// CCode with documentation
 
#include <stdio.h>
 
#include "JavaCode.h"  // Required header for JNI
 
// FORTRAN routines have to be prototyped as extern, and parameters are
// passed by reference.  Note also that for g77 the function name in C by
// default must be prefixed by a "_".
 
extern int sumsquaredf_(int *, int []);
 
// When calling C code from Java, main() must be replaced by a declaration
// similar to below, where the function name is given by "Java_" + the name
// of the class in the Java code that calls this C code, in this case
// "JavaCode", + "_" + the name of this C function called from Java, in this
// case "sumsquaredc".  This is followed by at least two parameters as below,
// plus possibly more if more are required.
 
JNIEXPORT jint JNICALL Java_JavaCode_sumsquaredc(JNIEnv *env,
                       jobject obj, jintArray ja) {
 
//  Data from any additional parameters are passed via special pointers as
//  shown here.
 
    jsize n = (*env)->GetArrayLength(env, ja);
    jint *a = (*env)->GetIntArrayElements(env, ja, 0);
    int i,result;
 
    printf("-- We are now in the C program CCode --\n");
    printf("Print contents of array a[] copied from arr[] in Java\n");
    for (i=0; i<n; i++)
        printf("%2d %5d\n",i,a[i]);
 
    printf("Call the FORTRAN code\n");
 
//  The data are passed to the FORTRAN program, then the results are returned
//  in a way similar to this.
 
    result = sumsquaredf(&n,a);
    printf("-- We have now returned back to the C program --\n");
 
    printf("Print contents of array a[]\n");
    for (i=0; i<n; i++)
       printf("%2d %5d\n",i,a[i]);
 
    printf("Sum of squares in array = %d\n",result);
 
//  Instead of ending as a normal C program, the pointers must be cleared
//  before returning to Java.
 
    (*env)->ReleaseIntArrayElements(env, ja, a, 0);
    return result;
}

/* DO NOT EDIT THIS FILE - it is machine generated */
#include <jni.h>
/* Header for class JavaCode */
 
#ifndef _Included_JavaCode
#define _Included_JavaCode
#ifdef __cplusplus
extern "C" {
#endif
#undef JavaCode_MAXSIZE
#define JavaCode_MAXSIZE 10L
/*
 * Class:     JavaCode
 * Method:    sumsquaredc
 * Signature: ([I)I
 */
JNIEXPORT jint JNICALL Java_JavaCode_sumsquaredc
  (JNIEnv *, jobject, jintArray);
 
#ifdef __cplusplus
}
#endif
#endif

      INTEGER FUNCTION SUMSQUAREDF(N,A)
      INTEGER A(*)
      WRITE(6,'("-- We are now in the FORTRAN program FortranCode --")')
      WRITE(6,'("Print contents of array A() copied from a[] in C "
     1          "program - note the unit offset")')
      DO I=1,N
        WRITE(6,'(2I5)')I,A(I)
      ENDDO
      WRITE(6,'("Calculate then print out squares of elements with "
     1          "accumulated sums")')
      ISUM=0
      DO I=1,N
        A(I)=A(I)*A(I)
        ISUM=ISUM+A(I)
        WRITE(6,'(3I5)')I,A(I),ISUM
      ENDDO
      SUMSQUAREDF=ISUM
      END