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/*
* Copyright 2015 The gRPC Authors
*
* 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 io.grpc;
import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;
import com.google.common.base.Joiner;
import java.nio.charset.Charset;
import java.util.Collections;
import java.util.HashSet;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Set;
import javax.annotation.Nullable;
import javax.annotation.concurrent.ThreadSafe;
/**
* Encloses classes related to the compression and decompression of messages.
*/
@ExperimentalApi("https://github.com/grpc/grpc-java/issues/1704")
@ThreadSafe
public final class DecompressorRegistry {
static final Joiner ACCEPT_ENCODING_JOINER = Joiner.on(',');
public static DecompressorRegistry emptyInstance() {
return new DecompressorRegistry();
}
private static final DecompressorRegistry DEFAULT_INSTANCE =
emptyInstance()
.with(new Codec.Gzip(), true)
.with(Codec.Identity.NONE, false);
public static DecompressorRegistry getDefaultInstance() {
return DEFAULT_INSTANCE;
}
private final Map decompressors;
private final byte[] advertisedDecompressors;
/**
* Registers a decompressor for both decompression and message encoding negotiation. Returns a
* new registry.
*
* @param d The decompressor to register
* @param advertised If true, the message encoding will be listed in the Accept-Encoding header.
*/
public DecompressorRegistry with(Decompressor d, boolean advertised) {
return new DecompressorRegistry(d, advertised, this);
}
private DecompressorRegistry(Decompressor d, boolean advertised, DecompressorRegistry parent) {
String encoding = d.getMessageEncoding();
checkArgument(!encoding.contains(","), "Comma is currently not allowed in message encoding");
int newSize = parent.decompressors.size();
if (!parent.decompressors.containsKey(d.getMessageEncoding())) {
newSize++;
}
Map newDecompressors =
new LinkedHashMap<>(newSize);
for (DecompressorInfo di : parent.decompressors.values()) {
String previousEncoding = di.decompressor.getMessageEncoding();
if (!previousEncoding.equals(encoding)) {
newDecompressors.put(
previousEncoding, new DecompressorInfo(di.decompressor, di.advertised));
}
}
newDecompressors.put(encoding, new DecompressorInfo(d, advertised));
decompressors = Collections.unmodifiableMap(newDecompressors);
advertisedDecompressors = ACCEPT_ENCODING_JOINER.join(getAdvertisedMessageEncodings())
.getBytes(Charset.forName("US-ASCII"));
}
private DecompressorRegistry() {
decompressors = new LinkedHashMap<>(0);
advertisedDecompressors = new byte[0];
}
/**
* Provides a list of all message encodings that have decompressors available.
*/
public Set getKnownMessageEncodings() {
return decompressors.keySet();
}
byte[] getRawAdvertisedMessageEncodings() {
return advertisedDecompressors;
}
/**
* Provides a list of all message encodings that have decompressors available and should be
* advertised.
*
* The specification doesn't say anything about ordering, or preference, so the returned codes
* can be arbitrary.
*/
@ExperimentalApi("https://github.com/grpc/grpc-java/issues/1704")
public Set getAdvertisedMessageEncodings() {
Set advertisedDecompressors = new HashSet<>(decompressors.size());
for (Map.Entry entry : decompressors.entrySet()) {
if (entry.getValue().advertised) {
advertisedDecompressors.add(entry.getKey());
}
}
return Collections.unmodifiableSet(advertisedDecompressors);
}
/**
* Returns a decompressor for the given message encoding, or {@code null} if none has been
* registered.
*
* This ignores whether the compressor is advertised. According to the spec, if we know how
* to process this encoding, we attempt to, regardless of whether or not it is part of the
* encodings sent to the remote host.
*/
@Nullable
public Decompressor lookupDecompressor(String messageEncoding) {
DecompressorInfo info = decompressors.get(messageEncoding);
return info != null ? info.decompressor : null;
}
/**
* Information about a decompressor.
*/
private static final class DecompressorInfo {
final Decompressor decompressor;
final boolean advertised;
DecompressorInfo(Decompressor decompressor, boolean advertised) {
this.decompressor = checkNotNull(decompressor, "decompressor");
this.advertised = advertised;
}
}
}