swig char*通过函数参数，以java的byte[]模式

example.i

%module example
%{
#include <example.h>
%}

%include "various.i"
extern void modifyString(char *BYTE, int maxlen);

 

example.h

#ifndef EXAMPLE_H
#define EXAMPLE_H

extern "C"{

extern int gcd(int x, int y);
extern double Foo;
extern char* modifyAndReturnNewString(const char* input);
extern void modifyString(char *str, int maxlen);
}

 #endif // EXAMPLE_H

example.cpp

#include "example.h"
#include <ctype.h>
#include <string.h>

/* A global variable */
double Foo = 3.0;

/* Compute the greatest common divisor of positive integers */
int gcd(int x, int y) {
int g;
g = y;
while (x > 0) {
g = x;
x = y % x;
y = g;
}
return g;
}

char* modifyAndReturnNewString(const char* input) {
char* result = strdup(input); // 复制输入
result[0] = 'X'; // 修改
return result; // 返回新字符串（需在 Java 端释放）
}

void modifyString(char *str, int maxlen) {
if (maxlen > 0) {
str[0] = 'X'; // 修改第一个字节
}
}

example_wrap.cxx

#include <example.h>

#ifdef __cplusplus
extern "C" {
#endif

SWIGEXPORT void JNICALL Java_com_example_exampleJNI_modifyString(JNIEnv *jenv, jclass jcls, jbyteArray jarg1, jint jarg2) {
char *arg1 = (char *) 0 ;
int arg2 ;

(void)jenv;
(void)jcls;
{
arg1 = (char *) jenv->GetByteArrayElements(jarg1, 0);
}
arg2 = (int)jarg2;
modifyString(arg1,arg2);
{
jenv->ReleaseByteArrayElements(jarg1, (jbyte *) arg1, 0);//0 将修改后的数据复制回 Java 数组，并释放本地数组
//JNI_COMMIT 将修改后的数据复制回 Java 数组，但不释放本地数组（仍可继续使用）
//JNI_ABORT 不复制修改回 Java 数组，直接释放本地数组
}

}

#ifdef __cplusplus
}
#endif

java

package Dialog;

import org.eclipse.swt.SWT;
import org.eclipse.swt.events.SelectionAdapter;
import org.eclipse.swt.events.SelectionEvent;
import org.eclipse.swt.widgets.Button;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Shell;

import com.example.example;
import com.example.exampleJNI;

public class MainWindow {

protected Shell shell;
static {
try {
//System.loadLibrary("example");
System.load("D:\\qtprojects\\example\\build\\Desktop_Qt_5_15_2_MSVC2019_64bit-Release\\release\\example.dll");
} catch (UnsatisfiedLinkError e) {
System.err.println("Native code library failed to load. See the chapter on Dynamic Linking Problems in the SWIG Java documentation for help.\n" + e);
System.exit(1);
}
}

/**
* Launch the application.
*
* @param args
*/
public static void main(String[] args) {
try {
MainWindow window = new MainWindow();
window.open();
} catch (Exception e) {
e.printStackTrace();
}
}

/**
* Open the window.
*/
public void open() {
Display display = Display.getDefault();
createContents();
shell.open();
shell.layout();
while (!shell.isDisposed()) {
if (!display.readAndDispatch()) {
display.sleep();
}
}
}

/**
* Create contents of the window.
*/
protected void createContents() {
shell = new Shell();
shell.setSize(585, 490);
shell.setText("SWT Application");

Button btnFun = new Button(shell, SWT.NONE);
btnFun.addSelectionListener(new SelectionAdapter() {
@Override
public void widgetSelected(SelectionEvent e) {
byte[] buffer = "test".getBytes();
example.modifyString(buffer, buffer.length);
String result = new String(buffer);
System.out.println(result); // 输出 "Xest"
}
});
btnFun.setBounds(10, 10, 80, 27);
btnFun.setText("fun1");
}

}