pkg/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 '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) {
+  var errorMessage = 'Invalid HTTP date "$date".';
+  var scanner = new StringScanner(date);
+
+  if (scanner.scan(_longWeekdayRegExp)) {
+    // RFC 850 starts with a long weekday.
+    scanner.expect(", ", errorMessage);
+    var day = _parseInt(scanner, errorMessage, 2);
+    scanner.expect("-", errorMessage);
+    var month = _parseMonth(scanner, errorMessage);
+    scanner.expect("-", errorMessage);
+    var year = 1900 + _parseInt(scanner, errorMessage, 2);
+    scanner.expect(" ", errorMessage);
+    var time = _parseTime(scanner, errorMessage);
+    scanner.expect(" GMT", errorMessage);
+    if (!scanner.isDone) throw new FormatException(errorMessage);
+
+    return _makeDateTime(year, month, day, time, errorMessage);
+  }
+
+  // RFC 1123 and asctime both start with a short weekday.
+  scanner.expect(_shortWeekdayRegExp, errorMessage);
+  if (scanner.scan(", ")) {
+    // RFC 1123 follows the weekday with a comma.
+    var day = _parseInt(scanner, errorMessage, 2);
+    scanner.expect(" ", errorMessage);
+    var month = _parseMonth(scanner, errorMessage);
+    scanner.expect(" ", errorMessage);
+    var year = _parseInt(scanner, errorMessage, 4);
+    scanner.expect(" ", errorMessage);
+    var time = _parseTime(scanner, errorMessage);
+    scanner.expect(" GMT", errorMessage);
+    if (!scanner.isDone) throw new FormatException(errorMessage);
+
+    return _makeDateTime(year, month, day, time, errorMessage);
+  }
+
+  // asctime follows the weekday with a space.
+  scanner.expect(" ", errorMessage);
+  var month = _parseMonth(scanner, errorMessage);
+  scanner.expect(" ", errorMessage);
+  var day = scanner.scan(" ") ?
+      _parseInt(scanner, errorMessage, 1) :
+      _parseInt(scanner, errorMessage, 2);
+  scanner.expect(" ", errorMessage);
+  var time = _parseTime(scanner, errorMessage);
+  scanner.expect(" ", errorMessage);
+  var year = _parseInt(scanner, errorMessage, 4);
+  if (!scanner.isDone) throw new FormatException(errorMessage);
+
+  return _makeDateTime(year, month, day, time, errorMessage);
+}
+
+/// Parses a short-form month name to a form accepted by [DateTime].
+int _parseMonth(StringScanner scanner, String errorMessage) {
+  scanner.expect(_monthRegExp, errorMessage);
+  // 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, String errorMessage, int digits) {
+  scanner.expect(_digitRegExp, errorMessage);
+  if (scanner.lastMatch[0].length != digits) {
+    throw new FormatException(errorMessage);
+  } 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, String errorMessage) {
+  var hours = _parseInt(scanner, errorMessage, 2);
+  scanner.expect(':', errorMessage);
+
+  var minutes = _parseInt(scanner, errorMessage, 2);
+  scanner.expect(':', errorMessage);
+
+  var seconds = _parseInt(scanner, errorMessage, 2);
+
+  if (hours >= 24 || minutes >= 60 || seconds >= 60) {
+    throw new FormatException(errorMessage);
+  }
+
+  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] with [errorMessage].
+DateTime _makeDateTime(int year, int month, int day, DateTime time,
+    String errorMessage) {
+  if (day < 1) throw new FormatException(errorMessage);
+  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(errorMessage);
+  return dateTime;
+}