add more doc

src/Tiny_httpd.mli

@@ -1,12 +1,34 @@
+
+(** {1 Tiny Http Server}
+
+    This library implements a very simple, basic HTTP/1.1 server using blocking
+    IOs and threads. Basic routing based on {!Scanf} is provided for convenience,
+    so that several handlers can be registered.
+
+    It is possible to use a thread pool, see {!create}'s argument [new_thread].
+*)
+
 type stream = {
   is_fill_buf: unit -> (bytes * int * int);
+  (** See the current slice of the internal buffer as [bytes, i, len],
+      where the slice is [bytes[i] .. [bytes[i+len-1]]].
+      Can block to refill the buffer if there is currently no content.
+      If [len=0] then there is no more data. *)
   is_consume: int -> unit;
+  (** Consume n bytes from the buffer. This should only be called with [n <= len]
+      after a call to [is_fill_buf] that returns a slice of length [len]. *)
   is_close: unit -> unit;
+  (** Close the stream. *)
 }
-(** A buffer input stream, with a view into the current buffer (or refill if empty),
-    and a function to consume [n] bytes *)
+(** A buffered stream, with a view into the current buffer (or refill if empty),
+    and a function to consume [n] bytes.
+    See {!Buf_} for more details. *)
 
-(** {2 Tiny buffer implementation} *)
+(** {2 Tiny buffer implementation}
+
+    These buffers are used to avoid allocating too many byte arrays when
+    processing streams and parsing requests.
+*)
 module Buf_ : sig
   type t
   val size : t -> int
@@ -15,19 +37,36 @@ module Buf_ : sig
   val contents : t -> string
 end
 
-(** {2 Generic stream of data} *)
+(** {2 Generic stream of data}
+
+  Streams are used to represent a series of bytes that can arrive progressively.
+    For example, an uploaded file will be sent as a series of chunks. *)
 module Stream_ : sig
   type t = stream
 
   val close : t -> unit
+
   val of_chan : in_channel -> t
+  (** Make a buffered stream from the given channel. *)
+
   val of_chan_close_noerr : in_channel -> t
+  (** Same as {!of_chan} but the [close] method will never fail. *)
+
   val of_bytes : ?i:int -> ?len:int -> bytes -> t
+  (** A stream that just returns the slice of bytes starting from [i]
+      and of length [len]. *)
+
   val with_file : string -> (t -> 'a) -> 'a
-  (** Open a file with given name, and obtain an input stream *)
+  (** Open a file with given name, and obtain an input stream
+      on its content. When the function returns, the stream (and file) are closed. *)
 
   val read_line : ?buf:Buf_.t -> t -> string
+  (** Read a line from the stream.
+      @param buf a buffer to (re)use. Its content will be cleared. *)
+
   val read_all : ?buf:Buf_.t -> t -> string
+  (** Read the whole stream into a string.
+      @param buf a buffer to (re)use. Its content will be cleared. *)
 end
 
 module Meth : sig
@@ -38,6 +77,10 @@ module Meth : sig
     | `HEAD
     | `DELETE
   ]
+  (** A HTTP method.
+      For now we only handle a subset of these.
+
+      See https://tools.ietf.org/html/rfc7231#section-4 *)
 
   val pp : Format.formatter -> t -> unit
   val to_string : t -> string
@@ -45,13 +88,32 @@ end
 
 module Headers : sig
   type t = (string * string) list
+  (** The header files of a request or response.
+
+      Neither the key nor the value can contain ['\r'] or ['\n'].
+      See https://tools.ietf.org/html/rfc7230#section-3.2 *)
+
   val get : ?f:(string->string) -> string -> t -> string option
+  (** [get k headers] looks for the header field with key [k].
+      @param f if provided, will transform the value before it is returned. *)
+
   val set : string -> string -> t -> t
+  (** [set k v headers] sets the key [k] to value [v].
+      It erases any previous entry for [k] *)
+
   val remove : string -> t -> t
+  (** Remove the key from the headers, if present. *)
+
   val contains : string -> t -> bool
+  (** Is there a header with the given key? *)
+
   val pp : Format.formatter -> t -> unit
+  (** Pretty print the headers. *)
 end
 
+(** {2 HTTP request}
+
+    A request sent by a client. *)
 module Request : sig
   type 'body t = {
     meth: Meth.t;
@@ -59,63 +121,110 @@ module Request : sig
     path: string;
     body: 'body;
   }
+(** A request with method, path, headers, and a body.
+
+    The body is polymorphic because the request goes through
+    several transformations. First it has no body, as only the request
+    and headers are read; then it has a stream body; then the body might be
+    entirely read as a string via {!read_body_full}. *)
 
   val pp : Format.formatter -> string t -> unit
+  (** Pretty print the request and its body *)
+
   val pp_ : Format.formatter -> _ t -> unit
+  (** Pretty print the request without its body *)
 
   val headers : _ t -> Headers.t
+
   val get_header : ?f:(string->string) -> _ t -> string -> string option
+
   val get_header_int : _ t -> string -> int option
+
   val set_header : 'a t -> string -> string -> 'a t
+
   val meth : _ t -> Meth.t
+
   val path : _ t -> string
+
   val body : 'b t -> 'b
+
   val read_body_full : stream t -> string t
+  (** Read the whole body into a string. Potentially blocking. *)
 end
 
+(** {2 Response code} *)
 module Response_code : sig
   type t = int
+  (** A standard HTTP code.
+
+      https://tools.ietf.org/html/rfc7231#section-6 *)
+
   val ok : t
+  (** The code [200] *)
+
   val not_found : t
+  (** The code [404] *)
+
   val descr : t -> string
+  (** A description of some of the error codes.
+      NOTE: this is not complete (yet). *)
 end
 
+(** {2 Response}
+
+    A response sent back to a client. *)
 module Response : sig
   type body = [`String of string | `Stream of stream]
+  (** Body of a response, either as a simple string,
+      or a stream of bytes. *)
+
   type t = {
-    code: Response_code.t;
-    headers: Headers.t;
-    body: body;
+    code: Response_code.t; (** HTTP response code. See {!Response_code}. *)
+    headers: Headers.t; (** Headers of the reply. Some will be set by [Tiny_httpd] automatically. *)
+    body: body; (** Body of the response. Can be empty. *)
   }
+  (** A response. *)
 
   val make_raw :
     ?headers:Headers.t ->
     code:Response_code.t ->
     string ->
     t
+  (** Make a response from its raw components, with a string body.
+      Use [""] to not send a body at all. *)
 
   val make_raw_stream :
     ?headers:Headers.t ->
     code:Response_code.t ->
     stream ->
     t
+  (** Same as {!make_raw} but with a stream body. The body will be sent with
+      the chunked transfer-encoding. *)
 
   val make :
     ?headers:Headers.t ->
     (body, Response_code.t * string) result -> t
+  (** [make r] turns a result into a response.
+
+      - [make (Ok body)] replies with [200] and the body.
+      - [make (Error (code,msg))] replies with the given error code
+        and message as body.
+  *)
 
   val make_string :
     ?headers:Headers.t ->
     (string, Response_code.t * string) result -> t
+  (** Same as {!make} but with a string body. *)
 
   val make_stream :
     ?headers:Headers.t ->
     (stream, Response_code.t * string) result -> t
+  (** Same as {!make} but with a stream body. *)
 
   val fail : ?headers:Headers.t -> code:int ->
     ('a, unit, string, t) format4 -> 'a
   (** Make the current request fail with the given code and message.
-      Example: [fail ~code:404 "oh noes, %s not found" "waldo"]
+      Example: [fail ~code:404 "oh noes, %s not found" "waldo"].
   *)
 
   val fail_raise : code:int -> ('a, unit, string, 'b) format4 -> 'a
@@ -125,9 +234,11 @@ module Response : sig
   *)
 
   val pp : Format.formatter -> t -> unit
+  (** Pretty print the response. *)
 end
 
 type t
+(** A HTTP server. See {!create} for more details. *)
 
 val create :
   ?masksigpipe:bool ->
@@ -136,10 +247,28 @@ val create :
   ?port:int ->
   unit ->
   t
-(** TODO: document *)
+(** Create a new webserver.
+
+    The server will not do anything until {!run} is called on it.
+    Before starting the server, one can use {!add_path_handler} and
+    {!set_top_handler} to specify how to handle incoming requests.
+
+    @param masksigpipe if true, block the signal {!Sys.sigpipe} which otherwise
+    tends to kill client threads when they try to write on broken sockets. Default: [true].
+
+    @param new_thread a function used to spawn a new thread to handle a
+    new client connection. By default it is {!Thread.create} but one
+    could use a thread pool instead.
+
+    @param addr the address (IPv4) to listen on. Default ["127.0.0.1"].
+    @param port to listen on. Default [8080].
+    *)
 
 val addr : t -> string
+(** Address on which the server listen. *)
+
 val port : t -> int
+(** Port on which the server listen. *)
 
 val add_decode_request_cb :
   t ->
@@ -147,6 +276,8 @@ val add_decode_request_cb :
 (** Add a callback for every request.
     The callback can provide a stream transformer and a new request (with
     modified headers, typically).
+    A possible use is to handle decompression by looking for a [Transfer-Encoding]
+    header and returning a stream transformer that decompresses on the fly.
 *)
 
 val add_encode_response_cb:
@@ -160,7 +291,10 @@ val add_encode_response_cb:
 
 val set_top_handler : t -> (string Request.t -> Response.t) -> unit
 (** Setup a handler called by default.
-    If not installed, unhandled paths will return a 404 not found. *)
+
+    This handler is called with any request not accepted by any handler
+    installed via {!add_path_handler}.
+    If no top handler is installed, unhandled paths will return a [404] not found. *)
 
 val add_path_handler :
   ?accept:(unit Request.t -> (unit, Response_code.t * string) result) ->
@@ -172,14 +306,22 @@ val add_path_handler :
 (** [add_path_handler server "/some/path/%s@/%d/" f]
     calls [f request "foo" 42 ()] when a request with path "some/path/foo/42/"
     is received.
+
     This uses {!Scanf}'s splitting, which has some gotchas (in particular,
     ["%s"] is eager, so it's generally necessary to delimit its
     scope with a ["@/"] delimiter. The "@" before a character indicates it's
     a separator.
-    @param meth if provided, only accept requests with the given method
-    @param accept should return [true] if the given request (before its body
-    is read) should be accepted, [false] if it's to be rejected (e.g. because
+
+    Note that the handlers are called in the reverse order of their addition,
+    so the last registered handler can override previously registered ones.
+
+    @param meth if provided, only accept requests with the given method.
+    Typically one could react to [`GET] or [`PUT].
+    @param accept should return [Ok()] if the given request (before its body
+    is read) should be accepted, [Error (code,message)] if it's to be rejected (e.g. because
     its content is too big, or for some permission error).
+    See the {!http_of_dir} program for an example of how to use [accept] to
+    filter uploads that are too large before the upload even starts.
 *)
 
 val stop : t -> unit
@@ -189,7 +331,10 @@ val stop : t -> unit
 val run : t -> (unit, exn) result
 (** Run the main loop of the server, listening on a socket
     described at the server's creation time, using [new_thread] to
-    start a thread for each new client. *)
+    start a thread for each new client. 
+
+    This returns [Ok ()] if the server exits gracefully, or [Error e] if
+    it exits with an error. *)
 
 (**/**)