HTTP2：是否可以在一个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.

然而节点代码库中包含这样的注释。

// 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.

是否可以在一个流上发送后续或额外的HEADER块？

如：伪代码。

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

And:

• 如果可能的话，请提供一些演示代码；或者

• 否则，何必 additionalHeaders 的功能，而作为 response 事件返回的头是什么点。headers 事件？

Answer 1

根据注释，以下是无效的HTTP2。

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

但下面是有效的

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

这允许你发送一个 页眉，通常用于对动态生成的内容进行校验和或其他完整性检查，这些内容无法在第一次Headers请求中提前知道发送（提前发送headers比之后发送headers更可取）。