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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.skyframe.serialization.ObjectCodec;
import com.google.devtools.build.lib.skyframe.serialization.autocodec.AutoCodec;
import com.google.devtools.build.lib.skyframe.serialization.autocodec.AutoCodec.VisibleForSerialization;
/**
* A cache of C link parameters.
*
* <p>The cache holds instances of {@link com.google.devtools.build.lib.rules.cpp.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 CcLinkParamsStore {
* private final AbstractCcLinkParamsStore ccLinkParamsStore = new AbstractCcLinkParamsStore() {
* @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 AbstractCcLinkParamsStore {
protected CcLinkParams staticSharedParams;
protected CcLinkParams staticNoSharedParams;
protected CcLinkParams noStaticSharedParams;
protected 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 com.google.devtools.build.lib.rules.cpp.CcLinkParams} for a combination of
* parameters.
*
* <p>The {@link com.google.devtools.build.lib.rules.cpp.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);
@AutoCodec
@VisibleForSerialization
static class EmptyCcLinkParamsStore extends AbstractCcLinkParamsStore {
public static final ObjectCodec<EmptyCcLinkParamsStore> CODEC =
new AbstractCcLinkParamsStore_EmptyCcLinkParamsStore_AutoCodec();
@Override
protected void collect(
CcLinkParams.Builder builder, boolean linkingStatically, boolean linkShared) {}
}
/** An empty CcLinkParamStore. */
public static final AbstractCcLinkParamsStore EMPTY = new EmptyCcLinkParamsStore();
}
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