Android Open Source - wristband-android Http Header Parser

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License

The source code is released under:

The Artistic License 2.0 Copyright (c) 2014 Allan Pichardo Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed...

Java Source Code

/*
 * Copyright (C) 2011 The Android Open Source Project
 */*w  w w. ja va 2s . com*/
 * 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.android.volley.toolbox;

import com.android.volley.Cache;
import com.android.volley.NetworkResponse;

import org.apache.http.impl.cookie.DateParseException;
import org.apache.http.impl.cookie.DateUtils;
import org.apache.http.protocol.HTTP;

import java.util.Map;

/**
 * Utility methods for parsing HTTP headers.
 */
public class HttpHeaderParser {

    /**
     * Extracts a {@link Cache.Entry} from a {@link NetworkResponse}.
     *
     * @param response The network response to parse headers from
     * @return a cache entry for the given response, or null if the response is not cacheable.
     */
    public static Cache.Entry parseCacheHeaders(NetworkResponse response) {
        long now = System.currentTimeMillis();

        Map<String, String> headers = response.headers;

        long serverDate = 0;
        long serverExpires = 0;
        long softExpire = 0;
        long maxAge = 0;
        boolean hasCacheControl = false;

        String serverEtag = null;
        String headerValue;

        headerValue = headers.get("Date");
        if (headerValue != null) {
            serverDate = parseDateAsEpoch(headerValue);
        }

        headerValue = headers.get("Cache-Control");
        if (headerValue != null) {
            hasCacheControl = true;
            String[] tokens = headerValue.split(",");
            for (int i = 0; i < tokens.length; i++) {
                String token = tokens[i].trim();
                if (token.equals("no-cache") || token.equals("no-store")) {
                    return null;
                } else if (token.startsWith("max-age=")) {
                    try {
                        maxAge = Long.parseLong(token.substring(8));
                    } catch (Exception e) {
                    }
                } else if (token.equals("must-revalidate") || token.equals("proxy-revalidate")) {
                    maxAge = 0;
                }
            }
        }

        headerValue = headers.get("Expires");
        if (headerValue != null) {
            serverExpires = parseDateAsEpoch(headerValue);
        }

        serverEtag = headers.get("ETag");

        // Cache-Control takes precedence over an Expires header, even if both exist and Expires
        // is more restrictive.
        if (hasCacheControl) {
            softExpire = now + maxAge * 1000;
        } else if (serverDate > 0 && serverExpires >= serverDate) {
            // Default semantic for Expire header in HTTP specification is softExpire.
            softExpire = now + (serverExpires - serverDate);
        }

        Cache.Entry entry = new Cache.Entry();
        entry.data = response.data;
        entry.etag = serverEtag;
        entry.softTtl = softExpire;
        entry.ttl = entry.softTtl;
        entry.serverDate = serverDate;
        entry.responseHeaders = headers;

        return entry;
    }

    /**
     * Parse date in RFC1123 format, and return its value as epoch
     */
    public static long parseDateAsEpoch(String dateStr) {
        try {
            // Parse date in RFC1123 format if this header contains one
            return DateUtils.parseDate(dateStr).getTime();
        } catch (DateParseException e) {
            // Date in invalid format, fallback to 0
            return 0;
        }
    }

    /**
     * Returns the charset specified in the Content-Type of this header,
     * or the HTTP default (ISO-8859-1) if none can be found.
     */
    public static String parseCharset(Map<String, String> headers) {
        String contentType = headers.get(HTTP.CONTENT_TYPE);
        if (contentType != null) {
            String[] params = contentType.split(";");
            for (int i = 1; i < params.length; i++) {
                String[] pair = params[i].trim().split("=");
                if (pair.length == 2) {
                    if (pair[0].equals("charset")) {
                        return pair[1];
                    }
                }
            }
        }

        return HTTP.DEFAULT_CONTENT_CHARSET;
    }
}

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