1 files changed, 136 insertions, 0 deletions
diff --git a/src/main/java/com/google/devtools/build/lib/rules/cpp/CcLinkParamsStore.java b/src/main/java/com/google/devtools/build/lib/rules/cpp/CcLinkParamsStore.java
new file mode 100644
index 0000000000..a150488d84
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/rules/cpp/CcLinkParamsStore.java
@@ -0,0 +1,136 @@
+// 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.cpp;
+
+import com.google.common.base.Preconditions;
+import com.google.devtools.build.lib.rules.cpp.CcLinkParams.Builder;
+
+/**
+ * A cache of C link parameters.
+ *
+ * <p>The cache holds instances of {@link CcLinkParams} for combinations of
+ * linkingStatically and linkShared. If a requested value is not available in
+ * the cache, it is computed and then stored.
+ *
+ * <p>Typically this class is used on targets that may be linked in as C
+ * libraries as in the following example:
+ *
+ * <pre>
+ * class SomeTarget implements CcLinkParamsProvider {
+ *   private final CcLinkParamsStore ccLinkParamsStore = new CcLinkParamsStore() {
+ *     @Override
+ *     protected void collect(CcLinkParams.Builder builder, boolean linkingStatically,
+ *                            boolean linkShared) {
+ *       builder.add[...]
+ *     }
+ *   };
+ *
+ *   @Override
+ *   public CcLinkParams getCcLinkParams(boolean linkingStatically, boolean linkShared) {
+ *     return ccLinkParamsStore.get(linkingStatically, linkShared);
+ *   }
+ * }
+ * </pre>
+ */
+public abstract class CcLinkParamsStore {
+
+  private CcLinkParams staticSharedParams;
+  private CcLinkParams staticNoSharedParams;
+  private CcLinkParams noStaticSharedParams;
+  private CcLinkParams noStaticNoSharedParams;
+
+  private CcLinkParams compute(boolean linkingStatically, boolean linkShared) {
+    CcLinkParams.Builder builder = CcLinkParams.builder(linkingStatically, linkShared);
+    collect(builder, linkingStatically, linkShared);
+    return builder.build();
+  }
+
+  /**
+   * Returns {@link CcLinkParams} for a combination of parameters.
+   *
+   * <p>The {@link CcLinkParams} instance is computed lazily and cached.
+   */
+  public synchronized CcLinkParams get(boolean linkingStatically, boolean linkShared) {
+    CcLinkParams result = lookup(linkingStatically, linkShared);
+    if (result == null) {
+      result = compute(linkingStatically, linkShared);
+      put(linkingStatically, linkShared, result);
+    }
+    return result;
+  }
+
+  private CcLinkParams lookup(boolean linkingStatically, boolean linkShared) {
+    if (linkingStatically) {
+      return linkShared ? staticSharedParams : staticNoSharedParams;
+    } else {
+      return linkShared ? noStaticSharedParams : noStaticNoSharedParams;
+    }
+  }
+
+  private void put(boolean linkingStatically, boolean linkShared, CcLinkParams params) {
+    Preconditions.checkNotNull(params);
+    if (linkingStatically) {
+      if (linkShared) {
+        staticSharedParams = params;
+      } else {
+        staticNoSharedParams = params;
+      }
+    } else {
+      if (linkShared) {
+        noStaticSharedParams = params;
+      } else {
+        noStaticNoSharedParams = params;
+      }
+    }
+  }
+
+  /**
+   * Hook for building the actual link params.
+   *
+   * <p>Users should override this method and call methods of the builder to
+   * set up the actual CcLinkParams objects.
+   *
+   * <p>Implementations of this method must not fail or try to report errors on the
+   * configured target.
+   */
+  protected abstract void collect(CcLinkParams.Builder builder, boolean linkingStatically,
+                                  boolean linkShared);
+
+  /**
+   * An empty CcLinkParamStore.
+   */
+  public static final CcLinkParamsStore EMPTY = new CcLinkParamsStore() {
+
+    @Override
+    protected void collect(Builder builder, boolean linkingStatically, boolean linkShared) {}
+  };
+
+  /**
+   * An implementation class for the CcLinkParamsStore.
+   */
+  public static final class CcLinkParamsStoreImpl extends CcLinkParamsStore {
+
+    public CcLinkParamsStoreImpl(CcLinkParamsStore store) {
+      super.staticSharedParams = store.get(true, true);
+      super.staticNoSharedParams = store.get(true, false);
+      super.noStaticSharedParams = store.get(false, true);
+      super.noStaticNoSharedParams = store.get(false, false);
+    }
+
+    @Override
+    protected void collect(Builder builder, boolean linkingStatically, boolean linkShared) {}
+  }
+}
+