HTTP2：是否可以在流上发送后续或额外的 HEADER 块？

Question

Node 提供了这个方法：

http2stream.additionalHeaders(headers)

哪个Sends an additional informational HEADERS frame to the connected HTTP/2 peer.

但是节点代码库包含此注释：

// Sends a block of informational headers. In theory, the HTTP/2 spec
// allows sending a HEADER block at any time during a streams lifecycle,
// but the HTTP request/response semantics defined in HTTP/2 places limits
// such that HEADERS may only be sent *before* or *after* DATA frames.
// If the block of headers being sent includes a status code, it MUST be
// a 1xx informational code and it MUST be sent before the request/response
// headers are sent, or an error will be thrown.

是否可以在流中发送后续或额外的 HEADER 块？

例如伪代码：

stream.respond(HEADER)
stream.write(DATA)
stream.additionalHeaders(HEADER)
stream.write(DATA)
stream.end(DATA)

并且：

• 如果可能请提供一些演示代码；或

• 如果不是additionalHeaders函数的意义是什么，作为response事件returnsheader是什么意义headers 事件?

Answer 1

根据评论，以下内容无效 HTTP/2：

stream.respond(HEADER)
stream.write(DATA)
stream.additionalHeaders(HEADER)
stream.write(DATA)
stream.end(DATA)

但以下是：

stream.respond(HEADER)
stream.write(DATA)
stream.additionalHeaders(HEADER)

这允许您发送一个 trailing header，通常用于动态生成的内容的校验和或其他完整性检查，这些动态生成的内容无法提前知道发送第一个 Headers 请求（它更适合于提前发送headers。