xgboost4j_wrapper.cpp

/*
 Copyright (c) 2014 by Contributors 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
 You may obtain a copy of the License at
    
 http://www.apache.org/licenses/LICENSE-2.0
 Unless required by applicable law or agreed to in writing, software
 distributed under the License is distributed on an "AS IS" BASIS,
 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 */

#include "xgboost/c_api.h"
#include "xgboost4j_wrapper.h"
#include <cstring>

//helper functions
//set handle
void setHandle(JNIEnv *jenv, jlongArray jhandle, void* handle) {
    long out[1];
    out[0] = (long) handle;
    jenv->SetLongArrayRegion(jhandle, 0, 1, (const jlong*) out);
}

JNIEXPORT jstring JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGBGetLastError
  (JNIEnv *jenv, jclass jcls) {
    jstring jresult = 0 ;
    const char* result = XGBGetLastError();
    if (result) jresult = jenv->NewStringUTF(result);
    return jresult;
}

JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGDMatrixCreateFromFile
  (JNIEnv *jenv, jclass jcls, jstring jfname, jint jsilent, jlongArray jout) {
    DMatrixHandle result;
    const char* fname = jenv->GetStringUTFChars(jfname, 0);
    int ret = XGDMatrixCreateFromFile(fname, jsilent, &result);
    if (fname) jenv->ReleaseStringUTFChars(jfname, fname);    
    setHandle(jenv, jout, result);
    return ret;
}

/*
 * Class:     org_dmlc_xgboost4j_wrapper_XgboostJNI
 * Method:    XGDMatrixCreateFromCSR
 * Signature: ([J[J[F)J
 */
JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGDMatrixCreateFromCSR
  (JNIEnv *jenv, jclass jcls, jlongArray jindptr, jintArray jindices, jfloatArray jdata, jlongArray jout) {
    DMatrixHandle result;
    jlong* indptr = jenv->GetLongArrayElements(jindptr, 0);
    jint* indices = jenv->GetIntArrayElements(jindices, 0);
    jfloat* data = jenv->GetFloatArrayElements(jdata, 0); 
    bst_ulong nindptr = (bst_ulong)jenv->GetArrayLength(jindptr); 
    bst_ulong nelem = (bst_ulong)jenv->GetArrayLength(jdata); 
    int ret = (jint) XGDMatrixCreateFromCSR((unsigned long const *)indptr, (unsigned int const *)indices, (float const *)data, nindptr, nelem, &result);    
    setHandle(jenv, jout, result);
    //Release
    jenv->ReleaseLongArrayElements(jindptr, indptr, 0);
    jenv->ReleaseIntArrayElements(jindices, indices, 0);
    jenv->ReleaseFloatArrayElements(jdata, data, 0);
    return ret;
}

/*
 * Class:     org_dmlc_xgboost4j_wrapper_XgboostJNI
 * Method:    XGDMatrixCreateFromCSC
 * Signature: ([J[J[F)J
 */
JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGDMatrixCreateFromCSC
  (JNIEnv *jenv, jclass jcls, jlongArray jindptr, jintArray jindices, jfloatArray jdata, jlongArray jout) {
    DMatrixHandle result;  
    jlong* indptr = jenv->GetLongArrayElements(jindptr, NULL);
    jint* indices = jenv->GetIntArrayElements(jindices, 0);
    jfloat* data = jenv->GetFloatArrayElements(jdata, NULL);
    bst_ulong nindptr = (bst_ulong)jenv->GetArrayLength(jindptr); 
    bst_ulong nelem = (bst_ulong)jenv->GetArrayLength(jdata); 

    int ret = (jint) XGDMatrixCreateFromCSC((unsigned long const *)indptr, (unsigned int const *)indices, (float const *)data, nindptr, nelem, &result);  
    setHandle(jenv, jout, result);   
    //release
    jenv->ReleaseLongArrayElements(jindptr, indptr, 0);
    jenv->ReleaseIntArrayElements(jindices, indices, 0);
    jenv->ReleaseFloatArrayElements(jdata, data, 0);
    
    return ret;
}

/*
 * Class:     org_dmlc_xgboost4j_wrapper_XgboostJNI
 * Method:    XGDMatrixCreateFromMat
 * Signature: ([FIIF)J
 */
JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGDMatrixCreateFromMat
  (JNIEnv *jenv, jclass jcls, jfloatArray jdata, jint jnrow, jint jncol, jfloat jmiss, jlongArray jout) {
    DMatrixHandle result;
    jfloat* data = jenv->GetFloatArrayElements(jdata, 0);
    bst_ulong nrow = (bst_ulong)jnrow; 
    bst_ulong ncol = (bst_ulong)jncol; 
    int ret = (jint) XGDMatrixCreateFromMat((float const *)data, nrow, ncol, jmiss, &result);
    setHandle(jenv, jout, result);
    //release
    jenv->ReleaseFloatArrayElements(jdata, data, 0);
    return ret;
}

/*
 * Class:     org_dmlc_xgboost4j_wrapper_XgboostJNI
 * Method:    XGDMatrixSliceDMatrix
 * Signature: (J[I)J
 */
JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGDMatrixSliceDMatrix
  (JNIEnv *jenv, jclass jcls, jlong jhandle, jintArray jindexset, jlongArray jout) {
    DMatrixHandle result;
    DMatrixHandle handle = (DMatrixHandle) jhandle; 

    jint* indexset = jenv->GetIntArrayElements(jindexset, 0);
    bst_ulong len = (bst_ulong)jenv->GetArrayLength(jindexset); 

    int ret = XGDMatrixSliceDMatrix(handle, (int const *)indexset, len, &result);
    setHandle(jenv, jout, result);
    //release
    jenv->ReleaseIntArrayElements(jindexset, indexset, 0);
    
    return ret;
}

/*
 * Class:     org_dmlc_xgboost4j_wrapper_XgboostJNI
 * Method:    XGDMatrixFree
 * Signature: (J)V
 */
JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGDMatrixFree
  (JNIEnv *jenv, jclass jcls, jlong jhandle) {    
    DMatrixHandle handle = (DMatrixHandle) jhandle;
    int ret = XGDMatrixFree(handle);
    return ret;
}

/*
 * Class:     org_dmlc_xgboost4j_wrapper_XgboostJNI
 * Method:    XGDMatrixSaveBinary
 * Signature: (JLjava/lang/String;I)V
 */
JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGDMatrixSaveBinary
  (JNIEnv *jenv, jclass jcls, jlong jhandle, jstring jfname, jint jsilent) {
    DMatrixHandle handle = (DMatrixHandle) jhandle;
    const char* fname = jenv->GetStringUTFChars(jfname, 0);
    int ret = XGDMatrixSaveBinary(handle, fname, jsilent);
    if (fname) jenv->ReleaseStringUTFChars(jfname, (const char *)fname);    
    return ret;
}

/*
 * Class:     org_dmlc_xgboost4j_wrapper_XgboostJNI
 * Method:    XGDMatrixSetFloatInfo
 * Signature: (JLjava/lang/String;[F)V
 */
JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGDMatrixSetFloatInfo
  (JNIEnv *jenv, jclass jcls, jlong jhandle, jstring jfield, jfloatArray jarray) {
    DMatrixHandle handle = (DMatrixHandle) jhandle;
    const char*  field = jenv->GetStringUTFChars(jfield, 0);
   
    jfloat* array = jenv->GetFloatArrayElements(jarray, NULL);
    bst_ulong len = (bst_ulong)jenv->GetArrayLength(jarray); 
    int ret = XGDMatrixSetFloatInfo(handle, field, (float const *)array, len);   
    //release
    if (field) jenv->ReleaseStringUTFChars(jfield, field);
    jenv->ReleaseFloatArrayElements(jarray, array, 0);   
    return ret;
}

/*
 * Class:     org_dmlc_xgboost4j_wrapper_XgboostJNI
 * Method:    XGDMatrixSetUIntInfo
 * Signature: (JLjava/lang/String;[I)V
 */
JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGDMatrixSetUIntInfo
  (JNIEnv *jenv, jclass jcls, jlong jhandle, jstring jfield, jintArray jarray) {
    DMatrixHandle handle = (DMatrixHandle) jhandle;
    const char*  field = jenv->GetStringUTFChars(jfield, 0);   
    jint* array = jenv->GetIntArrayElements(jarray, NULL);
    bst_ulong len = (bst_ulong)jenv->GetArrayLength(jarray);
    int ret = XGDMatrixSetUIntInfo(handle, (char const *)field, (unsigned int const *)array, len);
    //release
    if (field) jenv->ReleaseStringUTFChars(jfield, (const char *)field);
    jenv->ReleaseIntArrayElements(jarray, array, 0);
    
    return ret;
}

/*
 * Class:     org_dmlc_xgboost4j_wrapper_XgboostJNI
 * Method:    XGDMatrixSetGroup
 * Signature: (J[I)V
 */
JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGDMatrixSetGroup
  (JNIEnv * jenv, jclass jcls, jlong jhandle, jintArray jarray) {
    DMatrixHandle handle = (DMatrixHandle) jhandle;
    jint* array = jenv->GetIntArrayElements(jarray, NULL);
    bst_ulong len = (bst_ulong)jenv->GetArrayLength(jarray); 
    int ret = XGDMatrixSetGroup(handle, (unsigned int const *)array, len);    
    //release
    jenv->ReleaseIntArrayElements(jarray, array, 0);    
    return ret;
}

/*
 * Class:     org_dmlc_xgboost4j_wrapper_XgboostJNI
 * Method:    XGDMatrixGetFloatInfo
 * Signature: (JLjava/lang/String;)[F
 */
JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGDMatrixGetFloatInfo
  (JNIEnv *jenv, jclass jcls, jlong jhandle, jstring jfield, jobjectArray jout) {
    DMatrixHandle handle = (DMatrixHandle) jhandle;
    const char*  field = jenv->GetStringUTFChars(jfield, 0);
    bst_ulong len;
    float *result;    
    int ret = XGDMatrixGetFloatInfo(handle, field, &len, (const float**) &result);
    if (field) jenv->ReleaseStringUTFChars(jfield, field);
  
    jsize jlen = (jsize) len;
    jfloatArray jarray = jenv->NewFloatArray(jlen);
    jenv->SetFloatArrayRegion(jarray, 0, jlen, (jfloat *) result);
    jenv->SetObjectArrayElement(jout, 0, (jobject) jarray);
    
    return ret;
}

/*
 * Class:     org_dmlc_xgboost4j_wrapper_XgboostJNI
 * Method:    XGDMatrixGetUIntInfo
 * Signature: (JLjava/lang/String;)[I
 */
JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGDMatrixGetUIntInfo
  (JNIEnv *jenv, jclass jcls, jlong jhandle, jstring jfield, jobjectArray jout) {
    DMatrixHandle handle = (DMatrixHandle) jhandle;
    const char*  field = jenv->GetStringUTFChars(jfield, 0);
    bst_ulong len;
    unsigned int *result;    
    int ret = (jint) XGDMatrixGetUIntInfo(handle, field, &len, (const unsigned int **) &result);
    if (field) jenv->ReleaseStringUTFChars(jfield, field);
  
    jsize jlen = (jsize) len;
    jintArray jarray = jenv->NewIntArray(jlen);
    jenv->SetIntArrayRegion(jarray, 0, jlen, (jint *) result);
    jenv->SetObjectArrayElement(jout, 0, jarray);
    return ret;
}

/*
 * Class:     org_dmlc_xgboost4j_wrapper_XgboostJNI
 * Method:    XGDMatrixNumRow
 * Signature: (J)J
 */
JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGDMatrixNumRow
  (JNIEnv *jenv, jclass jcls, jlong jhandle, jlongArray jout) {
    DMatrixHandle handle = (DMatrixHandle) jhandle;
    bst_ulong result[1];
    int ret = (jint) XGDMatrixNumRow(handle, result);
    jenv->SetLongArrayRegion(jout, 0, 1, (const jlong *) result);
    return ret;
}

/*
 * Class:     org_dmlc_xgboost4j_wrapper_XgboostJNI
 * Method:    XGBoosterCreate
 * Signature: ([J)J
 */
JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGBoosterCreate
  (JNIEnv *jenv, jclass jcls, jlongArray jhandles, jlongArray jout) {
    DMatrixHandle* handles;
    bst_ulong len = 0;
    jlong* cjhandles = 0;
    BoosterHandle result;
    
    if(jhandles) {
        len = (bst_ulong)jenv->GetArrayLength(jhandles);
        handles = new DMatrixHandle[len];
        //put handle from jhandles to chandles
        cjhandles = jenv->GetLongArrayElements(jhandles, 0);
        for(bst_ulong i=0; i<len; i++) {
            handles[i] = (DMatrixHandle) cjhandles[i];
        }
    }
    
    int ret = XGBoosterCreate(handles, len, &result);    
    //release
    if(jhandles) {
        delete[] handles;
        jenv->ReleaseLongArrayElements(jhandles, cjhandles, 0);
    }
    setHandle(jenv, jout, result);
    
    return ret;
}

/*
 * Class:     org_dmlc_xgboost4j_wrapper_XgboostJNI
 * Method:    XGBoosterFree
 * Signature: (J)V
 */
JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGBoosterFree
  (JNIEnv *jenv, jclass jcls, jlong jhandle) {
    BoosterHandle handle = (BoosterHandle) jhandle;
    return XGBoosterFree(handle);
}


/*
 * Class:     org_dmlc_xgboost4j_wrapper_XgboostJNI
 * Method:    XGBoosterSetParam
 * Signature: (JLjava/lang/String;Ljava/lang/String;)V
 */
JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGBoosterSetParam
  (JNIEnv *jenv, jclass jcls, jlong jhandle, jstring jname, jstring jvalue) {
    BoosterHandle handle = (BoosterHandle) jhandle;    
    const char* name = jenv->GetStringUTFChars(jname, 0);
    const char* value = jenv->GetStringUTFChars(jvalue, 0);
    int ret = XGBoosterSetParam(handle, name, value);
    //release
    if (name) jenv->ReleaseStringUTFChars(jname, name);
    if (value) jenv->ReleaseStringUTFChars(jvalue, value);    
    return ret;
}

/*
 * Class:     org_dmlc_xgboost4j_wrapper_XgboostJNI
 * Method:    XGBoosterUpdateOneIter
 * Signature: (JIJ)V
 */
JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGBoosterUpdateOneIter
  (JNIEnv *jenv, jclass jcls, jlong jhandle, jint jiter, jlong jdtrain) {
    BoosterHandle handle = (BoosterHandle) jhandle;
    DMatrixHandle dtrain = (DMatrixHandle) jdtrain;
    return XGBoosterUpdateOneIter(handle, jiter, dtrain);
}

/*
 * Class:     org_dmlc_xgboost4j_wrapper_XgboostJNI
 * Method:    XGBoosterBoostOneIter
 * Signature: (JJ[F[F)V
 */
JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGBoosterBoostOneIter
  (JNIEnv *jenv, jclass jcls, jlong jhandle, jlong jdtrain, jfloatArray jgrad, jfloatArray jhess) {
    BoosterHandle handle = (BoosterHandle) jhandle;
    DMatrixHandle dtrain = (DMatrixHandle) jdtrain;
    jfloat* grad = jenv->GetFloatArrayElements(jgrad, 0);
    jfloat* hess = jenv->GetFloatArrayElements(jhess, 0);
    bst_ulong len = (bst_ulong)jenv->GetArrayLength(jgrad);
    int ret = XGBoosterBoostOneIter(handle, dtrain, grad, hess, len);    
    //release
    jenv->ReleaseFloatArrayElements(jgrad, grad, 0);
    jenv->ReleaseFloatArrayElements(jhess, hess, 0);    
    return ret;
}

/*
 * Class:     org_dmlc_xgboost4j_wrapper_XgboostJNI
 * Method:    XGBoosterEvalOneIter
 * Signature: (JI[J[Ljava/lang/String;)Ljava/lang/String;
 */
JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGBoosterEvalOneIter
  (JNIEnv *jenv, jclass jcls, jlong jhandle, jint jiter, jlongArray jdmats, jobjectArray jevnames, jobjectArray jout) {
    BoosterHandle handle = (BoosterHandle) jhandle;
    DMatrixHandle* dmats = 0;
    char **evnames = 0;
    char *result = 0;
    bst_ulong len = (bst_ulong)jenv->GetArrayLength(jdmats);     
    if(len > 0) {
        dmats = new DMatrixHandle[len];
        evnames = new char*[len];
    }
    //put handle from jhandles to chandles
    jlong* cjdmats = jenv->GetLongArrayElements(jdmats, 0);
    for(bst_ulong i=0; i<len; i++) {
        dmats[i] = (DMatrixHandle) cjdmats[i];
    }
    //transfer jObjectArray to char**, user strcpy and release JNI char* inplace
    for(bst_ulong i=0; i<len; i++) {
        jstring jevname = (jstring)jenv->GetObjectArrayElement(jevnames, i);
        const char* cevname = jenv->GetStringUTFChars(jevname, 0);
        evnames[i] = new char[jenv->GetStringLength(jevname)];
        strcpy(evnames[i], cevname);
        jenv->ReleaseStringUTFChars(jevname, cevname);
    }
    
    int ret = XGBoosterEvalOneIter(handle, jiter, dmats, (char const *(*)) evnames, len, (const char **) &result);    
    if(len > 0) {
        delete[] dmats;
        //release string chars
        for(bst_ulong i=0; i<len; i++) {
            delete[] evnames[i];
        }        
        delete[] evnames;
        jenv->ReleaseLongArrayElements(jdmats, cjdmats, 0);
    }
    
    jstring jinfo = 0;
    if (result) jinfo = jenv->NewStringUTF((const char *) result);
    jenv->SetObjectArrayElement(jout, 0, jinfo);
  
    return ret;
}

/*
 * Class:     org_dmlc_xgboost4j_wrapper_XgboostJNI
 * Method:    XGBoosterPredict
 * Signature: (JJIJ)[F
 */
JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGBoosterPredict
  (JNIEnv *jenv, jclass jcls, jlong jhandle, jlong jdmat, jint joption_mask, jint jntree_limit, jobjectArray jout) {
    BoosterHandle handle = (BoosterHandle) jhandle;
    DMatrixHandle dmat = (DMatrixHandle) jdmat;
    bst_ulong len;
    float *result;
    int ret = XGBoosterPredict(handle, dmat, joption_mask, (unsigned int) jntree_limit, &len, (const float **) &result);
    
    jsize jlen = (jsize) len;
    jfloatArray jarray = jenv->NewFloatArray(jlen);
    jenv->SetFloatArrayRegion(jarray, 0, jlen, (jfloat *) result);
    jenv->SetObjectArrayElement(jout, 0, jarray);    
    return ret;
}

/*
 * Class:     org_dmlc_xgboost4j_wrapper_XgboostJNI
 * Method:    XGBoosterLoadModel
 * Signature: (JLjava/lang/String;)V
 */
JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGBoosterLoadModel
  (JNIEnv *jenv, jclass jcls, jlong jhandle, jstring jfname) {
    BoosterHandle handle = (BoosterHandle) jhandle;
    const char* fname = jenv->GetStringUTFChars(jfname, 0);
  
    int ret = XGBoosterLoadModel(handle, fname);
    if (fname) jenv->ReleaseStringUTFChars(jfname,fname);
    return ret;
}

/*
 * Class:     org_dmlc_xgboost4j_wrapper_XgboostJNI
 * Method:    XGBoosterSaveModel
 * Signature: (JLjava/lang/String;)V
 */
JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGBoosterSaveModel
  (JNIEnv *jenv, jclass jcls, jlong jhandle, jstring jfname) {
    BoosterHandle handle = (BoosterHandle) jhandle;
    const char*  fname = jenv->GetStringUTFChars(jfname, 0);
    
    int ret = XGBoosterSaveModel(handle, fname);
    if (fname) jenv->ReleaseStringUTFChars(jfname, fname);
    
    return ret;
}

/*
 * Class:     org_dmlc_xgboost4j_wrapper_XgboostJNI
 * Method:    XGBoosterLoadModelFromBuffer
 * Signature: (JJJ)V
 */
JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGBoosterLoadModelFromBuffer
  (JNIEnv *jenv, jclass jcls, jlong jhandle, jlong jbuf, jlong jlen) {
    BoosterHandle handle = (BoosterHandle) jhandle;
    void *buf = (void*) jbuf;
    return XGBoosterLoadModelFromBuffer(handle, (void const *)buf, (bst_ulong) jlen);
}

/*
 * Class:     org_dmlc_xgboost4j_wrapper_XgboostJNI
 * Method:    XGBoosterGetModelRaw
 * Signature: (J)Ljava/lang/String;
 */
JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGBoosterGetModelRaw
  (JNIEnv * jenv, jclass jcls, jlong jhandle, jobjectArray jout) {
    BoosterHandle handle = (BoosterHandle) jhandle;
    bst_ulong len = 0;
    char *result;

    int ret = XGBoosterGetModelRaw(handle, &len, (const char **) &result);
    if (result){
        jstring jinfo = jenv->NewStringUTF((const char *) result);
        jenv->SetObjectArrayElement(jout, 0, jinfo);
    }
    return ret;
}

/*
 * Class:     org_dmlc_xgboost4j_wrapper_XgboostJNI
 * Method:    XGBoosterDumpModel
 * Signature: (JLjava/lang/String;I)[Ljava/lang/String;
 */
JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGBoosterDumpModel
  (JNIEnv *jenv, jclass jcls, jlong jhandle, jstring jfmap, jint jwith_stats, jobjectArray jout) {
    BoosterHandle handle = (BoosterHandle) jhandle;
    const char *fmap = jenv->GetStringUTFChars(jfmap, 0);
    bst_ulong len = 0; 
    char **result;
    
    int ret = XGBoosterDumpModel(handle, fmap, jwith_stats, &len, (const char ***) &result);
    
    jsize jlen = (jsize) len;
    jobjectArray jinfos = jenv->NewObjectArray(jlen, jenv->FindClass("java/lang/String"), jenv->NewStringUTF(""));
    for(int i=0 ; i<jlen; i++) {
        jenv->SetObjectArrayElement(jinfos, i, jenv->NewStringUTF((const char*) result[i]));
    }
    jenv->SetObjectArrayElement(jout, 0, jinfos);
    
    if (fmap) jenv->ReleaseStringUTFChars(jfmap, (const char *)fmap);   
    return ret;
}