[catapult] - Copy Telemetry's gsutilz over to third_party.

third_party/gsutil/third_party/protorpc/experimental/javascript/closure/string/string.js

Index: third_party/gsutil/third_party/protorpc/experimental/javascript/closure/string/string.js
diff --git a/third_party/gsutil/third_party/protorpc/experimental/javascript/closure/string/string.js b/third_party/gsutil/third_party/protorpc/experimental/javascript/closure/string/string.js
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+// Copyright 2006 The Closure Library Authors. All Rights Reserved.
+//
+// Licensed 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.
+
+/**
+ * @fileoverview Utilities for string manipulation.
+ */
+
+
+/**
+ * Namespace for string utilities
+ */
+goog.provide('goog.string');
+goog.provide('goog.string.Unicode');
+
+
+/**
+ * Common Unicode string characters.
+ * @enum {string}
+ */
+goog.string.Unicode = {
+  NBSP: '\xa0'
+};
+
+
+/**
+ * Fast prefix-checker.
+ * @param {string} str The string to check.
+ * @param {string} prefix A string to look for at the start of {@code str}.
+ * @return {boolean} True if {@code str} begins with {@code prefix}.
+ */
+goog.string.startsWith = function(str, prefix) {
+  return str.lastIndexOf(prefix, 0) == 0;
+};
+
+
+/**
+ * Fast suffix-checker.
+ * @param {string} str The string to check.
+ * @param {string} suffix A string to look for at the end of {@code str}.
+ * @return {boolean} True if {@code str} ends with {@code suffix}.
+ */
+goog.string.endsWith = function(str, suffix) {
+  var l = str.length - suffix.length;
+  return l >= 0 && str.indexOf(suffix, l) == l;
+};
+
+
+/**
+ * Case-insensitive prefix-checker.
+ * @param {string} str The string to check.
+ * @param {string} prefix  A string to look for at the end of {@code str}.
+ * @return {boolean} True if {@code str} begins with {@code prefix} (ignoring
+ *     case).
+ */
+goog.string.caseInsensitiveStartsWith = function(str, prefix) {
+  return goog.string.caseInsensitiveCompare(
+      prefix, str.substr(0, prefix.length)) == 0;
+};
+
+
+/**
+ * Case-insensitive suffix-checker.
+ * @param {string} str The string to check.
+ * @param {string} suffix A string to look for at the end of {@code str}.
+ * @return {boolean} True if {@code str} ends with {@code suffix} (ignoring
+ *     case).
+ */
+goog.string.caseInsensitiveEndsWith = function(str, suffix) {
+  return goog.string.caseInsensitiveCompare(
+      suffix, str.substr(str.length - suffix.length, suffix.length)) == 0;
+};
+
+
+/**
+ * Does simple python-style string substitution.
+ * subs("foo%s hot%s", "bar", "dog") becomes "foobar hotdog".
+ * @param {string} str The string containing the pattern.
+ * @param {...*} var_args The items to substitute into the pattern.
+ * @return {string} A copy of {@code str} in which each occurrence of
+ *     {@code %s} has been replaced an argument from {@code var_args}.
+ */
+goog.string.subs = function(str, var_args) {
+  // This appears to be slow, but testing shows it compares more or less
+  // equivalent to the regex.exec method.
+  for (var i = 1; i < arguments.length; i++) {
+    // We cast to String in case an argument is a Function.  Replacing $&, for
+    // example, with $$$& stops the replace from subsituting the whole match
+    // into the resultant string.  $$$& in the first replace becomes $$& in the
+    //  second, which leaves $& in the resultant string.  Also:
+    // $$, $`, $', $n $nn
+    var replacement = String(arguments[i]).replace(/\$/g, '$$$$');
+    str = str.replace(/\%s/, replacement);
+  }
+  return str;
+};
+
+
+/**
+ * Converts multiple whitespace chars (spaces, non-breaking-spaces, new lines
+ * and tabs) to a single space, and strips leading and trailing whitespace.
+ * @param {string} str Input string.
+ * @return {string} A copy of {@code str} with collapsed whitespace.
+ */
+goog.string.collapseWhitespace = function(str) {
+  // Since IE doesn't include non-breaking-space (0xa0) in their \s character
+  // class (as required by section 7.2 of the ECMAScript spec), we explicitly
+  // include it in the regexp to enforce consistent cross-browser behavior.
+  return str.replace(/[\s\xa0]+/g, ' ').replace(/^\s+|\s+$/g, '');
+};
+
+
+/**
+ * Checks if a string is empty or contains only whitespaces.
+ * @param {string} str The string to check.
+ * @return {boolean} True if {@code str} is empty or whitespace only.
+ */
+goog.string.isEmpty = function(str) {
+  // testing length == 0 first is actually slower in all browsers (about the
+  // same in Opera).
+  // Since IE doesn't include non-breaking-space (0xa0) in their \s character
+  // class (as required by section 7.2 of the ECMAScript spec), we explicitly
+  // include it in the regexp to enforce consistent cross-browser behavior.
+  return /^[\s\xa0]*$/.test(str);
+};
+
+
+/**
+ * Checks if a string is null, empty or contains only whitespaces.
+ * @param {*} str The string to check.
+ * @return {boolean} True if{@code str} is null, empty, or whitespace only.
+ */
+goog.string.isEmptySafe = function(str) {
+  return goog.string.isEmpty(goog.string.makeSafe(str));
+};
+
+
+/**
+ * Checks if a string is all breaking whitespace.
+ * @param {string} str The string to check.
+ * @return {boolean} Whether the string is all breaking whitespace.
+ */
+goog.string.isBreakingWhitespace = function(str) {
+  return !/[^\t\n\r ]/.test(str);
+};
+
+
+/**
+ * Checks if a string contains all letters.
+ * @param {string} str string to check.
+ * @return {boolean} True if {@code str} consists entirely of letters.
+ */
+goog.string.isAlpha = function(str) {
+  return !/[^a-zA-Z]/.test(str);
+};
+
+
+/**
+ * Checks if a string contains only numbers.
+ * @param {*} str string to check. If not a string, it will be
+ *     casted to one.
+ * @return {boolean} True if {@code str} is numeric.
+ */
+goog.string.isNumeric = function(str) {
+  return !/[^0-9]/.test(str);
+};
+
+
+/**
+ * Checks if a string contains only numbers or letters.
+ * @param {string} str string to check.
+ * @return {boolean} True if {@code str} is alphanumeric.
+ */
+goog.string.isAlphaNumeric = function(str) {
+  return !/[^a-zA-Z0-9]/.test(str);
+};
+
+
+/**
+ * Checks if a character is a space character.
+ * @param {string} ch Character to check.
+ * @return {boolean} True if {code ch} is a space.
+ */
+goog.string.isSpace = function(ch) {
+  return ch == ' ';
+};
+
+
+/**
+ * Checks if a character is a valid unicode character.
+ * @param {string} ch Character to check.
+ * @return {boolean} True if {code ch} is a valid unicode character.
+ */
+goog.string.isUnicodeChar = function(ch) {
+  return ch.length == 1 && ch >= ' ' && ch <= '~' ||
+         ch >= '\u0080' && ch <= '\uFFFD';
+};
+
+
+/**
+ * Takes a string and replaces newlines with a space. Multiple lines are
+ * replaced with a single space.
+ * @param {string} str The string from which to strip newlines.
+ * @return {string} A copy of {@code str} stripped of newlines.
+ */
+goog.string.stripNewlines = function(str) {
+  return str.replace(/(\r\n|\r|\n)+/g, ' ');
+};
+
+
+/**
+ * Replaces Windows and Mac new lines with unix style: \r or \r\n with \n.
+ * @param {string} str The string to in which to canonicalize newlines.
+ * @return {string} {@code str} A copy of {@code} with canonicalized newlines.
+ */
+goog.string.canonicalizeNewlines = function(str) {
+  return str.replace(/(\r\n|\r|\n)/g, '\n');
+};
+
+
+/**
+ * Normalizes whitespace in a string, replacing all whitespace chars with
+ * a space.
+ * @param {string} str The string in which to normalize whitespace.
+ * @return {string} A copy of {@code str} with all whitespace normalized.
+ */
+goog.string.normalizeWhitespace = function(str) {
+  return str.replace(/\xa0|\s/g, ' ');
+};
+
+
+/**
+ * Normalizes spaces in a string, replacing all consecutive spaces and tabs
+ * with a single space. Replaces non-breaking space with a space.
+ * @param {string} str The string in which to normalize spaces.
+ * @return {string} A copy of {@code str} with all consecutive spaces and tabs
+ *    replaced with a single space.
+ */
+goog.string.normalizeSpaces = function(str) {
+  return str.replace(/\xa0|[ \t]+/g, ' ');
+};
+
+
+/**
+ * Removes the breaking spaces from the left and right of the string and
+ * collapses the sequences of breaking spaces in the middle into single spaces.
+ * The original and the result strings render the same way in HTML.
+ * @param {string} str A string in which to collapse spaces.
+ * @return {string} Copy of the string with normalized breaking spaces.
+ */
+goog.string.collapseBreakingSpaces = function(str) {
+  return str.replace(/[\t\r\n ]+/g, ' ').replace(
+      /^[\t\r\n ]+|[\t\r\n ]+$/g, '');
+};
+
+
+/**
+ * Trims white spaces to the left and right of a string.
+ * @param {string} str The string to trim.
+ * @return {string} A trimmed copy of {@code str}.
+ */
+goog.string.trim = function(str) {
+  // Since IE doesn't include non-breaking-space (0xa0) in their \s character
+  // class (as required by section 7.2 of the ECMAScript spec), we explicitly
+  // include it in the regexp to enforce consistent cross-browser behavior.
+  return str.replace(/^[\s\xa0]+|[\s\xa0]+$/g, '');
+};
+
+
+/**
+ * Trims whitespaces at the left end of a string.
+ * @param {string} str The string to left trim.
+ * @return {string} A trimmed copy of {@code str}.
+ */
+goog.string.trimLeft = function(str) {
+  // Since IE doesn't include non-breaking-space (0xa0) in their \s character
+  // class (as required by section 7.2 of the ECMAScript spec), we explicitly
+  // include it in the regexp to enforce consistent cross-browser behavior.
+  return str.replace(/^[\s\xa0]+/, '');
+};
+
+
+/**
+ * Trims whitespaces at the right end of a string.
+ * @param {string} str The string to right trim.
+ * @return {string} A trimmed copy of {@code str}.
+ */
+goog.string.trimRight = function(str) {
+  // Since IE doesn't include non-breaking-space (0xa0) in their \s character
+  // class (as required by section 7.2 of the ECMAScript spec), we explicitly
+  // include it in the regexp to enforce consistent cross-browser behavior.
+  return str.replace(/[\s\xa0]+$/, '');
+};
+
+
+/**
+ * A string comparator that ignores case.
+ * -1 = str1 less than str2
+ *  0 = str1 equals str2
+ *  1 = str1 greater than str2
+ *
+ * @param {string} str1 The string to compare.
+ * @param {string} str2 The string to compare {@code str1} to.
+ * @return {number} The comparator result, as described above.
+ */
+goog.string.caseInsensitiveCompare = function(str1, str2) {
+  var test1 = String(str1).toLowerCase();
+  var test2 = String(str2).toLowerCase();
+
+  if (test1 < test2) {
+    return -1;
+  } else if (test1 == test2) {
+    return 0;
+  } else {
+    return 1;
+  }
+};
+
+
+/**
+ * Regular expression used for splitting a string into substrings of fractional
+ * numbers, integers, and non-numeric characters.
+ * @type {RegExp}
+ * @private
+ */
+goog.string.numerateCompareRegExp_ = /(\.\d+)|(\d+)|(\D+)/g;
+
+
+/**
+ * String comparison function that handles numbers in a way humans might expect.
+ * Using this function, the string "File 2.jpg" sorts before "File 10.jpg". The
+ * comparison is mostly case-insensitive, though strings that are identical
+ * except for case are sorted with the upper-case strings before lower-case.
+ *
+ * This comparison function is significantly slower (about 500x) than either
+ * the default or the case-insensitive compare. It should not be used in
+ * time-critical code, but should be fast enough to sort several hundred short
+ * strings (like filenames) with a reasonable delay.
+ *
+ * @param {string} str1 The string to compare in a numerically sensitive way.
+ * @param {string} str2 The string to compare {@code str1} to.
+ * @return {number} less than 0 if str1 < str2, 0 if str1 == str2, greater than
+ *     0 if str1 > str2.
+ */
+goog.string.numerateCompare = function(str1, str2) {
+  if (str1 == str2) {
+    return 0;
+  }
+  if (!str1) {
+    return -1;
+  }
+  if (!str2) {
+    return 1;
+  }
+
+  // Using match to split the entire string ahead of time turns out to be faster
+  // for most inputs than using RegExp.exec or iterating over each character.
+  var tokens1 = str1.toLowerCase().match(goog.string.numerateCompareRegExp_);
+  var tokens2 = str2.toLowerCase().match(goog.string.numerateCompareRegExp_);
+
+  var count = Math.min(tokens1.length, tokens2.length);
+
+  for (var i = 0; i < count; i++) {
+    var a = tokens1[i];
+    var b = tokens2[i];
+
+    // Compare pairs of tokens, returning if one token sorts before the other.
+    if (a != b) {
+
+      // Only if both tokens are integers is a special comparison required.
+      // Decimal numbers are sorted as strings (e.g., '.09' < '.1').
+      var num1 = parseInt(a, 10);
+      if (!isNaN(num1)) {
+        var num2 = parseInt(b, 10);
+        if (!isNaN(num2) && num1 - num2) {
+          return num1 - num2;
+        }
+      }
+      return a < b ? -1 : 1;
+    }
+  }
+
+  // If one string is a substring of the other, the shorter string sorts first.
+  if (tokens1.length != tokens2.length) {
+    return tokens1.length - tokens2.length;
+  }
+
+  // The two strings must be equivalent except for case (perfect equality is
+  // tested at the head of the function.) Revert to default ASCII-betical string
+  // comparison to stablize the sort.
+  return str1 < str2 ? -1 : 1;
+};
+
+
+/**
+ * Regular expression used for determining if a string needs to be encoded.
+ * @type {RegExp}
+ * @private
+ */
+goog.string.encodeUriRegExp_ = /^[a-zA-Z0-9\-_.!~*'()]*$/;
+
+
+/**
+ * URL-encodes a string
+ * @param {*} str The string to url-encode.
+ * @return {string} An encoded copy of {@code str} that is safe for urls.
+ *     Note that '#', ':', and other characters used to delimit portions
+ *     of URLs *will* be encoded.
+ */
+goog.string.urlEncode = function(str) {
+  str = String(str);
+  // Checking if the search matches before calling encodeURIComponent avoids an
+  // extra allocation in IE6. This adds about 10us time in FF and a similiar
+  // over head in IE6 for lower working set apps, but for large working set
+  // apps like Gmail, it saves about 70us per call.
+  if (!goog.string.encodeUriRegExp_.test(str)) {
+    return encodeURIComponent(str);
+  }
+  return str;
+};
+
+
+/**
+ * URL-decodes the string. We need to specially handle '+'s because
+ * the javascript library doesn't convert them to spaces.
+ * @param {string} str The string to url decode.
+ * @return {string} The decoded {@code str}.
+ */
+goog.string.urlDecode = function(str) {
+  return decodeURIComponent(str.replace(/\+/g, ' '));
+};
+
+
+/**
+ * Converts \n to <br>s or <br />s.
+ * @param {string} str The string in which to convert newlines.
+ * @param {boolean=} opt_xml Whether to use XML compatible tags.
+ * @return {string} A copy of {@code str} with converted newlines.
+ */
+goog.string.newLineToBr = function(str, opt_xml) {
+  return str.replace(/(\r\n|\r|\n)/g, opt_xml ? '<br />' : '<br>');
+};
+
+
+/**
+ * Escape double quote '"' characters in addition to '&', '<', and '>' so that a
+ * string can be included in an HTML tag attribute value within double quotes.
+ *
+ * It should be noted that > doesn't need to be escaped for the HTML or XML to
+ * be valid, but it has been decided to escape it for consistency with other
+ * implementations.
+ *
+ * NOTE(user):
+ * HtmlEscape is often called during the generation of large blocks of HTML.
+ * Using statics for the regular expressions and strings is an optimization
+ * that can more than half the amount of time IE spends in this function for
+ * large apps, since strings and regexes both contribute to GC allocations.
+ *
+ * Testing for the presence of a character before escaping increases the number
+ * of function calls, but actually provides a speed increase for the average
+ * case -- since the average case often doesn't require the escaping of all 4
+ * characters and indexOf() is much cheaper than replace().
+ * The worst case does suffer slightly from the additional calls, therefore the
+ * opt_isLikelyToContainHtmlChars option has been included for situations
+ * where all 4 HTML entities are very likely to be present and need escaping.
+ *
+ * Some benchmarks (times tended to fluctuate +-0.05ms):
+ *                                     FireFox                     IE6
+ * (no chars / average (mix of cases) / all 4 chars)
+ * no checks                     0.13 / 0.22 / 0.22         0.23 / 0.53 / 0.80
+ * indexOf                       0.08 / 0.17 / 0.26         0.22 / 0.54 / 0.84
+ * indexOf + re test             0.07 / 0.17 / 0.28         0.19 / 0.50 / 0.85
+ *
+ * An additional advantage of checking if replace actually needs to be called
+ * is a reduction in the number of object allocations, so as the size of the
+ * application grows the difference between the various methods would increase.
+ *
+ * @param {string} str string to be escaped.
+ * @param {boolean=} opt_isLikelyToContainHtmlChars Don't perform a check to see
+ *     if the character needs replacing - use this option if you expect each of
+ *     the characters to appear often. Leave false if you expect few html
+ *     characters to occur in your strings, such as if you are escaping HTML.
+ * @return {string} An escaped copy of {@code str}.
+ */
+goog.string.htmlEscape = function(str, opt_isLikelyToContainHtmlChars) {
+
+  if (opt_isLikelyToContainHtmlChars) {
+    return str.replace(goog.string.amperRe_, '&amp;')
+          .replace(goog.string.ltRe_, '&lt;')
+          .replace(goog.string.gtRe_, '&gt;')
+          .replace(goog.string.quotRe_, '&quot;');
+
+  } else {
+    // quick test helps in the case when there are no chars to replace, in
+    // worst case this makes barely a difference to the time taken
+    if (!goog.string.allRe_.test(str)) return str;
+
+    // str.indexOf is faster than regex.test in this case
+    if (str.indexOf('&') != -1) {
+      str = str.replace(goog.string.amperRe_, '&amp;');
+    }
+    if (str.indexOf('<') != -1) {
+      str = str.replace(goog.string.ltRe_, '&lt;');
+    }
+    if (str.indexOf('>') != -1) {
+      str = str.replace(goog.string.gtRe_, '&gt;');
+    }
+    if (str.indexOf('"') != -1) {
+      str = str.replace(goog.string.quotRe_, '&quot;');
+    }
+    return str;
+  }
+};
+
+
+/**
+ * Regular expression that matches an ampersand, for use in escaping.
+ * @type {RegExp}
+ * @private
+ */
+goog.string.amperRe_ = /&/g;
+
+
+/**
+ * Regular expression that matches a less than sign, for use in escaping.
+ * @type {RegExp}
+ * @private
+ */
+goog.string.ltRe_ = /</g;
+
+
+/**
+ * Regular expression that matches a greater than sign, for use in escaping.
+ * @type {RegExp}
+ * @private
+ */
+goog.string.gtRe_ = />/g;
+
+
+/**
+ * Regular expression that matches a double quote, for use in escaping.
+ * @type {RegExp}
+ * @private
+ */
+goog.string.quotRe_ = /\"/g;
+
+
+/**
+ * Regular expression that matches any character that needs to be escaped.
+ * @type {RegExp}
+ * @private
+ */
+goog.string.allRe_ = /[&<>\"]/;
+
+
+/**
+ * Unescapes an HTML string.
+ *
+ * @param {string} str The string to unescape.
+ * @return {string} An unescaped copy of {@code str}.
+ */
+goog.string.unescapeEntities = function(str) {
+  if (goog.string.contains(str, '&')) {
+    // We are careful not to use a DOM if we do not have one. We use the []
+    // notation so that the JSCompiler will not complain about these objects and
+    // fields in the case where we have no DOM.
+    if ('document' in goog.global) {
+      return goog.string.unescapeEntitiesUsingDom_(str);
+    } else {
+      // Fall back on pure XML entities
+      return goog.string.unescapePureXmlEntities_(str);
+    }
+  }
+  return str;
+};
+
+
+/**
+ * Unescapes an HTML string using a DOM to resolve non-XML, non-numeric
+ * entities. This function is XSS-safe and whitespace-preserving.
+ * @private
+ * @param {string} str The string to unescape.
+ * @return {string} The unescaped {@code str} string.
+ */
+goog.string.unescapeEntitiesUsingDom_ = function(str) {
+  var seen = {'&amp;': '&', '&lt;': '<', '&gt;': '>', '&quot;': '"'};
+  var div = document.createElement('div');
+  // Match as many valid entity characters as possible. If the actual entity
+  // happens to be shorter, it will still work as innerHTML will return the
+  // trailing characters unchanged. Since the entity characters do not include
+  // open angle bracket, there is no chance of XSS from the innerHTML use.
+  // Since no whitespace is passed to innerHTML, whitespace is preserved.
+  return str.replace(goog.string.HTML_ENTITY_PATTERN_, function(s, entity) {
+    // Check for cached entity.
+    var value = seen[s];
+    if (value) {
+      return value;
+    }
+    // Check for numeric entity.
+    if (entity.charAt(0) == '#') {
+      // Prefix with 0 so that hex entities (e.g. &#x10) parse as hex numbers.
+      var n = Number('0' + entity.substr(1));
+      if (!isNaN(n)) {
+        value = String.fromCharCode(n);
+      }
+    }
+    // Fall back to innerHTML otherwise.
+    if (!value) {
+      // Append a non-entity character to avoid a bug in Webkit that parses
+      // an invalid entity at the end of innerHTML text as the empty string.
+      div.innerHTML = s + ' ';
+      // Then remove the trailing character from the result.
+      value = div.firstChild.nodeValue.slice(0, -1);
+    }
+    // Cache and return.
+    return seen[s] = value;
+  });
+};
+
+
+/**
+ * Unescapes XML entities.
+ * @private
+ * @param {string} str The string to unescape.
+ * @return {string} An unescaped copy of {@code str}.
+ */
+goog.string.unescapePureXmlEntities_ = function(str) {
+  return str.replace(/&([^;]+);/g, function(s, entity) {
+    switch (entity) {
+      case 'amp':
+        return '&';
+      case 'lt':
+        return '<';
+      case 'gt':
+        return '>';
+      case 'quot':
+        return '"';
+      default:
+        if (entity.charAt(0) == '#') {
+          // Prefix with 0 so that hex entities (e.g. &#x10) parse as hex.
+          var n = Number('0' + entity.substr(1));
+          if (!isNaN(n)) {
+            return String.fromCharCode(n);
+          }
+        }
+        // For invalid entities we just return the entity
+        return s;
+    }
+  });
+};
+
+
+/**
+ * Regular expression that matches an HTML entity.
+ * See also HTML5: Tokenization / Tokenizing character references.
+ * @private
+ * @type {!RegExp}
+ */
+goog.string.HTML_ENTITY_PATTERN_ = /&([^;\s<&]+);?/g;
+
+
+/**
+ * Do escaping of whitespace to preserve spatial formatting. We use character
+ * entity #160 to make it safer for xml.
+ * @param {string} str The string in which to escape whitespace.
+ * @param {boolean=} opt_xml Whether to use XML compatible tags.
+ * @return {string} An escaped copy of {@code str}.
+ */
+goog.string.whitespaceEscape = function(str, opt_xml) {
+  return goog.string.newLineToBr(str.replace(/  /g, ' &#160;'), opt_xml);
+};
+
+
+/**
+ * Strip quote characters around a string.  The second argument is a string of
+ * characters to treat as quotes.  This can be a single character or a string of
+ * multiple character and in that case each of those are treated as possible
+ * quote characters. For example:
+ *
+ * <pre>
+ * goog.string.stripQuotes('"abc"', '"`') --> 'abc'
+ * goog.string.stripQuotes('`abc`', '"`') --> 'abc'
+ * </pre>
+ *
+ * @param {string} str The string to strip.
+ * @param {string} quoteChars The quote characters to strip.
+ * @return {string} A copy of {@code str} without the quotes.
+ */
+goog.string.stripQuotes = function(str, quoteChars) {
+  var length = quoteChars.length;
+  for (var i = 0; i < length; i++) {
+    var quoteChar = length == 1 ? quoteChars : quoteChars.charAt(i);
+    if (str.charAt(0) == quoteChar && str.charAt(str.length - 1) == quoteChar) {
+      return str.substring(1, str.length - 1);
+    }
+  }
+  return str;
+};
+
+
+/**
+ * Truncates a string to a certain length and adds '...' if necessary.  The
+ * length also accounts for the ellipsis, so a maximum length of 10 and a string
+ * 'Hello World!' produces 'Hello W...'.
+ * @param {string} str The string to truncate.
+ * @param {number} chars Max number of characters.
+ * @param {boolean=} opt_protectEscapedCharacters Whether to protect escaped
+ *     characters from being cut off in the middle.
+ * @return {string} The truncated {@code str} string.
+ */
+goog.string.truncate = function(str, chars, opt_protectEscapedCharacters) {
+  if (opt_protectEscapedCharacters) {
+    str = goog.string.unescapeEntities(str);
+  }
+
+  if (str.length > chars) {
+    str = str.substring(0, chars - 3) + '...';
+  }
+
+  if (opt_protectEscapedCharacters) {
+    str = goog.string.htmlEscape(str);
+  }
+
+  return str;
+};
+
+
+/**
+ * Truncate a string in the middle, adding "..." if necessary,
+ * and favoring the beginning of the string.
+ * @param {string} str The string to truncate the middle of.
+ * @param {number} chars Max number of characters.
+ * @param {boolean=} opt_protectEscapedCharacters Whether to protect escaped
+ *     characters from being cutoff in the middle.
+ * @param {number=} opt_trailingChars Optional number of trailing characters to
+ *     leave at the end of the string, instead of truncating as close to the
+ *     middle as possible.
+ * @return {string} A truncated copy of {@code str}.
+ */
+goog.string.truncateMiddle = function(str, chars,
+    opt_protectEscapedCharacters, opt_trailingChars) {
+  if (opt_protectEscapedCharacters) {
+    str = goog.string.unescapeEntities(str);
+  }
+
+  if (opt_trailingChars && str.length > chars) {
+    if (opt_trailingChars > chars) {
+      opt_trailingChars = chars;
+    }
+    var endPoint = str.length - opt_trailingChars;
+    var startPoint = chars - opt_trailingChars;
+    str = str.substring(0, startPoint) + '...' + str.substring(endPoint);
+  } else if (str.length > chars) {
+    // Favor the beginning of the string:
+    var half = Math.floor(chars / 2);
+    var endPos = str.length - half;
+    half += chars % 2;
+    str = str.substring(0, half) + '...' + str.substring(endPos);
+  }
+
+  if (opt_protectEscapedCharacters) {
+    str = goog.string.htmlEscape(str);
+  }
+
+  return str;
+};
+
+
+/**
+ * Special chars that need to be escaped for goog.string.quote.
+ * @private
+ * @type {Object}
+ */
+goog.string.specialEscapeChars_ = {
+  '\0': '\\0',
+  '\b': '\\b',
+  '\f': '\\f',
+  '\n': '\\n',
+  '\r': '\\r',
+  '\t': '\\t',
+  '\x0B': '\\x0B', // '\v' is not supported in JScript
+  '"': '\\"',
+  '\\': '\\\\'
+};
+
+
+/**
+ * Character mappings used internally for goog.string.escapeChar.
+ * @private
+ * @type {Object}
+ */
+goog.string.jsEscapeCache_ = {
+  '\'': '\\\''
+};
+
+
+/**
+ * Encloses a string in double quotes and escapes characters so that the
+ * string is a valid JS string.
+ * @param {string} s The string to quote.
+ * @return {string} A copy of {@code s} surrounded by double quotes.
+ */
+goog.string.quote = function(s) {
+  s = String(s);
+  if (s.quote) {
+    return s.quote();
+  } else {
+    var sb = ['"'];
+    for (var i = 0; i < s.length; i++) {
+      var ch = s.charAt(i);
+      var cc = ch.charCodeAt(0);
+      sb[i + 1] = goog.string.specialEscapeChars_[ch] ||
+          ((cc > 31 && cc < 127) ? ch : goog.string.escapeChar(ch));
+    }
+    sb.push('"');
+    return sb.join('');
+  }
+};
+
+
+/**
+ * Takes a string and returns the escaped string for that character.
+ * @param {string} str The string to escape.
+ * @return {string} An escaped string representing {@code str}.
+ */
+goog.string.escapeString = function(str) {
+  var sb = [];
+  for (var i = 0; i < str.length; i++) {
+    sb[i] = goog.string.escapeChar(str.charAt(i));
+  }
+  return sb.join('');
+};
+
+
+/**
+ * Takes a character and returns the escaped string for that character. For
+ * example escapeChar(String.fromCharCode(15)) -> "\\x0E".
+ * @param {string} c The character to escape.
+ * @return {string} An escaped string representing {@code c}.
+ */
+goog.string.escapeChar = function(c) {
+  if (c in goog.string.jsEscapeCache_) {
+    return goog.string.jsEscapeCache_[c];
+  }
+
+  if (c in goog.string.specialEscapeChars_) {
+    return goog.string.jsEscapeCache_[c] = goog.string.specialEscapeChars_[c];
+  }
+
+  var rv = c;
+  var cc = c.charCodeAt(0);
+  if (cc > 31 && cc < 127) {
+    rv = c;
+  } else {
+    // tab is 9 but handled above
+    if (cc < 256) {
+      rv = '\\x';
+      if (cc < 16 || cc > 256) {
+        rv += '0';
+      }
+    } else {
+      rv = '\\u';
+      if (cc < 4096) { // \u1000
+        rv += '0';
+      }
+    }
+    rv += cc.toString(16).toUpperCase();
+  }
+
+  return goog.string.jsEscapeCache_[c] = rv;
+};
+
+
+/**
+ * Takes a string and creates a map (Object) in which the keys are the
+ * characters in the string. The value for the key is set to true. You can
+ * then use goog.object.map or goog.array.map to change the values.
+ * @param {string} s The string to build the map from.
+ * @return {Object} The map of characters used.
+ */
+// TODO(arv): It seems like we should have a generic goog.array.toMap. But do
+//            we want a dependency on goog.array in goog.string?
+goog.string.toMap = function(s) {
+  var rv = {};
+  for (var i = 0; i < s.length; i++) {
+    rv[s.charAt(i)] = true;
+  }
+  return rv;
+};
+
+
+/**
+ * Checks whether a string contains a given character.
+ * @param {string} s The string to test.
+ * @param {string} ss The substring to test for.
+ * @return {boolean} True if {@code s} contains {@code ss}.
+ */
+goog.string.contains = function(s, ss) {
+  return s.indexOf(ss) != -1;
+};
+
+
+/**
+ * Removes a substring of a specified length at a specific
+ * index in a string.
+ * @param {string} s The base string from which to remove.
+ * @param {number} index The index at which to remove the substring.
+ * @param {number} stringLength The length of the substring to remove.
+ * @return {string} A copy of {@code s} with the substring removed or the full
+ *     string if nothing is removed or the input is invalid.
+ */
+goog.string.removeAt = function(s, index, stringLength) {
+  var resultStr = s;
+  // If the index is greater or equal to 0 then remove substring
+  if (index >= 0 && index < s.length && stringLength > 0) {
+    resultStr = s.substr(0, index) +
+        s.substr(index + stringLength, s.length - index - stringLength);
+  }
+  return resultStr;
+};
+
+
+/**
+ *  Removes the first occurrence of a substring from a string.
+ *  @param {string} s The base string from which to remove.
+ *  @param {string} ss The string to remove.
+ *  @return {string} A copy of {@code s} with {@code ss} removed or the full
+ *      string if nothing is removed.
+ */
+goog.string.remove = function(s, ss) {
+  var re = new RegExp(goog.string.regExpEscape(ss), '');
+  return s.replace(re, '');
+};
+
+
+/**
+ *  Removes all occurrences of a substring from a string.
+ *  @param {string} s The base string from which to remove.
+ *  @param {string} ss The string to remove.
+ *  @return {string} A copy of {@code s} with {@code ss} removed or the full
+ *      string if nothing is removed.
+ */
+goog.string.removeAll = function(s, ss) {
+  var re = new RegExp(goog.string.regExpEscape(ss), 'g');
+  return s.replace(re, '');
+};
+
+
+/**
+ * Escapes characters in the string that are not safe to use in a RegExp.
+ * @param {*} s The string to escape. If not a string, it will be casted
+ *     to one.
+ * @return {string} A RegExp safe, escaped copy of {@code s}.
+ */
+goog.string.regExpEscape = function(s) {
+  return String(s).replace(/([-()\[\]{}+?*.$\^|,:#<!\\])/g, '\\$1').
+      replace(/\x08/g, '\\x08');
+};
+
+
+/**
+ * Repeats a string n times.
+ * @param {string} string The string to repeat.
+ * @param {number} length The number of times to repeat.
+ * @return {string} A string containing {@code length} repetitions of
+ *     {@code string}.
+ */
+goog.string.repeat = function(string, length) {
+  return new Array(length + 1).join(string);
+};
+
+
+/**
+ * Pads number to given length and optionally rounds it to a given precision.
+ * For example:
+ * <pre>padNumber(1.25, 2, 3) -> '01.250'
+ * padNumber(1.25, 2) -> '01.25'
+ * padNumber(1.25, 2, 1) -> '01.3'
+ * padNumber(1.25, 0) -> '1.25'</pre>
+ *
+ * @param {number} num The number to pad.
+ * @param {number} length The desired length.
+ * @param {number=} opt_precision The desired precision.
+ * @return {string} {@code num} as a string with the given options.
+ */
+goog.string.padNumber = function(num, length, opt_precision) {
+  var s = goog.isDef(opt_precision) ? num.toFixed(opt_precision) : String(num);
+  var index = s.indexOf('.');
+  if (index == -1) {
+    index = s.length;
+  }
+  return goog.string.repeat('0', Math.max(0, length - index)) + s;
+};
+
+
+/**
+ * Returns a string representation of the given object, with
+ * null and undefined being returned as the empty string.
+ *
+ * @param {*} obj The object to convert.
+ * @return {string} A string representation of the {@code obj}.
+ */
+goog.string.makeSafe = function(obj) {
+  return obj == null ? '' : String(obj);
+};
+
+
+/**
+ * Concatenates string expressions. This is useful
+ * since some browsers are very inefficient when it comes to using plus to
+ * concat strings. Be careful when using null and undefined here since
+ * these will not be included in the result. If you need to represent these
+ * be sure to cast the argument to a String first.
+ * For example:
+ * <pre>buildString('a', 'b', 'c', 'd') -> 'abcd'
+ * buildString(null, undefined) -> ''
+ * </pre>
+ * @param {...*} var_args A list of strings to concatenate. If not a string,
+ *     it will be casted to one.
+ * @return {string} The concatenation of {@code var_args}.
+ */
+goog.string.buildString = function(var_args) {
+  return Array.prototype.join.call(arguments, '');
+};
+
+
+/**
+ * Returns a string with at least 64-bits of randomness.
+ *
+ * Doesn't trust Javascript's random function entirely. Uses a combination of
+ * random and current timestamp, and then encodes the string in base-36 to
+ * make it shorter.
+ *
+ * @return {string} A random string, e.g. sn1s7vb4gcic.
+ */
+goog.string.getRandomString = function() {
+  var x = 2147483648;
+  return Math.floor(Math.random() * x).toString(36) +
+         Math.abs(Math.floor(Math.random() * x) ^ goog.now()).toString(36);
+};
+
+
+/**
+ * Compares two version numbers.
+ *
+ * @param {string|number} version1 Version of first item.
+ * @param {string|number} version2 Version of second item.
+ *
+ * @return {number}  1 if {@code version1} is higher.
+ *                   0 if arguments are equal.
+ *                  -1 if {@code version2} is higher.
+ */
+goog.string.compareVersions = function(version1, version2) {
+  var order = 0;
+  // Trim leading and trailing whitespace and split the versions into
+  // subversions.
+  var v1Subs = goog.string.trim(String(version1)).split('.');
+  var v2Subs = goog.string.trim(String(version2)).split('.');
+  var subCount = Math.max(v1Subs.length, v2Subs.length);
+
+  // Iterate over the subversions, as long as they appear to be equivalent.
+  for (var subIdx = 0; order == 0 && subIdx < subCount; subIdx++) {
+    var v1Sub = v1Subs[subIdx] || '';
+    var v2Sub = v2Subs[subIdx] || '';
+
+    // Split the subversions into pairs of numbers and qualifiers (like 'b').
+    // Two different RegExp objects are needed because they are both using
+    // the 'g' flag.
+    var v1CompParser = new RegExp('(\\d*)(\\D*)', 'g');
+    var v2CompParser = new RegExp('(\\d*)(\\D*)', 'g');
+    do {
+      var v1Comp = v1CompParser.exec(v1Sub) || ['', '', ''];
+      var v2Comp = v2CompParser.exec(v2Sub) || ['', '', ''];
+      // Break if there are no more matches.
+      if (v1Comp[0].length == 0 && v2Comp[0].length == 0) {
+        break;
+      }
+
+      // Parse the numeric part of the subversion. A missing number is
+      // equivalent to 0.
+      var v1CompNum = v1Comp[1].length == 0 ? 0 : parseInt(v1Comp[1], 10);
+      var v2CompNum = v2Comp[1].length == 0 ? 0 : parseInt(v2Comp[1], 10);
+
+      // Compare the subversion components. The number has the highest
+      // precedence. Next, if the numbers are equal, a subversion without any
+      // qualifier is always higher than a subversion with any qualifier. Next,
+      // the qualifiers are compared as strings.
+      order = goog.string.compareElements_(v1CompNum, v2CompNum) ||
+          goog.string.compareElements_(v1Comp[2].length == 0,
+              v2Comp[2].length == 0) ||
+          goog.string.compareElements_(v1Comp[2], v2Comp[2]);
+      // Stop as soon as an inequality is discovered.
+    } while (order == 0);
+  }
+
+  return order;
+};
+
+
+/**
+ * Compares elements of a version number.
+ *
+ * @param {string|number|boolean} left An element from a version number.
+ * @param {string|number|boolean} right An element from a version number.
+ *
+ * @return {number}  1 if {@code left} is higher.
+ *                   0 if arguments are equal.
+ *                  -1 if {@code right} is higher.
+ * @private
+ */
+goog.string.compareElements_ = function(left, right) {
+  if (left < right) {
+    return -1;
+  } else if (left > right) {
+    return 1;
+  }
+  return 0;
+};
+
+
+/**
+ * Maximum value of #goog.string.hashCode, exclusive. 2^32.
+ * @type {number}
+ * @private
+ */
+goog.string.HASHCODE_MAX_ = 0x100000000;
+
+
+/**
+ * String hash function similar to java.lang.String.hashCode().
+ * The hash code for a string is computed as
+ * s[0] * 31 ^ (n - 1) + s[1] * 31 ^ (n - 2) + ... + s[n - 1],
+ * where s[i] is the ith character of the string and n is the length of
+ * the string. We mod the result to make it between 0 (inclusive) and 2^32
+ * (exclusive).
+ * @param {string} str A string.
+ * @return {number} Hash value for {@code str}, between 0 (inclusive) and 2^32
+ *  (exclusive). The empty string returns 0.
+ */
+goog.string.hashCode = function(str) {
+  var result = 0;
+  for (var i = 0; i < str.length; ++i) {
+    result = 31 * result + str.charCodeAt(i);
+    // Normalize to 4 byte range, 0 ... 2^32.
+    result %= goog.string.HASHCODE_MAX_;
+  }
+  return result;
+};
+
+
+/**
+ * The most recent unique ID. |0 is equivalent to Math.floor in this case.
+ * @type {number}
+ * @private
+ */
+goog.string.uniqueStringCounter_ = Math.random() * 0x80000000 | 0;
+
+
+/**
+ * Generates and returns a string which is unique in the current document.
+ * This is useful, for example, to create unique IDs for DOM elements.
+ * @return {string} A unique id.
+ */
+goog.string.createUniqueString = function() {
+  return 'goog_' + goog.string.uniqueStringCounter_++;
+};
+
+
+/**
+ * Converts the supplied string to a number, which may be Ininity or NaN.
+ * This function strips whitespace: (toNumber(' 123') === 123)
+ * This function accepts scientific notation: (toNumber('1e1') === 10)
+ *
+ * This is better than Javascript's built-in conversions because, sadly:
+ *     (Number(' ') === 0) and (parseFloat('123a') === 123)
+ *
+ * @param {string} str The string to convert.
+ * @return {number} The number the supplied string represents, or NaN.
+ */
+goog.string.toNumber = function(str) {
+  var num = Number(str);
+  if (num == 0 && goog.string.isEmpty(str)) {
+    return NaN;
+  }
+  return num;
+};
+
+
+/**
+ * A memoized cache for goog.string.toCamelCase.
+ * @type {Object.<string>}
+ * @private
+ */
+goog.string.toCamelCaseCache_ = {};
+
+
+/**
+ * Converts a string from selector-case to camelCase (e.g. from
+ * "multi-part-string" to "multiPartString"), useful for converting
+ * CSS selectors and HTML dataset keys to their equivalent JS properties.
+ * @param {string} str The string in selector-case form.
+ * @return {string} The string in camelCase form.
+ */
+goog.string.toCamelCase = function(str) {
+  return goog.string.toCamelCaseCache_[str] ||
+      (goog.string.toCamelCaseCache_[str] =
+          String(str).replace(/\-([a-z])/g, function(all, match) {
+            return match.toUpperCase();
+          }));
+};
+
+
+/**
+ * A memoized cache for goog.string.toSelectorCase.
+ * @type {Object.<string>}
+ * @private
+ */
+goog.string.toSelectorCaseCache_ = {};
+
+
+/**
+ * Converts a string from camelCase to selector-case (e.g. from
+ * "multiPartString" to "multi-part-string"), useful for converting JS
+ * style and dataset properties to equivalent CSS selectors and HTML keys.
+ * @param {string} str The string in camelCase form.
+ * @return {string} The string in selector-case form.
+ */
+goog.string.toSelectorCase = function(str) {
+  return goog.string.toSelectorCaseCache_[str] ||
+      (goog.string.toSelectorCaseCache_[str] =
+          String(str).replace(/([A-Z])/g, '-$1').toLowerCase());
+};