title: Passing a byte[] in Java to a function in C through JNI: how to use jarraybyte
body: <p>This is the first time that I use the JNI and also the first time that I have to write some lines in C.</p>
  
  <p>What I am trying to do is very simple. I'm just trying to switch the endiannes of a byte[] using a C routine. </p>
  
  <p>In java it is done like this:</p>
  
  <pre><code>public void switchEndianness(byte[] array){
  
          byte byte1;
          byte byte2;
  
          for(int i = 0; i &lt; array.length ; i+=2){
              byte1 = array[i];
              byte2 = array[i+1];
  
              array[i] = byte2;
              array[i+1] = byte1;
          }
  }</code></pre>
  
  <p>So to do this using JNI, I've tried to imlpement the same routine in the JNICALL, but it doesn't compile. What I've written so far is this:</p>
  
  <pre><code>JNIEXPORT void JNICALL Java_CEndianness_switchEndianness(JNIEnv *env, jobject obj, jbyteArray array, jint offset, jint length){
  
      char byte1;
      char byte2;
  
      int i;
      for(i = offset; i  &lt; length ; i+=2){
          byte1 = array[i];
          byte2 = array[i+1];
  
          array[i] = byte2;
          array[i+1] = byte1;
      }
  }</code></pre>
  
  <p>I have no clue how to use the jbyteArray type of data. is it possible to store a jbyte in a char??? Another question is.. when this routine is over...will the byte[] in java be modified?? Or is it only modified inside the C call?</p>
  
  <p>Any help???</p>
  
  <p>Thanks to everybody!</p>