Method writeVLong

src/HBaseRpc.java:1237–1298

Writes a variable-length Long value. @param buf The buffer to write to. @param n The value to write.

(final ChannelBuffer buf, long n)

   * @param n The value to write.
   */
  @SuppressWarnings("fallthrough")
  static void writeVLong(final ChannelBuffer buf, long n) {
    // All those values can be encoded on 1 byte.
    if (n >= -112 && n <= 127) {
      buf.writeByte((byte) n);
      return;
    }

    // Set the high bit to indicate that more bytes are to come.
    // Both 0x90 and 0x88 have the high bit set (and are thus negative).
    byte b = (byte) 0x90; // 0b10010000
    if (n < 0) {
      n = ~n;
      b = (byte) 0x88;    // 0b10001000
    }

    {
      long tmp = n;
      do {
        tmp >>>= 8;
        // The first time we decrement `b' here, it's going to move the
        // rightmost `1' in `b' to the right, due to the way 2's complement
        // representation works.  So if `n' is positive, and we started with
        // b = 0b10010000, now we'll have b = 0b10001111, which correctly
        // indicates that `n' is positive (5th bit set) and has 1 byte so far
        // (last 3 bits are set).  If `n' is negative, and we started with
        // b = 0b10001000, now we'll have b = 0b10000111, which correctly
        // indicates that `n' is negative (5th bit not set) and has 1 byte.
        // Each time we keep decrementing this value, the last remaining 3
        // bits are going to change according to the format described above.
        b--;
      } while (tmp != 0);
    }

    buf.writeByte(b);
    switch (b & 0x07) {  // Look at the low 3 bits (the length).
      case 0x00:
        buf.writeLong(n);
        break;
      case 0x01:
        buf.writeInt((int) (n >>> 24));
        buf.writeMedium((int) n);
        break;
      case 0x02:
        buf.writeMedium((int) (n >>> 24));
        buf.writeMedium((int) n);
        break;
      case 0x03:
        buf.writeByte((byte) (n >>> 32));
      case 0x04:
        buf.writeInt((int) n);
        break;
      case 0x05:
        buf.writeMedium((int) n);
        break;
      case 0x06:
        buf.writeShort((short) n);
        break;