samples/src/jvmMain/java/okio/samples/Randoms.java

/*
 * Copyright (C) 2018 Square, Inc.
 *
 * 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 okio.samples;

import java.io.IOException;
import java.util.Random;
import okio.Buffer;
import okio.BufferedSource;
import okio.Okio;
import okio.Source;
import okio.Timeout;

public final class Randoms {
  public void run() throws IOException, InterruptedException {
    Random random = new Random(3782615686L);
    BufferedSource source = Okio.buffer(new RandomSource(random, 5));
    System.out.println(source.readUtf8());
  }

  static final class RandomSource implements Source {
    private final Random random;
    private long bytesLeft;

    RandomSource(Random random, long bytesLeft) {
      this.random = random;
      this.bytesLeft = bytesLeft;
    }

    @Override public long read(Buffer sink, long byteCount) throws IOException {
      if (bytesLeft == -1L) throw new IllegalStateException("closed");
      if (bytesLeft == 0L) return -1L;
      if (byteCount > Integer.MAX_VALUE) byteCount = Integer.MAX_VALUE;
      if (byteCount > bytesLeft) byteCount = bytesLeft;

      // Random is most efficient when computing 32 bits of randomness. Start with that.
      int ints = (int) (byteCount / 4);
      for (int i = 0; i < ints; i++) {
        sink.writeInt(random.nextInt());
      }

      // If we need 1, 2, or 3 bytes more, keep going. We'll discard 24, 16 or 8 random bits!
      int bytes = (int) (byteCount - ints * 4);
      if (bytes > 0) {
        int bits = random.nextInt();
        for (int i = 0; i < bytes; i++) {
          sink.writeByte(bits & 0xff);
          bits >>>= 8;
        }
      }

      bytesLeft -= byteCount;
      return byteCount;
    }

    @Override public Timeout timeout() {
      return Timeout.NONE;
    }

    @Override public void close() throws IOException {
      bytesLeft = -1L;
    }
  }

  public static void main(String... args) throws Exception {
    new Randoms().run();
  }
}