com.google.common.io.MultiInputStream Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of guava Show documentation
Builds the guava lib. Requires the jsr305 be built first.
There is a newer version: 33.3.0-jre-r3
/*
 * Copyright (C) 2007 The Guava 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 com.google.common.io;

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

import com.google.common.annotations.GwtIncompatible;
import com.google.common.annotations.J2ktIncompatible;
import java.io.IOException;
import java.io.InputStream;
import java.util.Iterator;
import javax.annotation.CheckForNull;

/**
 * An {@link InputStream} that concatenates multiple substreams. At most one stream will be open at
 * a time.
 *
 * @author Chris Nokleberg
 * @since 1.0
 */
@J2ktIncompatible
@GwtIncompatible
@ElementTypesAreNonnullByDefault
final class MultiInputStream extends InputStream {

  private Iterator it;
  @CheckForNull private InputStream in;

  /**
   * Creates a new instance.
   *
   * @param it an iterator of I/O suppliers that will provide each substream
   */
  public MultiInputStream(Iterator it) throws IOException {
    this.it = checkNotNull(it);
    advance();
  }

  @Override
  public void close() throws IOException {
    if (in != null) {
      try {
        in.close();
      } finally {
        in = null;
      }
    }
  }

  /** Closes the current input stream and opens the next one, if any. */
  private void advance() throws IOException {
    close();
    if (it.hasNext()) {
      in = it.next().openStream();
    }
  }

  @Override
  public int available() throws IOException {
    if (in == null) {
      return 0;
    }
    return in.available();
  }

  @Override
  public boolean markSupported() {
    return false;
  }

  @Override
  public int read() throws IOException {
    while (in != null) {
      int result = in.read();
      if (result != -1) {
        return result;
      }
      advance();
    }
    return -1;
  }

  @Override
  public int read(byte[] b, int off, int len) throws IOException {
    checkNotNull(b);
    while (in != null) {
      int result = in.read(b, off, len);
      if (result != -1) {
        return result;
      }
      advance();
    }
    return -1;
  }

  @Override
  public long skip(long n) throws IOException {
    if (in == null || n <= 0) {
      return 0;
    }
    long result = in.skip(n);
    if (result != 0) {
      return result;
    }
    if (read() == -1) {
      return 0;
    }
    return 1 + in.skip(n - 1);
  }
}