1 files changed, 88 insertions, 0 deletions
diff --git a/src/main/java/com/google/devtools/build/lib/analysis/PlatformSemantics.java b/src/main/java/com/google/devtools/build/lib/analysis/PlatformSemantics.java
new file mode 100644
index 0000000000..7da9d4cafa
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+++ b/src/main/java/com/google/devtools/build/lib/analysis/PlatformSemantics.java
@@ -0,0 +1,88 @@
+// Copyright 2017 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.analysis;
+
+import static com.google.devtools.build.lib.packages.Attribute.attr;
+import static com.google.devtools.build.lib.packages.BuildType.LABEL;
+import static com.google.devtools.build.lib.packages.BuildType.LABEL_LIST;
+
+import com.google.devtools.build.lib.analysis.config.BuildConfiguration;
+import com.google.devtools.build.lib.analysis.platform.PlatformInfo;
+import com.google.devtools.build.lib.analysis.platform.PlatformProviderUtils;
+import com.google.devtools.build.lib.cmdline.Label;
+import com.google.devtools.build.lib.packages.Attribute;
+import com.google.devtools.build.lib.packages.AttributeMap;
+import com.google.devtools.build.lib.packages.Rule;
+import com.google.devtools.build.lib.packages.RuleClass;
+import java.util.List;
+
+/** Helper class to manage rules' use of platforms. */
+public class PlatformSemantics {
+
+  public static final String TARGET_PLATFORMS_ATTR = ":target_platforms";
+  public static final String EXECUTION_PLATFORM_ATTR = ":execution_platform";
+
+  public Iterable<PlatformInfo> getTargetPlatforms(RuleContext ruleContext) {
+    Iterable<PlatformInfo> platform =
+        PlatformProviderUtils.platforms(
+            ruleContext.getPrerequisites(
+                TARGET_PLATFORMS_ATTR, RuleConfiguredTarget.Mode.DONT_CHECK));
+    return platform;
+  }
+
+  public PlatformInfo getExecutionPlatform(RuleContext ruleContext) {
+    PlatformInfo platform =
+        PlatformProviderUtils.platform(
+            ruleContext.getPrerequisite(
+                EXECUTION_PLATFORM_ATTR, RuleConfiguredTarget.Mode.DONT_CHECK));
+    return platform;
+  }
+
+  /** Implementation for the :target_platform attribute. */
+  public static final Attribute.LateBoundLabelList<BuildConfiguration> TARGET_PLATFORM =
+      new Attribute.LateBoundLabelList<BuildConfiguration>(PlatformConfiguration.class) {
+        @Override
+        public List<Label> resolve(
+            Rule rule, AttributeMap attributes, BuildConfiguration configuration) {
+          if (rule.getRuleClassObject().getRequiredToolchains().isEmpty()) {
+            return null;
+          }
+          return configuration.getFragment(PlatformConfiguration.class).getTargetPlatforms();
+        }
+      };
+  /** Implementation for the :execution_platform attribute. */
+  public static final Attribute.LateBoundLabel<BuildConfiguration> EXECUTION_PLATFORM =
+      new Attribute.LateBoundLabel<BuildConfiguration>(PlatformConfiguration.class) {
+        @Override
+        public Label resolve(Rule rule, AttributeMap attributes, BuildConfiguration configuration) {
+          if (rule.getRuleClassObject().getRequiredToolchains().isEmpty()) {
+            return null;
+          }
+          return configuration.getFragment(PlatformConfiguration.class).getExecutionPlatform();
+        }
+      };
+
+  public static RuleClass.Builder platformAttributes(RuleClass.Builder builder) {
+    return builder
+        .add(
+            attr(TARGET_PLATFORMS_ATTR, LABEL_LIST)
+                .value(TARGET_PLATFORM)
+                .nonconfigurable("Used in toolchain resolution"))
+        .add(
+            attr(EXECUTION_PLATFORM_ATTR, LABEL)
+                .value(EXECUTION_PLATFORM)
+                .nonconfigurable("Used in toolchain resolution"));
+  }
+}