// Copyright 2006 Google Inc.
// All Rights Reserved.
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
// 
//  * Redistributions of source code must retain the above copyright
//    notice, this list of conditions and the following disclaimer.
//  * Redistributions in binary form must reproduce the above copyright
//    notice, this list of conditions and the following disclaimer in
//    the documentation and/or other materials provided with the
//    distribution.
// 
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
// FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
// COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
// BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
// LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
// LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
// ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
// POSSIBILITY OF SUCH DAMAGE. 

/**
 * @fileoverview Utilities for manipulating arrays.
 *
 */


goog.provide('goog.array');


/**
 * @type {Array|NodeList|Arguments|{length: number}}
 */
goog.array.ArrayLike = goog.typedef;


/**
 * Returns the last element in an array without removing it.
 * @param {goog.array.ArrayLike} array The array.
 * @return {*} Last item in array.
 */
goog.array.peek = function(array) {
  return array[array.length - 1];
};


/**
 * Returns the index of the first element of an array with a specified
 * value, or -1 if the element is not present in the array.
 *
 * See {@link http://tinyurl.com/nga8b}
 *
 * @param {goog.array.ArrayLike} arr The array to be searched.
 * @param {*} obj The object for which we are searching.
 * @param {number} opt_fromIndex The index at which to start the search. If
 *     omitted the search starts at index 0.
 * @return {number} The index of the first matching array element.
 */
goog.array.indexOf = function(arr, obj, opt_fromIndex) {
  if (arr.indexOf) {
    return arr.indexOf(obj, opt_fromIndex);
  }
  if (Array.indexOf) {
    return Array.indexOf(arr, obj, opt_fromIndex);
  }

  var fromIndex = opt_fromIndex == null ?
      0 : (opt_fromIndex < 0 ?
           Math.max(0, arr.length + opt_fromIndex) : opt_fromIndex);
  for (var i = fromIndex; i < arr.length; i++) {
    if (i in arr && arr[i] === obj)
      return i;
  }
  return -1;
};


/**
 * Returns the index of the last element of an array with a specified value, or
 * -1 if the element is not present in the array.
 *
 * See {@link http://tinyurl.com/ru6lg}
 *
 * @param {goog.array.ArrayLike} arr The array to be searched.
 * @param {*} obj The object for which we are searching.
 * @param {number?} opt_fromIndex The index at which to start the search. If
 *     omitted the search starts at the end of the array.
 * @return {number} The index of the last matching array element.
 */
goog.array.lastIndexOf = function(arr, obj, opt_fromIndex) {
  // if undefined or null are passed then that is treated as 0 which will
  // always return -1;
  var fromIndex = opt_fromIndex == null ? arr.length - 1 : opt_fromIndex;

  if (arr.lastIndexOf) {
    return arr.lastIndexOf(obj, fromIndex);
  }
  if (Array.lastIndexOf) {
    return Array.lastIndexOf(arr, obj, fromIndex);
  }

  if (fromIndex < 0) {
    fromIndex = Math.max(0, arr.length + fromIndex);
  }
  for (var i = fromIndex; i >= 0; i--) {
    if (i in arr && arr[i] === obj)
      return i;
  }
  return -1;
};


/**
 * Calls a function for each element in an array.
 *
 * See {@link http://tinyurl.com/jrvcb}
 *
 * @param {goog.array.ArrayLike} arr Array or array like object over
 *     which to iterate.
 * @param {Function} f The function to call for every element. This function
 *     takes 3 arguments (the element, the index and the array). The return
 *     value is ignored. The function is called only for indexes of the array
 *     which have assigned values; it is not called for indexes which have
 *     been deleted or which have never been assigned values. See {@link
 *     https://developer.mozilla.org/En/Core_JavaScript_1.5_Reference:Objects:
 *     Array:forEach}.
 *
 * @param {Object} opt_obj The object to be used as the value of 'this'
 *     within f.
 */
goog.array.forEach = function(arr, f, opt_obj) {
  if (arr.forEach) {
    arr.forEach(f, opt_obj);
  } else if (Array.forEach) {
    Array.forEach(/** @type {Array} */ (arr), f, opt_obj);
  } else {
    var l = arr.length;  // must be fixed during loop... see docs
    var arr2 = goog.isString(arr) ? arr.split('') : arr;
    for (var i = 0; i < l; i++) {
      if (i in arr2) {
        f.call(opt_obj, arr2[i], i, arr);
      }
    }
  }
};


/**
 * Calls a function for each element in an array, starting from the last
 * element rather than the first.
 *
 * @param {goog.Array.ArrayLike} arr The array over which to iterate.
 * @param {Function} f The function to call for every element. This function
 *     takes 3 arguments (the element, the index and the array). The return
 *     value is ignored.
 * @param {Object} opt_obj The object to be used as the value of 'this'
 *     within f.
 */
goog.array.forEachRight = function(arr, f, opt_obj) {
  var l = arr.length;  // must be fixed during loop... see docs
  var arr2 = goog.isString(arr) ? arr.split('') : arr;
  for (var i = l - 1; i >= 0; --i) {
    if (i in arr2) {
      f.call(opt_obj, arr2[i], i, arr);
    }
  }
};


/**
 * Calls a function for each element in an array, and if the function returns
 * true adds the element to a new array.
 *
 * See {@link http://tinyurl.com/rmtuo}
 *
 * @param {Array} arr The array over which to iterate.
 * @param {Function} f The function to call for every element. This function
 *     takes 3 arguments (the element, the index and the array) and must
 *     return a Boolean. If the return value is true the element is added to the
 *     result array. If it is false the element is not included.
 * @param {Object} opt_obj The object to be used as the value of 'this'
 *     within f.
 * @return {Array} a new array in which only elements that passed the test are
 *     present.
 */
goog.array.filter = function(arr, f, opt_obj) {
  if (arr.filter) {
    return arr.filter(f, opt_obj);
  }
  if (Array.filter) {
    return Array.filter(arr, f, opt_obj);
  }

  var l = arr.length;  // must be fixed during loop... see docs
  var res = [];
  var resLength = 0;
  var arr2 = goog.isString(arr) ? arr.split('') : arr;
  for (var i = 0; i < l; i++) {
    if (i in arr2) {
      var val = arr2[i];  // in case f mutates arr2
      if (f.call(opt_obj, val, i, arr)) {
        res[resLength++] = val;
      }
    }
  }
  return res;
};


/**
 * Calls a function for each element in an array and inserts the result into a
 * new array.
 *
 * See {@link http://tinyurl.com/hlx5p}
 *
 * @param {Array} arr The array over which to iterate.
 * @param {Function} f The function to call for every element. This function
 *     takes 3 arguments (the element, the index and the array) and should
 *     return something. The result will be inserted into a new array.
 * @param {Object} opt_obj The object to be used as the value of 'this'
 *     within f.
 * @return {Array} a new array with the results from f.
 */
goog.array.map = function(arr, f, opt_obj) {
  if (arr.map) {
    return arr.map(f, opt_obj);
  }
  if (Array.map) {
    return Array.map(arr, f, opt_obj);
  }

  var l = arr.length;  // must be fixed during loop... see docs
  var res = [];
  var resLength = 0;
  var arr2 = goog.isString(arr) ? arr.split('') : arr;
  for (var i = 0; i < l; i++) {
    if (i in arr2) {
      res[resLength++] = f.call(opt_obj, arr2[i], i, arr);
    }
  }
  return res;
};


/**
 * Passes every element of an array into a function and accumulates the result.
 * We're google; we can't have "map" without "reduce" can we?
 *
 * Passes through to:
 *     http://developer.mozilla.org/en/docs/Core_JavaScript_1.5_Reference:
 *     Objects:Array:reduce
 * when available.
 *
 * For example:
 * var a = [1, 2, 3, 4];
 * goog.array.reduce(a, function(r, v, i, arr) {return r + v;}, 0);
 * returns 10
 *
 * @param {goog.array.ArrayLike} arr The array over which to iterate.
 * @param {Function} f The function to call for every element. This function
 *     takes 4 arguments (the function's previous result or the initial value,
 *     the value of the current array element, the current array index, and the
 *     array itself)
 *     function(previousValue, currentValue, index, array).
 * @param {*} val The initial value to pass into the function on the first call.
 * @param {Object} opt_obj  The object to be used as the value of 'this'
 *     within f.
 * @return {*} Result of evaluating f repeatedly across the values of the array.
 * @notypecheck See http://b/1342779
 */
goog.array.reduce = function(arr, f, val, opt_obj) {
  if (arr.reduce) {
    if (opt_obj) {
      return arr.reduce(goog.bind(f, opt_obj), val);
    } else {
      return arr.reduce(f, val);
    }
  }
  var rval = val;
  goog.array.forEach(arr, function(val, index) {
    rval = f.call(opt_obj, rval, val, index, arr);
  });
  return rval;
};


/**
 * Passes every element of an array into a function and accumulates the result,
 * starting from the last element and working towards the first.
 *
 * Passes through to:
 *     http://developer.mozilla.org/en/docs/Core_JavaScript_1.5_Reference:
 *     Objects:Array:reduceRight
 * when available.
 *
 * For example:
 * var a = ['a', 'b', 'c'];
 * goog.array.reduceRight(a, function(r, v, i, arr) {return r + v;}, '');
 * returns 'cba'
 *
 * @param {goog.array.ArrayLike} arr The array over which to iterate.
 * @param {Function} f The function to call for every element. This function
 *     takes 4 arguments (the function's previous result or the initial value,
 *     the value of the current array element, the current array index, and the
 *     array itself)
 *     function(previousValue, currentValue, index, array).
 * @param {*} val The initial value to pass into the function on the first call.
 * @param {Object} opt_obj The object to be used as the value of 'this'
 *     within f.
 * @return {*} Object returned as a result of evaluating f repeatedly across the
 *     values of the array.
 * @notypecheck See http://b/1342779
 */
goog.array.reduceRight = function(arr, f, val, opt_obj) {
  if (arr.reduceRight) {
    if (opt_obj) {
      return arr.reduceRight(goog.bind(f, opt_obj), val);
    } else {
      return arr.reduceRight(f, val);
    }
  }
  var rval = val;
  goog.array.forEachRight(arr, function(val, index) {
    rval = f.call(opt_obj, rval, val, index, arr);
  });
  return rval;
};


/**
 * Calls f for each element of an array. If any call returns true, some()
 * returns true (without checking the remaining elements). If all calls
 * return false, some() returns false.
 *
 * See {@link http://tinyurl.com/ekkc2}
 *
 * @param {Array} arr The array to check.
 * @param {Function} f The function to call for every element. This function
 *     takes 3 arguments (the element, the index and the array) and must
 *     return a Boolean.
 * @param {Object} opt_obj  The object to be used as the value of 'this'
 *     within f.
 * @return {boolean} true if any element passes the test.
 */
goog.array.some = function(arr, f, opt_obj) {
  if (arr.some) {
    return arr.some(f, opt_obj);
  }
  if (Array.some) {
    return Array.some(arr, f, opt_obj);
  }

  var l = arr.length;  // must be fixed during loop... see docs
  var arr2 = goog.isString(arr) ? arr.split('') : arr;
  for (var i = 0; i < l; i++) {
    if (i in arr2 && f.call(opt_obj, arr2[i], i, arr)) {
      return true;
    }
  }
  return false;
};


/**
 * Call f for each element of an array. If all calls return true, every()
 * returns true. If any call returns false, every() returns false and
 * does not continue to check the remaining elements.
 *
 * See {@link http://tinyurl.com/rx3mg}
 *
 * @param {Array} arr The array to check.
 * @param {Function} f The function to call for every element. This function
 *     takes 3 arguments (the element, the index and the array) and must
 *     return a Boolean.
 * @param {Object} opt_obj The object to be used as the value of 'this'
 *     within f.
 * @return {boolean} false if any element fails the test.
 */
goog.array.every = function(arr, f, opt_obj) {
  if (arr.every) {
    return arr.every(f, opt_obj);
  }
  if (Array.every) {
    return Array.every(arr, f, opt_obj);
  }

  var l = arr.length;  // must be fixed during loop... see docs
  var arr2 = goog.isString(arr) ? arr.split('') : arr;
  for (var i = 0; i < l; i++) {
    if (i in arr2 && !f.call(opt_obj, arr2[i], i, arr)) {
      return false;
    }
  }
  return true;
};


/**
 * Search an array for the first element that satisfies a given condition and
 * return that element.
 * @param {goog.array.ArrayLike} arr The array to search.
 * @param {Function} f The function to call for every element. This function
 *     takes 3 arguments (the element, the index and the array) and should
 *     return a boolean.
 * @param {Object} opt_obj An optional "this" context for the function.
 * @return {*} The first array element that passes the test, or null if no
 *     element is found.
 */
goog.array.find = function(arr, f, opt_obj) {
  var i = goog.array.findIndex(arr, f, opt_obj);
  return i < 0 ? null : goog.isString(arr) ? arr.charAt(i) : arr[i];
};


/**
 * Search an array for the first element that satisfies a given condition and
 * return its index.
 * @param {goog.array.ArrayLike} arr The array to search.
 * @param {Function} f The function to call for every element. This function
 *     takes 3 arguments (the element, the index and the array) and should
 *     return a boolean.
 * @param {Object} opt_obj An optional "this" context for the function.
 * @return {number} The index of the first array element that passes the test,
 *     or -1 if no element is found.
 */
goog.array.findIndex = function(arr, f, opt_obj) {
  var l = arr.length;  // must be fixed during loop... see docs
  var arr2 = goog.isString(arr) ? arr.split('') : arr;
  for (var i = 0; i < l; i++) {
    if (i in arr2 && f.call(opt_obj, arr2[i], i, arr)) {
      return i;
    }
  }
  return -1;
};


/**
 * Search an array (in reverse order) for the last element that satisfies a
 * given condition and return that element.
 * @param {goog.array.ArrayLike} arr The array to search.
 * @param {Function} f The function to call for every element. This function
 *     takes 3 arguments (the element, the index and the array) and should
 *     return a boolean.
 * @param {Object} opt_obj An optional "this" context for the function.
 * @return {*} The last array element that passes the test, or null if no
 *     element is found.
 */
goog.array.findRight = function(arr, f, opt_obj) {
  var i = goog.array.findIndexRight(arr, f, opt_obj);
  return i < 0 ? null : goog.isString(arr) ? arr.charAt(i) : arr[i];
};


/**
 * Search an array (in reverse order) for the last element that satisfies a
 * given condition and return its index.
 * @param {goog.array.ArrayLike} arr The array to search.
 * @param {Function} f The function to call for every element. This function
 *     takes 3 arguments (the element, the index and the array) and should
 *     return a boolean.
 * @param {Object} opt_obj An optional "this" context for the function.
 * @return {number} The index of the last array element that passes the test,
 *     or -1 if no element is found.
 */
goog.array.findIndexRight = function(arr, f, opt_obj) {
  var l = arr.length;  // must be fixed during loop... see docs
  var arr2 = goog.isString(arr) ? arr.split('') : arr;
  for (var i = l - 1; i >= 0; i--) {
    if (i in arr2 && f.call(opt_obj, arr2[i], i, arr)) {
      return i;
    }
  }
  return -1;
};


/**
 * Whether the array contains the given object.
 * @param {goog.array.ArrayLike} arr The array to test for the presence of the
 *     element.
 * @param {*} obj The object for which to test.
 * @return {boolean} true if obj is present.
 */
goog.array.contains = function(arr, obj) {
  if (arr.contains) {
    return arr.contains(obj);
  }

  return goog.array.indexOf(arr, obj) > -1;
};


/**
 * Whether the array is empty.
 * @param {goog.array.ArrayLike} arr The array to test.
 * @return {boolean} true if empty.
 */
goog.array.isEmpty = function(arr) {
  return arr.length == 0;
};


/**
 * Clears the array.
 * @param {goog.array.ArrayLike} arr Array or array like object to clear.
 */
goog.array.clear = function(arr) {
  // for non real arrays we don't have the magic length so we delete the
  // indices
  if (!goog.isArray(arr)) {
    for (var i = arr.length - 1; i >= 0; i--) {
      delete arr[i];
    }
  }
  arr.length = 0;
};


/**
 * Pushes an item into an array, if it's not already in the array.
 * @param {Array} arr Array into which to insert the item.
 * @param {*} obj Value to add.
 */
goog.array.insert = function(arr, obj) {
  if (!goog.array.contains(arr, obj)) {
    arr.push(obj);
  }
};


/**
 * Inserts an object at the given index of the array.
 * @param {goog.array.ArrayLike} arr The array to modify.
 * @param {*} obj The object to insert.
 * @param {number} opt_i The index at which to insert the object. If omitted,
 *      treated as 0. A negative index is counted from the end of the array.
 */
goog.array.insertAt = function(arr, obj, opt_i) {
  goog.array.splice(arr, opt_i, 0, obj);
};


/**
 * Inserts at the given index of the array, all elements of another array.
 * @param {goog.array.ArrayLike} arr The array to modify.
 * @param {goog.array.ArrayLike} elementsToAdd The array of elements to add.
 * @param {number} opt_i The index at which to insert the object. If omitted,
 *      treated as 0. A negative index is counted from the end of the array.
 */
goog.array.insertArrayAt = function(arr, elementsToAdd, opt_i) {
  goog.partial(goog.array.splice, arr, opt_i, 0).apply(null, elementsToAdd);
};


/**
 * Inserts an object into an array before a specified object.
 * @param {Array} arr The array to modify.
 * @param {*} obj The object to insert.
 * @param {*} opt_obj2 The object before which obj should be inserted. If obj2
 *     is omitted or not found, obj is inserted at the end of the array.
 */
goog.array.insertBefore = function(arr, obj, opt_obj2) {
  var i;
  if (arguments.length == 2 || (i = goog.array.indexOf(arr, opt_obj2)) == -1) {
    arr.push(obj);
  } else {
    goog.array.insertAt(arr, obj, i);
  }
};


/**
 * Removes the first occurrence of a particular value from an array.
 * @param {goog.array.ArrayLike} arr Array from which to remove value.
 * @param {*} obj Object to remove.
 * @return {boolean} True if an element was removed.
 */
goog.array.remove = function(arr, obj) {
  var i = goog.array.indexOf(arr, obj);
  var rv;
  if ((rv = i != -1)) {
    goog.array.removeAt(arr, i);
  }
  return rv;
};


/**
 * Removes from an array the element at index i
 * @param {goog.array.ArrayLike} arr Array or array like object from which to
 *     remove value.
 * @param {number} i The index to remove.
 * @return {boolean} True if an element was removed.
 */
goog.array.removeAt = function(arr, i) {
  // use generic form of splice
  // splice returns the removed items and if successful the length of that
  // will be 1
  return Array.prototype.splice.call(arr, i, 1).length == 1;
};


/**
 * Removes the first value that satisfies the given condition.
 * @param {goog.array.ArrayLike} arr Array from which to remove value.
 * @param {Function} f The function to call for every element. This function
 *     takes 3 arguments (the element, the index and the array) and should
 *     return a boolean.
 * @param {Object} opt_obj An optional "this" context for the function.
 * @return {boolean} True if an element was removed.
 */
goog.array.removeIf = function(arr, f, opt_obj) {
  var i = goog.array.findIndex(arr, f, opt_obj);
  if (i >= 0) {
    goog.array.removeAt(arr, i);
    return true;
  }
  return false;
};


/**
 * Does a shallow copy of an array.
 * @param {goog.array.ArrayLike} arr  Array or array-like object to clone.
 * @return {Array} Clone of the input array.
 */
goog.array.clone = function(arr) {
  if (goog.isArray(arr)) {
    // Generic concat does not seem to work so lets just use the plain old
    // instance method.
    return arr.concat();
  } else { // array like
    // Concat does not work with non arrays
    var rv = [];
    for (var i = 0, len = arr.length; i < len; i++) {
      rv[i] = arr[i];
    }
    return rv;
  }
};


/**
 * Converts an object to an array.
 * @param {goog.array.ArrayLike} object  The object to convert to an array.
 * @return {Array} The object converted into an array. If object has a
 *     length property, every property indexed with a non-negative number
 *     less than length will be included in the result. If object does not
 *     have a length property, an empty array will be returned.
 */
goog.array.toArray = function(object) {
  if (goog.isArray(object)) {
    // This fixes the JS compiler warning and forces the Object to an Array type
    return object.concat();
  }
  // Clone what we hope to be an array-like object to an array.
  // We could check isArrayLike() first, but no check we perform would be as
  // reliable as simply making the call.
  return goog.array.clone(/** @type {Array} */ (object));
};


/**
 * Extends an array with another array, element, or "array like" object.
 * This function operates 'in-place', it does not create a new Array.
 *
 * Example:
 * var a = [];
 * goog.array.extend(a, [0, 1]);
 * a; // [0, 1]
 * goog.array.extend(a, 2);
 * a; // [0, 1, 2]
 *
 * @param {Array} arr1  The array to modify.
 * @param {*} var_args The elements or arrays of elements to add to arr1.
 */
goog.array.extend = function(arr1, var_args) {
  for (var i = 1; i < arguments.length; i++) {
    var arr2 = arguments[i];
    if (goog.isArrayLike(arr2)) {
      // Make sure arr2 is a real array, and not just "array like."
      arr2 = goog.array.toArray(arr2);
      arr1.push.apply(arr1, arr2);
    } else {
      arr1.push(arr2);
    }
  }
};


/**
 * Adds or removes elements from an array. This is a generic version of Array
 * splice. This means that it might work on other objects similar to arrays,
 * such as the arguments object.
 *
 * @param {goog.array.ArrayLike} arr The array to modify.
 * @param {number|undefined} index The index at which to start changing the
 *     array. If not defined, treated as 0.
 * @param {number} howMany How many elements to remove (0 means no removal. A
 *     value below 0 is treated as zero and so is any other non number. Numbers
 *     are floored).
 * @param {*} var_args Optional, additional elements to insert into the
 *     array.
 * @return {Array} the removed elements.
 */
goog.array.splice = function(arr, index, howMany, var_args) {
  return Array.prototype.splice.apply(arr, goog.array.slice(arguments, 1));
};


/**
 * Returns a new array from a segment of an array. This is a generic version of
 * Array slice. This means that it might work on other objects similar to
 * arrays, such as the arguments object.
 *
 * @param {goog.array.ArrayLike} arr The array from which to copy a segment.
 * @param {number} start The index of the first element to copy.
 * @param {number} opt_end The index after the last element to copy.
 * @return {Array} A new array containing the specified segment of the original
 *     array.
 */
goog.array.slice = function(arr, start, opt_end) {
  // passing 1 arg to slice is not the same as passing 2 where the second is
  // null or undefined (in that case the second argument is treated as 0).
  // we could use slice on the arguments object and then use apply instead of
  // testing the length
  if (arguments.length <= 2) {
    return Array.prototype.slice.call(arr, start);
  } else {
    return Array.prototype.slice.call(arr, start, opt_end);
  }
};


/**
 * Removes all duplicates from an array (retaining only the first
 * occurrence of each array element).  This function modifies the
 * array in place and doesn't change the order of the non-duplicate items.
 *
 * For objects, duplicates are identified as having the same hash code property
 * as defined by {@see goog.getHashCode}.
 *
 * Runtime: N,
 * Worstcase space: 2N (no dupes)
 *
 * @param {goog.array.ArrayLike} arr The array from which to remove duplicates.
 * @param {Array} opt_rv An optional array in which to return the results,
 *     instead of performing the removal inplace.  If specified, the original
 *     array will remain unchanged.
 */
goog.array.removeDuplicates = function(arr, opt_rv) {
  var rv = opt_rv || arr;
  var seen = {}, cursorInsert = 0, cursorRead = 0;
  while (cursorRead < arr.length) {
    var current = arr[cursorRead++];
    var hc = goog.isObject(current) ? goog.getHashCode(current) : current;
    if (!(hc in seen)) {
      seen[hc] = true;
      rv[cursorInsert++] = current;
    }
  }
  rv.length = cursorInsert;
};


/**
 * Searches the specified array for the specified target using the binary
 * search algorithm.  If no opt_compareFn is specified, elements are compared
 * using <code>goog.array.defaultCompare</code>, which compares the elements
 * using the built in < and > operators.  This will produce the expected
 * behavior for homogeneous arrays of String(s) and Number(s). The array
 * specified <b>must</b> be sorted in ascending order (as defined by the
 * comparison function).  If the array is not sorted, results are undefined.
 * If the array contains multiple instances of the specified target value, any
 * of these instances may be found.
 *
 * Runtime: O(log n)
 *
 * @param {goog.array.ArrayLike} arr The array to be searched.
 * @param {*} target The sought value.
 * @param {Function} opt_compareFn Optional comparison function by which the
 *     array is ordered. Should take 2 arguments to compare, and return a
 *     negative integer, zero, or a positive integer depending on whether the
 *     first argument is less than, equal to, or greater than the second.
 * @return {number} Index of the target value if found, otherwise
 *     (-(insertion point) - 1). The insertion point is where the value should
 *     be inserted into arr to preserve the sorted property.  Return value >= 0
 *     iff target is found.
 */
goog.array.binarySearch = function(arr, target, opt_compareFn) {
  var left = 0;
  var right = arr.length - 1;
  var compareFn = opt_compareFn || goog.array.defaultCompare;
  while (left <= right) {
    var mid = (left + right) >> 1;
    var compareResult = compareFn(target, arr[mid]);
    if (compareResult > 0) {
      left = mid + 1;
    } else if (compareResult < 0) {
      right = mid - 1;
    } else {
      return mid;
    }
  }
  // Not found, left is the insertion point.
  return -(left + 1);
};


/**
 * Sorts the specified array into ascending order.  If no opt_compareFn is
 * specified, elements are compared using
 * <code>goog.array.defaultCompare</code>, which compares the elements using
 * the built in < and > operators.  This will produce the expected behavior
 * for homogeneous arrays of String(s) and Number(s).
 *
 * This sort is not guaranteed to be stable.
 *
 * Runtime: Same as <code>Array.prototype.sort</code>
 *
 * @param {Array} arr The array to be sorted.
 * @param {Function} opt_compareFn Optional comparison function by which the
 *     array is to be ordered. Should take 2 arguments to compare, and return a
 *     negative integer, zero, or a positive integer depending on whether the
 *     first argument is less than, equal to, or greater than the second.
 */
goog.array.sort = function(arr, opt_compareFn) {
  Array.prototype.sort.call(arr, opt_compareFn || goog.array.defaultCompare);
};


/**
 * Sorts the specified array into ascending order in a stable way.  If no
 * opt_compareFn is specified, elements are compared using
 * <code>goog.array.defaultCompare</code>, which compares the elements using
 * the built in < and > operators.  This will produce the expected behavior
 * for homogeneous arrays of String(s) and Number(s).
 *
 * Runtime: Same as <code>Array.prototype.sort</code>, plus an additional
 * O(n) overhead of copying the array twice.
 *
 * @param {Array} arr The array to be sorted.
 * @param {function(*, *): number} opt_compareFn Optional comparison function by
 *     which the array is to be ordered. Should take 2 arguments to compare, and
 *     return a negative integer, zero, or a positive integer depending on
 *     whether the first argument is less than, equal to, or greater than the
 *     second.
 */
goog.array.stableSort = function(arr, opt_compareFn) {
  for (var i = 0; i < arr.length; i++) {
    arr[i] = {index: i, value: arr[i]};
  }
  var valueCompareFn = opt_compareFn || goog.array.defaultCompare;
  function stableCompareFn(obj1, obj2) {
    return valueCompareFn(obj1.value, obj2.value) || obj1.index - obj2.index;
  };
  goog.array.sort(arr, stableCompareFn);
  for (var i = 0; i < arr.length; i++) {
    arr[i] = arr[i].value;
  }
};


/**
 * Sorts an array of objects by the specified object key and compare
 * function. If no compare function is provided, the key values are
 * compared in ascending order using <code>goog.array.defaultCompare</code>.
 * This won't work for keys that get renamed by the compiler. So use
 * {'foo': 1, 'bar': 2} rather than {foo: 1, bar: 2}.
 * @param {Array.<Object>} arr An array of objects to sort.
 * @param {string} key The object key to sort by.
 * @param {Function} opt_compareFn The function to use to compare key
 *     values.
 */
goog.array.sortObjectsByKey = function(arr, key, opt_compareFn) {
  var compare = opt_compareFn || goog.array.defaultCompare;
  goog.array.sort(arr, function(a, b) {
    return compare(a[key], b[key]);
  });
};


/**
 * Compares two arrays for equality.  If no opt_compareFn is specified, uses
 * <code>goog.array.defaultCompareEquality</code>, which compares the elements
 * using the built-in '===' operator. Two arrays are considered equal if they
 * have the same length and their corresponding elements are equal according to
 * the comparison function.
 *
 * @param {Array} arr1 The first array to compare.
 * @param {Array} arr2 The second array to compare.
 * @param {Function} opt_compareFn  Optional comparison function.
 *     Should take 2 arguments to compare, and return true if the arguments
 *     are equal.
 * @return {boolean} True if the two arrays are equal.
 */
goog.array.compare = function(arr1, arr2, opt_compareFn) {
  if (!goog.isArrayLike(arr1) || !goog.isArrayLike(arr2) ||
      arr1.length != arr2.length) {
    return false;
  }
  var l = arr1.length;
  var compareFn = opt_compareFn || goog.array.defaultCompareEquality;
  for (var i = 0; i < l; i++) {
    if (!compareFn.call(null, arr1[i], arr2[i])) {
      return false;
    }
  }
  return true;
};


/**
 * Compares its two arguments for order, using the built in < and >
 * operators.
 * @param {*} a The first object to be compared.
 * @param {*} b The second object to be compared.
 * @return {number} a negative integer, zero, or a positive integer
 *     as the first argument is less than, equal to, or greater than the
 *     second.
 */
goog.array.defaultCompare = function(a, b) {
  return a > b ? 1 : a < b ? -1 : 0;
};


/**
 * Compares its two arguments for equality, using the built in === operator.
 * @param {*} a The first object to compare.
 * @param {*} b The second object to compare.
 * @return {boolean} True if the two arguments are equal, false otherwise.
 */
goog.array.defaultCompareEquality = function(a, b) {
  return a === b;
};


/**
 * Inserts a value into a sorted array. The array is not modified if the
 * value is already present.
 * @param {Array} array The array to modify.
 * @param {*} value The object to insert.
 * @param {Function} opt_compareFn Optional comparison function by which the
 *     array is ordered. Should take 2 arguments to compare, and
 *     return a negative integer, zero, or a positive integer depending on
 *     whether the first argument is less than, equal to, or greater than the
 *     second.
 * @return {boolean} True if an element was inserted.
 */
goog.array.binaryInsert = function(array, value, opt_compareFn) {
  var index = goog.array.binarySearch(array, value, opt_compareFn);
  if (index < 0) {
    goog.array.insertAt(array, value, -(index + 1));
    return true;
  }
  return false;
};


/**
 * Removes a value from a sorted array.
 * @param {Array} array The array to modify.
 * @param {*} value The object to remove.
 * @param {Function} opt_compareFn Optional comparison function by which the
 *     array is ordered. Should take 2 arguments to compare, and
 *     return a negative integer, zero, or a positive integer depending on
 *     whether the first argument is less than, equal to, or greater than the
 *     second.
 * @return {boolean} True if an element was removed.
 */
goog.array.binaryRemove = function(array, value, opt_compareFn) {
  var index = goog.array.binarySearch(array, value, opt_compareFn);
  return (index >= 0) ? goog.array.removeAt(array, index) : false;
};


/**
 * Splits an array into disjoint buckets according to a splitting function.
 * @param {Array} array The array.
 * @param {Function} sorter Function to call for every element.  This
 *     takes 3 arguments (the element, the index and the array) and must
 *     return a valid object key (a string, number, etc), or undefined, if
 *     that object should not be placed in a bucket.
 * @return {Object} An object, with keys being all of the unique return values
 *     of sorter, and values being arrays containing the items for
 *     which the splitter returned that key.
 */
goog.array.bucket = function(array, sorter) {
  var buckets = {};

  for (var i = 0; i < array.length; i++) {
    var value = array[i];
    var key = sorter(value, i, array);
    if (goog.isDef(key)) {
      // Push the value to the right bucket, creating it if necessary.
      var bucket = buckets[key] || (buckets[key] = []);
      bucket.push(value);
    }
  }

  return buckets;
};


/**
 * Returns an array consisting of the given value repeated N times.
 *
 * @param {*} value The value to repeat.
 * @param {number} n The repeat count.
 * @return {Array.<*>} An array with the repeated value.
 */
goog.array.repeat = function(value, n) {
  var array = [];
  for (var i = 0; i < n; i++) {
    array[i] = value;
  }
  return array;
};


/**
 * Returns an array consisting of every argument with all arrays
 * expanded in-place recursively.
 *
 * @param {*} var_args The values to flatten.
 * @return {Array.<*>} An array containing the flattened values.
 */
goog.array.flatten = function(var_args) {
  var result = [];
  for (var i = 0; i < arguments.length; i++) {
    var element = arguments[i];
    if (goog.isArray(element)) {
      result.push.apply(result, goog.array.flatten.apply(null, element));
    } else {
      result.push(element);
    }
  }
  return result;
};