Java native method source code

Question

Where can I download the java native method source code? For example, I want to know the source code of System.arraycopy(), but I can't find.

Answer 1

You can download OpenJdk source code here.

In the folder jdk\src\share you can get source code.

jdk\src\share\native is the natice method souce write in c and c++.

1. jdk\src\linux source for linux.
2. jdk\src\windows source for windows.
3. jdk\src\solaris souce for solaris.
4. jd\src\share common source.

eg: System.arrayCopy();

int file hotspot\src\share\vm\oops\objArrayKlass.cpp line 168:

void objArrayKlass::copy_array(arrayOop s, int src_pos, arrayOop d,
                           int dst_pos, int length, TRAPS) {
assert(s->is_objArray(), "must be obj array");

if (!d->is_objArray()) {
  THROW(vmSymbols::java_lang_ArrayStoreException());
}

// Check is all offsets and lengths are non negative
if (src_pos < 0 || dst_pos < 0 || length < 0) {
  THROW(vmSymbols::java_lang_ArrayIndexOutOfBoundsException());
}
// Check if the ranges are valid
if  ( (((unsigned int) length + (unsigned int) src_pos) > (unsigned int) s->length())
   || (((unsigned int) length + (unsigned int) dst_pos) > (unsigned int) d->length()) )   {
  THROW(vmSymbols::java_lang_ArrayIndexOutOfBoundsException());
}

// Special case. Boundary cases must be checked first
// This allows the following call: copy_array(s, s.length(), d.length(), 0).
// This is correct, since the position is supposed to be an 'in between point', i.e., s.length(),
// points to the right of the last element.
if (length==0) {
  return;
}
if (UseCompressedOops) {
  narrowOop* const src = objArrayOop(s)->obj_at_addr<narrowOop>(src_pos);
  narrowOop* const dst = objArrayOop(d)->obj_at_addr<narrowOop>(dst_pos);
  do_copy<narrowOop>(s, src, d, dst, length, CHECK);
} else {
  oop* const src = objArrayOop(s)->obj_at_addr<oop>(src_pos);
  oop* const dst = objArrayOop(d)->obj_at_addr<oop>(dst_pos);
  do_copy<oop> (s, src, d, dst, length, CHECK);
  }
}

Answer 2

Native methods and implemented differently by the Virtual Machine you are using. There is no one implementation of this method, and in fact different code may be executed on different architectures or VMs.