Best way to read structured binary files with Java

Question

I have to read a binary file in a legacy format with Java.

In a nutshell the file has a header consisting of several integers, bytes and fixed-length char arrays, f

Answer 1

I used Javolution and javastruct, both handles the conversion between bytes and objects.

Javolution provides classes that represent C types. All you need to do is to write a class that describes the C structure. For example, from the C header file,

struct Date {
    unsigned short year;
    unsigned byte month;
    unsigned byte day;
};

should be translated into:

public static class Date extends Struct {
    public final Unsigned16 year = new Unsigned16();
    public final Unsigned8 month = new Unsigned8();
    public final Unsigned8 day   = new Unsigned8();
}

Then call setByteBuffer to initialize the object:

Date date = new Date();
date.setByteBuffer(ByteBuffer.wrap(bytes), 0);

javastruct uses annotation to define fields in a C structure.

@StructClass
public class Foo{

    @StructField(order = 0)
    public byte b;

    @StructField(order = 1)
    public int i;
}

To initialize an object:

Foo f2 = new Foo();
JavaStruct.unpack(f2, b);