src/main/java/com/google/devtools/build/lib/windows/jni/WindowsJniLoader.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.windows.jni;

import com.google.devtools.build.runfiles.Runfiles;
import java.io.IOException;

/** Loads native code under Windows. */
public class WindowsJniLoader {
  private static boolean jniLoaded = false;

  public static synchronized void loadJni() {
    if (jniLoaded) {
      return;
    }

    try {
      System.loadLibrary("windows_jni");
    } catch (UnsatisfiedLinkError ex) {
      Runfiles runfiles = null;
      try {
        runfiles = Runfiles.create();
      } catch (IOException e) {
        throw new RuntimeException(e);
      }

      String rloc = runfiles.rlocation("io_bazel/src/main/native/windows/windows_jni.dll");
      if (rloc == null) {
        rloc = runfiles.rlocation("bazel_tools/src/main/native/windows/windows_jni.dll");
        if (rloc == null) {
          throw ex;
        }
      }
      System.load(rloc);
    }
    jniLoaded = true;
  }
}