Re: Reading a C struct in java

Mark <i@dontgetlotsofspamanymore.invalid>
Wed, 30 Sep 2009 16:48:21 +0100
On Wed, 30 Sep 2009 10:44:46 +0100, RedGrittyBrick
<RedGrittyBrick@spamweary.invalid> wrote:

Mark wrote:

On Tue, 29 Sep 2009 11:33:29 +0200, Lothar Kimmeringer
<> wrote:

Mark wrote:

I am writing an app in java which reads data from a socket from a C
language program. The data is encoded as a C struct of char arrays
something like this;

typedef struct {
    char type[1];
    char length[6];
    char acknowledge[1];
    char duplicate[1];
} type_t;

How can I decode a structure like this in Java without using JNI (a


The data arrives to my code in already in a byte array.

I guess I want to know if there is an easy way to map the C structure
to a java class or whether I will have to dissect the byte array
completely manually.

Someone please put me out of my misery, I'm missing something obvious,
why can't Mark do something like

import java.util.Arrays;

public class DecodeStruct {
    public static void main(String[] args) {

        char[] struct = {'t','0','0','0','0','2','1','N','A'};

        Foo foo = new Foo(struct);

        System.out.println("length is " + foo.getLengthAsString());

class Foo {
    private char type;
    private char[] length;
    private char duplicate;
    private char acknowledge;

    Foo (char[] struct) {
        type = struct[0];
        length = Arrays.copyOfRange(struct, 1, 7);
        duplicate = struct[7];
        acknowledge = struct[8];

    public String getLengthAsString() {
        return new String(length);
length is 000021

Yes. Something like this.
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