2019-04-08 Swig java Jni开发指南

oracle3

发布于 2022-05-13 08:32:25

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发布于 2022-05-13 08:32:25

Swig java Jni开发指南目录 Swig java Jni开发指南

Swig参考文档
全局变量
常量
只读变量
枚举
函数
结构体
类
调用函数指针
回调
类型转换
两个常用命令

简介： JNI：Java Native Interface，它允许Java代码和其他语言（尤其C/C++）写的代码进行交互，只要遵守调用约定即可。 JNA：Java Native Access是一个开源的Java框架，是Sun公司推出的一种调用本地方法的技术，是建立在经典的JNI基础之上的一个框架。之所以说它是JNI的替代者，是因为JNA大大简化了调用本地方法的过程，使用很方便，基本上不需要脱离Java环境就可以完成。 Swig可以根据c或c++代码生成jni代码的工具，大大简化jni的开发 Jnaerator可以根据c或c++代码生成jna代码的工具，大大简化jna的开发从难易度看，使用jnaerator开发jna最简单，代码基本都是自动生成，但是jna开发有个很大的缺点，就是如果c代码过于复杂，比如出现java调用c，然后c再回调java，java返回的结果c还需要继续处理的时候，经常出现不可控制的crash，而jna算是中间层，这个层出现的错误完全无法调试，被逼无奈，我们的项目先用jna开发，不得不转jni开发，在使用swig的过程中，也遇到不少问题，因此总结如下：

Swig参考文档 http://www.swig.org/Doc3.0/SWIGDocumentation.html swig是一个编译时软件开发工具，它能生成将用c/c++编写的原生模块与包括java在内的其他编程语言进行链接的必要代码。Swig不仅是一个代码生成器，还是一个接口编译器。它不定义新的协议，也不是一个组件框架或者一个特定的运行时库。Swig把接口文件看做输入，并生成必要的代码在java中展示接口，从而让java能够理解原生代码中的接口定义。Swig不是一个存根生成器；它产生将要被编译和运行的代码。 Swig可应用于包括windows、mac os x和linux在内的大多数操作系统平台。大家可以参考官网文档安装。使用swig需要生成一个.i的接口文件，swig接口文件包含函数原型、类和变量声明，它的语法和普通的c/c++头文件一样。除了c/c++关键字和预处理器指令，接口文件还包含swig特有的预处理器指令，该指令可用于优化生成封装代码。
全局变量 a) 编写example.h

int counter = 0;

b) 编写example.i

%module example  
%{  
#include "example.h"  
%}  
  
extern int counter;

c) 编写runme.java

/ runme.java  
 
ublic class runme {  
 static {  
   System.loadLibrary("example");  
 }  
 
 public static void main(String argv[]) {  
   System.out.println(example.getCounter());  
   example.setCounter(1);  
   System.out.println(example.getCounter());  
 }

d) 执行以下命令

swig -java example.i  
gcc -Wall -Wl,--kill-at -I "%JAVA_HOME%/include" -I "%JAVA_HOME%/include/win32" -shared -s -o example.dll *.c  
javac -d . *.java  
java -cp . runme

常量 a) 编写example.i

%module example  
  
/* 用define指令定义常量 */  
#define MAX_WIDTH 640  
/* 用%constant指令定义常量 */  
%constant int MAX_HEIGHT = 320;

b) 编写runme.java

// runme.java  
  
public class runme {  
  static {  
    System.loadLibrary("example");  
  }  
  
  public static void main(String argv[]) {  
    System.out.println(example.MAX_WIDTH);  
        System.out.println(example.MAX_HEIGHT);  
      }  
    }

c) 执行以下命令，同1.d

只读变量区别只是在生成的包装类中，只读的只有get函数，读写的有get和set函数 a) 编写example.h

/* 只读变量 */  
int readOnly;  
  
/* 读-写变量 */  
int readWrite;

b) 编写example.i

%module example  
%{  
#include "example.h"  
%}  
  
/* 只读变量 */  
%immutable readOnly;  
int readOnly;  
  
/* 读-写变量 */  
int readWrite;

c) 编写runme.java

// runme.java  
  
public class runme {  
  static {  
    System.loadLibrary("example");  
  }  
  
  public static void main(String argv[]) {  
    System.out.println(example.getReadOnly());  
    example.setReadWrite(10);  
    System.out.println(example.getReadWrite());  
  }  
}

d) 执行以下命令，同1.d

枚举 a) 编写example.h

/* 匿名枚举 */  
enum {ONE = 1, TWO = 2, THREE, FOUR};  
/* 命名枚举 */  
enum Color { RED = 1, GREEN, BLANK, YELLOW};  
  
enum SeasonEnum{ SPRING = 1,SUMMER,AUTUMN,WINTER};

b) 编写example.i

%module example  
%{  
#include "example.h"  
%}  
  
/* 匿名枚举 */
enum {ONE = 1, TWO = 2, THREE, FOUR};  
/* 命名枚举 */  
enum Color { RED = 1, GREEN, BLANK, YELLOW};  
/* 类型不安全，这个用起来最简单 */  
%include "enumtypeunsafe.swg"  
%javaconst(1);  
enum SeasonEnum{ SPRING = 1,SUMMER,AUTUMN,WINTER};

c) 编写runme.java

// runme.java  
  
public class runme {  
  static {  
    System.loadLibrary("example");  
  }  
  
  public static void main(String argv[]) {  
    System.out.println(example.ONE + "," + example.TWO + "," + example.THREE + "," + example.FOUR);  
    System.out.println(Color.RED.swigValue() + "," + Color.GREEN.swigValue() + "," + Color.BLANK.swigValue() + "," + Color.YELLOW.swigValue());  
    System.out.println(SeasonEnum.SPRING + "," + SeasonEnum.SUMMER + "," + SeasonEnum.AUTUMN + "," + SeasonEnum.WINTER);  
  }  
}

d) 执行以下命令，同1.d

函数这里直接抄swigwin-3.0.12\Examples\java\simple a) 编写example.c

/* File : example.c */  
  
/* 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;  
}

b) 编写example.i

/* File : example.i */  
%module example  
  
%inline %{  
extern int    gcd(int x, int y);  
extern double Foo;  
%}

c) 编写runme.java

public class runme {  
  
  static {  
    try {  
    System.loadLibrary("example");  
    } 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);  
    }  
  }  
  
  public static void main(String argv[]) {  
    // Call our gcd() function  
      
    int x = 42;  
    int y = 105;  
    int g = example.gcd(x,y);  
    System.out.println("The gcd of " + x + " and " + y + " is " + g);  
      
    // Manipulate the Foo global variable  
      
    // Output its current value  
    System.out.println("Foo = " + example.getFoo());  
      
    // Change its value  
    example.setFoo(3.1415926);  
      
    // See if the change took effect  
    System.out.println("Foo = " + example.getFoo());  
  }  
}

d) 执行以下命令，同1.d

结构体 a) 编写example.h

// example.h  
  
struct Books  
{  
   char  title[50];  
   char  author[50];  
   char  subject[100];  
   int   book_id;  
};  
  
extern void show(struct Books* book);

b) 编写example.c

// example.c  
#include <stdio.h>  
#include "example.h"  
  
// struct Books book = {"C 语言", "RUNOOB", "编程语言", 123456};  
void show(struct Books* book)  
{  
    printf("title : %s\nauthor: %s\nsubject: %s\nbook_id: %d\n", book->title, book->author, book->subject, book->book_id);  
}

c) 编写example.i

/* File : example.i */  
%module example  
  
%{  
#include "example.h"  
%}  
  
%include "example.h"

d) 编写runme.java

// runme.java  
  
public class runme {  
  static {  
    System.loadLibrary("example");  
  }  
  
  public static void main(String argv[]) {  
      
    Books book = new Books();  
    book.setTitle("C 语言");  
    book.setAuthor("RUNOOB");  
    book.setSubject("编程语言");  
    book.setBook_id(123456);  
      
    example.show(book);  
  }  
}

e) 执行以下命令，同1.d

类这里直接抄swigwin-3.0.12\Examples\java\ class，对比java调用c的结构体来看，两个的处理完全一样，都是把c的结构或类包装成java类使用 a) 编写example.h

/* File : example.h */  
  
class Shape {  
public:  
  Shape() {  
    nshapes++;  
  }  
  virtual ~Shape() {  
    nshapes--;  
  }  
  double  x, y;  
  void    move(double dx, double dy);  
  virtual double area() = 0;  
  virtual double perimeter() = 0;  
  static  int nshapes;  
};  
  
class Circle : public Shape {  
private:  
  double radius;  
public:  
  Circle(double r) : radius(r) { }  
  virtual double area();  
  virtual double perimeter();  
};  
  
class Square : public Shape {  
private:  
  double width;  
public:  
  Square(double w) : width(w) { }  
  virtual double area();  
  virtual double perimeter();  
};

b) 编写example.cxx

/* File : example.cxx */  
  
#include "example.h"  
#define M_PI 3.14159265358979323846  
  
/* Move the shape to a new location */  
void Shape::move(double dx, double dy) {  
  x += dx;  
  y += dy;  
}  
  
int Shape::nshapes = 0;  
  
double Circle::area() {  
  return M_PI*radius*radius;  
}  
  
double Circle::perimeter() {  
  return 2*M_PI*radius;  
}  
  
double Square::area() {  
  return width*width;  
}  
  
double Square::perimeter() {  
  return 4*width;  
}

c) 编写example.i

/* File : example.i */  
%module example  
  
%{  
#include "example.h"  
%}  
  
/* Let's just grab the original header file here */  
%include "example.h"

d) 编写runme.java

// This example illustrates how C++ classes can be used from Java using SWIG.  
// The Java class gets mapped onto the C++ class and behaves as if it is a Java class.  
  
public class runme {  
  static {  
    try {  
        System.loadLibrary("example");  
    } 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);  
    }  
  }  
  
  public static void main(String argv[])   
  {  
    // ----- Object creation -----  
      
    System.out.println( "Creating some objects:" );  
    Circle c = new Circle(10);  
    System.out.println( "    Created circle " + c );  
    Square s = new Square(10);  
    System.out.println( "    Created square " + s );  
      
    // ----- Access a static member -----  
      
    System.out.println( "\nA total of " + Shape.getNshapes() + " shapes were created" );  
      
    // ----- Member data access -----  
      
    // Notice how we can do this using functions specific to  
    // the 'Circle' class.  
    c.setX(20);  
    c.setY(30);  
      
    // Now use the same functions in the base class  
    Shape shape = s;  
    shape.setX(-10);  
    shape.setY(5);  
      
    System.out.println( "\nHere is their current position:" );  
    System.out.println( "    Circle = (" + c.getX() + " " + c.getY() + ")" );  
    System.out.println( "    Square = (" + s.getX() + " " + s.getY() + ")" );  
      
    // ----- Call some methods -----  
      
    System.out.println( "\nHere are some properties of the shapes:" );  
    Shape[] shapes = {c,s};  
    for (int i=0; i<shapes.length; i++)  
    {  
          System.out.println( "   " + shapes[i].toString() );  
          System.out.println( "        area      = " + shapes[i].area() );  
          System.out.println( "        perimeter = " + shapes[i].perimeter() );  
    }  
      
    // Notice how the area() and perimeter() functions really  
    // invoke the appropriate virtual method on each object.  
      
    // ----- Delete everything -----  
      
    System.out.println( "\nGuess I'll clean up now" );  
      
    // Note: this invokes the virtual destructor  
    // You could leave this to the garbage collector  
    c.delete();  
    s.delete();  
      
    System.out.println( Shape.getNshapes() + " shapes remain" );  
    System.out.println( "Goodbye" );  
  }  
}

e) 执行以下命令

swig -c++ -java example.i  
g++ -Wall -Wl,--kill-at -I "%JAVA_HOME%/include" -I "%JAVA_HOME%/include/win32" -shared -s -o example.dll *.cxx  
javac -d . *.java  
java -cp . runme

调用函数指针重点：这个只能获得函数指针，然后多写个函数把函数指针传递给c层来调用，java层没有找到方法调用这种方法会出现一些比较奇怪的类名，例如：SWIGTYPE_p_f_float_float__float，为了类名可读，可以用下一部分说的回调来处理，只是不需要java继承，直接get出来，然后调用run就可以用了 a) 编写example.h

/**************************************** 
 * 函数指针结构体 
 ***************************************/  
typedef float (*callback_t)(float a, float b);  
  
typedef struct _OP {  
    callback_t p_add;   
    callback_t p_sub;   
    callback_t p_mul;   
    callback_t p_div;   
} OP;   
  
extern OP* get_init_op(void);  
extern float add_sub_mul_div(float a, float b, callback_t fun);

b) 编写example.i

/* File : example.i */  
%module example  
%{  
#include "example.h"  
%}  
  
%include "example.h"

c) 编写example.c

#include <stdio.h>  
#include <stdlib.h>  
#include "example.h"  
  
/**************************************** 
 * 加减乘除函数 
 ***************************************/  
float ADD(float a, float b)   
{  
    return a + b;  
}  
  
float SUB(float a, float b)   
{  
    return a - b;  
}  
  
float MUL(float a, float b)   
{  
    return a * b;  
}  
  
float DIV(float a, float b)   
{  
    return a / b;  
}  
  
/**************************************** 
 * 初始化函数指针 
 ***************************************/  
OP* get_init_op(void)  
{  
        OP *op = (OP *)malloc(sizeof(OP));   
    op->p_add = ADD;  
    op->p_sub = SUB;  
    op->p_mul = MUL;  
    op->p_div = DIV;  
    return op;  
}  
  
/**************************************** 
 * 库函数 
 ***************************************/  
float add_sub_mul_div(float a, float b, callback_t fun)  
{  
    return fun(a, b);  
}  
  
int main()   
{  
    OP *op = get_init_op();   
          
    /* 直接使用函数指针调用函数 */   
    printf("ADD = %f, SUB = %f, MUL = %f, DIV = %f\n", (op->p_add)(1.3, 2.2), (*op->p_sub)(1.3, 2.2),   
            (op->p_mul)(1.3, 2.2), (*op->p_div)(1.3, 2.2));  
       
    /* 调用回调函数 */   
    printf("ADD = %f, SUB = %f, MUL = %f, DIV = %f\n",   
            add_sub_mul_div(1.3, 2.2, ADD),   
            add_sub_mul_div(1.3, 2.2, SUB),   
            add_sub_mul_div(1.3, 2.2, MUL),   
            add_sub_mul_div(1.3, 2.2, DIV));  
  
    return 0;   
}

d) 编写runme.java

// runme.java  
  
public class runme {  
  static {  
    System.loadLibrary("example");  
  }  
  
  public static void main(String argv[]) {  
      
    OP op = example.get_init_op();  
  
    System.out.println(example.add_sub_mul_div(1.3f, 2.2f,op.getP_add()));  
    System.out.println(example.add_sub_mul_div(1.3f, 2.2f,op.getP_sub()));  
    System.out.println(example.add_sub_mul_div(1.3f, 2.2f,op.getP_mul()));  
    System.out.println(example.add_sub_mul_div(1.3f, 2.2f,op.getP_div()));  
  }  
}

e) 执行以下命令，同1.d

回调这个c代码搞不定，只能通过c++类实现，参考上例修改实现参考：swigwin-3.0.12\Examples\java\callback a) 编写example.h

class Callback {  
public:  
    virtual ~Callback() {}  
    virtual float run(float a, float b) {return 0;}  
};  
  
class OP {  
public:  
    Callback *p_add;  
    Callback *p_sub;  
    Callback *p_mul;  
    Callback *p_div;  
      
public:  
    OP(): p_add(0),p_sub(0),p_mul(0),p_div(0) {}  
    ~OP() {   
    }  
      
    float add_sub_mul_div(float a, float b, Callback* fun) {  
        if(fun != NULL) {  
            return fun->run(a, b);  
        }  
        printf("add_sub_mul_div error\n");  
        return 0;  
    }  
};

b) 编写example.i 重点：这里必须设置%module(directors="1") example 并且指定回调类： %feature("director") Callback;

/* File : example.i */  
%module(directors="1") example  
%{  
#include "example.h"  
%}  
  
%feature("director") Callback;  
%include "example.h"

c) 编写runme.java

// runme.java  
  
public class runme {  
  static {  
    System.loadLibrary("example");  
  }  
  
  public static void main(String argv[]) {  
      
    OP op = new OP();  
    op.setP_add(new JavaCallbackAdd());  
    op.setP_sub(new JavaCallbackSub());  
    op.setP_mul(new JavaCallbackMul());  
    op.setP_div(new JavaCallbackDiv());  
  
    System.out.println(op.add_sub_mul_div(1.3f, 2.2f,op.getP_add()));  
    System.out.println(op.add_sub_mul_div(1.3f, 2.2f,op.getP_sub()));  
    System.out.println(op.add_sub_mul_div(1.3f, 2.2f,op.getP_mul()));  
    System.out.println(op.add_sub_mul_div(1.3f, 2.2f,op.getP_div()));  
      
    System.out.println(op.getP_add().run(1.3f, 2.2f));  
    System.out.println(op.getP_sub().run(1.3f, 2.2f));  
    System.out.println(op.getP_mul().run(1.3f, 2.2f));  
    System.out.println(op.getP_div().run(1.3f, 2.2f));  
      
  }  
}  
  
  
class JavaCallbackAdd extends Callback  
{  
  public float run(float a, float b) {  
    return a + b;  
  }  
}  
  
class JavaCallbackSub extends Callback  
{  
  public float run(float a, float b) {  
    return a - b;  
  }  
}  
  
class JavaCallbackMul extends Callback  
{  
  public float run(float a, float b) {  
    return a * b;  
  }  
}  
  
class JavaCallbackDiv extends Callback  
{  
  public float run(float a, float b) {  
    return a / b;  
  }  
}

d) 执行以下命令

swig -c++ -java example.i  
g++ -Wall -Wl,--kill-at -I "%JAVA_HOME%/include" -I "%JAVA_HOME%/include/win32" -shared -s -o example.dll *.cxx  
javac -d . *.java  
java -cp . runme

类型转换 a) 错误的情况 C函数包装

%module example  
  
int add_option(const unsigned char *data);

得到的包装函数： public static int add_option(SWIGTYPE_p_unsigned_char data) 其中SWIGTYPE_p_unsigned_char完全无法赋值，也就是无法使用 b) 正确的处理

%module example  
  
%include <arrays_java.i>  
%apply signed char *INOUT { unsigned char * };  
%apply signed char[] { const unsigned char * };  
  
int add_option(const unsigned char *data);

这样就可以得到包装函数： public static int add_option(byte[] data) c) 更多的类型转换

%include "typemaps.i"  
%include "stdint.i"  
%include "arrays_java.i"  
%include "carrays.i"  
  
typedef int8_t Int8;  
typedef uint8_t Uint8;  
typedef int16_t Int16;  
typedef uint16_t Uint16;  
typedef uint32_t Int32;  
typedef uint32_t Uint32;