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Signal Service communication library for Java

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package org.whispersystems.signalservice.internal.crypto;


import org.whispersystems.signalservice.internal.util.Util;

import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;

public class PaddingInputStream extends FilterInputStream {

  private long paddingRemaining;

  public PaddingInputStream(InputStream inputStream, long plaintextLength) {
    super(inputStream);
    this.paddingRemaining = getPaddedSize(plaintextLength) - plaintextLength;
  }

  @Override
  public int read() throws IOException {
    int result = super.read();
    if (result != -1) return result;

    if (paddingRemaining > 0) {
      paddingRemaining--;
      return 0x00;
    }

    return -1;
  }

  @Override
  public int read(byte[] buffer, int offset, int length) throws IOException {
    int result = super.read(buffer, offset, length);
    if (result != -1) return result;

    if (paddingRemaining > 0) {
      length = Math.min(length, Util.toIntExact(paddingRemaining));
      paddingRemaining -= length;
      return length;
    }

    return -1;
  }

  @Override
  public int read(byte[] buffer) throws IOException {
    return read(buffer, 0, buffer.length);
  }

  @Override
  public int available() throws IOException {
    return super.available() + Util.toIntExact(paddingRemaining);
  }

  public static long getPaddedSize(long size) {
    return (int) Math.max(541, Math.floor(Math.pow(1.05, Math.ceil(Math.log(size) / Math.log(1.05)))));
  }
}