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// Copyright 2014 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.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) {}
}
}
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