复制与JNI一个字节的缓冲区 [英] Copying a byte buffer with JNI

问题描述

我发现很多的StackOverflow是处理从C / JNI端复制字符数组变得像Java中的byte []的教程/的问题，而不是周围的其他方式。

I've found plenty of tutorials / questions on Stackoverflow that deal with copying char arrays from C/JNI side into something like a byte[] in Java, but not the other way around.

我使用的是本地C库，预计一个字节数组。我只是想从Java中的byte []的获取数据，为preferably C中的无符号字符[]。

I am using a native C library which expects a byte array. I simply want to get data from a byte[] in java, into preferably an unsigned char[] in C.

长话短说：什么是从jBytearray JNI中复制数据的最佳方式？有什么方法来检测它的大小？

Long story short: What is the best way of copying data from a jBytearray in JNI? Is there any way to detect it's size?

推荐答案

下面是一个工作的例子，我只是从我的AS / 400 JNI库举起来解决本地用户队列指针来测试队列的存在 - 它复制队列库并从Java字节数组（已转换为作业CCSID）到本机code的名字，并使用它。请注意释放函数调用的;这些是可以改变的，以本地阵列内容复制回到Java字节阵列来移动数据的其他方式：

Here's a working example I just lifted from my AS/400 JNI library to resolve a native user-queue pointer to test the queue's existence - it copies the queue library and name from a Java byte array (already translated to job's CCSID) into native code and uses it. Take note of the release function calls; these can be changed to copy the native array contents back into the Java byte arrays to move data the other way:

JNIEXPORT jboolean JNICALL Java_com_mycompany_jni400_UserQueue_jniResolve(JNIEnv *jep,jobject thsObj,                
jbyteArray queueLibrary,jbyteArray queueName) {                                                                             
    jbyte            *lib,*nam;                                                                                             
    bool             rtn;                                                                                                   

    thsObj=thsObj;                                                                                                          
    lib=(*jep)->GetByteArrayElements(jep,queueLibrary,0);                                                                   
    nam=(*jep)->GetByteArrayElements(jep,queueName,0);                                                                      
    rtn=(usrq_resolve((byte*)lib,(byte*)nam)!=NULL);                                                                        
    (*jep)->ReleaseByteArrayElements(jep,queueLibrary,lib,JNI_ABORT); /* abort to not copy back contents */                 
    (*jep)->ReleaseByteArrayElements(jep,queueName   ,nam,JNI_ABORT); /* abort to not copy back contents */                 
    if(rtn) { return JNI_TRUE;  }                                                                                           
    else    { return JNI_FALSE; }                                                                                           
    }                                                                                                                       

这篇关于复制与JNI一个字节的缓冲区的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！