Add handling of HTTP header "Expires"

runtime/bin/http_utils.dart

Index: runtime/bin/http_utils.dart
diff --git a/runtime/bin/http_utils.dart b/runtime/bin/http_utils.dart
index 1e5d84c0d12e176d24731f9da713456c0f829563..3b120fd53ee2992bfd1bf3e54715b9b1379c9090 100644
--- a/runtime/bin/http_utils.dart
+++ b/runtime/bin/http_utils.dart
@@ -59,4 +59,172 @@ class _HttpUtils {
     }
     return result;
   }
+
+  // From RFC 2616 section "3.3.1 Full Date"
+  // HTTP-date    = rfc1123-date | rfc850-date | asctime-date
+  // rfc1123-date = wkday "," SP date1 SP time SP "GMT"
+  // rfc850-date  = weekday "," SP date2 SP time SP "GMT"
+  // asctime-date = wkday SP date3 SP time SP 4DIGIT
+  // date1        = 2DIGIT SP month SP 4DIGIT
+  //                ; day month year (e.g., 02 Jun 1982)
+  // date2        = 2DIGIT "-" month "-" 2DIGIT
+  //                ; day-month-year (e.g., 02-Jun-82)
+  // date3        = month SP ( 2DIGIT | ( SP 1DIGIT ))
+  //                ; month day (e.g., Jun  2)
+  // time         = 2DIGIT ":" 2DIGIT ":" 2DIGIT
+  //                ; 00:00:00 - 23:59:59
+  // wkday        = "Mon" | "Tue" | "Wed"
+  //              | "Thu" | "Fri" | "Sat" | "Sun"
+  // weekday      = "Monday" | "Tuesday" | "Wednesday"
+  //              | "Thursday" | "Friday" | "Saturday" | "Sunday"
+  // month        = "Jan" | "Feb" | "Mar" | "Apr"
+  //              | "May" | "Jun" | "Jul" | "Aug"
+  //              | "Sep" | "Oct" | "Nov" | "Dec"
+
+  // Format as RFC 1123 date.
+  static String formatDate(Date date) {
+    List wkday = ["Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun"];
+    List month = ["Jan", "Feb", "Mar", "Apr", "May", "Jun",
+                  "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"];
+
+    Date d = date.changeTimeZone(new TimeZone.utc());
+    StringBuffer sb = new StringBuffer();
+    sb.add(wkday[d.weekday]);
+    sb.add(", ");
+    sb.add(d.day.toString());
+    sb.add(" ");
+    sb.add(month[d.month - 1]);
+    sb.add(" ");
+    sb.add(d.year.toString());
+    d.hours < 9 ? sb.add(" 0") : sb.add(" ");
+    sb.add(d.hours.toString());
+    d.minutes < 9 ? sb.add(":0") : sb.add(":");
+    sb.add(d.minutes.toString());
+    d.seconds < 9 ? sb.add(":0") : sb.add(":");
+    sb.add(d.seconds.toString());
+    sb.add(" GMT");
+    return sb.toString();
+  }
+
+  static Date parseDate(String date) {
+    final int SP = 32;
+    List wkdays = ["Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun"];
+    List weekdays = ["Monday", "Tuesday", "Wednesday", "Thursday",
+                     "Friday", "Saturday", "Sunday"];
+    List months = ["Jan", "Feb", "Mar", "Apr", "May", "Jun",
+                   "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"];
+
+    final int formatRfc1123 = 0;
+    final int formatRfc850 = 1;
+    final int formatAsctime = 2;
+
+    int index = 0;
+    String tmp;
+    int format;
+
+    void expect(String s) {
+      if (date.length - index < s.length) {
+        throw new HttpException("Invalid HTTP date $date");
+      }
+      String tmp = date.substring(index, index + s.length);
+      if (tmp != s) {
+        throw new HttpException("Invalid HTTP date $date");
+      }
+      index += s.length;
+    }
+
+    int expectWeekday() {
+      int weekday;
+      // The formatting of the weekday signals the format of the date string.
+      int pos = date.indexOf(",", index);
+      if (pos == -1) {
+        int pos = date.indexOf(" ", index);
+        if (pos == -1) throw new HttpException("Invalid HTTP date $date");
+        tmp = date.substring(index, pos);
+        index = pos + 1;
+        weekday = wkdays.indexOf(tmp);
+        if (weekday != -1) {
+          format = formatAsctime;
+          return weekday;
+        }
+      } else {
+        tmp = date.substring(index, pos);
+        index = pos + 1;
+        weekday = wkdays.indexOf(tmp);
+        if (weekday != -1) {
+          format = formatRfc1123;
+          return weekday;
+        }
+        weekday = weekdays.indexOf(tmp);
+        if (weekday != -1) {
+          format = formatRfc850;
+          return weekday;
+        }
+      }
+      throw new HttpException("Invalid HTTP date $date");
+    }
+
+    int expectMonth(String separator) {
+      int pos = date.indexOf(separator, index);
+      if (pos - index != 3) throw new HttpException("Invalid HTTP date $date");
+      tmp = date.substring(index, pos);
+      index = pos + 1;
+      int month = months.indexOf(tmp);
+      if (month != -1) return month;
+      throw new HttpException("Invalid HTTP date $date");
+    }
+
+    int expectNum(String separator) {
+      int pos;
+      if (separator.length > 0) {
+        pos = date.indexOf(separator, index);
+      } else {
+        pos = date.length;
+      }
+      String tmp = date.substring(index, pos);
+      index = pos + separator.length;
+      try {
+        int value = Math.parseInt(tmp);
+        return value;
+      } catch (BadNumberFormatException e) {
+        throw new HttpException("Invalid HTTP date $date");
+      }
+    }
+
+    void expectEnd() {
+      if (index != date.length) {
+        throw new HttpException("Invalid HTTP date $date");
+      }
+    }
+
+    int weekday = expectWeekday();
+    int day;
+    int month;
+    int year;
+    int hours;
+    int minutes;
+    int seconds;
+    if (format == formatAsctime) {
+      month = expectMonth(" ");
+      if (date.charCodeAt(index) == SP) index++;
+      day = expectNum(" ");
+      hours = expectNum(":");
+      minutes = expectNum(":");
+      seconds = expectNum(" ");
+      year = expectNum("");
+    } else {
+      expect(" ");
+      day = expectNum(format == formatRfc1123 ? " " : "-");
+      month = expectMonth(format == formatRfc1123 ? " " : "-");
+      year = expectNum(" ");
+      hours = expectNum(":");
+      minutes = expectNum(":");
+      seconds = expectNum(" ");
+      expect("GMT");
+    }
+    expectEnd();
+    TimeZone utc = new TimeZone.utc();
+    return new Date.withTimeZone(
+        year, month + 1, day, hours, minutes, seconds, 0, utc);
+  }
 }