core/src/main/java/io/grpc/CompressorRegistry.java

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package io.grpc;

import static com.google.common.base.Preconditions.checkArgument;

import com.google.common.annotations.VisibleForTesting;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
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 CompressorRegistry {
  private static final CompressorRegistry DEFAULT_INSTANCE = new CompressorRegistry(
      new Codec.Gzip(),
      Codec.Identity.NONE);

  public static CompressorRegistry getDefaultInstance() {
    return DEFAULT_INSTANCE;
  }

  public static CompressorRegistry newEmptyInstance() {
    return new CompressorRegistry();
  }

  private final ConcurrentMap<String, Compressor> compressors;

  @VisibleForTesting
  CompressorRegistry(Compressor ...cs) {
    compressors = new ConcurrentHashMap<String, Compressor>();
    for (Compressor c : cs) {
      compressors.put(c.getMessageEncoding(), c);
    }
  }

  @Nullable
  public Compressor lookupCompressor(String compressorName) {
    return compressors.get(compressorName);
  }

  /**
   * Registers a compressor for both decompression and message encoding negotiation.
   *
   * @param c The compressor to register
   */
  public void register(Compressor c) {
    String encoding = c.getMessageEncoding();
    checkArgument(!encoding.contains(","), "Comma is currently not allowed in message encoding");
    compressors.put(encoding, c);
  }
}