org.dynalang.dynalink

Class ChainedCallSite

java.lang.Object

java.lang.invoke.CallSite

java.lang.invoke.MutableCallSite

org.dynalang.dynalink.support.AbstractRelinkableCallSite

org.dynalang.dynalink.ChainedCallSite

All Implemented Interfaces:

RelinkableCallSite

public class ChainedCallSite
extends AbstractRelinkableCallSite

A relinkable call site that maintains a chain of linked method handles. In the default implementation, up to 8 method handles can be chained, cascading from one to the other through MethodHandles.guardWithTest(MethodHandle, MethodHandle, MethodHandle). When this call site has to link a new method handle and the length of the chain is already at the maximum, it will throw away the oldest method handle. Switchpoint-invalidated handles in the chain are removed eagerly (on each linking request, and whenever a switchpoint-invalidated method handle is traversed during invocation). There is currently no profiling attached to the handles in the chain, so they are never reordered based on usage; the most recently linked method handle is always at the start of the chain.

Constructor Summary

Constructors

Constructor and Description
ChainedCallSite(CallSiteDescriptor descriptor) Creates a new chained call site.

Method Summary

Modifier and Type	Method and Description
protected int	getMaxChainLength() The maximum number of method handles in the chain.
void	relink(GuardedInvocation guardedInvocation, MethodHandle fallback) This method will be called by the dynamic linker every time the call site is normally relinked.
void	resetAndRelink(GuardedInvocation guardedInvocation, MethodHandle fallback) This method will be called by the dynamic linker every time the call site is relinked and the linker wishes the call site to throw away any prior linkage state.

Methods inherited from class org.dynalang.dynalink.support.AbstractRelinkableCallSite

getDescriptor, initialize

Methods inherited from class java.lang.invoke.MutableCallSite

dynamicInvoker, getTarget, setTarget, syncAll

Methods inherited from class java.lang.invoke.CallSite

type

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

ChainedCallSite

public ChainedCallSite(CallSiteDescriptor descriptor)

Creates a new chained call site.

Parameters:

descriptor - the descriptor for the call site.

Method Detail

getMaxChainLength

protected int getMaxChainLength()

The maximum number of method handles in the chain. Defaults to 8. You can override it in a subclass if you need to change the value. If your override returns a value less than 1, the code will break.

Returns:

the maximum number of method handles in the chain.

relink

public void relink(GuardedInvocation guardedInvocation,
                   MethodHandle fallback)

Description copied from interface: RelinkableCallSite

This method will be called by the dynamic linker every time the call site is normally relinked. It will be passed a GuardedInvocation that the call site should incorporate into its target method handle. When this method is called, the call site is allowed to keep other non-invalidated invocations around for implementation of polymorphic inline caches and compose them with this invocation to form its final target.

Parameters:

guardedInvocation - the guarded invocation that the call site should incorporate into its target method handle.

fallback - the fallback method. This is a method matching the method type of the call site that is supplied by the DynamicLinker to be used by this call site as a fallback when it can't invoke its target with the passed arguments. The fallback method is such that when it's invoked, it'll try to discover the adequate target for the invocation, subsequently invoke RelinkableCallSite.relink(GuardedInvocation, MethodHandle) or RelinkableCallSite.resetAndRelink(GuardedInvocation, MethodHandle), and finally invoke the target.

resetAndRelink

public void resetAndRelink(GuardedInvocation guardedInvocation,
                           MethodHandle fallback)

Description copied from interface: RelinkableCallSite

This method will be called by the dynamic linker every time the call site is relinked and the linker wishes the call site to throw away any prior linkage state. It will be passed a GuardedInvocation that the call site should use to build its target method handle. When this method is called, the call site is discouraged from keeping previous state around, and is supposed to only link the current invocation.

Parameters:

guardedInvocation - the guarded invocation that the call site should use to build its target method handle.

fallback - the fallback method. This is a method matching the method type of the call site that is supplied by the DynamicLinker to be used by this call site as a fallback when it can't invoke its target with the passed arguments. The fallback method is such that when it's invoked, it'll try to discover the adequate target for the invocation, subsequently invoke RelinkableCallSite.relink(GuardedInvocation, MethodHandle) or RelinkableCallSite.resetAndRelink(GuardedInvocation, MethodHandle), and finally invoke the target.