CODEWITHSUNDEEP
javaarraysbyte
ssk
ssk

Reputation: 9255

Assign a String to byte and specify string length at the start on Java

I would like to assign a String data to the byte array and also put a 4-byte String data length at the start. What is the best way to accomplish? I need this for transmitting the byte data over the socket connection. Server side reads as many bytes mentioned at the start.

Is there a better way of doing this?

private byte[] getDataSendBytes(String data) {
    int numberOfDataBytes = data.getBytes().length;

    ByteBuffer bb = ByteBuffer.allocate(HEADER_LENGTH_BYTES);
    bb.putInt(numberOfDataBytes);
    byte[] headerBytes = bb.array();
    byte[] dataBytes = data.getBytes();

    // create a Datagram packet
    byte[] sendDataBytes = new byte[HEADER_LENGTH_BYTES + dataBytes.length];

    System.arraycopy(headerBytes, 0, sendDataBytes, 0, headerBytes.length);
    System.arraycopy(dataBytes, 0, sendDataBytes, headerBytes.length,
            dataBytes.length);
    return sendDataBytes;
}

Upvotes: 0

Views: 128

Answers (1)

Peter Lawrey
Peter Lawrey

Reputation: 533530

I would use either DataOutputStream 

public byte[] getDataSendBytes(String text) {
    ByteArrayOutputStream baos = new ByteArrayOutputStream();
    try {
        new DataOutputStream(baos).writeUTF(text);
    } catch (IOException e) {
        throw new AssertionError(e);
    }
    return baos.toByteArray();
}

or ByteBuffer for control of the length type and endianess.

public byte[] getDataSendBytes(String text) {
    try {
        byte[] bytes = text.getBytes("UTF-8");
        ByteBuffer bb = ByteBuffer.allocate(4 + bytes.length).order(ByteOrder.LITTLE_ENDIAN);
        bb.putInt(bytes.length);
        bb.put(bytes);
        return bb.array();
    } catch (UnsupportedEncodingException e) {
        throw new AssertionError(e);
    }
}

or for performance, reuse the ByteBuffer and assume a ISO-8859-1 character encoding

// GC-less method.
public void writeAsciiText(ByteBuffer bb, String text) {
    assert text.length() < (1 << 16);
    bb.putShort((short) text.length());
    for(int i=0;i<text.length();i++)
        bb.put((byte) text.charAt(i));
}

Upvotes: 1

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