java/org/brotli/dec/Utils.java

/* Copyright 2015 Google Inc. All Rights Reserved.

   Distributed under MIT license.
   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
*/

package org.brotli.dec;

import static org.brotli.dec.BrotliError.BROTLI_ERROR_READ_FAILED;
import static org.brotli.dec.BrotliError.BROTLI_OK;
import static org.brotli.dec.BrotliError.BROTLI_PANIC;

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.UnsupportedEncodingException;
import java.nio.Buffer;
import java.nio.ByteBuffer;

/**
 * A set of utility methods.
 */
final class Utils {

  private static final byte[] BYTE_ZEROES = new byte[1024];

  private static final int[] INT_ZEROES = new int[1024];

  /**
   * Fills byte array with zeroes.
   *
   * <p> Current implementation uses {@link System#arraycopy}, so it should be used for length not
   * less than 16.
   *
   * @param dest array to fill with zeroes
   * @param start the first item to fill
   * @param end the last item to fill (exclusive)
   */
  static void fillBytesWithZeroes(byte[] dest, int start, int end) {
    int cursor = start;
    while (cursor < end) {
      int step = Math.min(cursor + 1024, end) - cursor;
      System.arraycopy(BYTE_ZEROES, 0, dest, cursor, step);
      cursor += step;
    }
  }

  /**
   * Fills int array with zeroes.
   *
   * <p> Current implementation uses {@link System#arraycopy}, so it should be used for length not
   * less than 16.
   *
   * @param dest array to fill with zeroes
   * @param start the first item to fill
   * @param end the last item to fill (exclusive)
   */
  static void fillIntsWithZeroes(int[] dest, int start, int end) {
    int cursor = start;
    while (cursor < end) {
      int step = Math.min(cursor + 1024, end) - cursor;
      System.arraycopy(INT_ZEROES, 0, dest, cursor, step);
      cursor += step;
    }
  }

  static void copyBytes(byte[] dst, int target, byte[] src, int start, int end) {
    System.arraycopy(src, start, dst, target, end - start);
  }

  static void copyBytesWithin(byte[] bytes, int target, int start, int end) {
    System.arraycopy(bytes, start, bytes, target, end - start);
  }

  static int readInput(State s, byte[] dst, int offset, int length) {
    try {
      return s.input.read(dst, offset, length);
    } catch (IOException e) {
      return makeError(s, BROTLI_ERROR_READ_FAILED);
    }
  }

  static InputStream makeEmptyInput() {
    return new ByteArrayInputStream(new byte[0]);
  }

  static void closeInput(State s) throws IOException {
    s.input.close();
    s.input = makeEmptyInput();
  }

  static byte[] toUsAsciiBytes(String src) {
    try {
      // NB: String#getBytes(String) is present in JDK 1.1, while other variants require JDK 1.6 and
      // above.
      return src.getBytes("US-ASCII");
    } catch (UnsupportedEncodingException e) {
      throw new RuntimeException(e); // cannot happen
    }
  }

  static int[] toUtf8Runes(String src) {
    int[] result = new int[src.length()];
    for (int i = 0; i < src.length(); i++) {
      result[i] = (int) src.charAt(i);
    }
    return result;
  }

  static ByteBuffer asReadOnlyBuffer(ByteBuffer src) {
    return src.asReadOnlyBuffer();
  }

  static int isReadOnly(ByteBuffer src) {
    return src.isReadOnly() ? 1 : 0;
  }

  static int isDirect(ByteBuffer src) {
    return src.isDirect() ? 1 : 0;
  }

  // Crazy pills factory: code compiled for JDK8 does not work on JRE9.
  static void flipBuffer(Buffer buffer) {
    buffer.flip();
  }

  static int isDebugMode() {
    boolean assertsEnabled = Boolean.parseBoolean(System.getProperty("BROTLI_ENABLE_ASSERTS"));
    return assertsEnabled ? 1 : 0;
  }

  // See BitReader.LOG_BITNESS
  static int getLogBintness() {
    boolean isLongExpensive = Boolean.parseBoolean(System.getProperty("BROTLI_32_BIT_CPU"));
    return isLongExpensive ? 5 : 6;
  }

  static int shr32(int x, int y) {
    return x >>> y;
  }

  static long shr64(long x, int y) {
    return x >>> y;
  }

  static int min(int a, int b) {
    return Math.min(a, b);
  }

  static int makeError(State s, int code) {
    if (code >= BROTLI_OK) {
      return code;
    }
    if (s.runningState >= 0) {
      s.runningState = code;  // Only the first error is remembered.
    }
    // TODO(eustas): expand codes to messages, if ever necessary.
    if (code <= BROTLI_PANIC) {
      throw new IllegalStateException("Brotli error code: " + code);
    }
    throw new BrotliRuntimeException("Error code: " + code);
  }
}