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POReading/writing binary structures: how to simplify this code?
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copied!<p>I'm writing a network app, which sends and receives a lot of different kinds of binary packets, and I'm trying to make adding new kinds of packets to my app as easy as possible.</p> <p>For now, I created a <code>Packet</code> class, and I create subclasses of it for each different kind of packet. However, it isn't as clean as it seems; I've ended up with code like this:</p> <pre><code>static class ItemDesc extends Packet { public final int item_id; public final int desc_type; public final String filename; public final String buf; public ItemDesc(Type t, int item_id, int desc_type, String filename, String buf) { super(t); // sets type for use in packet header this.item_id = item_id; this.desc_type = desc_type; this.filename = filename; this.buf = buf; } public ItemDesc(InputStream i) throws IOException { super(i); // reads packet header and sets this.input item_id = input.readInt(); desc_type = input.readByte(); filename = input.readStringWithLength(); buf = input.readStringWithLength(); } public void writeTo(OutputStream o) throws IOException { MyOutputStream dataOutput = new MyOutputStream(); dataOutput.writeInt(item_id); dataOutput.writeByte(desc_type); dataOutput.writeStringWithLength(filename); dataOutput.writeStringWithLength(buf); super.write(dataOutput.toByteArray(), o); } } </code></pre> <p>What bothers me about this approach is the code repetition - I'm repeating the packet structure four times. I'd be glad to avoid this, but I can't see a reasonable way to simplify it.</p> <p>If I was writing in Python I would create a dictionary of all possible field types, and then define new packet types like this:</p> <pre><code>ItemDesc = [('item_id', 'int'), ('desc_type', 'byte'), ...] </code></pre> <p>I suppose that I could do something similar in any functional language. However, I can't see a way to take this approach to Java.</p> <p>(Maybe I'm just too pedantic, or I got used to functional programming and writing code that writes code, so I could avoid any repetition :))</p> <p>Thank you in advance for any suggestions.</p>

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