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diff --git a/guide/internals.md b/guide/internals.md index 431ca01..8acf75b 100644 --- a/guide/internals.md +++ b/guide/internals.md @@ -6,6 +6,30 @@ Architecture @todo Describe. +Lowercase header names +---------------------- + +For consistency reasons it has been chosen to convert all header names +to lowercase binary strings. This prevents the programmer from making +case mistakes, and is possible because header names are case insensitive. + +This works fine for the large majority of clients. However, some badly +implemented clients, especially ones found in corporate code or closed +source products, may not handle header names in a case insensitive manner. +This means that when Cowboy returns lowercase header names, these clients +will not find the headers they are looking for. + +A simple way to solve this is to create an `onresponse` hook that will +format the header names with the expected case. + +``` erlang +capitalize_hook(Status, Headers, Body, Req) -> + Headers2 = [{cowboy_bstr:capitalize_token(N), V} + || {N, V} <- Headers], + {ok, Req2} = cowboy_req:reply(State, Headers2, Body, Req), + Req2. +``` + Efficiency considerations ------------------------- |