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Signal Service communication library for Java
There is a newer version: 2.15.3
/**
 * Copyright (C) 2014-2016 Open Whisper Systems
 *
 * Licensed according to the LICENSE file in this repository.
 */

package org.whispersystems.signalservice.internal.util;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;

public class Util {

  public static byte[] join(byte[]... input) {
    try {
      ByteArrayOutputStream baos = new ByteArrayOutputStream();
      for (byte[] part : input) {
        baos.write(part);
      }

      return baos.toByteArray();
    } catch (IOException e) {
      throw new AssertionError(e);
    }
  }

  public static byte[][] split(byte[] input, int firstLength, int secondLength) {
    byte[][] parts = new byte[2][];

    parts[0] = new byte[firstLength];
    System.arraycopy(input, 0, parts[0], 0, firstLength);

    parts[1] = new byte[secondLength];
    System.arraycopy(input, firstLength, parts[1], 0, secondLength);

    return parts;
  }

  public static byte[] trim(byte[] input, int length) {
    byte[] result = new byte[length];
    System.arraycopy(input, 0, result, 0, result.length);

    return result;
  }

  public static boolean isEmpty(String value) {
    return value == null || value.trim().length() == 0;
  }

  public static byte[] getSecretBytes(int size) {
    try {
      byte[] secret = new byte[size];
      SecureRandom.getInstance("SHA1PRNG").nextBytes(secret);
      return secret;
    } catch (NoSuchAlgorithmException e) {
      throw new AssertionError(e);
    }
  }

  public static String readFully(InputStream in) throws IOException {
    ByteArrayOutputStream bout = new ByteArrayOutputStream();
    byte[] buffer              = new byte[4096];
    int read;

    while ((read = in.read(buffer)) != -1) {
      bout.write(buffer, 0, read);
    }

    in.close();

    return new String(bout.toByteArray());
  }

  public static void readFully(InputStream in, byte[] buffer) throws IOException {
    int offset = 0;

    for (;;) {
      int read = in.read(buffer, offset, buffer.length - offset);

      if (read + offset < buffer.length) offset += read;
      else                		           return;
    }
  }

  public static void copy(InputStream in, OutputStream out) throws IOException {
    byte[] buffer = new byte[4096];
    int read;

    while ((read = in.read(buffer)) != -1) {
      out.write(buffer, 0, read);
    }

    in.close();
    out.close();
  }

  public static void sleep(long millis) {
    try {
      Thread.sleep(millis);
    } catch (InterruptedException e) {
      throw new AssertionError(e);
    }
  }

  public static void wait(Object lock, long millis) {
    try {
      lock.wait(millis);
    } catch (InterruptedException e) {
      throw new AssertionError(e);
    }
  }

  public static int toIntExact(long value) {
    if ((int)value != value) {
      throw new ArithmeticException("integer overflow");
    }
    return (int)value;
  }

}