Get<PrimitiveType>ArrayElements Routines - GetLongArrayElements
NativeType
*Get<PrimitiveType>ArrayElements(JNIEnv *env,ArrayType array, jboolean *isCopy);
A family of functions that returns the body of the primitive array. The result is valid until the correspondingRelease
<PrimitiveType>ArrayElements() function is called. Since the returned array may be a copy of the Java array, changes made to the returned array will not necessarily be reflected in the original array until Release<PrimitiveType>ArrayElements() is called. (GetLongArrayElements)
If
isCopy is not NULL, then *isCopy is set to JNI_TRUE if a copy is made; or it is set to JNI_FALSE if no copy is made.
The following table describes the specific primitive array element accessors. You should make the following substitutions: (GetLongArrayElements)
- Replace Get<PrimitiveType>ArrayElements with one of the actual primitive element accessor routine names from the table.
- Replace ArrayType with the corresponding array type.
- Replace NativeType with the corresponding native type for that routine.
Regardless of how boolean arrays are represented in the Java VM,
GetBooleanArrayElements() always returns a pointer tojbooleans, with each byte denoting an element (the unpacked representation). All arrays of other types are guaranteed to be contiguous in memory.
Table 4-9a Get<PrimitiveType>ArrayElements Family of Accessor Routines
LINKAGE:
Indices in the JNIEnv interface function table.
Table 4-9b Get<PrimitiveType>ArrayElements Family of Accessor Routines
PARAMETERS of GetLongArrayElements
env: the JNI interface pointer.array: a Java string object.isCopy: a pointer to a boolean.RETURNS of GetLongArrayElements
Returns a pointer to the array elements, or
NULL if the operation fails.
Example of GetLongArrayElements
package com.example.aslrtest;
public class Test {
private static native void test(long[] heapa);
public void doTest()
{
long[] a=new long[size_of_available_heap/8];
for (long i=0; i!=a.length; i++)
a[i]=i;
test(a);
System.out.println(a[0]);
}
}
Then with something like this JNI code, you can get the address of that array.
JNIEXPORT void JNICALL Java_com_example_aslrtest_Test_test(JNIEnv * env, jclass jc, jlongArray heapa)
{
jlong* heapp;
jboolean jniNoCopy = JNI_FALSE;
heapp = (*env)->GetLongArrayElements(env, heapa, &jniNoCopy);
heapp[0] = (jlong)heapp;
(*env)->ReleaseLongArrayElements(env,heapa,heapp,0);
}