如何在JNI中读取字节数组？ [英] How to read a bytearray in JNI?

问题描述

是否可以在JNI中引用整个字节数组而不调用任何副本？

Is it possible to just reference a entire bytearray in JNI but not invoking any copy ?

在本机C代码中，我有一个从Java传递过来的字节数组，我只想比较一些数据到这个字节数组，所以我不想做任何内存复制。

In native C code, I have a bytearray passing from Java, and I just want to compare some data to this bytearray so I do not want to do any memory copy. Is it possible ?

我知道我可以通过使用GetPrimitiveArrayCritical之类的东西来获取本机字节数组的指针

I know I could get the pointer of a bytearray in native by using GetPrimitiveArrayCritical something like that

JNIEXPORT jbyteArray JNICALL Java_nfore_android_bt_pro_nfhfp_dsp
(JNIEnv *env, jobject jobj, jbyteArray jbIn, jbyteArray jbBase){

    jbyte *bufferIn;
    jbyte *bufferBase;
    bufferIn = (*env)->GetPrimitiveArrayCritical(env, jbIn, NULL);

    LOGD("Begin of dsp()"); 
    LOGD("In dsp() Before Comparing...");

        // Compare bufferIn with bufferBase here...

    LOGD("In dsp() After Comparing...");
    LOGD("End of dsp()");

    (*env)->ReleasePrimitiveArrayCritical(env, jbIn, bufferIn, 0);

    return jbIn;
}

如您所见，因为我可能会更改jbIn中的数据，应该使用GetPrimitiveArrayCritical来获取它的指针并在以后释放它。

As you could see, because I might change the data in the jbIn, I should use GetPrimitiveArrayCritical to get its pointer and release it later.

但是，如果我只想读取字节数组jbBase，我怎么能获得jbBase的指针却没有呢？使用GetPrimitiveArrayCritical吗？

However, if I just want to READ the bytearray jbBase, how could I get the pointer of the jbBase but not using GetPrimitiveArrayCritical ?

任何建议将不胜感激。非常感谢。

Any suggestion would be appreciated. Thanks a lot.

推荐答案

我使用以下内容读取字节数组...

I use the following to read byte arrays...

jbyte *b = (jbyte *)env->GetByteArrayElements(jbBase, NULL);
// read bytes in *b here
...
// release it
env->ReleaseByteArrayElements(jbBase, b, 0 );

您仍然需要释放它，因为这可能会阻止垃圾收集器在您仍在使用时将其清除使用它。

You still need to release it as that stops the Garbage collector getting rid of it potentially while you are still using it.

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