convert c++ primitive type vector to java primitive type array

Question

I'm using a third party C++ API for my project and it has functions with return values with types std::vector<int>, std::vector<bool>, std::vector<double>. I need to pass variables with these types to Java. So I'm using JNI and my function has return values with types jintArray, jbooleanArray, jdoubleArray.

I'm using following code to convert double type:

std::vector<double> data;
//fill data
jdouble *outArray = &data[0];
jdoubleArray outJNIArray = (*env).NewDoubleArray(data.size());  // allocate
if (NULL == outJNIArray) return NULL;
(*env).SetDoubleArrayRegion(outJNIArray, 0 , data.size(), outArray);  // copy
return outJNIArray;

I've no problem with this code block. But when I want to do this for int and bool types there is a problem at the following:

std::vector<int> data;
//fill data
jint *outArray = &data[0];

and

std::vector<bool> data;
//fill data
jboolean *outArray = &data[0];

The problem is with definitions of jint and jboolean, since:

typedef long            jint;
typedef unsigned char   jboolean;

and for jdouble:

typedef double          jdouble;

As, you can see my convenient solution for double doesn't work for int and bool types since their typedefs doesn't match.

So, my question is how can I do this conversion for all primitive types conveniently?

Thanks in advance

Roland W · Accepted Answer · 2014-06-05 09:24:47Z

2

Since the data types might have different sizes you have to copy the vector. The simplest way to do this is

std::vector<jboolean> tmp(data.begin(), data.end());
jboolean *outArray = &tmp[0];

Of course, you can allocate the jBooleanArray and set the elements in a for loop or write a wrapper for it that behaves like an STL container.

answered Jun 5, 2014 at 9:24

Roland W

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