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013package org.apache.juneau.http;
014
015/**
016 * Represents a parsed <l>Content-Range</l> HTTP response header.
017 * 
018 * <p>
019 * Where in a full body message this partial message belongs.
020 * 
021 * <h5 class='figure'>Example</h5>
022 * <p class='bcode'>
023 *    Content-Range: bytes 21010-47021/47022
024 * </p>
025 * 
026 * <h5 class='topic'>RFC2616 Specification</h5>
027 * 
028 * The Content-Range entity-header is sent with a partial entity-body to specify where in the full entity-body the
029 * partial body should be applied.
030 * Range units are defined in section 3.12.
031 * <p class='bcode'>
032 *    Content-Range = "Content-Range" ":" content-range-spec
033 *    content-range-spec      = byte-content-range-spec
034 *    byte-content-range-spec = bytes-unit SP
035 *                              byte-range-resp-spec "/"
036 *                              ( instance-length | "*" )
037 *    byte-range-resp-spec = (first-byte-pos "-" last-byte-pos)
038 *                                   | "*"
039 *    instance-length           = 1*DIGIT
040 * </p>
041 * 
042 * <p>
043 * The header SHOULD indicate the total length of the full entity-body, unless this length is unknown or difficult to
044 * determine.
045 * The asterisk "*" character means that the instance-length is unknown at the time when the response was generated.
046 * 
047 * <p>
048 * Unlike byte-ranges-specifier values (see section 14.35.1), a byte- range-resp-spec MUST only specify one range, and
049 * MUST contain absolute byte positions for both the first and last byte of the range.
050 * 
051 * <p>
052 * A byte-content-range-spec with a byte-range-resp-spec whose last- byte-pos value is less than its first-byte-pos
053 * value, or whose instance-length value is less than or equal to its last-byte-pos value, is invalid.
054 * The recipient of an invalid byte-content-range- spec MUST ignore it and any content transferred along with it.
055 * 
056 * <p>
057 * A server sending a response with status code 416 (Requested range not satisfiable) SHOULD include a Content-Range
058 * field with a byte-range- resp-spec of "*".
059 * The instance-length specifies the current length of the selected resource.
060 * A response with status code 206 (Partial Content) MUST NOT include a Content-Range field with a byte-range-resp-spec
061 * of "*".
062 * 
063 * <p>
064 * Examples of byte-content-range-spec values, assuming that the entity contains a total of 1234 bytes:
065 * <p class='bcode'>
066 *    The first 500 bytes:
067 *     bytes 0-499/1234
068 *    The second 500 bytes:
069 *     bytes 500-999/1234
070 *    All except for the first 500 bytes:
071 *     bytes 500-1233/1234
072 *    The last 500 bytes:
073 *     bytes 734-1233/1234
074 * </p>
075 * 
076 * <p>
077 * When an HTTP message includes the content of a single range (for example, a response to a request for a single range,
078 * or to a request for a set of ranges that overlap without any holes), this content is transmitted with a Content-Range
079 * header, and a Content-Length header showing the number of bytes actually transferred.
080 * For example:
081 * <p class='bcode'>
082 *    HTTP/1.1 206 Partial content
083 *    Date: Wed, 15 Nov 1995 06:25:24 GMT
084 *    Last-Modified: Wed, 15 Nov 1995 04:58:08 GMT
085 *    Content-Range: bytes 21010-47021/47022
086 *    Content-Length: 26012
087 *    Content-Type: image/gif
088 * </p>
089 * 
090 * <p>
091 * When an HTTP message includes the content of multiple ranges (for example, a response to a request for multiple
092 * non-overlapping ranges), these are transmitted as a multipart message.
093 * The multipart media type used for this purpose is "multipart/byteranges" as defined in appendix 19.2.
094 * See appendix 19.6.3 for a compatibility issue.
095 * 
096 * <p>
097 * A response to a request for a single range MUST NOT be sent using the multipart/byteranges media type.
098 * A response to a request for multiple ranges, whose result is a single range, MAY be sent as a multipart/byteranges
099 * media type with one part.
100 * A client that cannot decode a multipart/byteranges message MUST NOT ask for multiple byte-ranges in a single request.
101 * 
102 * <p>
103 * When a client requests multiple byte-ranges in one request, the server SHOULD return them in the order that they
104 * appeared in the request.
105 * 
106 * <p>
107 * If the server ignores a byte-range-spec because it is syntactically invalid, the server SHOULD treat the request as
108 * if the invalid Range header field did not exist.
109 * (Normally, this means return a 200 response containing the full entity).
110 * 
111 * <p>
112 * If the server receives a request (other than one including an If- Range request-header field) with an unsatisfiable
113 * Range request- header field
114 * (that is, all of whose byte-range-spec values have a first-byte-pos value greater than the current length of the
115 * selected resource),
116 * it SHOULD return a response code of 416 (Requested range not satisfiable) (section 10.4.17).
117 * 
118 * <p>
119 * Note: clients cannot depend on servers to send a 416 (Requested range not satisfiable) response instead of a 200 (OK)
120 * response for
121 * an unsatisfiable Range request-header, since not all servers implement this request-header.
122 * 
123 * <h5 class='section'>See Also:</h5>
124 * <ul class='doctree'>
125 *    <li class='extlink'><a class='doclink' href='https://www.w3.org/Protocols/rfc2616/rfc2616.html'>Hypertext Transfer Protocol -- HTTP/1.1</a>
126 * </ul>
127 */
128public final class ContentRange extends HeaderString {
129
130   /**
131    * Returns a parsed <code>Content-Range</code> header.
132    * 
133    * @param value The <code>Content-Range</code> header string.
134    * @return The parsed <code>Content-Range</code> header, or <jk>null</jk> if the string was null.
135    */
136   public static ContentRange forString(String value) {
137      if (value == null)
138         return null;
139      return new ContentRange(value);
140   }
141
142   private ContentRange(String value) {
143      super(value);
144   }
145}