Add built-in cowboy_http_static handler.

src/cowboy_http_static.erl

@@ -0,0 +1,349 @@
+%% Copyright (c) 2011, Magnus Klaar <magnus.klaar@gmail.com>
+%%
+%% Permission to use, copy, modify, and/or distribute this software for any
+%% purpose with or without fee is hereby granted, provided that the above
+%% copyright notice and this permission notice appear in all copies.
+%%
+%% THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+%% WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+%% MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+%% ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+%% WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+%% ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+%% OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+
+%% @doc Static resource handler.
+%%
+%% This built in HTTP handler provides a simple file serving capability for
+%% cowboy applications. It should be considered an experimental feature because
+%% of it's dependency on the experimental REST handler. It's recommended to be
+%% used for small or temporary environments where it is not preferrable to set
+%% up a second server just to serve files.
+%%
+%% == Base configuration ==
+%%
+%% The handler must be configured with a request path prefix to serve files
+%% under and the path to a directory to read files from. The request path prefix
+%% is defined in the path pattern of the cowboy dispatch rule for the handler.
+%% The request path pattern must end with a ``'...''' token.
+%% The directory path can be set to either an absolute or relative path in the
+%% form of a list or binary string representation of a file system path. A list
+%% of binary path segments, as is used throughout cowboy, is also a valid
+%% directory path.
+%%
+%% The directory path can also be set to a relative path within the `priv/'
+%% directory of an application. This is configured by setting the value of the
+%% directory option to a tuple of the form `{priv_dir, Application, Relpath}'.
+%%
+%% ==== Examples ====
+%% ```
+%% %% Serve files from /var/www/ under http://example.com/static/
+%% {[<<"static">>, '...'], cowboy_http_static,
+%%     [{directory, "/var/www"}]}
+%%
+%% %% Serve files from the current working directory under http://example.com/static/
+%% {[<<"static">>, '...'], cowboy_http_static,
+%%     [{directory, <<"./">>}]}
+%%
+%% %% Serve files from cowboy/priv/www under http://example.com/
+%% {['...'], cowboy_http_static,
+%%     [{directory, {priv_dir, cowboy, [<<"www">>]}}]}
+%% '''
+%%
+%% == Content type configuration  ==
+%%
+%% By default the content type of all static resources will be set to
+%% `application/octet-stream'. This can be overriden by supplying a list
+%% of filename extension to mimetypes pairs in the `mimetypes' option.
+%% The filename extension should be a binary string including the leading dot.
+%% The mimetypes must be of a type that the `cowboy_http_rest' protocol can
+%% handle.
+%%
+%% ==== Example ====
+%% ```
+%% {[<<"static">>, '...'], cowboy_http_static,
+%%     [{directory, {priv_dir, cowboy, []}},
+%%      {mimetypes, [
+%%          {<<".css">>, [<<"text/css">>]},
+%%          {<<".js">>, [<<"application/javascript">>]}]}]}
+%% '''
+-module(cowboy_http_static).
+
+%% include files
+-include("http.hrl").
+-include_lib("kernel/include/file.hrl").
+
+%% cowboy_http_protocol callbacks
+-export([init/3]).
+
+%% cowboy_http_rest callbacks
+-export([rest_init/2, allowed_methods/2, malformed_request/2, resource_exists/2,
+	forbidden/2, last_modified/2, content_types_provided/2, file_contents/2]).
+
+%% internal
+-export([path_to_mimetypes/2]).
+
+%% types
+-type dirpath() :: string() | binary() | [binary()].
+-type dirspec() :: dirpath() | {priv, atom(), dirpath()}.
+-type mimedef() :: {binary(), binary(), [{binary(), binary()}]}.
+
+%% handler state
+-record(state, {
+	filepath  :: binary() | error,
+	fileinfo  :: {ok, #file_info{}} | {error, _} | error,
+	mimetypes :: {fun((binary(), T) -> [mimedef()]), T} | undefined}).
+
+
+%% @private Upgrade from HTTP handler to REST handler.
+init({_Transport, http}, _Req, _Opts) ->
+	{upgrade, protocol, cowboy_http_rest}.
+
+
+%% @private Set up initial state of REST handler.
+-spec rest_init(#http_req{}, list()) -> {ok, #http_req{}, #state{}}.
+rest_init(Req, Opts) ->
+	Directory = proplists:get_value(directory, Opts),
+	Directory1 = directory_path(Directory),
+	Mimetypes = proplists:get_value(mimetypes, Opts, []),
+	Mimetypes1 = case Mimetypes of
+		{_, _} -> Mimetypes;
+		[] -> {fun path_to_mimetypes/2, []};
+		[_|_] -> {fun path_to_mimetypes/2, Mimetypes}
+	end,
+	{Filepath, Req1} = cowboy_http_req:path_info(Req),
+	State = case check_path(Filepath) of
+		error ->
+			#state{filepath=error, fileinfo=error, mimetypes=undefined};
+		ok ->
+			Filepath1 = join_paths(Directory1, Filepath),
+			Fileinfo = file:read_file_info(Filepath1),
+			#state{filepath=Filepath1, fileinfo=Fileinfo, mimetypes=Mimetypes1}
+	end,
+	{ok, Req1, State}.
+
+
+%% @private Only allow GET and HEAD requests on files.
+-spec allowed_methods(#http_req{}, #state{}) ->
+		{[atom()], #http_req{}, #state{}}.
+allowed_methods(Req, State) ->
+	{['GET', 'HEAD'], Req, State}.
+
+%% @private
+-spec malformed_request(#http_req{}, #state{}) ->
+		{boolean(), #http_req{}, #state{}}.
+malformed_request(Req, #state{filepath=error}=State) ->
+	{true, Req, State};
+malformed_request(Req, State) ->
+	{false, Req, State}.
+
+
+%% @private Check if the resource exists under the document root.
+-spec resource_exists(#http_req{}, #state{}) ->
+		{boolean(), #http_req{}, #state{}}.
+resource_exists(Req, #state{fileinfo={error, _}}=State) ->
+	{false, Req, State};
+resource_exists(Req, #state{fileinfo={ok, Fileinfo}}=State) ->
+	{Fileinfo#file_info.type =:= regular, Req, State}.
+
+
+%% @private
+%% Access to a file resource is forbidden if it exists and the local node does
+%% not have permission to read it. Directory listings are always forbidden.
+-spec forbidden(#http_req{}, #state{}) -> {boolean(), #http_req{}, #state{}}.
+forbidden(Req, #state{fileinfo={_, #file_info{type=directory}}}=State) ->
+	{true, Req, State};
+forbidden(Req, #state{fileinfo={error, eacces}}=State) ->
+	{true, Req, State};
+forbidden(Req, #state{fileinfo={error, _}}=State) ->
+	{false, Req, State};
+forbidden(Req, #state{fileinfo={ok, #file_info{access=Access}}}=State) ->
+	{not (Access =:= read orelse Access =:= read_write), Req, State}.
+
+
+%% @private Read the time a file system system object was last modified.
+-spec last_modified(#http_req{}, #state{}) ->
+		{cowboy_clock:datetime(), #http_req{}, #state{}}.
+last_modified(Req, #state{fileinfo={ok, #file_info{mtime=Modified}}}=State) ->
+	{Modified, Req, State}.
+
+
+%% @private Return the content type of a file.
+-spec content_types_provided(#http_req{}, #state{}) -> tuple().
+content_types_provided(Req, #state{filepath=Filepath,
+		mimetypes={MimetypesFun, MimetypesData}}=State) ->
+	Mimetypes = [{T, file_contents}
+		|| T <- MimetypesFun(Filepath, MimetypesData)],
+	{Mimetypes, Req, State}.
+
+
+%% @private Return a function that writes a file directly to the socket.
+-spec file_contents(#http_req{}, #state{}) -> tuple().
+file_contents(Req, #state{filepath=Filepath,
+		fileinfo={ok, #file_info{size=Filesize}}}=State) ->
+	{ok, Transport, Socket} = cowboy_http_req:transport(Req),
+	Writefile = content_function(Transport, Socket, Filepath),
+	{{stream, Filesize, Writefile}, Req, State}.
+
+
+%% @private Return a function writing the contents of a file to a socket.
+%% The function returns the number of bytes written to the socket to enable
+%% the calling function to determine if the expected number of bytes were
+%% written to the socket.
+-spec content_function(module(), inet:socket(), binary()) ->
+	fun(() -> {sent, non_neg_integer()}).
+content_function(Transport, Socket, Filepath) ->
+	%% `file:sendfile/2' will only work with the `cowboy_tcp_transport'
+	%% transport module. SSL or future SPDY transports that require the
+	%% content to be encrypted or framed as the content is sent.
+	case erlang:function_exported(file, sendfile, 2) of
+		false ->
+			fun() -> sfallback(Transport, Socket, Filepath) end;
+		_ when Transport =/= cowboy_tcp_transport ->
+			fun() -> sfallback(Transport, Socket, Filepath) end;
+		true ->
+			fun() -> sendfile(Socket, Filepath) end
+	end.
+
+
+%% @private Sendfile fallback function.
+-spec sfallback(module(), inet:socket(), binary()) -> {sent, non_neg_integer()}.
+sfallback(Transport, Socket, Filepath) ->
+	{ok, File} = file:open(Filepath, [read,binary,raw]),
+	sfallback(Transport, Socket, File, 0).
+
+-spec sfallback(module(), inet:socket(), file:io_device(),
+		non_neg_integer()) -> {sent, non_neg_integer()}.
+sfallback(Transport, Socket, File, Sent) ->
+	case file:read(File, 16#1FFF) of
+		eof ->
+			ok = file:close(File),
+			{sent, Sent};
+		{ok, Bin} ->
+			ok = Transport:send(Socket, Bin),
+			sfallback(Transport, Socket, File, Sent + byte_size(Bin))
+	end.
+
+
+%% @private Wrapper for sendfile function.
+-spec sendfile(inet:socket(), binary()) -> {sent, non_neg_integer()}.
+sendfile(Socket, Filepath) ->
+	{ok, Sent} = file:sendfile(Filepath, Socket),
+	{sent, Sent}.
+
+-spec directory_path(dirspec()) -> dirpath().
+directory_path({priv_dir, App, []}) ->
+	priv_dir_path(App);
+directory_path({priv_dir, App, [H|_]=Path}) when is_integer(H) ->
+	filename:join(priv_dir_path(App), Path);
+directory_path({priv_dir, App, [H|_]=Path}) when is_binary(H) ->
+	filename:join(filename:split(priv_dir_path(App)) ++ Path);
+directory_path({priv_dir, App, Path}) when is_binary(Path) ->
+	filename:join(priv_dir_path(App), Path);
+directory_path(Path) ->
+	Path.
+
+
+%% @private Validate a request path for unsafe characters.
+%% There is no way to escape special characters in a filesystem path.
+-spec check_path(Path::[binary()]) -> ok | error.
+check_path([]) -> ok;
+check_path([<<"">>|_T]) -> error;
+check_path([<<".">>|_T]) -> error;
+check_path([<<"..">>|_T]) -> error;
+check_path([H|T]) ->
+	case binary:match(H, <<"/">>) of
+		{_, _} -> error;
+		nomatch -> check_path(T)
+	end.
+
+
+%% @private Join the the directory and request paths.
+-spec join_paths(dirpath(), [binary()]) -> binary().
+join_paths([H|_]=Dirpath, Filepath) when is_integer(H) ->
+	filename:join(filename:split(Dirpath) ++ Filepath);
+join_paths([H|_]=Dirpath, Filepath) when is_binary(H) ->
+	filename:join(Dirpath ++ Filepath);
+join_paths(Dirpath, Filepath) when is_binary(Dirpath) ->
+	filename:join([Dirpath] ++ Filepath);
+join_paths([], Filepath) ->
+	filename:join(Filepath).
+
+
+%% @private Return the path to the priv/ directory of an application.
+-spec priv_dir_path(atom()) -> string().
+priv_dir_path(App) ->
+	case code:priv_dir(App) of
+		{error, bad_name} -> priv_dir_mod(App);
+		Dir -> Dir
+	end.
+
+-spec priv_dir_mod(atom()) -> string().
+priv_dir_mod(Mod) ->
+	case code:which(Mod) of
+		File when not is_list(File) -> "../priv";
+		File -> filename:join([filename:dirname(File),"../priv"])
+	end.
+
+
+%% @private Use application/octet-stream as the default mimetype.
+%% If a list of extension - mimetype pairs are provided as the mimetypes
+%% an attempt to find the mimetype using the file extension. If no match
+%% is found the default mimetype is returned.
+-spec path_to_mimetypes(binary(), [{binary(), [mimedef()]}]) ->
+		[mimedef()].
+path_to_mimetypes(Filepath, Extensions) when is_binary(Filepath) ->
+	Ext = filename:extension(Filepath),
+	case Ext of
+		<<>> -> default_mimetype();
+		_Ext -> path_to_mimetypes_(Ext, Extensions)
+	end.
+
+-spec path_to_mimetypes_(binary(), [{binary(), [mimedef()]}]) -> [mimedef()].
+path_to_mimetypes_(Ext, Extensions) ->
+	case lists:keyfind(Ext, 1, Extensions) of
+		{_, MTs} -> MTs;
+		_Unknown -> default_mimetype()
+	end.
+
+-spec default_mimetype() -> [mimedef()].
+default_mimetype() ->
+	[{<<"application">>, <<"octet-stream">>, []}].
+
+
+-ifdef(TEST).
+-include_lib("eunit/include/eunit.hrl").
+-define(_eq(E, I), ?_assertEqual(E, I)).
+
+check_path_test_() ->
+	C = fun check_path/1,
+	[?_eq(error, C([<<>>])),
+	 ?_eq(ok, C([<<"abc">>])),
+	 ?_eq(error, C([<<".">>])),
+	 ?_eq(error, C([<<"..">>])),
+	 ?_eq(error, C([<<"/">>]))
+	].
+
+join_paths_test_() ->
+	P = fun join_paths/2,
+	[?_eq(<<"a">>, P([], [<<"a">>])),
+	 ?_eq(<<"a/b/c">>, P(<<"a/b">>, [<<"c">>])),
+	 ?_eq(<<"a/b/c">>, P("a/b", [<<"c">>])),
+	 ?_eq(<<"a/b/c">>, P([<<"a">>, <<"b">>], [<<"c">>]))
+	].
+
+directory_path_test_() ->
+	P = fun directory_path/1,
+	PL = fun(I) -> length(filename:split(P(I))) end,
+	Base = PL({priv_dir, cowboy, []}),
+	[?_eq(Base + 1, PL({priv_dir, cowboy, "a"})),
+	 ?_eq(Base + 1, PL({priv_dir, cowboy, <<"a">>})),
+	 ?_eq(Base + 1, PL({priv_dir, cowboy, [<<"a">>]})),
+	 ?_eq(Base + 2, PL({priv_dir, cowboy, "a/b"})),
+	 ?_eq(Base + 2, PL({priv_dir, cowboy, <<"a/b">>})),
+	 ?_eq(Base + 2, PL({priv_dir, cowboy, [<<"a">>, <<"b">>]})),
+	 ?_eq("a/b", P("a/b"))
+	].
+
+
+-endif.