@JRubyMethod(required = 1, optional = 1)
  @Override
  public IRubyObject seek(IRubyObject[] args) {
    checkOpen();
    checkFinalized();
    long amount = RubyNumeric.num2long(args[0]);
    int whence = Stream.SEEK_SET;
    long newPosition = data.pos;

    if (args.length > 1 && !args[0].isNil()) whence = RubyNumeric.fix2int(args[1]);

    if (whence == Stream.SEEK_CUR) {
      newPosition += amount;
    } else if (whence == Stream.SEEK_END) {
      newPosition = data.internal.getByteList().length() + amount;
    } else if (whence == Stream.SEEK_SET) {
      newPosition = amount;
    } else {
      throw getRuntime().newErrnoEINVALError("invalid whence");
    }

    if (newPosition < 0) throw getRuntime().newErrnoEINVALError("invalid seek value");

    data.pos = newPosition;
    data.eof = false;

    return RubyFixnum.zero(getRuntime());
  }
  @JRubyMethod(name = "pos=", required = 1)
  @Override
  public IRubyObject set_pos(IRubyObject arg) {
    data.pos = RubyNumeric.fix2int(arg);

    if (data.pos < 0) throw getRuntime().newErrnoEINVALError("Invalid argument");

    if (!isEndOfString()) data.eof = false;

    return getRuntime().getNil();
  }
  @SuppressWarnings("fallthrough")
  @JRubyMethod(name = "read", optional = 2)
  @Override
  public IRubyObject read(IRubyObject[] args) {
    checkReadable();

    ByteList buf = null;
    int length = 0;
    int oldLength = 0;
    RubyString originalString = null;

    switch (args.length) {
      case 2:
        originalString = args[1].convertToString();
        // must let original string know we're modifying, so shared buffers aren't damaged
        originalString.modify();
        buf = originalString.getByteList();
      case 1:
        if (!args[0].isNil()) {
          length = RubyNumeric.fix2int(args[0]);
          oldLength = length;

          if (length < 0) {
            throw getRuntime().newArgumentError("negative length " + length + " given");
          }
          if (length > 0 && isEndOfString()) {
            data.eof = true;
            if (buf != null) buf.setRealSize(0);
            return getRuntime().getNil();
          } else if (data.eof) {
            if (buf != null) buf.setRealSize(0);
            return getRuntime().getNil();
          }
          break;
        }
      case 0:
        oldLength = -1;
        length = data.internal.getByteList().length();

        if (length <= data.pos) {
          data.eof = true;
          if (buf == null) {
            buf = new ByteList();
          } else {
            buf.setRealSize(0);
          }

          return makeString(getRuntime(), buf);
        } else {
          length -= data.pos;
        }
        break;
      default:
        getRuntime().newArgumentError(args.length, 0);
    }

    if (buf == null) {
      int internalLength = data.internal.getByteList().length();

      if (internalLength > 0) {
        if (internalLength >= data.pos + length) {
          buf = new ByteList(data.internal.getByteList(), (int) data.pos, length);
        } else {
          int rest = (int) (data.internal.getByteList().length() - data.pos);

          if (length > rest) length = rest;
          buf = new ByteList(data.internal.getByteList(), (int) data.pos, length);
        }
      }
    } else {
      int rest = (int) (data.internal.getByteList().length() - data.pos);

      if (length > rest) length = rest;

      // Yow...this is still ugly
      byte[] target = buf.getUnsafeBytes();
      if (target.length > length) {
        System.arraycopy(
            data.internal.getByteList().getUnsafeBytes(), (int) data.pos, target, 0, length);
        buf.setBegin(0);
        buf.setRealSize(length);
      } else {
        target = new byte[length];
        System.arraycopy(
            data.internal.getByteList().getUnsafeBytes(), (int) data.pos, target, 0, length);
        buf.setBegin(0);
        buf.setRealSize(length);
        buf.setUnsafeBytes(target);
      }
    }

    if (buf == null) {
      if (!data.eof) buf = new ByteList();
      length = 0;
    } else {
      length = buf.length();
      data.pos += length;
    }

    if (oldLength < 0 || oldLength > length) data.eof = true;

    return originalString != null ? originalString : makeString(getRuntime(), buf);
  }