jbytearray转c++byte数组

谁践踏了优雅 2022-08-10 09:19 185阅读 0赞

### jbytearray转c++byte数组  `jbyte * arrayBody = env->GetByteArrayElements(data,0); jsize theArrayLengthJ = env->GetArrayLength(data); BYTE * starter = (BYTE *)arrayBody;`  jbyteArray 转 c++中的BYTE\[\]    ###

//jbytearray strIn
    jbyte * olddata = (jbyte*)env->GetByteArrayElements(strIn, 0);
    jsize  oldsize = env->GetArrayLength(strIn);
    BYTE* bytearr = (BYTE*)olddata;
    int len = (int)oldsize;

C++中的BYTE\[\]转jbyteArray

//nOutSize是BYTE数组的长度 BYTE pData[]
    jbyte *by = (jbyte*)pData;
    jbyteArray jarray = env->NewByteArray(nOutSize);
    env->SetByteArrayRegin(jarray, 0, nOutSize, by);

jbyteArray 转 char \*

char* data = (char*)env->GetByteArrayElements(strIn, 0);

char\* 转jstring

jstring WindowsTojstring(JNIEnv* env, char* str_tmp)
    {
     jstring rtn=0;
     int slen = (int)strlen(str_tmp);
     unsigned short* buffer=0;
     
     if(slen == 0)
     {
      rtn = env->NewStringUTF(str_tmp);
     }
     else
     {
      int length = MultiByteToWideChar(CP_ACP, 0, (LPCSTR)str_tmp, slen, NULL, 0);
      buffer = (unsigned short*)malloc(length*2+1);
      if(MultiByteToWideChar(CP_ACP, 0, (LPCSTR)str_tmp, slen, (LPWSTR)buffer, length) > 0)
      {
       rtn = env->NewString((jchar*)buffer, length);
      }
     }
     if(buffer)
     {
      free(buffer);
     }
     return rtn;
    }

下面这个没有用过，刚看到，也写进来，以后如果遇到可以验证下看。

**jstring 转 char\* 或者 const char\***

// jstring str
    const char *key = env->GetStringUTFChars(str, 0);
    //jboolean isOffer
    jsClient->modify(key, isOffer);
    env->ReleaseStringUTFChars(str, key);

JNI 返回 jbyteArray

JNIEXPORT jbyteArray JNICALL Java_Test_getByteArray(JNIEnv *env, jobject obj)
    {
    jbyteArray firstMacArray = env->NewByteArray( 6 );
    
    ..elided...
    
    jbyte *bytes = env->GetByteArrayElements( firstMacArray, 0);
    
    for ( int i = 0; i < sizeof( pAdapterInfo->Address ); i++ )
    {
    bytes[ i ] = pAdapterInfo->Address[ i ];
    }
    
    env->SetByteArrayRegion(firstMacArray, 0, 6, bytes );
    
    return firstMacArray;
    }
     
    //jstring to char*
    char* jstringTostring(JNIEnv* env, jstring jstr)
    {        
    char* rtn = NULL;
    jclass clsstring = env->FindClass("java/lang/String");
    jstring strencode = env->NewStringUTF("utf-8");
    jmethodID mid = env->GetMethodID(clsstring, "getBytes", "(Ljava/lang/String;)[B");
    jbyteArray barr= (jbyteArray)env->CallObjectMethod(jstr, mid, strencode);
    jsize alen = env->GetArrayLength(barr);
    jbyte* ba = env->GetByteArrayElements(barr, JNI_FALSE);
    if (alen > 0)
    {
    rtn = (char*)malloc(alen + 1);
    memcpy(rtn, ba, alen);
    rtn[alen] = 0;
    }
    env->ReleaseByteArrayElements(barr, ba, 0);
    return rtn;
    }
    
    //char* to jstring
    jstring stoJstring(JNIEnv* env, const char* pat)
    {
    jclass strClass = env->FindClass("Ljava/lang/String;");
    jmethodID ctorID = env->GetMethodID(strClass, "<init>", "([BLjava/lang/String;)V");
    jbyteArray bytes = env->NewByteArray(strlen(pat));
    env->SetByteArrayRegion(bytes, 0, strlen(pat), (jbyte*)pat);
    jstring encoding = env->NewStringUTF("utf-8");
    return (jstring)env->NewObject(strClass, ctorID, bytes, encoding);
    } 
    
    //将jstring类型转换成windows类型
    char* jstringToWindows( JNIEnv *env, jstring jstr )
    {
    int length = (env)->GetStringLength(jstr );
    const jchar* jcstr = (env)->GetStringChars(jstr, 0 );
    char* rtn = (char*)malloc( length*2+1 );
    int size = 0;
    size = WideCharToMultiByte( CP_ACP, 0, (LPCWSTR)jcstr, length, rtn,(length*2+1), NULL, NULL );
    if( size <= 0 )
    return NULL;
    (env)->ReleaseStringChars(jstr, jcstr );
    rtn[size] = 0;
    return rtn;
    }
    //将windows类型转换成jstring类型
    jstring WindowsTojstring( JNIEnv* env, char* str )
    {
    jstring rtn = 0;
    int slen = strlen(str);
    unsigned short * buffer = 0;
    if( slen == 0 )
    rtn = (env)->NewStringUTF(str );
    else
    {
    int length = MultiByteToWideChar( CP_ACP, 0, (LPCSTR)str, slen, NULL, 0 );
    buffer = (unsigned short *)malloc( length*2 + 1 );
    if( MultiByteToWideChar( CP_ACP, 0, (LPCSTR)str, slen, (LPWSTR)buffer, length ) >0 )
    rtn = (env)->NewString( (jchar*)buffer, length );
    }
    if( buffer )
    free( buffer );
    return rtn;
    }
    /*JNIEXPORT jstring JNICALL Java_test_cs_web_SWIFTAlianceCASmfTest_strcal
    (JNIEnv *env, jclass obj, jstring jstr1, jstring jstr2)
    {
    jbyteArray bytes = 0;
    jthrowable exc;
    char *pszResult = NULL;    
    char *pszSTR1 = NULL;
    char *pszSTR2 = NULL;
    
    pszSTR1 = jstringTostring(env, jstr1);
    pszSTR2 = jstringTostring(env, jstr2);
    
    int nlen = sizeof(char)*(strlen(pszSTR1)+strlen(pszSTR2));
    pszResult = (char*)malloc(nlen);
    strcpy(pszResult, pszSTR1);
    strcat(pszResult, pszSTR2);
    
    jstring jstrRe = stoJstring(env, pszResult);
    free(pszSTR1);
    free(pszSTR2);
    free(pszResult);
    return(jstrRe);
    }
    */

jni object的使用  
  
每一个jni格式的dll中的object对应该java里面的一个类。  
如下例有一个 ObjData类，类中有成员bData ,Len

public class ObjData {
    
    public byte[]  bData; 
    public int Len;        
    }
    //------------------------jni获得传过来的Object类型的变量objDataIn--------
    
    jclass clazz =(env)->FindClass("ObjData"); 
    
    //从传进来的对象中取出byte[]
    jfieldID byteData = (env)->GetFieldID(clazz,"bData","[B");
    jbyteArray pDataIn = (jbyteArray) (env)->GetObjectField(objDataIn, byteData);
    jsize theArrayLeng = env->GetArrayLength(pDataIn);
    
    //byte[]转为BYTE[]
    jbyte * arrayBody = env->GetByteArrayElements(pDataIn,0); 
    BYTE * jDataIn = (BYTE *)arrayBody; 
    
    
    //将BYTE数组转为jarray
    jbyte* byte = (jbyte*)jDataOut;    
    jbyteArray jarray = env->NewByteArray(theArrayLeng);
    env->SetByteArrayRegion(jarray, 0, theArrayLeng, byte);
    
    //给每一个实例的变量付值
    (env)->SetObjectField(objDataIn,byteData,jarray);
    (env)->SetIntField(objDataIn,pDataInLen,jDataInLen);
    
    (env)->ReleaseByteArrayElements(pDataIn, arrayBody, 0);

转帖：http://104zz.iteye.com/blog/1883386