com.weaverplatform.util.ProgressInputStream Maven / Gradle / Ivy

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package com.weaverplatform.util;

import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.List;

// Based on https://stackoverflow.com/questions/27890287/how-to-publish-progress-for-large-json-file-parsing-with-gson

public class ProgressInputStream extends FilterInputStream {
  private final int size;
  private long bytesRead;
  private int percent;
  private List listeners = new ArrayList<>();

  // If size is less than 1 the value is interpret to be unknown
  public ProgressInputStream(InputStream in, int size) {
    super(in);
    this.size = size;
    bytesRead = 0;
    percent = 0;
  }

  public void addListener(Listener listener) {
    listeners.add(listener);
  }

  public void removeListener(Listener listener) {
    listeners.remove(listener);
  }

  @Override
  public int read() throws IOException {
    int b = super.read();
    updateProgress(1);
    return b;
  }

  @Override
  public int read(byte[] b) throws IOException {
    return updateProgress(super.read(b));
  }

  @Override
  public int read(byte[] b, int off, int len) throws IOException {
    return updateProgress(super.read(b, off, len));
  }

  @Override
  public long skip(long n) throws IOException {
    return updateProgress(super.skip(n));
  }

  @Override
  public void mark(int readLimit) {
    throw new UnsupportedOperationException();
  }

  @Override
  public void reset() throws IOException {
    throw new UnsupportedOperationException();
  }

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

  private  T updateProgress(T numBytesRead) {
    if(size < 1) {
      return numBytesRead;
    }
    if (numBytesRead.longValue() > 0) {
      bytesRead += numBytesRead.longValue();
      if (bytesRead * 100 / size > percent) {
        percent = (int) (bytesRead * 100 / size);
        for (Listener listener : listeners) {
          listener.onProgressChanged(Math.min(percent, 100));
        }
      }
    }
    return numBytesRead;
  }

  public interface Listener {
    void onProgressChanged(int percentage);
  }
}