= U+0021 U+007E
Since all HTTP entities are represented in HTTP messages as sequences of bytes, the concept of a byte range is meaningful for any HTTP entity. (However, not all clients and servers need to support byte-range operations.)
Byte range specifications in HTTP apply to the sequence of bytes in the entity-body (not necessarily the same as the message-body).
HTTP でのバイト範囲指定は、
A byte range operation
mayMAY specify a single range of bytes, or a set of ranges within a single entity.
バイト範囲操作は単一の範囲か、または単一の実体内の範囲の集合を指定して構いません。
- ranges-specifier = byte-ranges-specifier
- byte-ranges-specifier = bytes-unit "=" byte-range-set
- byte-range-set = 1#( byte-range-spec | suffix-byte-range-spec )
- byte-range-spec = first-byte-pos "-" [last-byte-pos]
- first-byte-pos = 1*DIGIT
- last-byte-pos = 1*DIGIT
The first-byte-pos value in a byte-range-spec gives the byte-offset of the first byte in a range. The last-byte-pos value gives the byte-offset of the last byte in the range; that is, the byte positions specified are inclusive. Byte offsets start at zero.
byte-range-spec の first-byte-pos
値は、範囲中の最初のバイトのバイト offset
を与えます。 last-byte-pos 値は範囲中の最後のバイトのバイト
offset を与えます。つまり、指定されたバイト位置は範囲に含まれます。
バイト offset は零から始めます。
If the last-byte-pos value is present, it
mustMUST be greater than or equal to the first-byte-pos in that byte-range-spec, or the byte-range-spec is syntactically invalid. The recipient of a byte-range-set that includes one or more syntacticallyaninvalid byte-range-spec values MUSTmustignoreitthe header field that includes that byte-range-set.
last-byte-pos 値が示されるときは、その byte-range-spec
の first-byte-pos 以上でなければなりません。
そうでなければ構文的に不当です。一つ以上の構文的に不正な
byte-range-spec 値を含む byte-range-set
の受信者は、その byte-range-set を含む頭欄を無視しなければなりません。
If the last-byte-pos value is absent, or if the value is greater than or equal to the current length of the entity-body, last-byte-pos is taken to be equal to one less than the current length of the entity-body in bytes.
last-byte-pos が欠けている場合、あるいは entity-body
の現在の長さ以上のときは、 last-byte-pos は現在の
entity-body のバイト長より一小さいものと取ります。
By its choice of last-byte-pos, a client can limit the number of bytes retrieved without knowing the size of the entity.
last-byte-pos を選ぶことにより、クライアントは実体の寸法を知らなくても取り出すバイト数を制限できます。
- suffix-byte-range-spec = "-" suffix-length
- suffix-length = 1*DIGIT
A suffix-byte-range-spec is used to specify the suffix of the entity-body, of a length given by the suffix-length value. (That is, this form specifies the last N bytes of an entity-body.) If the entity is shorter than the specified suffix-length, the entire entity-body is used.
suffix-byte-range-spec は、 entity-body
の接尾部を suffix-length 値で与えた長さ分指定するのに使います。
(つまり、この書式は entity-body の最後の N
バイトを指定します。) suffix-length
よりも短い場合には、 entity-body 全体を使います。
If a syntactically valid byte-range-set includes at least one byte-range-spec whose first-byte-pos is less than the current length of the entity-body, or at least one suffix-byte-range-spec with a non-zero suffix-length, then the byte-range-set is satisfiable. Otherwise, the byte-range-set is unsatisfiable. If the byte-range-set is unsatisfiable, the server SHOULD return a response with a status of 416 (Requested range not satisfiable). Otherwise, the server SHOULD return a response with a status of 206 (Partial Content) containing the satisfiable ranges of the entity-body.
構文的に妥当な byte-range-set が entity-body
の現在の長さより小さい first-byte-pos の
byte-range-spec を最低一つ含んでいる場合や、
非零 suffix-length の suffix-byte-range-spec
を最低一つ含んでいる場合には、 byte-range-set は満足可能です。
そうでなければ、 byte-range-set は満足不能です。
byte-range-set が満足不能であれば、鯖は状態
entity-body
を含んだ
Examples of byte-ranges-specifier values (assuming an entity-body of length 10000):
byte-ranges-specifier 値の例
(長さ 10000 の entity-body を仮定):
o- The first 500 bytes (byte offsets 0-499, inclusive): bytes=0-499o- The second 500 bytes (byte offsets 500-999, inclusive): bytes=500-999o- The final 500 bytes (byte offsets 9500-9999, inclusive): bytes=-500o- Or bytes=9500-o- The first and last bytes only (bytes 0 and 9999): bytes=0-0,-1o- Several legal but not canonical specifications of the second 500 bytes (byte offsets 500-999, inclusive):
- bytes=500-600,601-999
- bytes=500-700,601-999
HTTP retrieval requests using conditional or unconditional GET methods
mayMAY request one or more sub-ranges of the entity, instead of the entire entity, using the Range request header, which applies to the entity returned as the result of the request:
条件付または条件付でない Range 要求頭を使って、
実体全体ではなく、実体の一つ以上の部分範囲を要求して構いません。
- Range = "Range" ":" ranges-specifier
A server MAY ignore the Range header. However, HTTP/1.1 origin servers and intermediate caches
SHOULDought to support byte ranges when possible, since Range supports efficient recovery from partially failed transfers, and supports efficient partial retrieval of large entities.
鯖は、 Range 頭を無視しても構いません。
しかし、 HTTP/1.1 Range は部分的に失敗した転送から効率よく回復することや大きな実体の部分を効率的に取り出すことを支援するからです。
If the server supports the Range header and the specified range or ranges are appropriate for the entity:
o- The presence of a Range header in an unconditional GET modifies what is returned if the GET is otherwise successful. In other words, the response carries a status code of 206 (Partial Content) instead of 200 (OK).o- The presence of a Range header in a conditional GET (a request using one or both of If-Modified-Since and If-None-Match, or one or both of If-Unmodified-Since and If-Match) modifies what is returned if the GET is otherwise successful and the condition is true. It does not affect the 304 (Not Modified) response returned if the conditional is false.
鯖が Range 頭に対応し、指定された範囲(群)がその実体について適当であるなら、
GET での Range 頭の存在は、
GET が本来成功であるなら返されるものを修飾します。
言い換えれば、応答は状態符号 200 206 GET
(If-Modified-Since If-None-Match If-Unmodified-Since If-Match Range 頭の存在は、 GET
が本来成功であって、条件が真であるなら返されるものを修飾します。
条件が偽であるときに返される 304 In some cases, it
maymight be more appropriate to use the If-Range header (see section 14.27) in addition to the Range header.
場合によっては、 Range 頭に加えて
If a proxy that supports ranges receives a Range request, forwards the request to an inbound server, and receives an entire entity in reply, it SHOULD only return the requested range to its client. It SHOULD store the entire received response in its cache
,if that is consistent with its cache allocation policies.
範囲に対応したRange 要求を受信し、
This header will be mandatory in version 2.0. It should tell the bounding box for an area on the globe for which data are requested.
Range: xpointer=element(a12)
結果は
XPointer scheme として
大変面白いアイデアですが、技術的問題点を指摘しておくなら、
U+0000 U+10FFFF などの問題を解決する必要があります。
xpointer=
が抜けた構文になっていて、 HTTP 的には最悪な状況になっています。
これは
Range の構文は更にひどくて、 XPointer ですらなく、単なる RDQL
直書きになってしまっています。)
結果は複数の
こちらは
This request and response header field specifies a range of time. The range can be specified in a number of units. This specification defines the smpte (Section 3.5), npt (Section 3.6), and clock (Section 3.7) range units. Within RTSP, byte ranges [H14.36.1] are not meaningful and MUST NOT be used. The header may also contain a time parameter in UTC, specifying the time at which the operation is to be made effective. Servers supporting the Range header MUST understand the NPT range format and SHOULD understand the SMPTE range format. The Range response header indicates what range of time is actually being played or recorded. If the Range header is given in a time format that is not understood, the recipient should return "501 Not Implemented".
Ranges are half-open intervals, including the lower point, but excluding the upper point. In other words, a range of a-b starts exactly at time a, but stops just before b. Only the start time of a media unit such as a video or audio frame is relevant. As an example, assume that video frames are generated every 40 ms. A range of 10.0-10.1 would include a video frame starting at 10.0 or later time and would include a video frame starting at 10.08, even though it lasted beyond the interval. A range of 10.0-10.08, on the other hand, would exclude the frame at 10.08.
10.0 かそれ以降の時刻に始まる動画枠を含み、
10.08 に始まる動画枠も (終わるのは間隔を超えますが) 含みます。
一方範囲 10.0-10.08 は 10.08 の枠を除きます。
訳注:
Example:
[5] Range: clock=19960213T143205Z-;time=19970123T143720Z
The notation is similar to that used for the HTTP/1.1 [2] byte-range header. It allows clients to select an excerpt from the media object, and to play from a given point to the end as well as from the current location to a given point. The start of playback can be scheduled for any time in the future, although a server may refuse to keep server resources for extended idle periods.
byte
範囲頭に使われているものと似ています。
これによりクライアントが媒体物体からの除外を選択出来、指定点から演奏して指定点で終えることや現在位置から指定点まで演奏することが出来ます。
録音再生の開始は将来のどの時刻にも予定出来ますが、サーバーは待機期間を延ばすためのサーバー資源の確保を拒むかもしれません。