/*
    * Copyright 2015 The Netty Project
    *
    * The Netty Project licenses this file to you 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:
    *
    *   https://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 io.netty.handler.codec.http;
  
  import java.net.InetSocketAddress;
  import java.net.URI;
  import java.nio.charset.Charset;
  import java.nio.charset.IllegalCharsetNameException;
  import java.nio.charset.UnsupportedCharsetException;
  import java.util.ArrayList;
  import java.util.Iterator;
  import java.util.List;
  
  import io.netty.util.AsciiString;
  import io.netty.util.CharsetUtil;
  import io.netty.util.NetUtil;
  import io.netty.util.internal.ObjectUtil;
  import io.netty.util.internal.UnstableApi;
  
  import static io.netty.util.internal.StringUtil.COMMA;
  import static io.netty.util.internal.ObjectUtil.checkPositiveOrZero;
  
  /**
   * Utility methods useful in the HTTP context.
   */
  public final class HttpUtil {
  
      private static final AsciiString CHARSET_EQUALS = AsciiString.of(HttpHeaderValues.CHARSET + "=");
      private static final AsciiString SEMICOLON = AsciiString.cached(";");
      private static final String COMMA_STRING = String.valueOf(COMMA);
  
      private HttpUtil() { }
  
      /**
       * Determine if a uri is in origin-form according to
       * <a href="https://tools.ietf.org/html/rfc7230#section-5.3">rfc7230, 5.3</a>.
       */
      public static boolean isOriginForm(URI uri) {
          return isOriginForm(uri.toString());
      }
  
      /**
       * Determine if a string uri is in origin-form according to
       * <a href="https://tools.ietf.org/html/rfc7230#section-5.3">rfc7230, 5.3</a>.
       */
      public static boolean isOriginForm(String uri) {
          return uri.startsWith("/");
      }
  
      /**
       * Determine if a uri is in asterisk-form according to
       * <a href="https://tools.ietf.org/html/rfc7230#section-5.3">rfc7230, 5.3</a>.
       */
      public static boolean isAsteriskForm(URI uri) {
          return isAsteriskForm(uri.toString());
      }
  
      /**
       * Determine if a string uri is in asterisk-form according to
       * <a href="https://tools.ietf.org/html/rfc7230#section-5.3">rfc7230, 5.3</a>.
       */
      public static boolean isAsteriskForm(String uri) {
          return "*".equals(uri);
      }
  
      /**
       * Returns {@code true} if and only if the connection can remain open and
       * thus 'kept alive'.  This methods respects the value of the.
       *
       * {@code "Connection"} header first and then the return value of
       * {@link HttpVersion#isKeepAliveDefault()}.
       */
      public static boolean isKeepAlive(HttpMessage message) {
          return !message.headers().containsValue(HttpHeaderNames.CONNECTION, HttpHeaderValues.CLOSE, true) &&
                 (message.protocolVersion().isKeepAliveDefault() ||
                  message.headers().containsValue(HttpHeaderNames.CONNECTION, HttpHeaderValues.KEEP_ALIVE, true));
      }
  
      /**
       * Sets the value of the {@code "Connection"} header depending on the
       * protocol version of the specified message. This getMethod sets or removes
       * the {@code "Connection"} header depending on what the default keep alive
       * mode of the message's protocol version is, as specified by
       * {@link HttpVersion#isKeepAliveDefault()}.
       * <ul>
       * <li>If the connection is kept alive by default:
      *     <ul>
      *     <li>set to {@code "close"} if {@code keepAlive} is {@code false}.</li>
      *     <li>remove otherwise.</li>
      *     </ul></li>
      * <li>If the connection is closed by default:
      *     <ul>
      *     <li>set to {@code "keep-alive"} if {@code keepAlive} is {@code true}.</li>
      *     <li>remove otherwise.</li>
      *     </ul></li>
      * </ul>
      * @see #setKeepAlive(HttpHeaders, HttpVersion, boolean)
      */
     public static void setKeepAlive(HttpMessage message, boolean keepAlive) {
         setKeepAlive(message.headers(), message.protocolVersion(), keepAlive);
     }
 
     /**
      * Sets the value of the {@code "Connection"} header depending on the
      * protocol version of the specified message. This getMethod sets or removes
      * the {@code "Connection"} header depending on what the default keep alive
      * mode of the message's protocol version is, as specified by
      * {@link HttpVersion#isKeepAliveDefault()}.
      * <ul>
      * <li>If the connection is kept alive by default:
      *     <ul>
      *     <li>set to {@code "close"} if {@code keepAlive} is {@code false}.</li>
      *     <li>remove otherwise.</li>
      *     </ul></li>
      * <li>If the connection is closed by default:
      *     <ul>
      *     <li>set to {@code "keep-alive"} if {@code keepAlive} is {@code true}.</li>
      *     <li>remove otherwise.</li>
      *     </ul></li>
      * </ul>
      */
     public static void setKeepAlive(HttpHeaders h, HttpVersion httpVersion, boolean keepAlive) {
         if (httpVersion.isKeepAliveDefault()) {
             if (keepAlive) {
                 h.remove(HttpHeaderNames.CONNECTION);
             } else {
                 h.set(HttpHeaderNames.CONNECTION, HttpHeaderValues.CLOSE);
             }
         } else {
             if (keepAlive) {
                 h.set(HttpHeaderNames.CONNECTION, HttpHeaderValues.KEEP_ALIVE);
             } else {
                 h.remove(HttpHeaderNames.CONNECTION);
             }
         }
     }
 
     /**
      * Returns the length of the content. Please note that this value is
      * not retrieved from {@link HttpContent#content()} but from the
      * {@code "Content-Length"} header, and thus they are independent from each
      * other.
      *
      * @return the content length
      *
      * @throws NumberFormatException
      *         if the message does not have the {@code "Content-Length"} header
      *         or its value is not a number
      */
     public static long getContentLength(HttpMessage message) {
         String value = message.headers().get(HttpHeaderNames.CONTENT_LENGTH);
         if (value != null) {
             return Long.parseLong(value);
         }
 
         // We know the content length if it's a Web Socket message even if
         // Content-Length header is missing.
         long webSocketContentLength = getWebSocketContentLength(message);
         if (webSocketContentLength >= 0) {
             return webSocketContentLength;
         }
 
         // Otherwise we don't.
         throw new NumberFormatException("header not found: " + HttpHeaderNames.CONTENT_LENGTH);
     }
 
     /**
      * Returns the length of the content or the specified default value if the message does not have the {@code
      * "Content-Length" header}. Please note that this value is not retrieved from {@link HttpContent#content()} but
      * from the {@code "Content-Length"} header, and thus they are independent from each other.
      *
      * @param message      the message
      * @param defaultValue the default value
      * @return the content length or the specified default value
      * @throws NumberFormatException if the {@code "Content-Length"} header does not parse as a long
      */
     public static long getContentLength(HttpMessage message, long defaultValue) {
         String value = message.headers().get(HttpHeaderNames.CONTENT_LENGTH);
         if (value != null) {
             return Long.parseLong(value);
         }
 
         // We know the content length if it's a Web Socket message even if
         // Content-Length header is missing.
         long webSocketContentLength = getWebSocketContentLength(message);
         if (webSocketContentLength >= 0) {
             return webSocketContentLength;
         }
 
         // Otherwise we don't.
         return defaultValue;
     }
 
     /**
      * Get an {@code int} representation of {@link #getContentLength(HttpMessage, long)}.
      *
      * @return the content length or {@code defaultValue} if this message does
      *         not have the {@code "Content-Length"} header.
      *
      * @throws NumberFormatException if the {@code "Content-Length"} header does not parse as an int
      */
     public static int getContentLength(HttpMessage message, int defaultValue) {
         return (int) Math.min(Integer.MAX_VALUE, getContentLength(message, (long) defaultValue));
     }
 
     /**
      * Returns the content length of the specified web socket message. If the
      * specified message is not a web socket message, {@code -1} is returned.
      */
     static int getWebSocketContentLength(HttpMessage message) {
         // WebSocket messages have constant content-lengths.
         HttpHeaders h = message.headers();
         if (message instanceof HttpRequest) {
             HttpRequest req = (HttpRequest) message;
             if (HttpMethod.GET.equals(req.method()) &&
                     h.contains(HttpHeaderNames.SEC_WEBSOCKET_KEY1) &&
                     h.contains(HttpHeaderNames.SEC_WEBSOCKET_KEY2)) {
                 return 8;
             }
         } else if (message instanceof HttpResponse) {
             HttpResponse res = (HttpResponse) message;
             if (res.status().code() == 101 &&
                     h.contains(HttpHeaderNames.SEC_WEBSOCKET_ORIGIN) &&
                     h.contains(HttpHeaderNames.SEC_WEBSOCKET_LOCATION)) {
                 return 16;
             }
         }
 
         // Not a web socket message
         return -1;
     }
 
     /**
      * Sets the {@code "Content-Length"} header.
      */
     public static void setContentLength(HttpMessage message, long length) {
         message.headers().set(HttpHeaderNames.CONTENT_LENGTH, length);
     }
 
     public static boolean isContentLengthSet(HttpMessage m) {
         return m.headers().contains(HttpHeaderNames.CONTENT_LENGTH);
     }
 
     /**
      * Returns {@code true} if and only if the specified message contains an expect header and the only expectation
      * present is the 100-continue expectation. Note that this method returns {@code false} if the expect header is
      * not valid for the message (e.g., the message is a response, or the version on the message is HTTP/1.0).
      *
      * @param message the message
      * @return {@code true} if and only if the expectation 100-continue is present and it is the only expectation
      * present
      */
     public static boolean is100ContinueExpected(HttpMessage message) {
         return isExpectHeaderValid(message)
           // unquoted tokens in the expect header are case-insensitive, thus 100-continue is case insensitive
           && message.headers().contains(HttpHeaderNames.EXPECT, HttpHeaderValues.CONTINUE, true);
     }
 
     /**
      * Returns {@code true} if the specified message contains an expect header specifying an expectation that is not
      * supported. Note that this method returns {@code false} if the expect header is not valid for the message
      * (e.g., the message is a response, or the version on the message is HTTP/1.0).
      *
      * @param message the message
      * @return {@code true} if and only if an expectation is present that is not supported
      */
     static boolean isUnsupportedExpectation(HttpMessage message) {
         if (!isExpectHeaderValid(message)) {
             return false;
         }
 
         final String expectValue = message.headers().get(HttpHeaderNames.EXPECT);
         return expectValue != null && !HttpHeaderValues.CONTINUE.toString().equalsIgnoreCase(expectValue);
     }
 
     private static boolean isExpectHeaderValid(final HttpMessage message) {
         /*
          * Expect: 100-continue is for requests only and it works only on HTTP/1.1 or later. Note further that RFC 7231
          * section 5.1.1 says "A server that receives a 100-continue expectation in an HTTP/1.0 request MUST ignore
          * that expectation."
          */
         return message instanceof HttpRequest &&
                 message.protocolVersion().compareTo(HttpVersion.HTTP_1_1) >= 0;
     }
 
     /**
      * Sets or removes the {@code "Expect: 100-continue"} header to / from the
      * specified message. If {@code expected} is {@code true},
      * the {@code "Expect: 100-continue"} header is set and all other previous
      * {@code "Expect"} headers are removed.  Otherwise, all {@code "Expect"}
      * headers are removed completely.
      */
     public static void set100ContinueExpected(HttpMessage message, boolean expected) {
         if (expected) {
             message.headers().set(HttpHeaderNames.EXPECT, HttpHeaderValues.CONTINUE);
         } else {
             message.headers().remove(HttpHeaderNames.EXPECT);
         }
     }
 
     /**
      * Checks to see if the transfer encoding in a specified {@link HttpMessage} is chunked
      *
      * @param message The message to check
      * @return True if transfer encoding is chunked, otherwise false
      */
     public static boolean isTransferEncodingChunked(HttpMessage message) {
         return message.headers().containsValue(HttpHeaderNames.TRANSFER_ENCODING, HttpHeaderValues.CHUNKED, true);
     }
 
     /**
      * Set the {@link HttpHeaderNames#TRANSFER_ENCODING} to either include {@link HttpHeaderValues#CHUNKED} if
      * {@code chunked} is {@code true}, or remove {@link HttpHeaderValues#CHUNKED} if {@code chunked} is {@code false}.
      *
      * @param m The message which contains the headers to modify.
      * @param chunked if {@code true} then include {@link HttpHeaderValues#CHUNKED} in the headers. otherwise remove
      * {@link HttpHeaderValues#CHUNKED} from the headers.
      */
     public static void setTransferEncodingChunked(HttpMessage m, boolean chunked) {
         if (chunked) {
             m.headers().set(HttpHeaderNames.TRANSFER_ENCODING, HttpHeaderValues.CHUNKED);
             m.headers().remove(HttpHeaderNames.CONTENT_LENGTH);
         } else {
             List<String> encodings = m.headers().getAll(HttpHeaderNames.TRANSFER_ENCODING);
             if (encodings.isEmpty()) {
                 return;
             }
             List<CharSequence> values = new ArrayList<CharSequence>(encodings);
             Iterator<CharSequence> valuesIt = values.iterator();
             while (valuesIt.hasNext()) {
                 CharSequence value = valuesIt.next();
                 if (HttpHeaderValues.CHUNKED.contentEqualsIgnoreCase(value)) {
                     valuesIt.remove();
                 }
             }
             if (values.isEmpty()) {
                 m.headers().remove(HttpHeaderNames.TRANSFER_ENCODING);
             } else {
                 m.headers().set(HttpHeaderNames.TRANSFER_ENCODING, values);
             }
         }
     }
 
     /**
      * Fetch charset from message's Content-Type header.
      *
      * @param message entity to fetch Content-Type header from
      * @return the charset from message's Content-Type header or {@link CharsetUtil#ISO_8859_1}
      * if charset is not presented or unparsable
      */
     public static Charset getCharset(HttpMessage message) {
         return getCharset(message, CharsetUtil.ISO_8859_1);
     }
 
     /**
      * Fetch charset from Content-Type header value.
      *
      * @param contentTypeValue Content-Type header value to parse
      * @return the charset from message's Content-Type header or {@link CharsetUtil#ISO_8859_1}
      * if charset is not presented or unparsable
      */
     public static Charset getCharset(CharSequence contentTypeValue) {
         if (contentTypeValue != null) {
             return getCharset(contentTypeValue, CharsetUtil.ISO_8859_1);
         } else {
             return CharsetUtil.ISO_8859_1;
         }
     }
 
     /**
      * Fetch charset from message's Content-Type header.
      *
      * @param message        entity to fetch Content-Type header from
      * @param defaultCharset result to use in case of empty, incorrect or doesn't contain required part header value
      * @return the charset from message's Content-Type header or {@code defaultCharset}
      * if charset is not presented or unparsable
      */
     public static Charset getCharset(HttpMessage message, Charset defaultCharset) {
         CharSequence contentTypeValue = message.headers().get(HttpHeaderNames.CONTENT_TYPE);
         if (contentTypeValue != null) {
             return getCharset(contentTypeValue, defaultCharset);
         } else {
             return defaultCharset;
         }
     }
 
     /**
      * Fetch charset from Content-Type header value.
      *
      * @param contentTypeValue Content-Type header value to parse
      * @param defaultCharset   result to use in case of empty, incorrect or doesn't contain required part header value
      * @return the charset from message's Content-Type header or {@code defaultCharset}
      * if charset is not presented or unparsable
      */
     public static Charset getCharset(CharSequence contentTypeValue, Charset defaultCharset) {
         if (contentTypeValue != null) {
             CharSequence charsetRaw = getCharsetAsSequence(contentTypeValue);
             if (charsetRaw != null) {
                 if (charsetRaw.length() > 2) { // at least contains 2 quotes(")
                     if (charsetRaw.charAt(0) == '"' && charsetRaw.charAt(charsetRaw.length() - 1) == '"') {
                         charsetRaw = charsetRaw.subSequence(1, charsetRaw.length() - 1);
                     }
                 }
                 try {
                     return Charset.forName(charsetRaw.toString());
                 } catch (IllegalCharsetNameException ignored) {
                     // just return the default charset
                 } catch (UnsupportedCharsetException ignored) {
                     // just return the default charset
                 }
             }
         }
         return defaultCharset;
     }
 
     /**
      * Fetch charset from message's Content-Type header as a char sequence.
      *
      * A lot of sites/possibly clients have charset="CHARSET", for example charset="utf-8". Or "utf8" instead of "utf-8"
      * This is not according to standard, but this method provide an ability to catch desired mistakes manually in code
      *
      * @param message entity to fetch Content-Type header from
      * @return the {@code CharSequence} with charset from message's Content-Type header
      * or {@code null} if charset is not presented
      * @deprecated use {@link #getCharsetAsSequence(HttpMessage)}
      */
     @Deprecated
     public static CharSequence getCharsetAsString(HttpMessage message) {
         return getCharsetAsSequence(message);
     }
 
     /**
      * Fetch charset from message's Content-Type header as a char sequence.
      *
      * A lot of sites/possibly clients have charset="CHARSET", for example charset="utf-8". Or "utf8" instead of "utf-8"
      * This is not according to standard, but this method provide an ability to catch desired mistakes manually in code
      *
      * @return the {@code CharSequence} with charset from message's Content-Type header
      * or {@code null} if charset is not presented
      */
     public static CharSequence getCharsetAsSequence(HttpMessage message) {
         CharSequence contentTypeValue = message.headers().get(HttpHeaderNames.CONTENT_TYPE);
         if (contentTypeValue != null) {
             return getCharsetAsSequence(contentTypeValue);
         } else {
             return null;
         }
     }
 
     /**
      * Fetch charset from Content-Type header value as a char sequence.
      *
      * A lot of sites/possibly clients have charset="CHARSET", for example charset="utf-8". Or "utf8" instead of "utf-8"
      * This is not according to standard, but this method provide an ability to catch desired mistakes manually in code
      *
      * @param contentTypeValue Content-Type header value to parse
      * @return the {@code CharSequence} with charset from message's Content-Type header
      * or {@code null} if charset is not presented
      * @throws NullPointerException in case if {@code contentTypeValue == null}
      */
     public static CharSequence getCharsetAsSequence(CharSequence contentTypeValue) {
         ObjectUtil.checkNotNull(contentTypeValue, "contentTypeValue");
 
         int indexOfCharset = AsciiString.indexOfIgnoreCaseAscii(contentTypeValue, CHARSET_EQUALS, 0);
         if (indexOfCharset == AsciiString.INDEX_NOT_FOUND) {
             return null;
         }
 
         int indexOfEncoding = indexOfCharset + CHARSET_EQUALS.length();
         if (indexOfEncoding < contentTypeValue.length()) {
             CharSequence charsetCandidate = contentTypeValue.subSequence(indexOfEncoding, contentTypeValue.length());
             int indexOfSemicolon = AsciiString.indexOfIgnoreCaseAscii(charsetCandidate, SEMICOLON, 0);
             if (indexOfSemicolon == AsciiString.INDEX_NOT_FOUND) {
                 return charsetCandidate;
             }
 
             return charsetCandidate.subSequence(0, indexOfSemicolon);
         }
 
         return null;
     }
 
     /**
      * Fetch MIME type part from message's Content-Type header as a char sequence.
      *
      * @param message entity to fetch Content-Type header from
      * @return the MIME type as a {@code CharSequence} from message's Content-Type header
      * or {@code null} if content-type header or MIME type part of this header are not presented
      * <p/>
      * "content-type: text/html; charset=utf-8" - "text/html" will be returned <br/>
      * "content-type: text/html" - "text/html" will be returned <br/>
      * "content-type: " or no header - {@code null} we be returned
      */
     public static CharSequence getMimeType(HttpMessage message) {
         CharSequence contentTypeValue = message.headers().get(HttpHeaderNames.CONTENT_TYPE);
         if (contentTypeValue != null) {
             return getMimeType(contentTypeValue);
         } else {
             return null;
         }
     }
 
     /**
      * Fetch MIME type part from Content-Type header value as a char sequence.
      *
      * @param contentTypeValue Content-Type header value to parse
      * @return the MIME type as a {@code CharSequence} from message's Content-Type header
      * or {@code null} if content-type header or MIME type part of this header are not presented
      * <p/>
      * "content-type: text/html; charset=utf-8" - "text/html" will be returned <br/>
      * "content-type: text/html" - "text/html" will be returned <br/>
      * "content-type: empty header - {@code null} we be returned
      * @throws NullPointerException in case if {@code contentTypeValue == null}
      */
     public static CharSequence getMimeType(CharSequence contentTypeValue) {
         ObjectUtil.checkNotNull(contentTypeValue, "contentTypeValue");
 
         int indexOfSemicolon = AsciiString.indexOfIgnoreCaseAscii(contentTypeValue, SEMICOLON, 0);
         if (indexOfSemicolon != AsciiString.INDEX_NOT_FOUND) {
             return contentTypeValue.subSequence(0, indexOfSemicolon);
         } else {
             return contentTypeValue.length() > 0 ? contentTypeValue : null;
         }
     }
 
     /**
      * Formats the host string of an address so it can be used for computing an HTTP component
      * such as a URL or a Host header
      *
      * @param addr the address
      * @return the formatted String
      */
     public static String formatHostnameForHttp(InetSocketAddress addr) {
         String hostString = NetUtil.getHostname(addr);
         if (NetUtil.isValidIpV6Address(hostString)) {
             if (!addr.isUnresolved()) {
                 hostString = NetUtil.toAddressString(addr.getAddress());
             }
             return '[' + hostString + ']';
         }
         return hostString;
     }
 
     /**
      * Validates, and optionally extracts the content length from headers. This method is not intended for
      * general use, but is here to be shared between HTTP/1 and HTTP/2 parsing.
      *
      * @param contentLengthFields the content-length header fields.
      * @param isHttp10OrEarlier {@code true} if we are handling HTTP/1.0 or earlier
      * @param allowDuplicateContentLengths {@code true}  if multiple, identical-value content lengths should be allowed.
      * @return the normalized content length from the headers or {@code -1} if the fields were empty.
      * @throws IllegalArgumentException if the content-length fields are not valid
      */
     @UnstableApi
     public static long normalizeAndGetContentLength(
             List<? extends CharSequence> contentLengthFields, boolean isHttp10OrEarlier,
             boolean allowDuplicateContentLengths) {
         if (contentLengthFields.isEmpty()) {
             return -1;
         }
 
         // Guard against multiple Content-Length headers as stated in
         // https://tools.ietf.org/html/rfc7230#section-3.3.2:
         //
         // If a message is received that has multiple Content-Length header
         //   fields with field-values consisting of the same decimal value, or a
         //   single Content-Length header field with a field value containing a
         //   list of identical decimal values (e.g., "Content-Length: 42, 42"),
         //   indicating that duplicate Content-Length header fields have been
         //   generated or combined by an upstream message processor, then the
         //   recipient MUST either reject the message as invalid or replace the
         //   duplicated field-values with a single valid Content-Length field
         //   containing that decimal value prior to determining the message body
         //   length or forwarding the message.
         String firstField = contentLengthFields.get(0).toString();
         boolean multipleContentLengths =
                 contentLengthFields.size() > 1 || firstField.indexOf(COMMA) >= 0;
 
         if (multipleContentLengths && !isHttp10OrEarlier) {
             if (allowDuplicateContentLengths) {
                 // Find and enforce that all Content-Length values are the same
                 String firstValue = null;
                 for (CharSequence field : contentLengthFields) {
                     String[] tokens = field.toString().split(COMMA_STRING, -1);
                     for (String token : tokens) {
                         String trimmed = token.trim();
                         if (firstValue == null) {
                             firstValue = trimmed;
                         } else if (!trimmed.equals(firstValue)) {
                             throw new IllegalArgumentException(
                                     "Multiple Content-Length values found: " + contentLengthFields);
                         }
                     }
                 }
                 // Replace the duplicated field-values with a single valid Content-Length field
                 firstField = firstValue;
             } else {
                 // Reject the message as invalid
                 throw new IllegalArgumentException(
                         "Multiple Content-Length values found: " + contentLengthFields);
             }
         }
         // Ensure we not allow sign as part of the content-length:
         // See https://github.com/squid-cache/squid/security/advisories/GHSA-qf3v-rc95-96j5
         if (firstField.isEmpty() || !Character.isDigit(firstField.charAt(0))) {
             // Reject the message as invalid
             throw new IllegalArgumentException(
                     "Content-Length value is not a number: " + firstField);
         }
         try {
             final long value = Long.parseLong(firstField);
             return checkPositiveOrZero(value, "Content-Length value");
         } catch (NumberFormatException e) {
             // Reject the message as invalid
             throw new IllegalArgumentException(
                     "Content-Length value is not a number: " + firstField, e);
         }
     }
 }