core/src/main/java/io/grpc/proto/ProtoUtils.java

/*
 * Copyright 2014, Google Inc. All rights reserved.
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 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
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 *
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 * in the documentation and/or other materials provided with the
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 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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 */

package io.grpc.proto;

import com.google.protobuf.InvalidProtocolBufferException;
import com.google.protobuf.Message;
import com.google.protobuf.MessageLite;
import com.google.protobuf.Parser;

import io.grpc.Marshaller;
import io.grpc.Metadata;
import io.grpc.Status;

import java.io.InputStream;

/**
 * Utility methods for using protobuf with grpc.
 */
public class ProtoUtils {

  /** Adapt a {@code Parser} to a {@code Marshaller}. */
  public static <T extends MessageLite> Marshaller<T> marshaller(final Parser<T> parser) {
    return new Marshaller<T>() {
      @Override
      public InputStream stream(T value) {
        return new DeferredProtoInputStream(value);
      }

      @Override
      public T parse(InputStream stream) {
        try {
          return parser.parseFrom(stream);
        } catch (InvalidProtocolBufferException ipbe) {
          throw Status.INTERNAL.withDescription("Invalid protobuf byte sequence")
            .withCause(ipbe).asRuntimeException();
        }
      }
    };
  }

  /**
   * Produce a metadata key for a generated protobuf type.
   */
  public static <T extends Message> Metadata.Key<T> keyForProto(final T instance) {
    return Metadata.Key.of(
        instance.getDescriptorForType().getFullName() + Metadata.BINARY_HEADER_SUFFIX,
        new Metadata.BinaryMarshaller<T>() {
          @Override
          public byte[] toBytes(T value) {
            return value.toByteArray();
          }

          @Override
          @SuppressWarnings("unchecked")
          public T parseBytes(byte[] serialized) {
            try {
              return (T) instance.getParserForType().parseFrom(serialized);
            } catch (InvalidProtocolBufferException ipbe) {
              throw new IllegalArgumentException(ipbe);
            }
          }
        });
  }

  private ProtoUtils() {
  }
}