C Buffer

[lukouko]

I cannot seem to figure this one out. I'm sure the answer is simple, I just cannot get it right. Any help would be appreciated.

I'm using ref-array with node-ffi. I have a c library function which has a signature like this:

var ArrayType = require('ref-array')
var int8Array = ArrayType(ref.types.int8, 10000);
var uint32Ptr = ref.refType('uint32');

var libmylibrary = ffi.Library('libmylibrary', { ...,
  'readData': [ 'int' , [int8Array, uint32Ptr ] ]
});

readData populates the int8Array with a collection of header(uint16) and body (basically structures) pairs. The uint32Ptr argument is populated with the total number of bytes written to the passed int8Array.

My problem is that after I call readData, I cannot figure out how to reinterpret pieces of the int8Array as another data type. I'm fairly confident that the readData call is populating the array correctly.

I need to do something like this:

libmylibrary.readData(int8ArrayInst, uint32PtrInst);

var currentPosi = 0;
var endPosi = uint32PtrInst.deref();
while (currentPosi < endPosi) {
    var bodyLength = howToDoThis.reinterpret(int8ArrayInst, currentPosi, ref.types.uint16);
    currentPosi += ref.types.uint16.size;

    var bodyData = howToDoThis.reinterpret(int8ArrayInst, currentPosi, myTypes.someStruct);
    currentPosi += bodyLength;
}

Is this possible?

[TooTallNate]

So rather than using int8Array type, just specify "pointer" (or "void *"), and pass in a Buffer instance big enough to hold your data (10000 bytes it looks like from the code you've given).

Then, you'd basically use the built-in Buffer read functions (readUint16LE(), etc.) to read out the values, incrementing the position as you go along. You said that the body is basically a struct, so you might be able to utilize ref-struct here as well.

Hope that helps!