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The Header module provides types and functions for working with parsed HTTP headers.
Type Definition
type t =
{ name : Name.t
; name_span : Span.t
; value : Span.t
}
name_span field is only meaningful when name = Other.
Typed header name (e.g., Content_type, Authorization, or Other for unknown headers)
Span pointing to the header name in the buffer. Only used when name = Other to access the actual header name string.
Span pointing to the header value in the buffer
Module Alias
Name
module Name = Header_name
Header_name module for convenient access to header name types and functions. See the Header_name documentation for details.
Functions
find
val find : t list @ local -> Name.t -> t option @ local
find_string for Other headers.
List of headers to search
Typed header name to search for (e.g., Content_type, Authorization)
Some header if found, None if not found
Example:
open Httpz
let get_content_type headers =
match Header.find headers Header_name.Content_type with
| Some h -> Some (Span.to_string buf h.value)
| None -> None
Name.t enumeration. For custom/unknown headers (those parsed as Other), use find_string instead.
find_string
val find_string : Base_bigstring.t -> t list @ local -> string -> t option @ local
Buffer containing the header data
List of headers to search
Header name to search for (case-insensitive)
Some header if found, None if not found
Example:
(* Find a custom header *)
let get_custom_header buf headers =
match Header.find_string buf headers "X-Custom-Header" with
| Some h -> Some (Span.to_string buf h.value)
| None -> None
(* Case-insensitive matching *)
let auth = Header.find_string buf headers "authorization" in
let auth2 = Header.find_string buf headers "Authorization" in
(* Both will match the same header *)
pp_with_buf
val pp_with_buf : Base_bigstring.t -> Stdlib.Format.formatter -> t -> unit
Buffer containing the header data
Formatter to write output to
(* Prints: "Content-Type: application/json" *)
Header.pp_with_buf buf Format.std_formatter header
val pp : Stdlib.Format.formatter -> t -> unit
Formatter to write output to
(* Prints the record structure with span offsets *)
Header.pp Format.std_formatter header
(* Output: { name = Content_type; name_span = #{ off = 0; len = 12 }; value = #{ off = 14; len = 16 } } *)
Usage Examples
open Httpz
let process_headers buf headers =
(* Look up Content-Type *)
let content_type =
match Header.find headers Header_name.Content_type with
| Some h -> Span.to_string buf h.value
| None -> "application/octet-stream" (* default *)
in
(* Look up Authorization *)
let auth_token =
match Header.find headers Header_name.Authorization with
| Some h -> Some (Span.to_string buf h.value)
| None -> None
in
(content_type, auth_token)
let get_custom_headers buf headers =
(* Find custom application headers *)
let request_id = Header.find_string buf headers "X-Request-ID" in
let correlation_id = Header.find_string buf headers "X-Correlation-ID" in
let api_key = Header.find_string buf headers "X-API-Key" in
match (request_id, correlation_id, api_key) with
| (Some rid, Some cid, Some key) ->
{ request_id = Span.to_string buf rid.value
; correlation_id = Span.to_string buf cid.value
; api_key = Span.to_string buf key.value
}
| _ -> failwith "Missing required headers"
let requires_auth headers =
(* Check if Authorization header is present *)
match Header.find headers Header_name.Authorization with
| Some _ -> true
| None -> false
let is_json_content headers =
(* Check if Content-Type is JSON *)
match Header.find headers Header_name.Content_type with
| Some h when Span.equal buf h.value "application/json" -> true
| _ -> false
let print_all_headers buf headers =
List.iter headers ~f:(fun header ->
let name_str = match header.name with
| Header_name.Other -> Span.to_string buf header.name_span
| known -> Header_name.canonical known
in
let value_str = Span.to_string buf header.value in
Printf.printf "%s: %s\n" name_str value_str
)
let get_accept_headers buf headers =
(* Headers can appear multiple times *)
List.filter_map headers ~f:(fun h ->
match h.name with
| Header_name.Accept -> Some (Span.to_string buf h.value)
| _ -> None
)
Conditional Processing
let should_compress buf headers =
match Header.find headers Header_name.Accept_encoding with
| Some h ->
let encoding = Span.to_string buf h.value in
String.is_substring encoding ~substring:"gzip" ||
String.is_substring encoding ~substring:"deflate"
| None -> false
let get_cache_control buf headers =
match Header.find headers Header_name.Cache_control with
| Some h ->
let value = Span.to_string buf h.value in
if String.is_substring value ~substring:"no-cache" then
`No_cache
else if String.is_substring value ~substring:"no-store" then
`No_store
else
`Default
| None -> `Default
Working with Cookies
let get_cookies buf headers =
match Header.find headers Header_name.Cookie with
| Some h ->
let cookie_str = Span.to_string buf h.value in
(* Parse cookie string *)
String.split cookie_str ~on:';'
|> List.map ~f:String.strip
|> List.filter_map ~f:(fun pair ->
match String.lsplit2 pair ~on:'=' with
| Some (k, v) -> Some (String.strip k, String.strip v)
| None -> None
)
| None -> []
