code: /*
   * Copyright (c) 2016-present, RxJava Contributors.
   *
   * 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.reactivex.rxjava3.internal.operators.single;
  
  import io.reactivex.rxjava3.core.*;
  import io.reactivex.rxjava3.disposables.Disposable;
  import io.reactivex.rxjava3.exceptions.Exceptions;
  import io.reactivex.rxjava3.functions.Function;
  
  import java.util.Objects;
  
  public final class SingleMap<T, R> extends Single<R> {
      final SingleSource<? extends T> source;
  
      final Function<? super T, ? extends R> mapper;
  
      public SingleMap(SingleSource<? extends T> source, Function<? super T, ? extends R> mapper) {
          this.source = source;
          this.mapper = mapper;
      }
  
      @Override
      protected void subscribeActual(final SingleObserver<? super R> t) {
          source.subscribe(new MapSingleObserver<T, R>(t, mapper));
      }
  
      static final class MapSingleObserver<T, R> implements SingleObserver<T> {
  
          final SingleObserver<? super R> t;
  
          final Function<? super T, ? extends R> mapper;
  
          MapSingleObserver(SingleObserver<? super R> t, Function<? super T, ? extends R> mapper) {
              this.t = t;
              this.mapper = mapper;
          }
  
          @Override
          public void onSubscribe(Disposable d) {
              t.onSubscribe(d);
          }
  
          @Override
          public void onSuccess(T value) {
              R v;
              try {
                  v = Objects.requireNonNull(mapper.apply(value), "The mapper function returned a null value.");
              } catch (Throwable e) {
                  Exceptions.throwIfFatal(e);
                  onError(e);
                  return;
              }
  
              t.onSuccess(v);
          }
  
          @Override
          public void onError(Throwable e) {
              t.onError(e);
          }
      }
  }
  