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Bytes are numbered from 0. 022 * 023 * <h5 class='figure'>Example</h5> 024 * <p class='bcode w800'> 025 * Range: bytes=500-999 026 * </p> 027 * 028 * <h5 class='topic'>RFC2616 Specification</h5> 029 * 030 * Since all HTTP entities are represented in HTTP messages as sequences of bytes, the concept of a byte range is 031 * meaningful for any HTTP entity. 032 * (However, not all clients and servers need to support byte- range operations.) 033 * 034 * <p> 035 * Byte range specifications in HTTP apply to the sequence of bytes in the entity-body (not necessarily the same as the 036 * message-body). 037 * 038 * <p> 039 * A byte range operation MAY specify a single range of bytes, or a set of ranges within a single entity. 040 * <p class='bcode w800'> 041 * ranges-specifier = byte-ranges-specifier 042 * byte-ranges-specifier = bytes-unit "=" byte-range-set 043 * byte-range-set = 1#( byte-range-spec | suffix-byte-range-spec ) 044 * byte-range-spec = first-byte-pos "-" [last-byte-pos] 045 * first-byte-pos = 1*DIGIT 046 * last-byte-pos = 1*DIGIT 047 * </p> 048 * 049 * <p> 050 * The first-byte-pos value in a byte-range-spec gives the byte-offset of the first byte in a range. 051 * The last-byte-pos value gives the byte-offset of the last byte in the range; that is, the byte positions specified 052 * are inclusive. 053 * Byte offsets start at zero. 054 * 055 * <p> 056 * If the last-byte-pos value is present, it MUST be greater than or equal to the first-byte-pos in that 057 * byte-range-spec, or the byte- range-spec is syntactically invalid. 058 * The recipient of a byte-range- set that includes one or more syntactically invalid byte-range-spec values MUST 059 * ignore the header field that includes that byte-range-set. 060 * 061 * <p> 062 * If the last-byte-pos value is absent, or if the value is greater than or equal to the current length of the 063 * entity-body, last-byte-pos is taken to be equal to one less than the current length of the entity-body in bytes. 064 * 065 * <p> 066 * By its choice of last-byte-pos, a client can limit the number of bytes retrieved without knowing the size of the 067 * entity. 068 * <p class='bcode w800'> 069 * suffix-byte-range-spec = "-" suffix-length 070 * suffix-length = 1*DIGIT 071 * </p> 072 * 073 * <p> 074 * A suffix-byte-range-spec is used to specify the suffix of the entity-body, of a length given by the suffix-length 075 * value. 076 * (That is, this form specifies the last N bytes of an entity-body.) 077 * If the entity is shorter than the specified suffix-length, the entire entity-body is used. 078 * 079 * <p> 080 * If a syntactically valid byte-range-set includes at least one byte- range-spec whose first-byte-pos is less than the 081 * current length of the entity-body, or at least one suffix-byte-range-spec with a non-zero suffix-length, then the 082 * byte-range-set is satisfiable. 083 * Otherwise, the byte-range-set is unsatisfiable. 084 * If the byte-range-set is unsatisfiable, the server SHOULD return a response with a status of 416 (Requested range 085 * not satisfiable). 086 * Otherwise, the server SHOULD return a response with a status of 206 (Partial Content) containing the satisfiable 087 * ranges of the entity-body. 088 * 089 * <p> 090 * Examples of byte-ranges-specifier values (assuming an entity-body of length 10000): 091 * <p class='bcode w800'> 092 * - The first 500 bytes (byte offsets 0-499, inclusive): bytes=0-499 093 * - The second 500 bytes (byte offsets 500-999, inclusive): bytes=500-999 094 * - The final 500 bytes (byte offsets 9500-9999, inclusive): bytes=-500 095 * - Or bytes=9500- 096 * - The first and last bytes only (bytes 0 and 9999): bytes=0-0,-1 097 * - Several legal but not canonical specifications of the second 500 bytes (byte offsets 500-999, inclusive): 098 * bytes=500-600,601-999 099 * bytes=500-700,601-999 100 * </p> 101 * 102 * <p> 103 * HTTP retrieval requests using conditional or unconditional GET methods MAY request one or more sub-ranges of the 104 * entity, instead of the entire entity, using the Range request header, which applies to the entity returned as the 105 * result of the request: 106 * 107 * <p class='bcode w800'> 108 * Range = "Range" ":" ranges-specifier 109 * </p> 110 * 111 * <p> 112 * A server MAY ignore the Range header. 113 * However, HTTP/1.1 origin servers and intermediate caches ought to support byte ranges when possible, since Range 114 * supports efficient recovery from partially failed transfers, and supports efficient partial retrieval of large 115 * entities. 116 * 117 * <p> 118 * If the server supports the Range header and the specified range or ranges are appropriate for the entity: 119 * <ul> 120 * <li>The presence of a Range header in an unconditional GET modifies what is returned if the GET is otherwise 121 * successful. 122 * In other words, the response carries a status code of 206 (Partial Content) instead of 200 (OK). 123 * <li>The presence of a Range header in a conditional GET (a request using one or both of If-Modified-Since and 124 * If-None-Match, or one or both of If-Unmodified-Since and If-Match) modifies what is returned if the GET is 125 * otherwise successful and the condition is true. It does not affect the 304 (Not Modified) response returned if 126 * the conditional is false. 127 * </ul> 128 * 129 * <p> 130 * In some cases, it might be more appropriate to use the If-Range header (see section 14.27) in addition to the Range 131 * header. 132 * 133 * <p> 134 * If a proxy that supports ranges receives a Range request, forwards the request to an inbound server, and receives an 135 * entire entity in reply, it SHOULD only return the requested range to its client. 136 * It SHOULD store the entire received response in its cache if that is consistent with its cache allocation policies. 137 * 138 * <h5 class='section'>See Also:</h5> 139 * <ul class='doctree'> 140 * <li class='extlink'>{@doc RFC2616} 141 * </ul> 142 */ 143@Header("Range") 144public final class Range extends HeaderString { 145 146 /** 147 * Returns a parsed <code>Range</code> header. 148 * 149 * @param value The <code>Range</code> header string. 150 * @return The parsed <code>Range</code> header, or <jk>null</jk> if the string was null. 151 */ 152 public static Range forString(String value) { 153 if (value == null) 154 return null; 155 return new Range(value); 156 } 157 158 private Range(String value) { 159 super(value); 160 } 161}