Solution for Java to Call DLL with pointer or Variable Parameter

[Introduction] assume that I have a dynamic library named test. dll. One of the functions is as follows.

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Suppose I have a dynamic library named test. dll, and one of the functions is as follows:

 

Extern "C" int add (int * a, int * B, int * C, int D, char * picpath)

 

{

 

File * FP;

 

Fp = fopen (picpath, "WT ");

 

For (INT I = 0; I <p = ""> <>

 

{

 

C [I] = A [I] + B [I];

 

Fprintf (FP, "% d/N", C [I]);

 

}

 

Fclose (FP );

 

Return 1;

 

}

 

This function adds the values of arrays A and B, and writes to the specified file in array C, the dimension of the array.

 

It is determined by the input parameters.

 

Question:

 

1. How to call pointer-type parameters in Java;

 

2. Can Integer Parameters be passed in directly ?;

 

3. Why is picpath pointer-type and cstring-type;

 

4. How to obtain the return values of input parameters;

 

The Java code for calling the dynamic link library is as follows:

 

Jnative T = new jnative ("test. dll", "add"); // load the test. dll file and call the add method;

 

T. setretval (type. INT); // sets the return type after the call.

 

// Construct a pointer in Java and allocate space for the pointer

 

Pointer a = new pointer (memoryblockfactory. creatememoryblock (4*10 ));

 

Pointer B = new pointer (memoryblockfactory. creatememoryblock (4*10 ));

 

Pointer c = new pointer (memoryblockfactory. creatememoryblock (4*10 ));

 

Pointer STRP = createpointer (100 );

 

STRP. setstringat (0, "C: // 1.txt ");

 

Int d = 10;

 

// Assign values to arrays A and B

 

For (INT I = 0; I <= "">

 

A. setintat (4 * I, I );

 

B. setintat (4 * I, I );

 

}

 

// Set parameters:

 

T. setparameter (0, );

 

T. setparameter (1, B );

 

T. setparameter (2, c );

 

T. setparameter (3, D );

 

T. setparameter (4, STRP );

 

T. Invoke (); // call the function and execute

 

// Output and value. Note: an integer value must be stored in 4 bytes. Therefore, multiply the value before J by 4.

 

For (Int J = 0; j <= "" J ++) = "">

 

System. Out. println (C. getasint (4 * j ));

 

}

 

// Release the memory

 

A. Dispose ();

 

B. Dispose ();

 

C. Dispose ();

 

Well, this is the end of a complete call example. I just wrote the key code in the program.

 

Class, and inherit a base class, methods in the secondary base class, these are relatively simple, you can refer to other online

 

Example.

 

Answer:

 

1. Call pointer parameters in Java: You need to create a pointer variable and allocate space for it.

 

2. integer data can be passed in directly;

 

3. jnative does not support the cstring type very well. When calling the cstring method, some exceptions are often reported, so I change the path

 

Character pointer;

 

4. input parameters as output: see the preceding example to learn how to set and output array C.