pass uint_8 array using params

Question

I tryed to writer method like InputStream:read(byte[] buffer,int offset,int length):

/*
 * Class:     com_readium_ResourceStream
 * Method:    readNative
 * Signature: ([BII)I
 */
JNIEXPORT jint JNICALL Java_com_readium_ResourceStream_readNative
  (JNIEnv *, jobject, jbyteArray, jint, jint);

How can I write uint_8 array to jbyteArray from params?

spacifici · Accepted Answer · 2013-06-11 09:13:12Z

2

This is my answer. It must be compiled as a c++ compilation unit. Otherwise you have to pass env as the first param (ie env->GetArrayLength(...); become in c GetArrayLength(env, ...).

/*
 * Class:     com_readium_ResourceStream
 * Method:    readNative
 * Signature: ([BII)I
 */
JNIEXPORT jint JNICALL Java_com_readium_ResourceStream_readNative
  (JNIEnv *env, jobject obj, jbyteArray buffer, jint offset, jint len)
{
  jint readed;
  // Read data and set readed

  jboolean isCopy;
  jsize arrayLen = env->GetArrayLength(buffer);
  jbyte* array = env->GetByteArrayElements(env, buffer, &isCopy);

  // Use array here

  env->ReleaseByteArrayElements(buffer, array, 0);
  return readed;
}

Remeber, java bytes are always signed.

answered Jun 11, 2013 at 9:13

spacifici

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2 Comments

fadden Over a year ago

GetByteArrayElements gets a pointer to, or copy of, the byte[]. You can then modify it directly. The ReleaseByteArrayElements call unlocks or copies back the modified array.

spacifici Over a year ago

Thanks fadden and sorry Alex, I forgot to mention it.

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