* Add new @CriticalRegion annotation to allow zero-copy access to …

…data of Java arrays (pull #254)
bytedeco · Aug 25, 2018 · c50d69f · c50d69f
1 parent fa35503
commit c50d69f
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Showing 4 changed files with 41 additions and 3 deletions.
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -1,4 +1,5 @@
 
+ * Add new `@CriticalRegion` annotation to allow zero-copy access to data of Java arrays ([pull #254](https://github.com/bytedeco/javacpp/pull/254))
  * Allow `Builder` to create links for resource libraries even when no Java classes are built
  * Fix `Loader.cacheResource()` creating a subdirectory named "null" when caching a top-level file
  * Update `README.md` with reference to newly published [Mapping Recipes for C/C++ Libraries](https://github.com/bytedeco/javacpp/wiki/Mapping-Recipes)

diff --git a/src/main/java/org/bytedeco/javacpp/annotation/CriticalRegion.java b/src/main/java/org/bytedeco/javacpp/annotation/CriticalRegion.java
@@ -0,0 +1,18 @@
+package org.bytedeco.javacpp.annotation;
+
+import org.bytedeco.javacpp.tools.Generator;
+
+import java.lang.annotation.*;
+
+/**
+ * In some methods, {@link Generator} will generate code to transfer arrays from the
+ * JVM to native code using the {@code Get/Release<primitivetype>ArrayElements} methods.
+ * However these methods copy the underlying data. With this annotation, the generated
+ * code will always call the {@code Get/ReleasePrimitiveArrayCritical} methods instead.
+ *
+ * @see Generator
+ *
+ */
+@Documented @Retention(RetentionPolicy.RUNTIME)
+@Target({ElementType.TYPE, ElementType.METHOD})
+public @interface CriticalRegion { }
diff --git a/src/main/java/org/bytedeco/javacpp/tools/Generator.java b/src/main/java/org/bytedeco/javacpp/tools/Generator.java
@@ -72,6 +72,7 @@
 import org.bytedeco.javacpp.annotation.Cast;
 import org.bytedeco.javacpp.annotation.Const;
 import org.bytedeco.javacpp.annotation.Convention;
+import org.bytedeco.javacpp.annotation.CriticalRegion;
 import org.bytedeco.javacpp.annotation.Function;
 import org.bytedeco.javacpp.annotation.Index;
 import org.bytedeco.javacpp.annotation.MemberGetter;
@@ -113,6 +114,7 @@
  * @see Cast
  * @see Const
  * @see Convention
+ * @see CriticalRegion
  * @see Function
  * @see Index
  * @see MemberGetter
@@ -1871,7 +1873,7 @@ void parametersBefore(MethodInformation methodInfo) {
                         methodInfo.parameterTypes[j].getComponentType().isPrimitive()) {
                     out.print("arg" + j + " == NULL ? NULL : ");
                     String s = methodInfo.parameterTypes[j].getComponentType().getName();
-                    if (methodInfo.valueGetter || methodInfo.valueSetter ||
+                    if (methodInfo.criticalRegion || methodInfo.valueGetter || methodInfo.valueSetter ||
                             methodInfo.memberGetter || methodInfo.memberSetter) {
                         out.println("(j" + s + "*)env->GetPrimitiveArrayCritical(arg" + j + ", NULL);");
                     } else {
@@ -2502,7 +2504,7 @@ void parametersAfter(MethodInformation methodInfo) {
                     out.println("    }");
                 }
                 out.print("    if (arg" + j + " != NULL) ");
-                if (methodInfo.valueGetter || methodInfo.valueSetter ||
+                if (methodInfo.criticalRegion || methodInfo.valueGetter || methodInfo.valueSetter ||
                         methodInfo.memberGetter || methodInfo.memberSetter) {
                     out.println("env->ReleasePrimitiveArrayCritical(arg" + j + ", ptr" + j + ", " + releaseArrayFlag + ");");
                 } else {
@@ -3053,6 +3055,7 @@ MethodInformation methodInformation(Method method) {
         info.dim    = index != null ? index.value() : 0;
         info.parameterTypes       = method.getParameterTypes();
         info.parameterAnnotations = method.getParameterAnnotations();
+        info.criticalRegion = criticalRegion(info.cls, info.method);
         info.returnRaw = method.isAnnotationPresent(Raw.class);
         info.withEnv = info.returnRaw ? method.getAnnotation(Raw.class).withEnv() : false;
         info.parameterRaw = new boolean[info.parameterAnnotations.length];
@@ -3253,6 +3256,22 @@ MethodInformation methodInformation(Method method) {
         return info;
     }
 
+    static boolean criticalRegion(Class<?> cls, Method method) {
+        boolean criticalRegion = baseClasses.contains(cls) ||
+                method.isAnnotationPresent(CriticalRegion.class);
+        while (!criticalRegion && cls != null) {
+            if (criticalRegion = cls.isAnnotationPresent(CriticalRegion.class)) {
+                break;
+            }
+            if (cls.getEnclosingClass() != null) {
+                cls = cls.getEnclosingClass();
+            } else {
+                cls = cls.getSuperclass();
+            }
+        }
+        return criticalRegion;
+    }
+
     static boolean noException(Class<?> cls, Method method) {
         boolean noException = baseClasses.contains(cls) ||
                 method.isAnnotationPresent(NoException.class);

diff --git a/src/main/java/org/bytedeco/javacpp/tools/MethodInformation.java b/src/main/java/org/bytedeco/javacpp/tools/MethodInformation.java
@@ -40,7 +40,7 @@ public class MethodInformation {
     boolean[] parameterRaw;
     Class<?>[] parameterTypes;
     Annotation[][] parameterAnnotations;
-    boolean returnRaw, withEnv, overloaded, noOffset, deallocator, allocator, arrayAllocator,
+    boolean criticalRegion, returnRaw, withEnv, overloaded, noOffset, deallocator, allocator, arrayAllocator,
             bufferGetter, valueGetter, valueSetter, memberGetter, memberSetter, noReturnGetter;
     Method pairedMethod;
     Class<?> throwsException;