com.squareup.okhttp.internal.http.HttpDate.java Source code

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Here is the source code for com.squareup.okhttp.internal.http.HttpDate.java

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/*
 * Copyright (C) 2011 The Android Open Source Project
 *
 * 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.
 */

package com.squareup.okhttp.internal.http;

import java.text.DateFormat;
import java.text.ParsePosition;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Locale;
import java.util.TimeZone;

/**
 * Best-effort parser for HTTP dates.
 */
public final class HttpDate {

    private static final TimeZone GMT = TimeZone.getTimeZone("GMT");

    /**
     * Most websites serve cookies in the blessed format. Eagerly create the parser to ensure such
     * cookies are on the fast path.
     */
    private static final ThreadLocal<DateFormat> STANDARD_DATE_FORMAT = new ThreadLocal<DateFormat>() {
        @Override
        protected DateFormat initialValue() {
            // RFC 2616 specified: RFC 822, updated by RFC 1123 format with fixed GMT.
            DateFormat rfc1123 = new SimpleDateFormat("EEE, dd MMM yyyy HH:mm:ss 'GMT'", Locale.US);
            rfc1123.setLenient(false);
            rfc1123.setTimeZone(GMT);
            return rfc1123;
        }
    };

    /** If we fail to parse a date in a non-standard format, try each of these formats in sequence. */
    private static final String[] BROWSER_COMPATIBLE_DATE_FORMAT_STRINGS = new String[] {
            // HTTP formats required by RFC2616 but with any timezone.
            "EEE, dd MMM yyyy HH:mm:ss zzz", // RFC 822, updated by RFC 1123 with any TZ
            "EEEE, dd-MMM-yy HH:mm:ss zzz", // RFC 850, obsoleted by RFC 1036 with any TZ.
            "EEE MMM d HH:mm:ss yyyy", // ANSI C's asctime() format
            // Alternative formats.
            "EEE, dd-MMM-yyyy HH:mm:ss z", "EEE, dd-MMM-yyyy HH-mm-ss z", "EEE, dd MMM yy HH:mm:ss z",
            "EEE dd-MMM-yyyy HH:mm:ss z", "EEE dd MMM yyyy HH:mm:ss z", "EEE dd-MMM-yyyy HH-mm-ss z",
            "EEE dd-MMM-yy HH:mm:ss z", "EEE dd MMM yy HH:mm:ss z", "EEE,dd-MMM-yy HH:mm:ss z",
            "EEE,dd-MMM-yyyy HH:mm:ss z", "EEE, dd-MM-yyyy HH:mm:ss z",

            /* RI bug 6641315 claims a cookie of this format was once served by www.yahoo.com */
            "EEE MMM d yyyy HH:mm:ss z", };

    private static final DateFormat[] BROWSER_COMPATIBLE_DATE_FORMATS = new DateFormat[BROWSER_COMPATIBLE_DATE_FORMAT_STRINGS.length];

    /** Returns the date for {@code value}. Returns null if the value couldn't be parsed. */
    public static Date parse(String value) {
        if (value.length() == 0) {
            return null;
        }

        ParsePosition position = new ParsePosition(0);
        Date result = STANDARD_DATE_FORMAT.get().parse(value, position);
        if (position.getIndex() == value.length()) {
            // STANDARD_DATE_FORMAT must match exactly; all text must be consumed, e.g. no ignored
            // non-standard trailing "+01:00". Those cases are covered below.
            return result;
        }
        synchronized (BROWSER_COMPATIBLE_DATE_FORMAT_STRINGS) {
            for (int i = 0, count = BROWSER_COMPATIBLE_DATE_FORMAT_STRINGS.length; i < count; i++) {
                DateFormat format = BROWSER_COMPATIBLE_DATE_FORMATS[i];
                if (format == null) {
                    format = new SimpleDateFormat(BROWSER_COMPATIBLE_DATE_FORMAT_STRINGS[i], Locale.US);
                    // Set the timezone to use when interpreting formats that don't have a timezone. GMT is
                    // specified by RFC 2616.
                    format.setTimeZone(GMT);
                    BROWSER_COMPATIBLE_DATE_FORMATS[i] = format;
                }
                position.setIndex(0);
                result = format.parse(value, position);
                if (position.getIndex() != 0) {
                    // Something was parsed. It's possible the entire string was not consumed but we ignore
                    // that. If any of the BROWSER_COMPATIBLE_DATE_FORMAT_STRINGS ended in "'GMT'" we'd have
                    // to also check that position.getIndex() == value.length() otherwise parsing might have
                    // terminated early, ignoring things like "+01:00". Leaving this as != 0 means that any
                    // trailing junk is ignored.
                    return result;
                }
            }
        }
        return null;
    }

    /** Returns the string for {@code value}. */
    public static String format(Date value) {
        return STANDARD_DATE_FORMAT.get().format(value);
    }

    private HttpDate() {
    }
}