Extract an http_parser package from shelf.

pkg/shelf/lib/src/util.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library shelf.util;
 
 import 'dart:async';
 
 import 'package:stack_trace/stack_trace.dart';
-import 'package:string_scanner/string_scanner.dart';
 
 /// Like [Future.sync], but wraps the Future in [Chain.track] as well.
 Future syncFuture(callback()) => Chain.track(new Future.sync(callback));
-
-const _WEEKDAYS = const ["Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun"];
-const _MONTHS = const ["Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug",
-    "Sep", "Oct", "Nov", "Dec"];
-
-final _shortWeekdayRegExp = new RegExp(r"Mon|Tue|Wed|Thu|Fri|Sat|Sun");
-final _longWeekdayRegExp =
-    new RegExp(r"Monday|Tuesday|Wednesday|Thursday|Friday|Saturday|Sunday");
-final _monthRegExp =
-    new RegExp(r"Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec");
-final _digitRegExp = new RegExp(r"\d+");
-
-// TODO(nweiz): Move this into an http_parser package.
-/// Return a HTTP-formatted string representation of [date].
-///
-/// This follows [RFC 822](http://tools.ietf.org/html/rfc822) as updated by [RFC
-/// 1123](http://tools.ietf.org/html/rfc1123).
-String formatHttpDate(DateTime date) {
-  date = date.toUtc();
-  var buffer = new StringBuffer()
-      ..write(_WEEKDAYS[date.weekday - 1])
-      ..write(", ")
-      ..write(date.day.toString())
-      ..write(" ")
-      ..write(_MONTHS[date.month - 1])
-      ..write(" ")
-      ..write(date.year.toString())
-      ..write(date.hour < 9 ? " 0" : " ")
-      ..write(date.hour.toString())
-      ..write(date.minute < 9 ? ":0" : ":")
-      ..write(date.minute.toString())
-      ..write(date.second < 9 ? ":0" : ":")
-      ..write(date.second.toString())
-      ..write(" GMT");
-  return buffer.toString();
-}
-
-// TODO(nweiz): Move this into an http_parser package.
-/// Parses an HTTP-formatted date into a UTC [DateTime].
-///
-/// This follows [RFC
-/// 2616](http://www.w3.org/Protocols/rfc2616/rfc2616-sec3.html#sec3.3). It will
-/// throw a [FormatException] if [date] is invalid.
-DateTime parseHttpDate(String date) {
-  try {
-    var scanner = new StringScanner(date);
-
-    if (scanner.scan(_longWeekdayRegExp)) {
-      // RFC 850 starts with a long weekday.
-      scanner.expect(", ");
-      var day = _parseInt(scanner, 2);
-      scanner.expect("-");
-      var month = _parseMonth(scanner);
-      scanner.expect("-");
-      var year = 1900 + _parseInt(scanner, 2);
-      scanner.expect(" ");
-      var time = _parseTime(scanner);
-      scanner.expect(" GMT");
-      scanner.expectDone();
-
-      return _makeDateTime(year, month, day, time);
-    }
-
-    // RFC 1123 and asctime both start with a short weekday.
-    scanner.expect(_shortWeekdayRegExp);
-    if (scanner.scan(", ")) {
-      // RFC 1123 follows the weekday with a comma.
-      var day = _parseInt(scanner, 2);
-      scanner.expect(" ");
-      var month = _parseMonth(scanner);
-      scanner.expect(" ");
-      var year = _parseInt(scanner, 4);
-      scanner.expect(" ");
-      var time = _parseTime(scanner);
-      scanner.expect(" GMT");
-      scanner.expectDone();
-
-      return _makeDateTime(year, month, day, time);
-    }
-
-    // asctime follows the weekday with a space.
-    scanner.expect(" ");
-    var month = _parseMonth(scanner);
-    scanner.expect(" ");
-    var day = scanner.scan(" ") ?
-        _parseInt(scanner, 1) :
-        _parseInt(scanner, 2);
-    scanner.expect(" ");
-    var time = _parseTime(scanner);
-    scanner.expect(" ");
-    var year = _parseInt(scanner, 4);
-    scanner.expectDone();
-
-    return _makeDateTime(year, month, day, time);
-  } on FormatException catch (error) {
-    throw new FormatException('Invalid HTTP date "$date": ${error.message}');
-  }
-}
-
-/// Parses a short-form month name to a form accepted by [DateTime].
-int _parseMonth(StringScanner scanner) {
-  scanner.expect(_monthRegExp);
-  // DateTime uses 1-indexed months.
-  return _MONTHS.indexOf(scanner.lastMatch[0]) + 1;
-}
-
-/// Parses an int an enforces that it has exactly [digits] digits.
-int _parseInt(StringScanner scanner, int digits) {
-  scanner.expect(_digitRegExp);
-  if (scanner.lastMatch[0].length != digits) {
-    scanner.error("expected a $digits-digit number.");
-  } else {
-    return int.parse(scanner.lastMatch[0]);
-  }
-}
-
-/// Parses an timestamp of the form "HH:MM:SS" on a 24-hour clock.
-DateTime _parseTime(StringScanner scanner) {
-  var hours = _parseInt(scanner, 2);
-  if (hours >= 24) scanner.error("hours may not be greater than 24.");
-  scanner.expect(':');
-
-  var minutes = _parseInt(scanner, 2);
-  if (minutes >= 60) scanner.error("minutes may not be greater than 60.");
-  scanner.expect(':');
-
-  var seconds = _parseInt(scanner, 2);
-  if (seconds >= 60) scanner.error("seconds may not be greater than 60.");
-
-  return new DateTime(1, 1, 1, hours, minutes, seconds);
-}
-
-/// Returns a UTC [DateTime] from the given components.
-///
-/// Validates that [day] is a valid day for [month]. If it's not, throws a
-/// [FormatException].
-DateTime _makeDateTime(int year, int month, int day, DateTime time) {
-  var dateTime = new DateTime.utc(
-      year, month, day, time.hour, time.minute, time.second);
-
-  // If [day] was too large, it will cause [month] to overflow.
-  if (dateTime.month != month) {
-    throw new FormatException("invalid day '$day' for month '$month'.");
-  }
-  return dateTime;
-}