITS = "0123456789abcdef".toCharArray();
            for (int i = 0; i < 256; i ++) {
                HEXDUMP_TABLE[ i << 1     ] = DIGITS[i >>> 4 & 0x0F];
                HEXDUMP_TABLE[(i << 1) + 1] = DIGITS[i       & 0x0F];
            }

            int i;

            // Generate the lookup table for hex dump paddings
            for (i = 0; i < HEXPADDING.length; i ++) {
                int padding = HEXPADDING.length - i;
                StringBuilder buf = new StringBuilder(padding * 3);
                for (int j = 0; j < padding; j ++) {
                    buf.append("   ");
                }
                HEXPADDING[i] = buf.toString();
            }

            // Generate the lookup table for the start-offset header in each row (up to 64KiB).
            for (i = 0; i < HEXDUMP_ROWPREFIXES.length; i ++) {
                StringBuilder buf = new StringBuilder(12);
                buf.append(NEWLINE);
                buf.append(Long.toHexString(i << 4 & 0xFFFFFFFFL | 0x100000000L));
                buf.setCharAt(buf.length() - 9, '|');
                buf.append('|');
                HEXDUMP_ROWPREFIXES[i] = buf.toString();
            }

            // Generate the lookup table for byte-to-hex-dump conversion
            for (i = 0; i < BYTE2HEX.length; i ++) {
                BYTE2HEX[i] = ' ' + StringUtil.byteToHexStringPadded(i);
            }

            // Generate the lookup table for byte dump paddings
            for (i = 0; i < BYTEPADDING.length; i ++) {
                int padding = BYTEPADDING.length - i;
                StringBuilder buf = new StringBuilder(padding);
                for (int j = 0; j < padding; j ++) {
                    buf.append(' ');
                }
                BYTEPADDING[i] = buf.toString();
            }

            // Generate the lookup table for byte-to-char conversion
            for (i = 0; i < BYTE2CHAR.length; i ++) {
                if (i <= 0x1f || i >= 0x7f) {
                    BYTE2CHAR[i] = '.';
                } else {
                    BYTE2CHAR[i] = (char) i;
                }
            }
        }

        private static String hexDump(ByteBuf buffer, int fromIndex, int length) {
            checkPositiveOrZero(length, "length");
            if (length == 0) {
              return "";
            }

            int endIndex = fromIndex + length;
            char[] buf = new char[length << 1];

            int srcIdx = fromIndex;
            int dstIdx = 0;
            for (; srcIdx < endIndex; srcIdx ++, dstIdx += 2) {
              System.arraycopy(
                  HEXDUMP_TABLE, buffer.getUnsignedByte(srcIdx) << 1,
                  buf, dstIdx, 2);
            }

            return new String(buf);