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jonpryorjonpryor
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[Java.Interop] Zero-GREF marshaling for builtins.
Consider the innocuous JavaObjectArray_object_ContractTest, which effectively does: var array = new JavaObjectArray<object>(3); array [0] = new object (); array [1] = 42; array [2] = "C"; Reasonably straightforward, but there's a hidden GREF cost: because we have a JavaObjectArray<object>, we use JavaVM.GetJniMarshalInfoForType(typeof(object)), which doens't provide any marshaling info, so we use the fallback JavaProxyObject.GetProxy() method to "convert" e.g. 42 into an IJavaObject, and the proxy must use a GREF. Which is fine for array[0], but both array[1] and array[2] have proper marshaling support! Yet we'd still take out a GREF for the int and the string constant! Blech! Improve JniMarshal.CreateLocalRef<T>() and JniMarshal.GetValue<T>() so that they take the runtime type into consideration, ahead of `T`. Within JniMarshal.CreateLocalRef<T>(), this involves using JavaVM.GetJniMarshalInfoForType(value.GetType()) (if value is not null), falling back to using JavaVM.GetJniMarshalInfoForType(typeof(T)) if the value is either null or no marshaler was found for value.GetType(). Similarly, within JniMarshal.GetValue<T>(), before using JavaVM.GetObject() we first lookup the JNI type of the target value, and do the JavaVM.GetTypeForJniTypeRefererence() / JavaVM.GetJniMarshalInfoForType() dance to find an optimized marshaler. By doing this, we can ensure that no additional GREFs are used to store 42 or "C" within the JavaObjectArray<object>.
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‎src/Java.Interop/Java.Interop/JavaVM.cs‎

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@@ -749,22 +749,6 @@ public virtual Type GetTypeForJniSimplifiedTypeReference (string jniTypeReferenc
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return null;
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}
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static readonly KeyValuePair<Type, JniTypeInfo>[] JniBuiltinTypeNameMappings = new []{
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new KeyValuePair<Type, JniTypeInfo>(typeof (string), new JniTypeInfo ("java/lang/String")),
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new KeyValuePair<Type, JniTypeInfo>(typeof (void), new JniTypeInfo ("V", true)),
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new KeyValuePair<Type, JniTypeInfo>(typeof (sbyte), new JniTypeInfo ("B", true)),
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new KeyValuePair<Type, JniTypeInfo>(typeof (short), new JniTypeInfo ("S", true)),
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new KeyValuePair<Type, JniTypeInfo>(typeof (int), new JniTypeInfo ("I", true) {
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}),
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new KeyValuePair<Type, JniTypeInfo>(typeof (long), new JniTypeInfo ("J", true)),
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new KeyValuePair<Type, JniTypeInfo>(typeof (float), new JniTypeInfo ("F", true)),
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new KeyValuePair<Type, JniTypeInfo>(typeof (double), new JniTypeInfo ("D", true)),
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new KeyValuePair<Type, JniTypeInfo>(typeof (char), new JniTypeInfo ("C", true)),
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new KeyValuePair<Type, JniTypeInfo>(typeof (bool), new JniTypeInfo ("Z", true)),
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};
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public virtual JniMarshalInfo GetJniMarshalInfoForType (Type type)
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{
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if (type == null)

‎src/Java.Interop/Java.Interop/JniBuiltinMarshalers.cs‎

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@@ -6,6 +6,29 @@ namespace Java.Interop {
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partial class JavaVM {
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static readonly KeyValuePair<Type, JniTypeInfo>[] JniBuiltinTypeNameMappings = new []{
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new KeyValuePair<Type, JniTypeInfo>(typeof (string), new JniTypeInfo ("java/lang/String")),
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new KeyValuePair<Type, JniTypeInfo>(typeof (void), new JniTypeInfo ("V", typeIsKeyword: true)),
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new KeyValuePair<Type, JniTypeInfo>(typeof (void), new JniTypeInfo ("java/lang/Void")),
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new KeyValuePair<Type, JniTypeInfo>(typeof (sbyte), new JniTypeInfo ("B", true)),
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new KeyValuePair<Type, JniTypeInfo>(typeof (Boolean), new JniTypeInfo ("Z", typeIsKeyword: true)),
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new KeyValuePair<Type, JniTypeInfo>(typeof (Boolean), new JniTypeInfo ("java/lang/Boolean")),
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new KeyValuePair<Type, JniTypeInfo>(typeof (Char), new JniTypeInfo ("C", typeIsKeyword: true)),
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new KeyValuePair<Type, JniTypeInfo>(typeof (Char), new JniTypeInfo ("java/lang/Character")),
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new KeyValuePair<Type, JniTypeInfo>(typeof (Int16), new JniTypeInfo ("S", typeIsKeyword: true)),
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new KeyValuePair<Type, JniTypeInfo>(typeof (Int16), new JniTypeInfo ("java/lang/Short")),
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new KeyValuePair<Type, JniTypeInfo>(typeof (Int32), new JniTypeInfo ("I", typeIsKeyword: true)),
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new KeyValuePair<Type, JniTypeInfo>(typeof (Int32), new JniTypeInfo ("java/lang/Integer")),
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new KeyValuePair<Type, JniTypeInfo>(typeof (Int64), new JniTypeInfo ("J", typeIsKeyword: true)),
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new KeyValuePair<Type, JniTypeInfo>(typeof (Int64), new JniTypeInfo ("java/lang/Long")),
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new KeyValuePair<Type, JniTypeInfo>(typeof (Single), new JniTypeInfo ("F", typeIsKeyword: true)),
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new KeyValuePair<Type, JniTypeInfo>(typeof (Single), new JniTypeInfo ("java/lang/Float")),
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new KeyValuePair<Type, JniTypeInfo>(typeof (Double), new JniTypeInfo ("D", typeIsKeyword: true)),
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new KeyValuePair<Type, JniTypeInfo>(typeof (Double), new JniTypeInfo ("java/lang/Double")),
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};
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static readonly KeyValuePair<Type, JniMarshalInfo>[] JniBuiltinMarshalers = new []{
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new KeyValuePair<Type, JniMarshalInfo>(typeof (string), new JniMarshalInfo {
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GetValueFromJni = JniEnvironment.Strings.ToString,

‎src/Java.Interop/Java.Interop/JniBuiltinMarshalers.tt‎

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@@ -22,6 +22,23 @@ namespace Java.Interop {
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partial class JavaVM {
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static readonly KeyValuePair<Type, JniTypeInfo>[] JniBuiltinTypeNameMappings = new []{
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new KeyValuePair<Type, JniTypeInfo>(typeof (string), new JniTypeInfo ("java/lang/String")),
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new KeyValuePair<Type, JniTypeInfo>(typeof (void), new JniTypeInfo ("V", typeIsKeyword: true)),
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new KeyValuePair<Type, JniTypeInfo>(typeof (void), new JniTypeInfo ("java/lang/Void")),
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new KeyValuePair<Type, JniTypeInfo>(typeof (sbyte), new JniTypeInfo ("B", true)),
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<#
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foreach (var type in types) {
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#>
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new KeyValuePair<Type, JniTypeInfo>(typeof (<#= type.Type #>), new JniTypeInfo ("<#= type.JniType #>", typeIsKeyword: true)),
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new KeyValuePair<Type, JniTypeInfo>(typeof (<#= type.Type #>), new JniTypeInfo ("java/lang/<#= type.Name #>")),
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<#
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}
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#>
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};
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static readonly KeyValuePair<Type, JniMarshalInfo>[] JniBuiltinMarshalers = new []{
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new KeyValuePair<Type, JniMarshalInfo>(typeof (string), new JniMarshalInfo {
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GetValueFromJni = JniEnvironment.Strings.ToString,

‎src/Java.Interop/Java.Interop/JniMarshal.cs‎

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@@ -51,18 +51,36 @@ internal static T GetValue<T> (JniReferenceSafeHandle handle, JniHandleOwnership
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return (T) proxy.Value;
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}
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if (target is T) {
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JniEnvironment.Handles.Dispose (handle, transfer);
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return (T) target;
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}
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var info = jvm.GetJniMarshalInfoForType (typeof (T));
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if (info.GetValueFromJni != null) {
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return (T) info.GetValueFromJni (handle, transfer, typeof (T));
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}
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var targetType = jvm.GetTypeForJniTypeRefererence (handle.GetJniTypeName ());
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if (targetType != null &&
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typeof (T).IsAssignableFrom (targetType) &&
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(info = jvm.GetJniMarshalInfoForType (targetType)).GetValueFromJni != null) {
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return (T) info.GetValueFromJni (handle, transfer, targetType);
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}
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return (T) jvm.GetObject (handle, transfer, typeof (T));
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}
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internal static JniLocalReference CreateLocalRef<T> (T value)
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{
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var jvm = JniEnvironment.Current.JavaVM;
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var info = jvm.GetJniMarshalInfoForType (typeof (T));
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var info = new JniMarshalInfo ();
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if (value != null)
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info = jvm.GetJniMarshalInfoForType (value.GetType ());
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if (info.CreateLocalRef == null)
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info = jvm.GetJniMarshalInfoForType (typeof (T));
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if (info.CreateLocalRef != null) {
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return info.CreateLocalRef (value);
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}

‎src/Java.Interop/Tests/Java.Interop/JavaObjectArrayTest.cs‎

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Original file line numberDiff line numberDiff line change
@@ -129,9 +129,36 @@ public void ObjectArrayType ()
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[TestFixture]
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public class JavaObjectArray_object_ContractTest : JavaObjectArrayContractTest<object> {
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protected override object CreateValueA () {return new object ();}
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protected override object CreateValueB () {return new object ();}
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protected override object CreateValueC () {return new object ();}
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static readonly object a = new object ();
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protected override object CreateValueA () {return a;}
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protected override object CreateValueB () {return 42;}
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protected override object CreateValueC () {return "C";}
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int grefStartCount;
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[TestFixtureSetUp]
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public void BeginCheckGlobalRefCount ()
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{
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// For diagnostic tracking purposes
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using (var o = new JavaObject ())
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o.RegisterWithVM ();
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// So that the JavaProxyObject.TypeRef GREF isn't counted.
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using (var o = new JavaObjectArray<object> (1))
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o [0] = a;
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grefStartCount = JniEnvironment.Current.JavaVM.GlobalReferenceCount;
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}
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[TestFixtureTearDown]
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public void EndCheckGlobalRefCount ()
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{
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using (var o = new JavaObject ())
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o.RegisterWithVM ();
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int gref = JniEnvironment.Current.JavaVM.GlobalReferenceCount;
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Assert.IsTrue (gref <= (grefStartCount),
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string.Format ("JNI global references: grefStartCount={0}; gref={1}", grefStartCount, gref));
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GC.Collect ();
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}
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[Test]
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public void ObjectArrayType ()

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