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package org.luaj.vm2;
import java.lang.ref.WeakReference;
import org.luaj.vm2.LuaTable.Slot;
import org.luaj.vm2.LuaTable.StrongSlot;
/**
* Subclass of {@link LuaTable} that provides weak key and weak value semantics.
*
* Normally these are not created directly, but indirectly when changing the mode
* of a {@link LuaTable} as lua script executes.
*
* However, calling the constructors directly when weak tables are required from
* Java will reduce overhead.
*/
public class WeakTable implements Metatable {
private boolean weakkeys, weakvalues;
private LuaValue backing;
public static LuaTable make(boolean weakkeys, boolean weakvalues) {
LuaString mode;
if ( weakkeys && weakvalues ) {
mode = LuaString.valueOf("kv");
} else if ( weakkeys ) {
mode = LuaString.valueOf("k");
} else if ( weakvalues ) {
mode = LuaString.valueOf("v");
} else {
return LuaTable.tableOf();
}
LuaTable table = LuaTable.tableOf();
LuaTable mt = LuaTable.tableOf(new LuaValue[] { LuaValue.MODE, mode });
table.setmetatable(mt);
return table;
}
/**
* Construct a table with weak keys, weak values, or both
* @param weakkeys true to let the table have weak keys
* @param weakvalues true to let the table have weak values
*/
public WeakTable(boolean weakkeys, boolean weakvalues, LuaValue backing) {
this.weakkeys = weakkeys;
this.weakvalues = weakvalues;
this.backing = backing;
}
public boolean useWeakKeys() {
return weakkeys;
}
public boolean useWeakValues() {
return weakvalues;
}
public LuaValue toLuaValue() {
return backing;
}
public Slot entry(LuaValue key, LuaValue value) {
value = value.strongvalue();
if ( value == null )
return null;
if ( weakkeys && !( key.isnumber() || key.isstring() || key.isboolean() )) {
if ( weakvalues && !( value.isnumber() || value.isstring() || value.isboolean() )) {
return new WeakKeyAndValueSlot( key, value, null );
} else {
return new WeakKeySlot( key, value, null );
}
}
if ( weakvalues && ! (value.isnumber() || value.isstring() || value.isboolean() )) {
return new WeakValueSlot( key, value, null );
}
return LuaTable.defaultEntry( key, value );
}
public static abstract class WeakSlot implements Slot {
protected Object key;
protected Object value;
protected Slot next;
protected WeakSlot(Object key, Object value, Slot next) {
this.key = key;
this.value = value;
this.next = next;
}
public abstract int keyindex( int hashMask );
public abstract Slot set(LuaValue value);
public StrongSlot first() {
LuaValue key = strongkey();
LuaValue value = strongvalue();
if ( key != null && value != null ) {
return new LuaTable.NormalEntry(key, value);
} else {
this.key = null;
this.value = null;
return null;
}
}
public StrongSlot find(LuaValue key) {
StrongSlot first = first();
return ( first != null ) ? first.find( key ) : null;
}
public boolean keyeq(LuaValue key) {
StrongSlot first = first();
return ( first != null ) && first.keyeq( key );
}
public Slot rest() {
return next;
}
public int arraykey(int max) {
// Integer keys can never be weak.
return 0;
}
public Slot set(StrongSlot target, LuaValue value) {
LuaValue key = strongkey();
if ( key != null && target.find( key ) != null ) {
return set( value );
} else if ( key != null ) {
// Our key is still good.
next = next.set( target, value );
return this;
} else {
// our key was dropped, remove ourselves from the chain.
return next.set( target, value );
}
}
public Slot add( Slot entry ) {
next = ( next != null ) ? next.add( entry ) : entry;
if ( strongkey() != null && strongvalue() != null ) {
return this;
} else {
return next;
}
}
public Slot remove( StrongSlot target ) {
LuaValue key = strongkey();
if ( key == null ) {
return next.remove( target );
} else if ( target.keyeq( key ) ) {
this.value = null;
return this;
} else {
next = next.remove( target );
return this;
}
}
public Slot relink( Slot rest ) {
if ( strongkey() != null && strongvalue() != null ) {
if ( rest == null && this.next == null ) {
return this;
} else {
return copy( rest );
}
} else {
return rest;
}
}
public LuaValue strongkey() {
return (LuaValue) key;
}
public LuaValue strongvalue() {
return (LuaValue) value;
}
protected abstract WeakSlot copy( Slot next );
}
static class WeakKeySlot extends WeakSlot {
private final int keyhash;
protected WeakKeySlot( LuaValue key, LuaValue value, Slot next ) {
super(weaken(key), value, next);
keyhash = key.hashCode();
}
protected WeakKeySlot( WeakKeySlot copyFrom, Slot next ) {
super( copyFrom.key, copyFrom.value, next );
this.keyhash = copyFrom.keyhash;
}
public int keyindex( int mask ) {
return LuaTable.hashmod( keyhash, mask );
}
public Slot set(LuaValue value) {
this.value = value;
return this;
}
public LuaValue strongkey() {
return strengthen( key );
}
protected WeakSlot copy( Slot rest ) {
return new WeakKeySlot( this, rest );
}
}
static class WeakValueSlot extends WeakSlot {
protected WeakValueSlot( LuaValue key, LuaValue value, Slot next ) {
super( key, weaken(value), next);
}
protected WeakValueSlot( WeakValueSlot copyFrom, Slot next ) {
super( copyFrom.key, copyFrom.value, next );
}
public int keyindex( int mask ) {
return LuaTable.hashSlot( strongkey(), mask );
}
public Slot set(LuaValue value) {
this.value = weaken(value);
return this;
}
public LuaValue strongvalue() {
return strengthen( value );
}
protected WeakSlot copy(Slot next) {
return new WeakValueSlot( this, next );
}
}
static class WeakKeyAndValueSlot extends WeakSlot {
private final int keyhash;
protected WeakKeyAndValueSlot( LuaValue key, LuaValue value, Slot next ) {
super( weaken(key), weaken(value), next );
keyhash = key.hashCode();
}
protected WeakKeyAndValueSlot(WeakKeyAndValueSlot copyFrom, Slot next) {
super( copyFrom.key, copyFrom.value, next );
keyhash = copyFrom.keyhash;
}
public int keyindex( int hashMask ) {
return LuaTable.hashmod( keyhash, hashMask );
}
public Slot set(LuaValue value) {
this.value = weaken(value);
return this;
}
public LuaValue strongkey() {
return strengthen( key );
}
public LuaValue strongvalue() {
return strengthen( value );
}
protected WeakSlot copy( Slot next ) {
return new WeakKeyAndValueSlot( this, next );
}
}
/**
* Self-sent message to convert a value to its weak counterpart
* @param value value to convert
* @return {@link LuaValue} that is a strong or weak reference, depending on type of {@code value}
*/
protected static LuaValue weaken( LuaValue value ) {
switch ( value.type() ) {
case LuaValue.TFUNCTION:
case LuaValue.TTHREAD:
case LuaValue.TTABLE:
return new WeakValue(value);
case LuaValue.TUSERDATA:
return new WeakUserdata(value);
default:
return value;
}
}
/**
* Unwrap a LuaValue from a WeakReference and/or WeakUserdata.
* @param ref reference to convert
* @return LuaValue or null
* @see #weaken(LuaValue)
*/
protected static LuaValue strengthen(Object ref) {
if ( ref instanceof WeakReference ) {
ref = ((WeakReference) ref).get();
}
if ( ref instanceof WeakValue ) {
return ((WeakValue) ref).strongvalue();
}
return (LuaValue) ref;
}
/** Internal class to implement weak values.
* @see WeakTable
*/
static class WeakValue extends LuaValue {
WeakReference ref;
protected WeakValue(LuaValue value) {
ref = new WeakReference(value);
}
public int type() {
illegal("type","weak value");
return 0;
}
public String typename() {
illegal("typename","weak value");
return null;
}
public String toString() {
return "weak<"+ref.get()+">";
}
public LuaValue strongvalue() {
Object o = ref.get();
return (LuaValue)o;
}
public boolean raweq(LuaValue rhs) {
Object o = ref.get();
return o!=null && rhs.raweq((LuaValue)o);
}
}
/** Internal class to implement weak userdata values.
* @see WeakTable
*/
static final class WeakUserdata extends WeakValue {
private final WeakReference ob;
private final LuaValue mt;
private WeakUserdata(LuaValue value) {
super(value);
ob = new WeakReference(value.touserdata());
mt = value.getmetatable();
}
public LuaValue strongvalue() {
Object u = ref.get();
if ( u != null )
return (LuaValue) u;
Object o = ob.get();
if ( o != null ) {
LuaValue ud = LuaValue.userdataOf(o,mt);
ref = new WeakReference(ud);
return ud;
} else {
return null;
}
}
}
public LuaValue wrap(LuaValue value) {
return weakvalues ? weaken( value ) : value;
}
public LuaValue arrayget(LuaValue[] array, int index) {
LuaValue value = array[index];
if (value != null) {
value = strengthen(value);
if (value == null) {
array[index] = null;
}
}
return value;
}
}