Just as in HTTP/1, a header field in HTTP/2 is a name with one or more associated values. Header fields are used within HTTP request and response messages as well as in server push operations (see Section 8.2).
正如在HTTP/1里那样，HTTP/2里的首部字段也是一个键具有一个或多个值。这些首部字段用于HTTP请求和响应消息，也用于服务端推送操作( 8.2节 )。
Header lists are collections of zero or more header fields. When transmitted over a connection, a header list is serialized into a header block using HTTP header compression [COMPRESSION]. The serialized header block is then divided into one or more octet sequences, called header block fragments, and transmitted within the payload of HEADERS (Section 6.2), PUSH_PROMISE (Section 6.6), or CONTINUATION (Section 6.10) frames.
首部列表是零个或多个首部字段的集合。当通过连接传送时，首部列表被 HTTP首部压缩 *[COMPRESSION]*序列化成首部块。然后，序列化的首部块又被划分成一个或多个叫做首部块片段的字节序列，并通过HEADERS( 6.2节 )、PUSH_PROMISE( 6.6节 )，或者CONTINUATION( 6.10节 )帧的有效负载传送。
The Cookie header field [COOKIE] is treated specially by the HTTP mapping (see Section 8.1.2.5).
Cookie首部字段 [COOKIE] 需要HTTP映射特殊对待(参见 8.1.2.5节 )。
A receiving endpoint reassembles the header block by concatenating its fragments and then decompresses the block to reconstruct the header list.
接收端连接片段重组首部块，然后解压首部块重建首部列表。
A complete header block consists of either:
- a single HEADERS or PUSH_PROMISE frame, with the END_HEADERS flag set, or
- a HEADERS or PUSH_PROMISE frame with the END_HEADERS flag cleared and one or more CONTINUATION frames, where the last CONTINUATION frame has the END_HEADERS flag set.
一个完整的首部块包括以下二者之一：
- 一个单独的、设置了END_HEADERS标识的 HEADERS 或 PUSH_PROMISE 帧，或者
- 一个单独的、清除了END_HEADERS标识的 HEADERS 或 PUSH_PROMISE 帧，并有一个或多个 CONTINUATION 帧，且最后一个 CONTINUATION 帧设置了END_HEADERS标识。
Header compression is stateful. One compression context and one decompression context are used for the entire connection. A decoding error in a header block MUST be treated as a connection error (Section 5.4.1) of type COMPRESSION_ERROR.
首部压缩是有状态的。一个连接具有一个压缩上下文和一个解压缩上下文。必须将首部块解码错误当做类型为 COMPRESSION_ERROR 的连接错误( 5.4.1节 )处理。
Each header block is processed as a discrete unit. Header blocks MUST be transmitted as a contiguous sequence of frames, with no interleaved frames of any other type or from any other stream. The last frame in a sequence of HEADERS or CONTINUATION frames has the END_HEADERS flag set. The last frame in a sequence of PUSH_PROMISE or CONTINUATION frames has the END_HEADERS flag set. This allows a header block to be logically equivalent to a single frame.
将每个首部块当做离散的单元处理。必须将首部块作为连续的帧序列传送，而没有交错任何其他类型或其他流的帧。HEADERS 或 CONTINUATION 帧序列的最后一个帧设置END_HEADERS标识。PUSH_PROMISE 或 CONTINUATION 帧序列的最后一个帧设置END_HEADERS标识。这让首部块在逻辑上等价于一个单独的帧。
Header block fragments can only be sent as the payload of HEADERS, PUSH_PROMISE, or CONTINUATION frames because these frames carry data that can modify the compression context maintained by a receiver. An endpoint receiving HEADERS, PUSH_PROMISE, or CONTINUATION frames needs to reassemble header blocks and perform decompression even if the frames are to be discarded. A receiver MUST terminate the connection with a connection error (Section 5.4.1) of type COMPRESSION_ERROR if it does not decompress a header block.
首部块片段只能作为 HEADERS 、PUSH_PROMISE ，或 CONTINUATION 帧的有效载荷进行传送，因为这些帧携带的数据能修改接收端维护的压缩上下文。即使收到要被丢弃的 HEADERS 、PUSH_PROMISE ，或 CONTINUATION 帧，接收端点也需要重组首部块并解压。如果接收端不解压首部块，它必须用类型为 COMPRESSION_ERROR 的连接错误( 5.4.1节 )终止连接。