Question

I have a C function that takes an array of structures as an argument, and I want to call this function from Java by way of SWIG, but the documentation seems quite murky on this subject and I can’t find any stackoverflow questions that directly address this case. Here is an example that is similar to what I want to do:

C header file:

typedef struct {
  int timeToPayment;
  double paymentAmount;
} Payment;
double presentValue(Payment *payments, int nPayments);

Java code snippet:

...
Class Payment {
  public int timeToPayment;
  public double paymentAmount;
};
...
Payment[] payments = new Payment[3];
payments[0].timeToPayment = 30;
payments[0].paymentAmount = 1.0;
payments[1].timeToPayment = 60;
payments[1].paymentAmount = 2.0;
payments[2].timeToPayment = 90;
payments[2].paymentAmount = 3.0;
double pv = CLIBRARY.presentValue(payments);
// also acceptable: double pv = CLIBRARY.presentValue(payments, payments.length);

How can this be accomplished?

EDIT: to provide additional information, SWIG is a requirement because it is already used to incorporate simpler interfaces into the same Java codebase and supporting more than one approach for solving this problem will not be acceptable. Also, the signature of the C functions can’t be changed and this example has been extremely simplified; the actual problem involves multiple C functions with signatures requiring arrays of structs (multiple arrays of different structs in some cases) and some of the structs are quite large, so I would really, really prefer not to have to break them up into equivalent arrays of primitive types.

Answer 1

In the end, I was unable to make this work (although I’m not saying that it isn’t possible to do), and I created a translation layer in C that wraps everything into a single struct before passing it through.