How to unpack a c# packed struct in Node.js

Question

We using a private source library written in cpp with a binding in C# with some structs like this for getting the data from the cpp library into c# structs, but the problem is that i don't know how to unpack the CPP Marshalled buffer in Nodej.js :

The struct in C# :

[StructLayout(LayoutKind.Sequential, Pack = 1)]
unsafe public struct TheClass
{
    public byte XXX;
    public int XXX;
    public int XXX;
    public ushort XXX;
    public byte XXX;
    public byte XXX;
    public byte XXX;
    public byte XXX;
    public byte XXX;
    public byte XXX;
    public fixed byte XXX[12];
    public fixed byte XXX[5];
    public short XXX;
}

Thank for your help :)

cdhowie · Accepted Answer · 2018-05-17 15:33:45Z

2

Using the npm struct package:

const TheClass = Struct()
  .word8('XXX')
  .word32Sle('XXX')
  .word32Sle('XXX')
  .word16Ule('XXX')
  .word8('XXX')
  .word8('XXX')
  .word8('XXX')
  .word8('XXX')
  .word8('XXX')
  .word8('XXX')
  .array('XXX', 12, 'word8')
  .array('XXX', 5, 'word8')
  .word16Sle('XXX');

Of course, replace all the XXX with the correct field names.

Then you can use this object to parse the contents of a Buffer object:

TheClass._setBuff(yourBuffer);

// Read the data for field XXX (using a valid name).
var someField = TheClass.get('XXX');

// Or use the proxy object:
var someOtherField = TheClass.fields.XXX;

Using lodash you can write a helper method that will parse and return a copy of the struct's data:

Struct.prototype.parse = function (buffer) {
  const oldBuff = this.buffer();

  this._setBuff(buffer);
  const v = _.cloneDeep(this.fields);

  this._setBuff(oldBuff);

  return v;
};

edited May 17, 2018 at 15:33

answered May 17, 2018 at 15:26

cdhowie

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1 Comment

Nightwolf Over a year ago

Thank is that i needed

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