1 files changed, 71 insertions, 0 deletions
diff --git a/src/tools/xcode-common/java/com/google/devtools/build/xcode/util/Interspersing.java b/src/tools/xcode-common/java/com/google/devtools/build/xcode/util/Interspersing.java
new file mode 100644
index 0000000000..89bf487221
--- /dev/null
+++ b/src/tools/xcode-common/java/com/google/devtools/build/xcode/util/Interspersing.java
@@ -0,0 +1,71 @@
+// Copyright 2014 Google Inc. All rights reserved.
+//
+// Licensed 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.
+
+package com.google.devtools.build.xcode.util;
+
+import com.google.common.base.Function;
+import com.google.common.base.Preconditions;
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.Iterables;
+
+/**
+ * Utility code for interspersing items into sequences.
+ */
+public class Interspersing {
+  private Interspersing() {}
+
+  /**
+   * Inserts {@code what} before each item in {@code sequence}, returning a lazy sequence of twice
+   * the length.
+   */
+  public static <E> Iterable<E> beforeEach(final E what, Iterable<E> sequence) {
+    Preconditions.checkNotNull(what);
+    return Iterables.concat(
+        Iterables.transform(
+            sequence,
+            new Function<E, Iterable<E>>() {
+              @Override
+              public Iterable<E> apply(E element) {
+                return ImmutableList.of(what, element);
+              }
+            }
+        ));
+  }
+
+  /**
+   * Prepends {@code what} to each string in {@code sequence}, returning a lazy sequence of the 
+   * same length.
+   */
+  public static Iterable<String>
+      prependEach(final String what, Iterable<String> sequence) {
+    Preconditions.checkNotNull(what);
+    return Iterables.transform(
+        sequence,
+        new Function<String, String>() {
+          @Override
+          public String apply(String input) {
+            return what + input;
+          }
+        });
+  }
+
+  /**
+   * Similar to {@link #prependEach(String, Iterable)}, but also converts each item in the sequence
+   * to a string.
+   */
+  public static <E> Iterable<String>
+      prependEach(String what, Iterable<E> sequence, Function<? super E, String> toString) {
+    return prependEach(what, Iterables.transform(sequence, toString));
+  }
+}