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+/**
+ * @class jQuery.plugin.byteLimit
+ */
+( function ( $ ) {
+
+	/**
+	 * Utility function to trim down a string, based on byteLimit
+	 * and given a safe start position. It supports insertion anywhere
+	 * in the string, so "foo" to "fobaro" if limit is 4 will result in
+	 * "fobo", not "foba". Basically emulating the native maxlength by
+	 * reconstructing where the insertion occurred.
+	 *
+	 * @private
+	 * @param {string} safeVal Known value that was previously returned by this
+	 * function, if none, pass empty string.
+	 * @param {string} newVal New value that may have to be trimmed down.
+	 * @param {number} byteLimit Number of bytes the value may be in size.
+	 * @param {Function} [fn] See jQuery.byteLimit.
+	 * @return {Object}
+	 * @return {string} return.newVal
+	 * @return {boolean} return.trimmed
+	 */
+	function trimValForByteLength( safeVal, newVal, byteLimit, fn ) {
+		var startMatches, endMatches, matchesLen, inpParts,
+			oldVal = safeVal;
+
+		// Run the hook if one was provided, but only on the length
+		// assessment. The value itself is not to be affected by the hook.
+		if ( $.byteLength( fn ? fn( newVal ) : newVal ) <= byteLimit ) {
+			// Limit was not reached, just remember the new value
+			// and let the user continue.
+			return {
+				newVal: newVal,
+				trimmed: false
+			};
+		}
+
+		// Current input is longer than the active limit.
+		// Figure out what was added and limit the addition.
+		startMatches = 0;
+		endMatches = 0;
+
+		// It is important that we keep the search within the range of
+		// the shortest string's length.
+		// Imagine a user adds text that matches the end of the old value
+		// (e.g. "foo" -> "foofoo"). startMatches would be 3, but without
+		// limiting both searches to the shortest length, endMatches would
+		// also be 3.
+		matchesLen = Math.min( newVal.length, oldVal.length );
+
+		// Count same characters from the left, first.
+		// (if "foo" -> "foofoo", assume addition was at the end).
+		while (
+			startMatches < matchesLen &&
+			oldVal.charAt( startMatches ) === newVal.charAt( startMatches )
+		) {
+			startMatches += 1;
+		}
+
+		while (
+			endMatches < ( matchesLen - startMatches ) &&
+			oldVal.charAt( oldVal.length - 1 - endMatches ) === newVal.charAt( newVal.length - 1 - endMatches )
+		) {
+			endMatches += 1;
+		}
+
+		inpParts = [
+			// Same start
+			newVal.slice( 0, startMatches ),
+			// Inserted content
+			newVal.slice( startMatches, newVal.length - endMatches ),
+			// Same end
+			newVal.slice( newVal.length - endMatches )
+		];
+
+		// Chop off characters from the end of the "inserted content" string
+		// until the limit is statisfied.
+		if ( fn ) {
+			// stop, when there is nothing to slice - bug 41450
+			while ( $.byteLength( fn( inpParts.join( '' ) ) ) > byteLimit && inpParts[1].length > 0 ) {
+				inpParts[1] = inpParts[1].slice( 0, -1 );
+			}
+		} else {
+			while ( $.byteLength( inpParts.join( '' ) ) > byteLimit ) {
+				inpParts[1] = inpParts[1].slice( 0, -1 );
+			}
+		}
+
+		newVal = inpParts.join( '' );
+
+		return {
+			newVal: newVal,
+			trimmed: true
+		};
+	}
+
+	var eventKeys = [
+		'keyup.byteLimit',
+		'keydown.byteLimit',
+		'change.byteLimit',
+		'mouseup.byteLimit',
+		'cut.byteLimit',
+		'paste.byteLimit',
+		'focus.byteLimit',
+		'blur.byteLimit'
+	].join( ' ' );
+
+	/**
+	 * Enforces a byte limit on an input field, so that UTF-8 entries are counted as well,
+	 * when, for example, a database field has a byte limit rather than a character limit.
+	 * Plugin rationale: Browser has native maxlength for number of characters, this plugin
+	 * exists to limit number of bytes instead.
+	 *
+	 * Can be called with a custom limit (to use that limit instead of the maxlength attribute
+	 * value), a filter function (in case the limit should apply to something other than the
+	 * exact input value), or both. Order of parameters is important!
+	 *
+	 * @param {number} [limit] Limit to enforce, fallsback to maxLength-attribute,
+	 *  called with fetched value as argument.
+	 * @param {Function} [fn] Function to call on the string before assessing the length.
+	 * @return {jQuery}
+	 * @chainable
+	 */
+	$.fn.byteLimit = function ( limit, fn ) {
+		// If the first argument is the function,
+		// set fn to the first argument's value and ignore the second argument.
+		if ( $.isFunction( limit ) ) {
+			fn = limit;
+			limit = undefined;
+		// Either way, verify it is a function so we don't have to call
+		// isFunction again after this.
+		} else if ( !fn || !$.isFunction( fn ) ) {
+			fn = undefined;
+		}
+
+		// The following is specific to each element in the collection.
+		return this.each( function ( i, el ) {
+			var $el, elLimit, prevSafeVal;
+
+			$el = $( el );
+
+			// If no limit was passed to byteLimit(), use the maxlength value.
+			// Can't re-use 'limit' variable because it's in the higher scope
+			// that would affect the next each() iteration as well.
+			// Note that we use attribute to read the value instead of property,
+			// because in Chrome the maxLength property by default returns the
+			// highest supported value (no indication that it is being enforced
+			// by choice). We don't want to bind all of this for some ridiculously
+			// high default number, unless it was explicitly set in the HTML.
+			// Also cast to a (primitive) number (most commonly because the maxlength
+			// attribute contains a string, but theoretically the limit parameter
+			// could be something else as well).
+			elLimit = Number( limit === undefined ? $el.attr( 'maxlength' ) : limit );
+
+			// If there is no (valid) limit passed or found in the property,
+			// skip this. The < 0 check is required for Firefox, which returns
+			// -1  (instead of undefined) for maxLength if it is not set.
+			if ( !elLimit || elLimit < 0 ) {
+				return;
+			}
+
+			if ( fn ) {
+				// Save function for reference
+				$el.data( 'byteLimit.callback', fn );
+			}
+
+			// Remove old event handlers (if there are any)
+			$el.off( '.byteLimit' );
+
+			if ( fn ) {
+				// Disable the native maxLength (if there is any), because it interferes
+				// with the (differently calculated) byte limit.
+				// Aside from being differently calculated (average chars with byteLimit
+				// is lower), we also support a callback which can make it to allow longer
+				// values (e.g. count "Foo" from "User:Foo").
+				// maxLength is a strange property. Removing or setting the property to
+				// undefined directly doesn't work. Instead, it can only be unset internally
+				// by the browser when removing the associated attribute (Firefox/Chrome).
+				// http://code.google.com/p/chromium/issues/detail?id=136004
+				$el.removeAttr( 'maxlength' );
+
+			} else {
+				// If we don't have a callback the bytelimit can only be lower than the charlimit
+				// (that is, there are no characters less than 1 byte in size). So lets (re-)enforce
+				// the native limit for efficiency when possible (it will make the while-loop below
+				// faster by there being less left to interate over).
+				$el.attr( 'maxlength', elLimit );
+			}
+
+			// Safe base value, used to determine the path between the previous state
+			// and the state that triggered the event handler below - and enforce the
+			// limit approppiately (e.g. don't chop from the end if text was inserted
+			// at the beginning of the string).
+			prevSafeVal = '';
+
+			// We need to listen to after the change has already happened because we've
+			// learned that trying to guess the new value and canceling the event
+			// accordingly doesn't work because the new value is not always as simple as:
+			// oldValue + String.fromCharCode( e.which ); because of cut, paste, select-drag
+			// replacements, and custom input methods and what not.
+			// Even though we only trim input after it was changed (never prevent it), we do
+			// listen on events that input text, because there are cases where the text has
+			// changed while text is being entered and keyup/change will not be fired yet
+			// (such as holding down a single key, fires keydown, and after each keydown,
+			// we can trim the previous one).
+			// See http://www.w3.org/TR/DOM-Level-3-Events/#events-keyboard-event-order for
+			// the order and characteristics of the key events.
+			$el.on( eventKeys, function () {
+				var res = trimValForByteLength(
+					prevSafeVal,
+					this.value,
+					elLimit,
+					fn
+				);
+
+				// Only set value property if it was trimmed, because whenever the
+				// value property is set, the browser needs to re-initiate the text context,
+				// which moves the cursor at the end the input, moving it away from wherever it was.
+				// This is a side-effect of limiting after the fact.
+				if ( res.trimmed === true ) {
+					this.value = res.newVal;
+				}
+				// Always adjust prevSafeVal to reflect the input value. Not doing this could cause
+				// trimValForByteLength to compare the new value to an empty string instead of the
+				// old value, resulting in trimming always from the end (bug 40850).
+				prevSafeVal = res.newVal;
+			} );
+		} );
+	};
+
+	/**
+	 * @class jQuery
+	 * @mixins jQuery.plugin.byteLimit
+	 */
+}( jQuery ) );