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// Copyright 2018 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.skyframe.serialization;
import com.google.common.annotations.VisibleForTesting;
import com.google.devtools.build.lib.unsafe.StringUnsafe;
import com.google.protobuf.CodedInputStream;
import com.google.protobuf.CodedOutputStream;
import java.io.IOException;
import java.util.Arrays;
/**
* A high-performance {@link ObjectCodec} for {@link String} objects specialized for Strings in
* JDK9, where a String can be represented as a byte array together with a single byte (0 or 1) for
* Latin-1 or UTF16 encoding.
*/
public class UnsafeJdk9StringCodec implements ObjectCodec<String> {
@VisibleForTesting
public static boolean canUseUnsafeCodec() {
return StringUnsafe.canUse();
}
private final StringUnsafe stringUnsafe;
public UnsafeJdk9StringCodec() {
stringUnsafe = StringUnsafe.getInstance();
}
@Override
public Class<? extends String> getEncodedClass() {
return String.class;
}
@Override
public MemoizationStrategy getStrategy() {
// Don't memoize strings inside memoizing serialization, to preserve current behavior.
// TODO(janakr,brandjon,michajlo): Is it actually a problem to memoize strings? Doubt there
// would be much performance impact from increasing the size of the identity map, and we
// could potentially drop our string tables in the future.
return MemoizationStrategy.DO_NOT_MEMOIZE;
}
@Override
public void serialize(SerializationContext context, String obj, CodedOutputStream codedOut)
throws SerializationException, IOException {
byte coder = stringUnsafe.getCoder(obj);
byte[] value = stringUnsafe.getByteArray(obj);
// Optimize for the case that coder == 0, in which case we can just write the length here,
// potentially using just one byte. If coder != 0, we'll use 4 bytes, but that's vanishingly
// rare.
if (coder == 0) {
codedOut.writeInt32NoTag(value.length);
} else if (coder == 1) {
codedOut.writeInt32NoTag(-value.length);
} else {
throw new SerializationException("Unexpected coder value: " + coder + " for " + obj);
}
codedOut.writeRawBytes(value);
}
@Override
public String deserialize(DeserializationContext context, CodedInputStream codedIn)
throws SerializationException, IOException {
int length = codedIn.readInt32();
byte coder;
if (length >= 0) {
coder = 0;
} else {
coder = 1;
length = -length;
}
byte[] value = codedIn.readRawBytes(length);
try {
return stringUnsafe.newInstance(value, coder);
} catch (ReflectiveOperationException e) {
throw new SerializationException(
"Could not instantiate string: " + Arrays.toString(value) + ", " + coder, e);
}
}
}
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