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diff --git a/src/main/java/com/google/devtools/build/lib/packages/License.java b/src/main/java/com/google/devtools/build/lib/packages/License.java
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+++ b/src/main/java/com/google/devtools/build/lib/packages/License.java
@@ -0,0 +1,327 @@
+// 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.packages;
+
+import com.google.common.annotations.VisibleForTesting;
+import com.google.common.collect.HashBasedTable;
+import com.google.common.collect.ImmutableSet;
+import com.google.common.collect.ImmutableTable;
+import com.google.common.collect.Sets;
+import com.google.common.collect.Table;
+import com.google.devtools.build.lib.concurrent.ThreadSafety.Immutable;
+import com.google.devtools.build.lib.concurrent.ThreadSafety.ThreadSafe;
+import com.google.devtools.build.lib.events.Event;
+import com.google.devtools.build.lib.events.EventHandler;
+import com.google.devtools.build.lib.events.Location;
+import com.google.devtools.build.lib.syntax.Label;
+import com.google.devtools.build.lib.syntax.Label.SyntaxException;
+
+import java.util.Collection;
+import java.util.Collections;
+import java.util.EnumSet;
+import java.util.List;
+import java.util.Set;
+
+/**
+ * Support for license and distribution checking.
+ */
+@Immutable @ThreadSafe
+public final class License {
+
+  private final Set<LicenseType> licenseTypes;
+  private final Set<Label> exceptions;
+
+  /**
+   * The error that's thrown if a build file contains an invalid license string.
+   */
+  public static class LicenseParsingException extends Exception {
+    public LicenseParsingException(String s) {
+      super(s);
+    }
+  }
+
+  /**
+   * LicenseType is the basis of the License lattice - stricter licenses should
+   * be declared before less-strict licenses in the enum.
+   *
+   * <p>Note that the order is important for the purposes of finding the least
+   * restrictive license.
+   */
+  public enum LicenseType {
+    BY_EXCEPTION_ONLY,
+    RESTRICTED,
+    RESTRICTED_IF_STATICALLY_LINKED,
+    RECIPROCAL,
+    NOTICE,
+    PERMISSIVE,
+    UNENCUMBERED,
+    NONE
+  }
+
+  /**
+   * Gets the least restrictive license type from the list of licenses declared
+   * for a target. For the purposes of license checking, the license type set of
+   * a declared license can be reduced to its least restrictive member.
+   *
+   * @param types a collection of license types
+   * @return the least restrictive license type
+   */
+  @VisibleForTesting
+  static LicenseType leastRestrictive(Collection<LicenseType> types) {
+    return types.isEmpty() ? LicenseType.BY_EXCEPTION_ONLY : Collections.max(types);
+  }
+
+  /**
+   * An instance of LicenseType.None with no exceptions, used for packages
+   * outside of third_party which have no license clause in their BUILD files.
+   */
+  public static final License NO_LICENSE =
+      new License(ImmutableSet.of(LicenseType.NONE), Collections.<Label>emptySet());
+
+  /**
+   * A default instance of Distributions which is used for packages which
+   * have no "distribs" declaration. If nothing is declared, we opt for the
+   * most permissive kind of distribution, which is the internal-only distrib.
+   */
+  public static final Set<DistributionType> DEFAULT_DISTRIB =
+      Collections.singleton(DistributionType.INTERNAL);
+
+  /**
+   * The types of distribution that are supported.
+   */
+  public enum DistributionType {
+    INTERNAL,
+    WEB,
+    CLIENT,
+    EMBEDDED
+  }
+
+  /**
+   * Parses a set of strings declaring distribution types.
+   *
+   * @param distStrings strings containing distribution declarations from BUILD
+   *        files
+   * @return a new, unmodifiable set of DistributionTypes
+   * @throws LicenseParsingException
+   */
+  public static Set<DistributionType> parseDistributions(Collection<String> distStrings)
+      throws LicenseParsingException {
+    if (distStrings.isEmpty()) {
+      return Collections.unmodifiableSet(EnumSet.of(DistributionType.INTERNAL));
+    } else {
+      Set<DistributionType> result = EnumSet.noneOf(DistributionType.class);
+      for (String distStr : distStrings) {
+        try {
+          DistributionType dist = Enum.valueOf(DistributionType.class, distStr.toUpperCase());
+          result.add(dist);
+        } catch (IllegalArgumentException e) {
+          throw new LicenseParsingException("Invalid distribution type '" + distStr + "'");
+        }
+      }
+      return Collections.unmodifiableSet(result);
+    }
+  }
+
+  private static final Object MARKER = new Object();
+
+  /**
+   * The license incompatibility set. This contains the set of
+   * (Distribution,License) pairs that should generate errors.
+   */
+  private static Table<DistributionType, LicenseType, Object> LICENSE_INCOMPATIBILIES =
+      createLicenseIncompatibilitySet();
+
+  private static Table<DistributionType, LicenseType, Object> createLicenseIncompatibilitySet() {
+    Table<DistributionType, LicenseType, Object> result = HashBasedTable.create();
+    result.put(DistributionType.CLIENT, LicenseType.RESTRICTED, MARKER);
+    result.put(DistributionType.EMBEDDED, LicenseType.RESTRICTED, MARKER);
+    result.put(DistributionType.INTERNAL, LicenseType.BY_EXCEPTION_ONLY, MARKER);
+    result.put(DistributionType.CLIENT, LicenseType.BY_EXCEPTION_ONLY, MARKER);
+    result.put(DistributionType.WEB, LicenseType.BY_EXCEPTION_ONLY, MARKER);
+    result.put(DistributionType.EMBEDDED, LicenseType.BY_EXCEPTION_ONLY, MARKER);
+    return ImmutableTable.copyOf(result);
+  }
+
+  /**
+   * The license warning set. This contains the set of
+   * (Distribution,License) pairs that should generate warnings when the user
+   * requests verbose license checking.
+   */
+  private static Table<DistributionType, LicenseType, Object> LICENSE_WARNINGS =
+      createLicenseWarningsSet();
+
+  private static Table<DistributionType, LicenseType, Object> createLicenseWarningsSet() {
+    Table<DistributionType, LicenseType, Object> result = HashBasedTable.create();
+    result.put(DistributionType.CLIENT, LicenseType.RECIPROCAL, MARKER);
+    result.put(DistributionType.EMBEDDED, LicenseType.RECIPROCAL, MARKER);
+    result.put(DistributionType.CLIENT, LicenseType.NOTICE, MARKER);
+    result.put(DistributionType.EMBEDDED, LicenseType.NOTICE, MARKER);
+    return ImmutableTable.copyOf(result);
+  }
+
+  private License(Set<LicenseType> licenseTypes, Set<Label> exceptions) {
+    // Defensive copy is done in .of()
+    this.licenseTypes = licenseTypes;
+    this.exceptions = exceptions;
+  }
+
+  public static License of(Collection<LicenseType> licenses, Collection<Label> exceptions) {
+    Set<LicenseType> licenseSet = ImmutableSet.copyOf(licenses);
+    Set<Label> exceptionSet = ImmutableSet.copyOf(exceptions);
+
+    if (exceptionSet.isEmpty() && licenseSet.equals(ImmutableSet.of(LicenseType.NONE))) {
+      return License.NO_LICENSE;
+    }
+
+    return new License(licenseSet, exceptionSet);
+  }
+  /**
+   * Computes a license which can be used to check if a package is compatible
+   * with some kinds of distribution. The list of licenses is scanned for the
+   * least restrictive, and the exceptions are added.
+   *
+   * @param licStrings the list of license strings declared for the package
+   * @throws LicenseParsingException if there are any parsing problems
+   */
+  public static License parseLicense(List<String> licStrings) throws LicenseParsingException {
+    /*
+     * The semantics of comparison for licenses depends on a stable iteration
+     * order for both license types and exceptions. For licenseTypes, it will be
+     * the comparison order from the enumerated types; for exceptions, it will
+     * be lexicographic order achieved using TreeSets.
+     */
+    Set<LicenseType> licenseTypes = EnumSet.noneOf(LicenseType.class);
+    Set<Label> exceptions = Sets.newTreeSet();
+    for (String str : licStrings) {
+      if (str.startsWith("exception=")) {
+        try {
+          Label label = Label.parseAbsolute(str.substring("exception=".length()));
+          exceptions.add(label);
+        } catch (SyntaxException e) {
+          throw new LicenseParsingException(e.getMessage());
+        }
+      } else {
+        try {
+          licenseTypes.add(LicenseType.valueOf(str.toUpperCase()));
+        } catch (IllegalArgumentException e) {
+          throw new LicenseParsingException("invalid license type: '" + str + "'");
+        }
+      }
+    }
+
+    return License.of(licenseTypes, exceptions);
+  }
+
+  /**
+   * Checks if this license is compatible with distributing a particular target
+   * in some set of distribution modes.
+   *
+   * @param dists the modes of distribution
+   * @param target the target which is being checked, and which will be used for
+   *        checking exceptions
+   * @param licensedTarget the target which declared the license being checked.
+   * @param eventHandler a reporter where any licensing issues discovered should be
+   *        reported
+   * @param staticallyLinked whether the target is statically linked under this command
+   * @return true if the license is compatible with the distributions
+   */
+  public boolean checkCompatibility(Set<DistributionType> dists,
+      Target target, Label licensedTarget, EventHandler eventHandler,
+      boolean staticallyLinked) {
+    Location location = (target instanceof Rule) ? ((Rule) target).getLocation() : null;
+
+    LicenseType leastRestrictiveLicense;
+    if (licenseTypes.contains(LicenseType.RESTRICTED_IF_STATICALLY_LINKED)) {
+      Set<LicenseType> tempLicenses = EnumSet.copyOf(licenseTypes);
+      tempLicenses.remove(LicenseType.RESTRICTED_IF_STATICALLY_LINKED);
+      if (staticallyLinked) {
+        tempLicenses.add(LicenseType.RESTRICTED);
+      } else {
+        tempLicenses.add(LicenseType.UNENCUMBERED);
+      }
+      leastRestrictiveLicense = leastRestrictive(tempLicenses);
+    } else {
+      leastRestrictiveLicense = leastRestrictive(licenseTypes);
+    }
+    for (DistributionType dt : dists) {
+      if (LICENSE_INCOMPATIBILIES.contains(dt, leastRestrictiveLicense)) {
+        if (!exceptions.contains(target.getLabel())) {
+          eventHandler.handle(Event.error(location, "Build target '" + target.getLabel()
+              + "' is not compatible with license '" + this + "' from target '"
+                  + licensedTarget + "'"));
+          return false;
+        }
+      } else if (LICENSE_WARNINGS.contains(dt, leastRestrictiveLicense)) {
+        eventHandler.handle(
+            Event.warn(location, "Build target '" + target
+                + "' has a potential licensing issue "
+                + "with a '" + this + "' license from target '" + licensedTarget + "'"));
+      }
+    }
+    return true;
+  }
+
+  /**
+   * @return an immutable set of {@link LicenseType}s contained in this {@code
+   *         License}
+   */
+  public Set<LicenseType> getLicenseTypes() {
+    return licenseTypes;
+  }
+
+  /**
+   * @return an immutable set of {@link Label}s that describe exceptions to the
+   *         {@code License}
+   */
+  public Set<Label> getExceptions() {
+    return exceptions;
+  }
+
+  /**
+   * A simple toString implementation which generates a canonical form of the
+   * license. (The order of license types is guaranteed to be canonical by
+   * EnumSet, and the order of exceptions is guaranteed to be lexicographic
+   * order by TreeSet.)
+   */
+  @Override
+  public String toString() {
+    if (exceptions.isEmpty()) {
+      return licenseTypes.toString().toLowerCase();
+    } else {
+      return licenseTypes.toString().toLowerCase() + " with exceptions " + exceptions.toString();
+    }
+  }
+
+  /**
+   * A simple equals implementation leveraging the support built into Set that
+   * delegates to its contents.
+   */
+  @Override
+  public boolean equals(Object o) {
+    return o == this ||
+        o instanceof License &&
+        ((License) o).licenseTypes.equals(this.licenseTypes) &&
+        ((License) o).exceptions.equals(this.exceptions);
+  }
+
+  /**
+   * A simple hashCode implementation leveraging the support built into Set that
+   * delegates to its contents.
+   */
+  @Override
+  public int hashCode() {
+    return licenseTypes.hashCode() * 43 + exceptions.hashCode();
+  }
+}