scala调用c/c++代码

与java调用c/c++差不多。

1.在scala文件中对将要调用的方法做本地声明，关键字为native。且只需要声明，而不需要具体实现。

class MutiMatrix {

  //xM
  @native def vectorMutiMatrix(lx: Array[Double],rM:Array[Double]): Array[Double]
  //Mx
  @native def matrixMutiVector(lM: Array[Double], rx: Array[Double]): Array[Double]
  //MM
  @native def matrixMutiMatrix(lM: Array[Double],rM:Array[Double], k: Int): Array[Double]
  //xMx'
  @native def distance(x: Array[Double],M:Array[Double]): Double

}

2.调用scalac编译我们的scala类，获得class文件

scalac MutiMatrix.scala

3.使用javah命令来帮助生成这些方法的声明的头文件

SCALA_LIB_HOME=$SCALA_HOME/lib/
SCALA_CP=$SCALA_LIB_HOME/scala-library.jar:$SCALA_LIB_HOME/scala-reflect.jar
javah -cp $SCALA_CP:. MutiMatrix

生成的头文件为：

/* DO NOT EDIT THIS FILE - it is machine generated */
#include "jni.h"
/* Header for class MutiMatrix */

#ifndef _Included_MutiMatrix
#define _Included_MutiMatrix
#ifdef __cplusplus
extern "C" {
#endif
/*
 * Class:     MutiMatrix
 * Method:    vectorMutiMatrix
 * Signature: ([D[D)[D
 */
JNIEXPORT jdoubleArray JNICALL Java_MutiMatrix_vectorMutiMatrix
  (JNIEnv *, jobject, jdoubleArray, jdoubleArray);

/*
 * Class:     MutiMatrix
 * Method:    matrixMutiVector
 * Signature: ([D[D)[D
 */
JNIEXPORT jdoubleArray JNICALL Java_MutiMatrix_matrixMutiVector
  (JNIEnv *, jobject, jdoubleArray, jdoubleArray);

/*
 * Class:     MutiMatrix
 * Method:    matrixMutiMatrix
 * Signature: ([D[DI)[D
 */
JNIEXPORT jdoubleArray JNICALL Java_MutiMatrix_matrixMutiMatrix
  (JNIEnv *, jobject, jdoubleArray, jdoubleArray, jint);

/*
 * Class:     MutiMatrix
 * Method:    distance
 * Signature: ([D[D)D
 */
JNIEXPORT jdouble JNICALL Java_MutiMatrix_distance
  (JNIEnv *, jobject, jdoubleArray, jdoubleArray);

#ifdef __cplusplus
}
#endif
#endif

4.用C++将代码补充完整

其实现文件.cpp为：

#include "MutiMatrix.h"
//#include <iostream>
#include <string.h>
#include <stdlib.h>
//using namespace std;


JNIEXPORT jdoubleArray JNICALL Java_MutiMatrix_vectorMutiMatrix
  (JNIEnv *env, jobject obj, jdoubleArray lxs, jdoubleArray rMs)
{
	jsize xlen = env->GetArrayLength(lxs);
	jsize Mlen = env->GetArrayLength(rMs);
	jsize Mcol = Mlen/xlen;
	jdouble* lx = env->GetDoubleArrayElements(lxs,0);
	jdouble* rM = env->GetDoubleArrayElements(rMs,0);

	jdoubleArray result = env->NewDoubleArray(Mcol);
	jdouble* buff = new double[Mcol];
	memset(buff,Mcol*sizeof(jdouble),0);

	for(int i = 0; i< Mcol; i++){
		for(int j = 0; j < xlen; j++){
			buff[i] += lx[j]*rM[i*Mcol+j];
		}
	}

	env->ReleaseDoubleArrayElements(lxs, lx, 0);
	env->ReleaseDoubleArrayElements(rMs, rM, 0);
	env->SetDoubleArrayRegion(result,0,Mcol,buff);
	return result;
}

5.用g++生成.so文件

g++ -dynamiclib -shared -fPIC -I/usr/include -I$JAVA_HOME/include -I$JAVA_HOME/include/linux MutiMatrix.cpp -o libMutiMatrix.so

6.copy .so文件到scala代码目录下，并在VM arguments中加入该.so文件的路径

-Djava.library.path=/home/liujj/code/scala/testC++/

在run as 下的Run Configurations设置

7.测试

/**
 * @author liujj
 */
object test {
  def main(args: Array[String]) {
    System.loadLibrary("MutiMatrix")
    val x = Array(1.0,2.0)
    val M = Array(1.0,2.0,3.0,4.0)

    val mm = new MutiMatrix
    val c = mm.vectorMutiMatrix(x, M)
    println(c.toList)
  }
}

8.结果