Structured Header Mappings

This is a mapping of existing common (not all) HTTP headers into the closest Structured Headers, along with notes about potential issues, mismatches, etc.

Just because a header value fits into a structured header type syntactically, doesn't mean SH can be used for it; for example, error handling is probably different between SH and existing implementations.

• Accept
• Accept-Encoding
• Accept-Language
• Alt-Svc
• Content-Type - single value; parameterised item?
• Forwarded
• TE

• Cache-Control
• Pragma
• Surrogate-Control
• Prefer
• Preference-Applied
• Digest - dict of identifiers, digest values

• Age
• Content-Length
• Access-Control-Max-Age

See this issue

• Alt-Used: identifier - uses :
• Host - hostname
• Content-Encoding - token
• Expect - token
• Origin - hostname
• Access-Control-Allow-Credentials
• Access-Control-Request-Method - method
• X-Content-Type-Options
• Access-Control-Allow-Origin - uses :

• Accept-Patch
• Accept-Ranges
• Allow
• ALPN - percent-encoded
• Content-Language
• Transfer-Encoding
• Vary
• Trailer
• Access-Control-Allow-Headers - field-name
• Access-Control-Allow-Methods - method
• Access-Control-Request-Headers - field-name

A viable strategy might be to define a H2 SETTING (etc) that creates a mapping between new headers and "old" ones; e.g., Cookie -> SH-Cookie.

Serialise as string

• Content-Location
• Location
• Referer

Serialise as integer? See this issue

• Date
• Expires
• If-Modified-Since
• If-Unmodified-Since
• Last-Modified

• Early-Data - integer or boolean
• Retry-After - integer / Date
• Cookie: NO (semicolon-separated)
• Set-Cookie: NO (semicolon-separated)
• Strict-Transport-Security: NO (semicolon-separated)
• Authorization: NO
• WWW-Authenticate: NO
• Content-Disposition: NO (i18n)
• Content-Range: NO (range structure)
• Range: NO (range structure)
• ETag: NO (weak flag)
• If-None-Match: NO (weak flag)
• If-Match: NO (alternate forms, weak flag)
• If-Range: NO (alternate forms)
• Link: NO (link structure)
• Via: NO (product/comment)
• Server: NO (product/comment)
• User-Agent: NO (product/comment)