1 files changed, 89 insertions, 0 deletions
diff --git a/src/main/java/com/google/devtools/build/lib/rules/SkylarkCommandLine.java b/src/main/java/com/google/devtools/build/lib/rules/SkylarkCommandLine.java
new file mode 100644
index 0000000000..e51805e3e3
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+++ b/src/main/java/com/google/devtools/build/lib/rules/SkylarkCommandLine.java
@@ -0,0 +1,89 @@
+// 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.lib.rules;
+
+import com.google.common.base.Function;
+import com.google.common.collect.Iterables;
+import com.google.devtools.build.lib.actions.Artifact;
+import com.google.devtools.build.lib.collect.nestedset.NestedSet;
+import com.google.devtools.build.lib.events.Location;
+import com.google.devtools.build.lib.syntax.EvalException;
+import com.google.devtools.build.lib.syntax.SkylarkBuiltin;
+import com.google.devtools.build.lib.syntax.SkylarkBuiltin.Param;
+import com.google.devtools.build.lib.syntax.SkylarkFunction.SimpleSkylarkFunction;
+import com.google.devtools.build.lib.syntax.SkylarkList;
+import com.google.devtools.build.lib.syntax.SkylarkModule;
+import com.google.devtools.build.lib.syntax.SkylarkNestedSet;
+
+import java.util.Map;
+
+/**
+ * A Skylark module class to create memory efficient command lines.
+ */
+@SkylarkModule(name = "cmd_helper", namespace = true,
+    doc = "Module for creating memory efficient command lines.")
+public class SkylarkCommandLine {
+
+  @SkylarkBuiltin(name = "join_paths",
+      doc = "Creates a single command line argument joining the paths of a set "
+          + "of files on the separator string.",
+      objectType = SkylarkCommandLine.class,
+      returnType = String.class,
+      mandatoryParams = {
+      @Param(name = "separator", type = String.class, doc = "the separator string to join on"),
+      @Param(name = "files", type = SkylarkNestedSet.class, generic1 = Artifact.class,
+             doc = "the files to concatenate")})
+  private static SimpleSkylarkFunction joinPaths =
+      new SimpleSkylarkFunction("join_paths") {
+    @Override
+    public Object call(Map<String, Object> params, Location loc)
+        throws EvalException {
+      final String separator = (String) params.get("separator");
+      final NestedSet<Artifact> artifacts =
+          ((SkylarkNestedSet) params.get("files")).getSet(Artifact.class);
+      // TODO(bazel-team): lazy evaluate
+      return Artifact.joinExecPaths(separator, artifacts);
+    }
+  };
+
+  // TODO(bazel-team): this method should support sets of objects and substitute all struct fields.
+  @SkylarkBuiltin(name = "template",
+      doc = "Transforms a set of files to a list of strings using the template string.",
+      objectType = SkylarkCommandLine.class,
+      returnType = SkylarkList.class,
+      mandatoryParams = {
+      @Param(name = "items", type = SkylarkNestedSet.class, generic1 = Artifact.class,
+          doc = "The set of structs to transform."),
+      @Param(name = "template", type = String.class,
+          doc = "The template to use for the transformation, %{path} and %{short_path} "
+              + "being substituted with the corresponding fields of each file.")})
+  private static SimpleSkylarkFunction template = new SimpleSkylarkFunction("template") {
+    @Override
+    public Object call(Map<String, Object> params, Location loc)
+        throws EvalException {
+      final String template = (String) params.get("template");
+      SkylarkNestedSet items = (SkylarkNestedSet) params.get("items");
+      return SkylarkList.lazyList(Iterables.transform(items, new Function<Object, String>() {
+        @Override
+        public String apply(Object input) {
+          Artifact artifact = (Artifact) input;
+          return template
+              .replace("%{path}", artifact.getExecPathString())
+              .replace("%{short_path}", artifact.getRootRelativePathString());
+        }
+      }), String.class);
+    }
+  };
+}