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/*
 * Copyright 2014 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.internal;

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

import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Objects;
import com.google.common.base.Preconditions;
import com.google.common.base.Splitter;
import com.google.common.base.Stopwatch;
import com.google.common.base.Supplier;
import com.google.common.util.concurrent.ListenableFuture;
import com.google.common.util.concurrent.MoreExecutors;
import com.google.common.util.concurrent.ThreadFactoryBuilder;
import io.grpc.CallOptions;
import io.grpc.ClientStreamTracer;
import io.grpc.InternalChannelz.SocketStats;
import io.grpc.InternalLogId;
import io.grpc.InternalMetadata;
import io.grpc.InternalMetadata.TrustedAsciiMarshaller;
import io.grpc.LoadBalancer.PickResult;
import io.grpc.LoadBalancer.Subchannel;
import io.grpc.Metadata;
import io.grpc.MethodDescriptor;
import io.grpc.ProxiedSocketAddress;
import io.grpc.ProxyDetector;
import io.grpc.Status;
import io.grpc.internal.ClientStreamListener.RpcProgress;
import io.grpc.internal.SharedResourceHolder.Resource;
import io.grpc.internal.StreamListener.MessageProducer;
import java.io.IOException;
import java.io.InputStream;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.net.HttpURLConnection;
import java.net.InetSocketAddress;
import java.net.SocketAddress;
import java.net.URI;
import java.net.URISyntaxException;
import java.nio.charset.Charset;
import java.util.Collection;
import java.util.concurrent.Executor;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.TimeUnit;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.annotation.Nullable;

/**
 * Common utilities for GRPC.
 */
public final class GrpcUtil {

  private static final Logger log = Logger.getLogger(GrpcUtil.class.getName());

  public static final Charset US_ASCII = Charset.forName("US-ASCII");

  // AppEngine runtimes have constraints on threading and socket handling
  // that need to be accommodated.
  public static final boolean IS_RESTRICTED_APPENGINE =
      System.getProperty("com.google.appengine.runtime.environment") != null
          && "1.7".equals(System.getProperty("java.specification.version"));

  /**
   * {@link io.grpc.Metadata.Key} for the timeout header.
   */
  public static final Metadata.Key TIMEOUT_KEY =
          Metadata.Key.of(GrpcUtil.TIMEOUT, new TimeoutMarshaller());

  /**
   * {@link io.grpc.Metadata.Key} for the message encoding header.
   */
  public static final Metadata.Key MESSAGE_ENCODING_KEY =
          Metadata.Key.of(GrpcUtil.MESSAGE_ENCODING, Metadata.ASCII_STRING_MARSHALLER);

  /**
   * {@link io.grpc.Metadata.Key} for the accepted message encodings header.
   */
  public static final Metadata.Key MESSAGE_ACCEPT_ENCODING_KEY =
      InternalMetadata.keyOf(GrpcUtil.MESSAGE_ACCEPT_ENCODING, new AcceptEncodingMarshaller());

  /**
   * {@link io.grpc.Metadata.Key} for the stream's content encoding header.
   */
  public static final Metadata.Key CONTENT_ENCODING_KEY =
      Metadata.Key.of(GrpcUtil.CONTENT_ENCODING, Metadata.ASCII_STRING_MARSHALLER);

  /**
   * {@link io.grpc.Metadata.Key} for the stream's accepted content encoding header.
   */
  public static final Metadata.Key CONTENT_ACCEPT_ENCODING_KEY =
      InternalMetadata.keyOf(GrpcUtil.CONTENT_ACCEPT_ENCODING, new AcceptEncodingMarshaller());

  private static final class AcceptEncodingMarshaller implements TrustedAsciiMarshaller {
    @Override
    public byte[] toAsciiString(byte[] value) {
      return value;
    }

    @Override
    public byte[] parseAsciiString(byte[] serialized) {
      return serialized;
    }
  }

  /**
   * {@link io.grpc.Metadata.Key} for the Content-Type request/response header.
   */
  public static final Metadata.Key CONTENT_TYPE_KEY =
          Metadata.Key.of("content-type", Metadata.ASCII_STRING_MARSHALLER);

  /**
   * {@link io.grpc.Metadata.Key} for the Transfer encoding.
   */
  public static final Metadata.Key TE_HEADER =
      Metadata.Key.of("te", Metadata.ASCII_STRING_MARSHALLER);

  /**
   * {@link io.grpc.Metadata.Key} for the Content-Type request/response header.
   */
  public static final Metadata.Key USER_AGENT_KEY =
          Metadata.Key.of("user-agent", Metadata.ASCII_STRING_MARSHALLER);

  /**
   * The default port for plain-text connections.
   */
  public static final int DEFAULT_PORT_PLAINTEXT = 80;

  /**
   * The default port for SSL connections.
   */
  public static final int DEFAULT_PORT_SSL = 443;

  /**
   * Content-Type used for GRPC-over-HTTP/2.
   */
  public static final String CONTENT_TYPE_GRPC = "application/grpc";

  /**
   * The HTTP method used for GRPC requests.
   */
  public static final String HTTP_METHOD = "POST";

  /**
   * The TE (transport encoding) header for requests over HTTP/2.
   */
  public static final String TE_TRAILERS = "trailers";

  /**
   * The Timeout header name.
   */
  public static final String TIMEOUT = "grpc-timeout";

  /**
   * The message encoding (i.e. compression) that can be used in the stream.
   */
  public static final String MESSAGE_ENCODING = "grpc-encoding";

  /**
   * The accepted message encodings (i.e. compression) that can be used in the stream.
   */
  public static final String MESSAGE_ACCEPT_ENCODING = "grpc-accept-encoding";

  /**
   * The content-encoding used to compress the full gRPC stream.
   */
  public static final String CONTENT_ENCODING = "content-encoding";

  /**
   * The accepted content-encodings that can be used to compress the full gRPC stream.
   */
  public static final String CONTENT_ACCEPT_ENCODING = "accept-encoding";

  /**
   * The default maximum uncompressed size (in bytes) for inbound messages. Defaults to 4 MiB.
   */
  public static final int DEFAULT_MAX_MESSAGE_SIZE = 4 * 1024 * 1024;

  /**
   * The default maximum size (in bytes) for inbound header/trailer.
   */
  // Update documentation in public-facing Builders when changing this value.
  public static final int DEFAULT_MAX_HEADER_LIST_SIZE = 8192;

  public static final Splitter ACCEPT_ENCODING_SPLITTER = Splitter.on(',').trimResults();

  private static final String IMPLEMENTATION_VERSION = "1.19.0"; // CURRENT_GRPC_VERSION

  /**
   * The default delay in nanos before we send a keepalive.
   */
  public static final long DEFAULT_KEEPALIVE_TIME_NANOS = TimeUnit.MINUTES.toNanos(1);

  /**
   * The default timeout in nanos for a keepalive ping request.
   */
  public static final long DEFAULT_KEEPALIVE_TIMEOUT_NANOS = TimeUnit.SECONDS.toNanos(20L);

  /**
   * The magic keepalive time value that disables client keepalive.
   */
  public static final long KEEPALIVE_TIME_NANOS_DISABLED = Long.MAX_VALUE;

  /**
   * The default delay in nanos for server keepalive.
   */
  public static final long DEFAULT_SERVER_KEEPALIVE_TIME_NANOS = TimeUnit.HOURS.toNanos(2L);

  /**
   * The default timeout in nanos for a server keepalive ping request.
   */
  public static final long DEFAULT_SERVER_KEEPALIVE_TIMEOUT_NANOS = TimeUnit.SECONDS.toNanos(20L);

  /**
   * The magic keepalive time value that disables keepalive.
   */
  public static final long SERVER_KEEPALIVE_TIME_NANOS_DISABLED = Long.MAX_VALUE;

  /**
   * The default proxy detector.
   */
  public static final ProxyDetector DEFAULT_PROXY_DETECTOR = new ProxyDetectorImpl();

  /**
   * A proxy detector that always claims no proxy is needed.
   */
  public static final ProxyDetector NOOP_PROXY_DETECTOR = new ProxyDetector() {
    @Nullable
    @Override
    public ProxiedSocketAddress proxyFor(SocketAddress targetServerAddress) {
      return null;
    }
  };

  /**
   * The very default load-balancing policy.
   */
  public static final String DEFAULT_LB_POLICY = "pick_first";

  /**
   * RPCs created on the Channel returned by {@link io.grpc.LoadBalancer.Subchannel#asChannel}
   * will have this option with value {@code true}.  They will be treated differently from
   * the ones created by application.
   */
  public static final CallOptions.Key CALL_OPTIONS_RPC_OWNED_BY_BALANCER =
      CallOptions.Key.create("io.grpc.internal.CALL_OPTIONS_RPC_OWNED_BY_BALANCER");

  /**
   * Returns true if an RPC with the given properties should be counted when calculating the
   * in-use state of a transport.
   */
  public static boolean shouldBeCountedForInUse(CallOptions callOptions) {
    return !Boolean.TRUE.equals(callOptions.getOption(CALL_OPTIONS_RPC_OWNED_BY_BALANCER));
  }

  /**
   * Returns a proxy detector appropriate for the current environment.
   */
  public static ProxyDetector getDefaultProxyDetector() {
    if (IS_RESTRICTED_APPENGINE) {
      return NOOP_PROXY_DETECTOR;
    } else {
      return DEFAULT_PROXY_DETECTOR;
    }
  }

  /**
   * Maps HTTP error response status codes to transport codes, as defined in 
   * http-grpc-status-mapping.md. Never returns a status for which {@code status.isOk()} is
   * {@code true}.
   */
  public static Status httpStatusToGrpcStatus(int httpStatusCode) {
    return httpStatusToGrpcCode(httpStatusCode).toStatus()
        .withDescription("HTTP status code " + httpStatusCode);
  }

  private static Status.Code httpStatusToGrpcCode(int httpStatusCode) {
    if (httpStatusCode >= 100 && httpStatusCode < 200) {
      // 1xx. These headers should have been ignored.
      return Status.Code.INTERNAL;
    }
    switch (httpStatusCode) {
      case HttpURLConnection.HTTP_BAD_REQUEST:  // 400
      case 431: // Request Header Fields Too Large
        // TODO(carl-mastrangelo): this should be added to the http-grpc-status-mapping.md doc.
        return Status.Code.INTERNAL;
      case HttpURLConnection.HTTP_UNAUTHORIZED:  // 401
        return Status.Code.UNAUTHENTICATED;
      case HttpURLConnection.HTTP_FORBIDDEN:  // 403
        return Status.Code.PERMISSION_DENIED;
      case HttpURLConnection.HTTP_NOT_FOUND:  // 404
        return Status.Code.UNIMPLEMENTED;
      case 429:  // Too Many Requests
      case HttpURLConnection.HTTP_BAD_GATEWAY:  // 502
      case HttpURLConnection.HTTP_UNAVAILABLE:  // 503
      case HttpURLConnection.HTTP_GATEWAY_TIMEOUT:  // 504
        return Status.Code.UNAVAILABLE;
      default:
        return Status.Code.UNKNOWN;
    }
  }

  /**
   * All error codes identified by the HTTP/2 spec. Used in GOAWAY and RST_STREAM frames.
   */
  public enum Http2Error {
    /**
     * Servers implementing a graceful shutdown of the connection will send {@code GOAWAY} with
     * {@code NO_ERROR}. In this case it is important to indicate to the application that the
     * request should be retried (i.e. {@link Status#UNAVAILABLE}).
     */
    NO_ERROR(0x0, Status.UNAVAILABLE),
    PROTOCOL_ERROR(0x1, Status.INTERNAL),
    INTERNAL_ERROR(0x2, Status.INTERNAL),
    FLOW_CONTROL_ERROR(0x3, Status.INTERNAL),
    SETTINGS_TIMEOUT(0x4, Status.INTERNAL),
    STREAM_CLOSED(0x5, Status.INTERNAL),
    FRAME_SIZE_ERROR(0x6, Status.INTERNAL),
    REFUSED_STREAM(0x7, Status.UNAVAILABLE),
    CANCEL(0x8, Status.CANCELLED),
    COMPRESSION_ERROR(0x9, Status.INTERNAL),
    CONNECT_ERROR(0xA, Status.INTERNAL),
    ENHANCE_YOUR_CALM(0xB, Status.RESOURCE_EXHAUSTED.withDescription("Bandwidth exhausted")),
    INADEQUATE_SECURITY(0xC, Status.PERMISSION_DENIED.withDescription("Permission denied as "
        + "protocol is not secure enough to call")),
    HTTP_1_1_REQUIRED(0xD, Status.UNKNOWN);

    // Populate a mapping of code to enum value for quick look-up.
    private static final Http2Error[] codeMap = buildHttp2CodeMap();

    private static Http2Error[] buildHttp2CodeMap() {
      Http2Error[] errors = Http2Error.values();
      int size = (int) errors[errors.length - 1].code() + 1;
      Http2Error[] http2CodeMap = new Http2Error[size];
      for (Http2Error error : errors) {
        int index = (int) error.code();
        http2CodeMap[index] = error;
      }
      return http2CodeMap;
    }

    private final int code;
    // Status is not guaranteed to be deeply immutable. Don't care though, since that's only true
    // when there are exceptions in the Status, which is not true here.
    @SuppressWarnings("ImmutableEnumChecker")
    private final Status status;

    Http2Error(int code, Status status) {
      this.code = code;
      this.status = status.augmentDescription("HTTP/2 error code: " + this.name());
    }

    /**
     * Gets the code for this error used on the wire.
     */
    public long code() {
      return code;
    }

    /**
     * Gets the {@link Status} associated with this HTTP/2 code.
     */
    public Status status() {
      return status;
    }

    /**
     * Looks up the HTTP/2 error code enum value for the specified code.
     *
     * @param code an HTTP/2 error code value.
     * @return the HTTP/2 error code enum or {@code null} if not found.
     */
    public static Http2Error forCode(long code) {
      if (code >= codeMap.length || code < 0) {
        return null;
      }
      return codeMap[(int) code];
    }

    /**
     * Looks up the {@link Status} from the given HTTP/2 error code. This is preferred over {@code
     * forCode(code).status()}, to more easily conform to HTTP/2:
     *
     * 
Unknown or unsupported error codes MUST NOT trigger any special behavior. * These MAY be treated by an implementation as being equivalent to INTERNAL_ERROR.
* * @param code the HTTP/2 error code. * @return a {@link Status} representing the given error. */ public static Status statusForCode(long code) { Http2Error error = forCode(code); if (error == null) { // This "forgets" the message of INTERNAL_ERROR while keeping the same status code. Status.Code statusCode = INTERNAL_ERROR.status().getCode(); return Status.fromCodeValue(statusCode.value()) .withDescription("Unrecognized HTTP/2 error code: " + code); } return error.status(); } } /** * Indicates whether or not the given value is a valid gRPC content-type. */ public static boolean isGrpcContentType(String contentType) { if (contentType == null) { return false; } if (CONTENT_TYPE_GRPC.length() > contentType.length()) { return false; } contentType = contentType.toLowerCase(); if (!contentType.startsWith(CONTENT_TYPE_GRPC)) { // Not a gRPC content-type. return false; } if (contentType.length() == CONTENT_TYPE_GRPC.length()) { // The strings match exactly. return true; } // The contentType matches, but is longer than the expected string. // We need to support variations on the content-type (e.g. +proto, +json) as defined by the // gRPC wire spec. char nextChar = contentType.charAt(CONTENT_TYPE_GRPC.length()); return nextChar == '+' || nextChar == ';'; } /** * Gets the User-Agent string for the gRPC transport. */ public static String getGrpcUserAgent( String transportName, @Nullable String applicationUserAgent) { StringBuilder builder = new StringBuilder(); if (applicationUserAgent != null) { builder.append(applicationUserAgent); builder.append(' '); } builder.append("grpc-java-"); builder.append(transportName); builder.append('/'); builder.append(IMPLEMENTATION_VERSION); return builder.toString(); } /** * Parse an authority into a URI for retrieving the host and port. */ public static URI authorityToUri(String authority) { Preconditions.checkNotNull(authority, "authority"); URI uri; try { uri = new URI(null, authority, null, null, null); } catch (URISyntaxException ex) { throw new IllegalArgumentException("Invalid authority: " + authority, ex); } return uri; } /** * Verify {@code authority} is valid for use with gRPC. The syntax must be valid and it must not * include userinfo. * * @return the {@code authority} provided */ public static String checkAuthority(String authority) { URI uri = authorityToUri(authority); checkArgument(uri.getHost() != null, "No host in authority '%s'", authority); checkArgument(uri.getUserInfo() == null, "Userinfo must not be present on authority: '%s'", authority); return authority; } /** * Combine a host and port into an authority string. */ public static String authorityFromHostAndPort(String host, int port) { try { return new URI(null, null, host, port, null, null, null).getAuthority(); } catch (URISyntaxException ex) { throw new IllegalArgumentException("Invalid host or port: " + host + " " + port, ex); } } /** * Shared executor for channels. */ public static final Resource SHARED_CHANNEL_EXECUTOR = new Resource() { private static final String NAME = "grpc-default-executor"; @Override public Executor create() { return Executors.newCachedThreadPool(getThreadFactory(NAME + "-%d", true)); } @Override public void close(Executor instance) { ((ExecutorService) instance).shutdown(); } @Override public String toString() { return NAME; } }; /** * Shared single-threaded executor for managing channel timers. */ public static final Resource TIMER_SERVICE = new Resource() { @Override public ScheduledExecutorService create() { // We don't use newSingleThreadScheduledExecutor because it doesn't return a // ScheduledThreadPoolExecutor. ScheduledExecutorService service = Executors.newScheduledThreadPool( 1, getThreadFactory("grpc-timer-%d", true)); // If there are long timeouts that are cancelled, they will not actually be removed from // the executors queue. This forces immediate removal upon cancellation to avoid a // memory leak. Reflection is used because we cannot use methods added in Java 1.7. If // the method does not exist, we give up. Note that the method is not present in 1.6, but // _is_ present in the android standard library. try { Method method = service.getClass().getMethod("setRemoveOnCancelPolicy", boolean.class); method.invoke(service, true); } catch (NoSuchMethodException e) { // no op } catch (RuntimeException e) { throw e; } catch (Exception e) { throw new RuntimeException(e); } return Executors.unconfigurableScheduledExecutorService(service); } @Override public void close(ScheduledExecutorService instance) { instance.shutdown(); } }; /** * Get a {@link ThreadFactory} suitable for use in the current environment. * @param nameFormat to apply to threads created by the factory. * @param daemon {@code true} if the threads the factory creates are daemon threads, {@code false} * otherwise. * @return a {@link ThreadFactory}. */ public static ThreadFactory getThreadFactory(String nameFormat, boolean daemon) { if (IS_RESTRICTED_APPENGINE) { @SuppressWarnings("BetaApi") ThreadFactory factory = MoreExecutors.platformThreadFactory(); return factory; } else { return new ThreadFactoryBuilder() .setDaemon(daemon) .setNameFormat(nameFormat) .build(); } } /** * The factory of default Stopwatches. */ public static final Supplier STOPWATCH_SUPPLIER = new Supplier() { @Override public Stopwatch get() { return Stopwatch.createUnstarted(); } }; /** * Returns the host via {@link InetSocketAddress#getHostString} if it is possible, * i.e. in jdk >= 7. * Otherwise, return it via {@link InetSocketAddress#getHostName} which may incur a DNS lookup. */ public static String getHost(InetSocketAddress addr) { try { Method getHostStringMethod = InetSocketAddress.class.getMethod("getHostString"); return (String) getHostStringMethod.invoke(addr); } catch (NoSuchMethodException e) { // noop } catch (IllegalAccessException e) { // noop } catch (InvocationTargetException e) { // noop } return addr.getHostName(); } /** * Marshals a nanoseconds representation of the timeout to and from a string representation, * consisting of an ASCII decimal representation of a number with at most 8 digits, followed by a * unit: * n = nanoseconds * u = microseconds * m = milliseconds * S = seconds * M = minutes * H = hours * *

The representation is greedy with respect to precision. That is, 2 seconds will be * represented as `2000000u`.

* *

See the * request header definition

*/ @VisibleForTesting static class TimeoutMarshaller implements Metadata.AsciiMarshaller { @Override public String toAsciiString(Long timeoutNanos) { long cutoff = 100000000; TimeUnit unit = TimeUnit.NANOSECONDS; if (timeoutNanos < 0) { throw new IllegalArgumentException("Timeout too small"); } else if (timeoutNanos < cutoff) { return timeoutNanos + "n"; } else if (timeoutNanos < cutoff * 1000L) { return unit.toMicros(timeoutNanos) + "u"; } else if (timeoutNanos < cutoff * 1000L * 1000L) { return unit.toMillis(timeoutNanos) + "m"; } else if (timeoutNanos < cutoff * 1000L * 1000L * 1000L) { return unit.toSeconds(timeoutNanos) + "S"; } else if (timeoutNanos < cutoff * 1000L * 1000L * 1000L * 60L) { return unit.toMinutes(timeoutNanos) + "M"; } else { return unit.toHours(timeoutNanos) + "H"; } } @Override public Long parseAsciiString(String serialized) { checkArgument(serialized.length() > 0, "empty timeout"); checkArgument(serialized.length() <= 9, "bad timeout format"); long value = Long.parseLong(serialized.substring(0, serialized.length() - 1)); char unit = serialized.charAt(serialized.length() - 1); switch (unit) { case 'n': return value; case 'u': return TimeUnit.MICROSECONDS.toNanos(value); case 'm': return TimeUnit.MILLISECONDS.toNanos(value); case 'S': return TimeUnit.SECONDS.toNanos(value); case 'M': return TimeUnit.MINUTES.toNanos(value); case 'H': return TimeUnit.HOURS.toNanos(value); default: throw new IllegalArgumentException(String.format("Invalid timeout unit: %s", unit)); } } } /** * Returns a transport out of a PickResult, or {@code null} if the result is "buffer". */ @Nullable static ClientTransport getTransportFromPickResult(PickResult result, boolean isWaitForReady) { final ClientTransport transport; Subchannel subchannel = result.getSubchannel(); if (subchannel != null) { transport = ((AbstractSubchannel) subchannel).obtainActiveTransport(); } else { transport = null; } if (transport != null) { final ClientStreamTracer.Factory streamTracerFactory = result.getStreamTracerFactory(); if (streamTracerFactory == null) { return transport; } return new ClientTransport() { @Override public ClientStream newStream( MethodDescriptor method, Metadata headers, CallOptions callOptions) { return transport.newStream( method, headers, callOptions.withStreamTracerFactory(streamTracerFactory)); } @Override public void ping(PingCallback callback, Executor executor) { transport.ping(callback, executor); } @Override public InternalLogId getLogId() { return transport.getLogId(); } @Override public ListenableFuture getStats() { return transport.getStats(); } }; } if (!result.getStatus().isOk()) { if (result.isDrop()) { return new FailingClientTransport(result.getStatus(), RpcProgress.DROPPED); } if (!isWaitForReady) { return new FailingClientTransport(result.getStatus(), RpcProgress.PROCESSED); } } return null; } /** Quietly closes all messages in MessageProducer. */ static void closeQuietly(MessageProducer producer) { InputStream message; while ((message = producer.next()) != null) { closeQuietly(message); } } /** * Closes an InputStream, ignoring IOExceptions. * This method exists because Guava's {@code Closeables.closeQuietly()} is beta. */ public static void closeQuietly(@Nullable InputStream message) { if (message == null) { return; } try { message.close(); } catch (IOException ioException) { // do nothing except log log.log(Level.WARNING, "exception caught in closeQuietly", ioException); } } /** * Checks whether the given item exists in the iterable. This is copied from Guava Collect's * {@code Iterables.contains()} because Guava Collect is not Android-friendly thus core can't * depend on it. */ static boolean iterableContains(Iterable iterable, T item) { if (iterable instanceof Collection) { Collection collection = (Collection) iterable; try { return collection.contains(item); } catch (NullPointerException e) { return false; } catch (ClassCastException e) { return false; } } for (T i : iterable) { if (Objects.equal(i, item)) { return true; } } return false; } private GrpcUtil() {} }




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