Add two function types for Closable functions

ClosableFunction and ClosableThrowFunction are both function types that
are used for binding a auto-closable resource to a function,
representing a "thing that can only be done while a given resource is
open"

2 files changed, 69 insertions, 0 deletions

diff --git a/src/main/java/bjc/functypes/ClosableFunction.java b/src/main/java/bjc/functypes/ClosableFunction.java
new file mode 100644
index 0000000..a559bfc
--- /dev/null
+++ b/src/main/java/bjc/functypes/ClosableFunction.java
@@ -0,0 +1,34 @@
+package bjc.functypes;
+
+import java.util.function.Function;
+
+/**
+ * A function associated with a closable resource
+ * 
+ * @param <T> The input type
+ * @param <R> The result type
+ */
+public interface ClosableFunction<T, R> extends AutoCloseable, Function<T, R> {
+	/**
+	 * Create a ClosableFunction from a {@link AutoCloseable} and a {@link Function}
+	 * 
+	 * @param <T> The input type
+	 * @param <R> The result type
+	 * @param f The function
+	 * @param clos The AutoClosable
+	 * @return The closable function
+	 */
+	public static <T, R> ClosableFunction<T, R> bindFunction(Function<T, R> f, AutoCloseable clos) {
+		return new ClosableFunction<T, R>() {
+			@Override
+			public R apply(T t) {
+				return f.apply(t);
+			}
+			
+			@Override
+			public void close() throws Exception {
+				clos.close();
+			}
+		};
+	}
+}
diff --git a/src/main/java/bjc/functypes/ClosableThrowFunction.java b/src/main/java/bjc/functypes/ClosableThrowFunction.java
new file mode 100644
index 0000000..856f15d
--- /dev/null
+++ b/src/main/java/bjc/functypes/ClosableThrowFunction.java
@@ -0,0 +1,35 @@
+package bjc.functypes;
+
+import java.util.function.Function;
+
+/**
+ * A (possibly throwing) function associated with a closable resource
+ * 
+ * @param <T> The input type
+ * @param <R> The result type
+ * @param <E> The exception type
+ */
+public interface ClosableThrowFunction<T, R, E extends Throwable> extends AutoCloseable, ThrowFunction<T, R, E> {
+	/**
+	 * Create a ClosableFunction from a {@link AutoCloseable} and a {@link Function}
+	 * 
+	 * @param <T> The input type
+	 * @param <R> The result type
+	 * @param f The function
+	 * @param clos The AutoClosable
+	 * @return The closable function
+	 */
+	public static <T, R, E extends Throwable> ClosableThrowFunction<T, R, E> bindFunction(ThrowFunction<T, R, E> f, AutoCloseable clos) {
+		return new ClosableThrowFunction<T, R, E>() {
+			@Override
+			public R apply(T t) throws E {
+				return f.apply(t);
+			}
+			
+			@Override
+			public void close() throws Exception {
+				clos.close();
+			}
+		};
+	}
+}