diff --git a/httpcore5/src/main/java/org/apache/hc/core5/function/IOFunction.java b/httpcore5/src/main/java/org/apache/hc/core5/function/IOFunction.java
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+++ b/httpcore5/src/main/java/org/apache/hc/core5/function/IOFunction.java
@@ -0,0 +1,52 @@
+/*
+ * ====================================================================
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ * ====================================================================
+ *
+ * This software consists of voluntary contributions made by many
+ * individuals on behalf of the Apache Software Foundation.  For more
+ * information on the Apache Software Foundation, please see
+ * <http://www.apache.org/>.
+ *
+ */
+
+package org.apache.hc.core5.function;
+
+import java.io.IOException;
+
+/**
+ * Minimal equivalent of {@link java.util.function.Function} whose
+ * {@link #apply(Object)} method is allowed to throw {@link IOException}.
+ *
+ * @param <T> input type
+ * @param <R> result type
+ * @since 5.4
+ */
+@FunctionalInterface
+public interface IOFunction<T, R> {
+
+    /**
+     * Applies the transformation.
+     *
+     * @param value source value (never {@code null})
+     * @return transformed value
+     * @throws IOException if the transformation cannot be performed
+     */
+    R apply(T value) throws IOException;
+
+}
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