3 ms·

It'd be unusably slow. "sun.misc.Unsafe" compiles in the instruction stream. JNI implementation would need to go through a complicated calling mechanism. I thin

by vardump 11y ago

It'd be unusably slow. "sun.misc.Unsafe" compiles in the instruction stream. JNI implementation would need to go through a complicated calling mechanism. I think it'd be up to 100x slower.

karavelov 11y ago
At least in OpenJDK it is in fact implemented as a JNI package, so it is already going through the JNI calling convention: http://hg.openjdk.java.net/jdk7/jdk7/jdk/file/9b8c96f96a0f/src/share/classes/sun/misc/Unsafe.java http://hg.openjdk.java.net/jdk7/jdk7/jdk/file/9b8c96f96a0f/s...
- twic 11y ago
  That code shows that it's implemented as native methods, but not necessarily as JNI - these could be VM intrinsics, like Object::getClass and so on. This is the native code for Unsafe: https://github.com/openjdk-mirror/jdk7u-hotspot/blob/master/src/share/vm/prims/unsafe.cpp https://github.com/openjdk-mirror/jdk7u-hotspot/blob/master/... It's certainly JNI-ish. Whether it is actually called via the JNI mechanism, i can't tell.
- vardump 11y ago
  I think these are a strong hint they're not truly JNI: Line 61: * <p> Most methods in this class are very low-level, and correspond to a * small number of hardware instructions (on typical machines). Compilers * are encouraged to optimize these methods accordingly. Line 90: /// peek and poke operations /// (compilers should optimize these to memory ops)