src/main/java/com/google/devtools/build/lib/rules/objc/LipoSupport.java

// Copyright 2016 The Bazel Authors. 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.objc;

import com.google.common.collect.Iterables;
import com.google.devtools.build.lib.actions.Artifact;
import com.google.devtools.build.lib.analysis.RuleContext;
import com.google.devtools.build.lib.analysis.actions.CustomCommandLine;
import com.google.devtools.build.lib.analysis.actions.SymlinkAction;
import com.google.devtools.build.lib.collect.nestedset.NestedSet;
import com.google.devtools.build.lib.rules.apple.ApplePlatform;
import com.google.devtools.build.lib.rules.apple.XcodeConfigInfo;

/**
 * Support for registering actions using the Apple tool "lipo", which combines artifacts of
 * different architectures to make multi-architecture artifacts.
 */
public class LipoSupport {
  private final RuleContext ruleContext;
  
  public LipoSupport(RuleContext ruleContext) {
    this.ruleContext = ruleContext;
  }

  /**
   * Registers an action to invoke "lipo" on all artifacts in {@code inputBinaries} to create the
   * {@code outputBinary} multi-architecture artifact, built for platform {@code platform}.
   *
   * <p>If there is only one input binary given, since "lipo" is an expensive action, this will only
   * symlink the output location to the input binary.
   *
   * @return this object
   */
  public LipoSupport registerCombineArchitecturesAction(
      NestedSet<Artifact> inputBinaries, Artifact outputBinary, ApplePlatform platform) {
    if (inputBinaries.toList().size() > 1) {
      ruleContext.registerAction(
          ObjcRuleClasses.spawnAppleEnvActionBuilder(
                  XcodeConfigInfo.fromRuleContext(ruleContext), platform)
              .setMnemonic("ObjcCombiningArchitectures")
              .addTransitiveInputs(inputBinaries)
              .addOutput(outputBinary)
              .setExecutable(CompilationSupport.xcrunwrapper(ruleContext))
              .addCommandLine(
                  CustomCommandLine.builder()
                      .add(ObjcRuleClasses.LIPO)
                      .addExecPaths("-create", inputBinaries)
                      .addExecPath("-o", outputBinary)
                      .build())
              .build(ruleContext));
    } else {
      ruleContext.registerAction(SymlinkAction.toArtifact(
          ruleContext.getActionOwner(),
          Iterables.getOnlyElement(inputBinaries),
          outputBinary,
          "Symlinking single-architecture binary"));
    }
    return this;
  }
}