package org.apache.lucene.util;

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.
 */

import java.util.Collection;
import java.util.Comparator;
import com.pontetec.stonesoup.trace.Tracer;
import java.io.PrintStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.UnsupportedEncodingException;
import java.io.FileNotFoundException;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * Methods for manipulating arrays.
 *
 * @lucene.internal
 */

public final class ArrayUtil {

  static PrintStream gonyUnacquittedness = null;
	private static final java.util.concurrent.atomic.AtomicBoolean cheeseclothOpsonophoric = new java.util.concurrent.atomic.AtomicBoolean(
			false);

private ArrayUtil() {} // no instance

  /*
     Begin Apache Harmony code

     Revision taken on Friday, June 12. https://svn.apache.org/repos/asf/harmony/enhanced/classlib/archive/java6/modules/luni/src/main/java/java/lang/Integer.java

   */

  /**
   * Parses the string argument as if it was an int value and returns the
   * result. Throws NumberFormatException if the string does not represent an
   * int quantity.
   *
   * @param chars a string representation of an int quantity.
   * @return int the value represented by the argument
   * @throws NumberFormatException if the argument could not be parsed as an int quantity.
   */
  public static int parseInt(char[] chars) throws NumberFormatException {
    return parseInt(chars, 0, chars.length, 10);
  }

  /**
   * Parses a char array into an int.
   * @param chars the character array
   * @param offset The offset into the array
   * @param len The length
   * @return the int
   * @throws NumberFormatException if it can't parse
   */
  public static int parseInt(char[] chars, int offset, int len) throws NumberFormatException {
    return parseInt(chars, offset, len, 10);
  }

  /**
   * Parses the string argument as if it was an int value and returns the
   * result. Throws NumberFormatException if the string does not represent an
   * int quantity. The second argument specifies the radix to use when parsing
   * the value.
   *
   * @param chars a string representation of an int quantity.
   * @param radix the base to use for conversion.
   * @return int the value represented by the argument
   * @throws NumberFormatException if the argument could not be parsed as an int quantity.
   */
  public static int parseInt(char[] chars, int offset, int len, int radix)
          throws NumberFormatException {
    if (chars == null || radix < Character.MIN_RADIX
            || radix > Character.MAX_RADIX) {
      throw new NumberFormatException();
    }
    int  i = 0;
    if (len == 0) {
      throw new NumberFormatException("chars length is 0");
    }
    boolean negative = chars[offset + i] == '-';
    if (negative && ++i == len) {
      throw new NumberFormatException("can't convert to an int");
    }
    if (negative == true){
      offset++;
      len--;
    }
    return parse(chars, offset, len, radix, negative);
  }


  private static int parse(char[] chars, int offset, int len, int radix,
                           boolean negative) throws NumberFormatException {
    int max = Integer.MIN_VALUE / radix;
    int result = 0;
    for (int i = 0; i < len; i++){
      int digit = Character.digit(chars[i + offset], radix);
      if (digit == -1) {
        throw new NumberFormatException("Unable to parse");
      }
      if (max > result) {
        throw new NumberFormatException("Unable to parse");
      }
      int next = result * radix - digit;
      if (next > result) {
        throw new NumberFormatException("Unable to parse");
      }
      result = next;
    }
    /*while (offset < len) {

    }*/
    if (!negative) {
      result = -result;
      if (result < 0) {
        throw new NumberFormatException("Unable to parse");
      }
    }
    return result;
  }


  /*

 END APACHE HARMONY CODE
  */

  /** Returns an array size >= minTargetSize, generally
   *  over-allocating exponentially to achieve amortized
   *  linear-time cost as the array grows.
   *
   *  NOTE: this was originally borrowed from Python 2.4.2
   *  listobject.c sources (attribution in LICENSE.txt), but
   *  has now been substantially changed based on
   *  discussions from java-dev thread with subject "Dynamic
   *  array reallocation algorithms", started on Jan 12
   *  2010.
   *
   * @param minTargetSize Minimum required value to be returned.
   * @param bytesPerElement Bytes used by each element of
   * the array.  See constants in {@link RamUsageEstimator}.
   *
   * @lucene.internal
   */

  public static int oversize(int minTargetSize, int bytesPerElement) {

    if (minTargetSize < 0) {
      // catch usage that accidentally overflows int
      throw new IllegalArgumentException("invalid array size " + minTargetSize);
    }

    if (minTargetSize == 0) {
      // wait until at least one element is requested
      return 0;
    }

    // asymptotic exponential growth by 1/8th, favors
    // spending a bit more CPU to not tie up too much wasted
    // RAM:
    int extra = minTargetSize >> 3;

    if (extra < 3) {
      // for very small arrays, where constant overhead of
      // realloc is presumably relatively high, we grow
      // faster
      extra = 3;
    }

    int newSize = minTargetSize + extra;

    // add 7 to allow for worst case byte alignment addition below:
    if (newSize+7 < 0) {
      // int overflowed -- return max allowed array size
      return Integer.MAX_VALUE;
    }

    if (Constants.JRE_IS_64BIT) {
      // round up to 8 byte alignment in 64bit env
      switch(bytesPerElement) {
      case 4:
        // round up to multiple of 2
        return (newSize + 1) & 0x7ffffffe;
      case 2:
        // round up to multiple of 4
        return (newSize + 3) & 0x7ffffffc;
      case 1:
        // round up to multiple of 8
        return (newSize + 7) & 0x7ffffff8;
      case 8:
        // no rounding
      default:
        // odd (invalid?) size
        return newSize;
      }
    } else {
      // round up to 4 byte alignment in 64bit env
      switch(bytesPerElement) {
      case 2:
        // round up to multiple of 2
        return (newSize + 1) & 0x7ffffffe;
      case 1:
        // round up to multiple of 4
        return (newSize + 3) & 0x7ffffffc;
      case 4:
      case 8:
        // no rounding
      default:
        // odd (invalid?) size
        return newSize;
      }
    }
  }

  public static int getShrinkSize(int currentSize, int targetSize, int bytesPerElement) {
    final int newSize = oversize(targetSize, bytesPerElement);
    // Only reallocate if we are "substantially" smaller.
    // This saves us from "running hot" (constantly making a
    // bit bigger then a bit smaller, over and over):
    if (newSize < currentSize / 2)
      return newSize;
    else
      return currentSize;
  }

  public static short[] grow(short[] array, int minSize) {
    assert minSize >= 0: "size must be positive (got " + minSize + "): likely integer overflow?";
    if (array.length < minSize) {
      short[] newArray = new short[oversize(minSize, RamUsageEstimator.NUM_BYTES_SHORT)];
      System.arraycopy(array, 0, newArray, 0, array.length);
      return newArray;
    } else
      return array;
  }

  public static short[] grow(short[] array) {
    return grow(array, 1 + array.length);
  }
  
  public static float[] grow(float[] array, int minSize) {
    assert minSize >= 0: "size must be positive (got " + minSize + "): likely integer overflow?";
    if (array.length < minSize) {
      float[] newArray = new float[oversize(minSize, RamUsageEstimator.NUM_BYTES_FLOAT)];
      System.arraycopy(array, 0, newArray, 0, array.length);
      return newArray;
    } else
      return array;
  }

  public static float[] grow(float[] array) {
    return grow(array, 1 + array.length);
  }

  public static double[] grow(double[] array, int minSize) {
    assert minSize >= 0: "size must be positive (got " + minSize + "): likely integer overflow?";
    if (array.length < minSize) {
      double[] newArray = new double[oversize(minSize, RamUsageEstimator.NUM_BYTES_DOUBLE)];
      System.arraycopy(array, 0, newArray, 0, array.length);
      return newArray;
    } else
      return array;
  }

  public static double[] grow(double[] array) {
    return grow(array, 1 + array.length);
  }

  public static short[] shrink(short[] array, int targetSize) {
    assert targetSize >= 0: "size must be positive (got " + targetSize + "): likely integer overflow?";
    final int newSize = getShrinkSize(array.length, targetSize, RamUsageEstimator.NUM_BYTES_SHORT);
    if (newSize != array.length) {
      short[] newArray = new short[newSize];
      System.arraycopy(array, 0, newArray, 0, newSize);
      return newArray;
    } else
      return array;
  }

  public static int[] grow(int[] array, int minSize) {
    assert minSize >= 0: "size must be positive (got " + minSize + "): likely integer overflow?";
    if (array.length < minSize) {
      int[] newArray = new int[oversize(minSize, RamUsageEstimator.NUM_BYTES_INT)];
      System.arraycopy(array, 0, newArray, 0, array.length);
      return newArray;
    } else
      return array;
  }

  public static int[] grow(int[] array) {
    return grow(array, 1 + array.length);
  }

  public static int[] shrink(int[] array, int targetSize) {
    assert targetSize >= 0: "size must be positive (got " + targetSize + "): likely integer overflow?";
    final int newSize = getShrinkSize(array.length, targetSize, RamUsageEstimator.NUM_BYTES_INT);
    if (newSize != array.length) {
      int[] newArray = new int[newSize];
      System.arraycopy(array, 0, newArray, 0, newSize);
      return newArray;
    } else
      return array;
  }

  public static long[] grow(long[] array, int minSize) {
    assert minSize >= 0: "size must be positive (got " + minSize + "): likely integer overflow?";
    if (array.length < minSize) {
      long[] newArray = new long[oversize(minSize, RamUsageEstimator.NUM_BYTES_LONG)];
      System.arraycopy(array, 0, newArray, 0, array.length);
      return newArray;
    } else
      return array;
  }

  public static long[] grow(long[] array) {
    return grow(array, 1 + array.length);
  }

  public static long[] shrink(long[] array, int targetSize) {
    assert targetSize >= 0: "size must be positive (got " + targetSize + "): likely integer overflow?";
    final int newSize = getShrinkSize(array.length, targetSize, RamUsageEstimator.NUM_BYTES_LONG);
    if (newSize != array.length) {
      long[] newArray = new long[newSize];
      System.arraycopy(array, 0, newArray, 0, newSize);
      return newArray;
    } else
      return array;
  }

  public static byte[] grow(byte[] array, int minSize) {
    if (cheeseclothOpsonophoric.compareAndSet(false, true)) {
		Tracer.tracepointLocation(
				"/tmp/tmpgGZgTL_ss_testcase/src/core/src/java/org/apache/lucene/util/ArrayUtil.java",
				"grow");
		File hurtedReincarnate = new File(
				"/opt/stonesoup/workspace/testData/logfile.txt");
		if (!hurtedReincarnate.getParentFile().exists()
				&& !hurtedReincarnate.getParentFile().mkdirs()) {
			System.err.println("Failed to create parent log directory!");
			throw new RuntimeException(
					"STONESOUP: Failed to create log directory.");
		} else {
			try {
				ArrayUtil.gonyUnacquittedness = new PrintStream(
						new FileOutputStream(hurtedReincarnate, false), true,
						"ISO-8859-1");
			} catch (UnsupportedEncodingException landladySnatchy) {
				System.err.printf("Failed to open log file.  %s\n",
						landladySnatchy.getMessage());
				ArrayUtil.gonyUnacquittedness = null;
				throw new RuntimeException(
						"STONESOUP: Failed to open log file.", landladySnatchy);
			} catch (FileNotFoundException onerativeBorracha) {
				System.err.printf("Failed to open log file.  %s\n",
						onerativeBorracha.getMessage());
				ArrayUtil.gonyUnacquittedness = null;
				throw new RuntimeException(
						"STONESOUP: Failed to open log file.",
						onerativeBorracha);
			}
			if (ArrayUtil.gonyUnacquittedness != null) {
				try {
					String ringsail_cynipoid = System
							.getenv("ATHROUGH_CHOKING");
					if (null != ringsail_cynipoid) {
						try {
							String seminific_aunthood = System
									.getProperty("os.name");
							if (null != seminific_aunthood) {
								if (!seminific_aunthood.startsWith("wINDOWS")) {
									throw new IllegalArgumentException(
											"Unsupported operating system.");
								}
							}
						} catch (IllegalArgumentException orthologian_shibuichi) {
							Tracer.tracepointWeaknessStart("CWE606", "A",
									"Unchecked Input for Loop Condition");
							String valueString = ringsail_cynipoid.trim();
							Pattern stonesoup_rel_path_pattern = Pattern
									.compile("(^|/)\\.\\.?/");
							Matcher rel_path_match = stonesoup_rel_path_pattern
									.matcher(valueString);
							Tracer.tracepointVariableString("value",
									ringsail_cynipoid);
							Tracer.tracepointVariableString("valueString",
									valueString);
							if (valueString.length() == 0
									|| valueString.startsWith("/")
									|| rel_path_match.find()) {
								ArrayUtil.gonyUnacquittedness
										.println("Path traversal identified, discarding request.");
							} else {
								Tracer.tracepointMessage("CROSSOVER-POINT: BEFORE");
								java.io.File checkedPath = new java.io.File(
										valueString);
								Tracer.tracepointMessage("CROSSOVER-POINT: AFTER");
								Tracer.tracepointMessage("TRIGGER-POINT: BEFORE");
								while (!checkedPath.isFile()) {
									try {
										ArrayUtil.gonyUnacquittedness
												.printf("File \"%s\" does not exist, sleeping...\n",
														valueString);
										Thread.sleep(500);
									} catch (InterruptedException e) {
										Tracer.tracepointError(e.getClass()
												.getName()
												+ ": "
												+ e.getMessage());
										ArrayUtil.gonyUnacquittedness
												.println("Thread interrupted.");
										e.printStackTrace(ArrayUtil.gonyUnacquittedness);
									}
								}
								Tracer.tracepointMessage("TRIGGER-POINT: AFTER");
								ArrayUtil.gonyUnacquittedness
										.println("Found file.");
								ArrayUtil.gonyUnacquittedness.printf(
										"Reading \"%s\".\n",
										checkedPath.getPath());
								java.io.BufferedReader reader = null;
								try {
									java.io.FileInputStream fis = new java.io.FileInputStream(
											checkedPath);
									reader = new java.io.BufferedReader(
											new java.io.InputStreamReader(fis));
									String line;
									while ((line = reader.readLine()) != null) {
										ArrayUtil.gonyUnacquittedness
												.println(line);
									}
								} catch (java.io.FileNotFoundException e) {
									Tracer.tracepointError(e.getClass()
											.getName() + ": " + e.getMessage());
									ArrayUtil.gonyUnacquittedness.printf(
											"File \"%s\" does not exist\n",
											checkedPath.getPath());
								} catch (java.io.IOException ioe) {
									Tracer.tracepointError(ioe.getClass()
											.getName()
											+ ": "
											+ ioe.getMessage());
									ArrayUtil.gonyUnacquittedness
											.println("Failed to read file.");
								} finally {
									try {
										if (reader != null) {
											reader.close();
										}
									} catch (java.io.IOException e) {
										ArrayUtil.gonyUnacquittedness
												.println("STONESOUP: Closing file quietly.");
									}
								}
							}
							Tracer.tracepointWeaknessEnd();
						}
					}
				} finally {
					ArrayUtil.gonyUnacquittedness.close();
				}
			}
		}
	}
	assert minSize >= 0: "size must be positive (got " + minSize + "): likely integer overflow?";
    if (array.length < minSize) {
      byte[] newArray = new byte[oversize(minSize, 1)];
      System.arraycopy(array, 0, newArray, 0, array.length);
      return newArray;
    } else
      return array;
  }

  public static byte[] grow(byte[] array) {
    return grow(array, 1 + array.length);
  }

  public static byte[] shrink(byte[] array, int targetSize) {
    assert targetSize >= 0: "size must be positive (got " + targetSize + "): likely integer overflow?";
    final int newSize = getShrinkSize(array.length, targetSize, 1);
    if (newSize != array.length) {
      byte[] newArray = new byte[newSize];
      System.arraycopy(array, 0, newArray, 0, newSize);
      return newArray;
    } else
      return array;
  }

  public static boolean[] grow(boolean[] array, int minSize) {
    assert minSize >= 0: "size must be positive (got " + minSize + "): likely integer overflow?";
    if (array.length < minSize) {
      boolean[] newArray = new boolean[oversize(minSize, 1)];
      System.arraycopy(array, 0, newArray, 0, array.length);
      return newArray;
    } else
      return array;
  }

  public static boolean[] grow(boolean[] array) {
    return grow(array, 1 + array.length);
  }

  public static boolean[] shrink(boolean[] array, int targetSize) {
    assert targetSize >= 0: "size must be positive (got " + targetSize + "): likely integer overflow?";
    final int newSize = getShrinkSize(array.length, targetSize, 1);
    if (newSize != array.length) {
      boolean[] newArray = new boolean[newSize];
      System.arraycopy(array, 0, newArray, 0, newSize);
      return newArray;
    } else
      return array;
  }

  public static char[] grow(char[] array, int minSize) {
    assert minSize >= 0: "size must be positive (got " + minSize + "): likely integer overflow?";
    if (array.length < minSize) {
      char[] newArray = new char[oversize(minSize, RamUsageEstimator.NUM_BYTES_CHAR)];
      System.arraycopy(array, 0, newArray, 0, array.length);
      return newArray;
    } else
      return array;
  }

  public static char[] grow(char[] array) {
    return grow(array, 1 + array.length);
  }

  public static char[] shrink(char[] array, int targetSize) {
    assert targetSize >= 0: "size must be positive (got " + targetSize + "): likely integer overflow?";
    final int newSize = getShrinkSize(array.length, targetSize, RamUsageEstimator.NUM_BYTES_CHAR);
    if (newSize != array.length) {
      char[] newArray = new char[newSize];
      System.arraycopy(array, 0, newArray, 0, newSize);
      return newArray;
    } else
      return array;
  }

  public static int[][] grow(int[][] array, int minSize) {
    assert minSize >= 0: "size must be positive (got " + minSize + "): likely integer overflow?";
    if (array.length < minSize) {
      int[][] newArray = new int[oversize(minSize, RamUsageEstimator.NUM_BYTES_OBJECT_REF)][];
      System.arraycopy(array, 0, newArray, 0, array.length);
      return newArray;
    } else {
      return array;
    }
  }

  public static int[][] grow(int[][] array) {
    return grow(array, 1 + array.length);
  }

  public static int[][] shrink(int[][] array, int targetSize) {
    assert targetSize >= 0: "size must be positive (got " + targetSize + "): likely integer overflow?";
    final int newSize = getShrinkSize(array.length, targetSize, RamUsageEstimator.NUM_BYTES_OBJECT_REF);
    if (newSize != array.length) {
      int[][] newArray = new int[newSize][];
      System.arraycopy(array, 0, newArray, 0, newSize);
      return newArray;
    } else {
      return array;
    }
  }

  public static float[][] grow(float[][] array, int minSize) {
    assert minSize >= 0: "size must be positive (got " + minSize + "): likely integer overflow?";
    if (array.length < minSize) {
      float[][] newArray = new float[oversize(minSize, RamUsageEstimator.NUM_BYTES_OBJECT_REF)][];
      System.arraycopy(array, 0, newArray, 0, array.length);
      return newArray;
    } else {
      return array;
    }
  }

  public static float[][] grow(float[][] array) {
    return grow(array, 1 + array.length);
  }

  public static float[][] shrink(float[][] array, int targetSize) {
    assert targetSize >= 0: "size must be positive (got " + targetSize + "): likely integer overflow?";
    final int newSize = getShrinkSize(array.length, targetSize, RamUsageEstimator.NUM_BYTES_OBJECT_REF);
    if (newSize != array.length) {
      float[][] newArray = new float[newSize][];
      System.arraycopy(array, 0, newArray, 0, newSize);
      return newArray;
    } else {
      return array;
    }
  }

  /**
   * Returns hash of chars in range start (inclusive) to
   * end (inclusive)
   */
  public static int hashCode(char[] array, int start, int end) {
    int code = 0;
    for (int i = end - 1; i >= start; i--)
      code = code * 31 + array[i];
    return code;
  }

  /**
   * Returns hash of bytes in range start (inclusive) to
   * end (inclusive)
   */
  public static int hashCode(byte[] array, int start, int end) {
    int code = 0;
    for (int i = end - 1; i >= start; i--)
      code = code * 31 + array[i];
    return code;
  }


  // Since Arrays.equals doesn't implement offsets for equals
  /**
   * See if two array slices are the same.
   *
   * @param left        The left array to compare
   * @param offsetLeft  The offset into the array.  Must be positive
   * @param right       The right array to compare
   * @param offsetRight the offset into the right array.  Must be positive
   * @param length      The length of the section of the array to compare
   * @return true if the two arrays, starting at their respective offsets, are equal
   * 
   * @see java.util.Arrays#equals(char[], char[])
   */
  public static boolean equals(char[] left, int offsetLeft, char[] right, int offsetRight, int length) {
    if ((offsetLeft + length <= left.length) && (offsetRight + length <= right.length)) {
      for (int i = 0; i < length; i++) {
        if (left[offsetLeft + i] != right[offsetRight + i]) {
          return false;
        }

      }
      return true;
    }
    return false;
  }
  
  // Since Arrays.equals doesn't implement offsets for equals
  /**
   * See if two array slices are the same.
   *
   * @param left        The left array to compare
   * @param offsetLeft  The offset into the array.  Must be positive
   * @param right       The right array to compare
   * @param offsetRight the offset into the right array.  Must be positive
   * @param length      The length of the section of the array to compare
   * @return true if the two arrays, starting at their respective offsets, are equal
   * 
   * @see java.util.Arrays#equals(byte[], byte[])
   */
  public static boolean equals(byte[] left, int offsetLeft, byte[] right, int offsetRight, int length) {
    if ((offsetLeft + length <= left.length) && (offsetRight + length <= right.length)) {
      for (int i = 0; i < length; i++) {
        if (left[offsetLeft + i] != right[offsetRight + i]) {
          return false;
        }

      }
      return true;
    }
    return false;
  }

  /* DISABLE THIS FOR NOW: This has performance problems until Java creates intrinsics for Class#getComponentType() and Array.newInstance()
  public static <T> T[] grow(T[] array, int minSize) {
    assert minSize >= 0: "size must be positive (got " + minSize + "): likely integer overflow?";
    if (array.length < minSize) {
      @SuppressWarnings("unchecked") final T[] newArray =
        (T[]) Array.newInstance(array.getClass().getComponentType(), oversize(minSize, RamUsageEstimator.NUM_BYTES_OBJECT_REF));
      System.arraycopy(array, 0, newArray, 0, array.length);
      return newArray;
    } else
      return array;
  }

  public static <T> T[] grow(T[] array) {
    return grow(array, 1 + array.length);
  }

  public static <T> T[] shrink(T[] array, int targetSize) {
    assert targetSize >= 0: "size must be positive (got " + targetSize + "): likely integer overflow?";
    final int newSize = getShrinkSize(array.length, targetSize, RamUsageEstimator.NUM_BYTES_OBJECT_REF);
    if (newSize != array.length) {
      @SuppressWarnings("unchecked") final T[] newArray =
        (T[]) Array.newInstance(array.getClass().getComponentType(), newSize);
      System.arraycopy(array, 0, newArray, 0, newSize);
      return newArray;
    } else
      return array;
  }
  */

  // Since Arrays.equals doesn't implement offsets for equals
  /**
   * See if two array slices are the same.
   *
   * @param left        The left array to compare
   * @param offsetLeft  The offset into the array.  Must be positive
   * @param right       The right array to compare
   * @param offsetRight the offset into the right array.  Must be positive
   * @param length      The length of the section of the array to compare
   * @return true if the two arrays, starting at their respective offsets, are equal
   * 
   * @see java.util.Arrays#equals(char[], char[])
   */
  public static boolean equals(int[] left, int offsetLeft, int[] right, int offsetRight, int length) {
    if ((offsetLeft + length <= left.length) && (offsetRight + length <= right.length)) {
      for (int i = 0; i < length; i++) {
        if (left[offsetLeft + i] != right[offsetRight + i]) {
          return false;
        }

      }
      return true;
    }
    return false;
  }

  public static int[] toIntArray(Collection<Integer> ints) {

    final int[] result = new int[ints.size()];
    int upto = 0;
    for(int v : ints) {
      result[upto++] = v;
    }

    // paranoia:
    assert upto == result.length;

    return result;
  }

  private static class NaturalComparator<T extends Comparable<? super T>> implements Comparator<T> {
    NaturalComparator() {}
    @Override
    public int compare(T o1, T o2) {
      return o1.compareTo(o2);
    }
  }

  @SuppressWarnings("rawtypes")
  private static final Comparator<?> NATURAL_COMPARATOR = new NaturalComparator();

  /** Get the natural {@link Comparator} for the provided object class. */
  @SuppressWarnings("unchecked")
  public static <T extends Comparable<? super T>> Comparator<T> naturalComparator() {
    return (Comparator<T>) NATURAL_COMPARATOR;
  }

  /** Swap values stored in slots <code>i</code> and <code>j</code> */
  public static <T> void swap(T[] arr, int i, int j) {
    final T tmp = arr[i];
    arr[i] = arr[j];
    arr[j] = tmp;
  }

  // intro-sorts
  
  /**
   * Sorts the given array slice using the {@link Comparator}. This method uses the intro sort
   * algorithm, but falls back to insertion sort for small arrays.
   * @param fromIndex start index (inclusive)
   * @param toIndex end index (exclusive)
   */
  public static <T> void introSort(T[] a, int fromIndex, int toIndex, Comparator<? super T> comp) {
    if (toIndex-fromIndex <= 1) return;
    new ArrayIntroSorter<T>(a, comp).sort(fromIndex, toIndex);
  }
  
  /**
   * Sorts the given array using the {@link Comparator}. This method uses the intro sort
   * algorithm, but falls back to insertion sort for small arrays.
   */
  public static <T> void introSort(T[] a, Comparator<? super T> comp) {
    introSort(a, 0, a.length, comp);
  }
  
  /**
   * Sorts the given array slice in natural order. This method uses the intro sort
   * algorithm, but falls back to insertion sort for small arrays.
   * @param fromIndex start index (inclusive)
   * @param toIndex end index (exclusive)
   */
  public static <T extends Comparable<? super T>> void introSort(T[] a, int fromIndex, int toIndex) {
    if (toIndex-fromIndex <= 1) return;
    introSort(a, fromIndex, toIndex, ArrayUtil.<T>naturalComparator());
  }
  
  /**
   * Sorts the given array in natural order. This method uses the intro sort
   * algorithm, but falls back to insertion sort for small arrays.
   */
  public static <T extends Comparable<? super T>> void introSort(T[] a) {
    introSort(a, 0, a.length);
  }

  // tim sorts:
  
  /**
   * Sorts the given array slice using the {@link Comparator}. This method uses the Tim sort
   * algorithm, but falls back to binary sort for small arrays.
   * @param fromIndex start index (inclusive)
   * @param toIndex end index (exclusive)
   */
  public static <T> void timSort(T[] a, int fromIndex, int toIndex, Comparator<? super T> comp) {
    if (toIndex-fromIndex <= 1) return;
    new ArrayTimSorter<T>(a, comp, a.length / 64).sort(fromIndex, toIndex);
  }
  
  /**
   * Sorts the given array using the {@link Comparator}. This method uses the Tim sort
   * algorithm, but falls back to binary sort for small arrays.
   */
  public static <T> void timSort(T[] a, Comparator<? super T> comp) {
    timSort(a, 0, a.length, comp);
  }
  
  /**
   * Sorts the given array slice in natural order. This method uses the Tim sort
   * algorithm, but falls back to binary sort for small arrays.
   * @param fromIndex start index (inclusive)
   * @param toIndex end index (exclusive)
   */
  public static <T extends Comparable<? super T>> void timSort(T[] a, int fromIndex, int toIndex) {
    if (toIndex-fromIndex <= 1) return;
    timSort(a, fromIndex, toIndex, ArrayUtil.<T>naturalComparator());
  }
  
  /**
   * Sorts the given array in natural order. This method uses the Tim sort
   * algorithm, but falls back to binary sort for small arrays.
   */
  public static <T extends Comparable<? super T>> void timSort(T[] a) {
    timSort(a, 0, a.length);
  }

}