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%% @author Bob Ippolito <bob@mochimedia.com>
%% @copyright 2007 Mochi Media, Inc.
%% @doc Case preserving (but case insensitive) HTTP Header dictionary.
-module(mochiweb_headers).
-author('bob@mochimedia.com').
-export([empty/0, from_list/1, insert/3, enter/3, get_value/2, lookup/2]).
-export([get_primary_value/2]).
-export([default/3, enter_from_list/2, default_from_list/2]).
-export([to_list/1, make/1]).
-export([test/0]).
%% @type headers().
%% @type key() = atom() | binary() | string().
%% @type value() = atom() | binary() | string() | integer().
%% @spec test() -> ok
%% @doc Run tests for this module.
test() ->
H = ?MODULE:make([{hdr, foo}, {"Hdr", "bar"}, {'Hdr', 2}]),
[{hdr, "foo, bar, 2"}] = ?MODULE:to_list(H),
H1 = ?MODULE:insert(taco, grande, H),
[{hdr, "foo, bar, 2"}, {taco, "grande"}] = ?MODULE:to_list(H1),
H2 = ?MODULE:make([{"Set-Cookie", "foo"}]),
[{"Set-Cookie", "foo"}] = ?MODULE:to_list(H2),
H3 = ?MODULE:insert("Set-Cookie", "bar", H2),
[{"Set-Cookie", "foo"}, {"Set-Cookie", "bar"}] = ?MODULE:to_list(H3),
"foo, bar" = ?MODULE:get_value("set-cookie", H3),
{value, {"Set-Cookie", "foo, bar"}} = ?MODULE:lookup("set-cookie", H3),
undefined = ?MODULE:get_value("shibby", H3),
none = ?MODULE:lookup("shibby", H3),
H4 = ?MODULE:insert("content-type",
"application/x-www-form-urlencoded; charset=utf8",
H3),
"application/x-www-form-urlencoded" = ?MODULE:get_primary_value(
"content-type", H4),
ok.
%% @spec empty() -> headers()
%% @doc Create an empty headers structure.
empty() ->
gb_trees:empty().
%% @spec make(headers() | [{key(), value()}]) -> headers()
%% @doc Construct a headers() from the given list.
make(L) when is_list(L) ->
from_list(L);
%% assume a tuple is already mochiweb_headers.
make(T) when is_tuple(T) ->
T.
%% @spec from_list([{key(), value()}]) -> headers()
%% @doc Construct a headers() from the given list.
from_list(List) ->
lists:foldl(fun ({K, V}, T) -> insert(K, V, T) end, empty(), List).
%% @spec enter_from_list([{key(), value()}], headers()) -> headers()
%% @doc Insert pairs into the headers, replace any values for existing keys.
enter_from_list(List, T) ->
lists:foldl(fun ({K, V}, T1) -> enter(K, V, T1) end, T, List).
%% @spec default_from_list([{key(), value()}], headers()) -> headers()
%% @doc Insert pairs into the headers for keys that do not already exist.
default_from_list(List, T) ->
lists:foldl(fun ({K, V}, T1) -> default(K, V, T1) end, T, List).
%% @spec to_list(headers()) -> [{key(), string()}]
%% @doc Return the contents of the headers. The keys will be the exact key
%% that was first inserted (e.g. may be an atom or binary, case is
%% preserved).
to_list(T) ->
F = fun ({K, {array, L}}, Acc) ->
L1 = lists:reverse(L),
lists:foldl(fun (V, Acc1) -> [{K, V} | Acc1] end, Acc, L1);
(Pair, Acc) ->
[Pair | Acc]
end,
lists:reverse(lists:foldl(F, [], gb_trees:values(T))).
%% @spec get_value(key(), headers()) -> string() | undefined
%% @doc Return the value of the given header using a case insensitive search.
%% undefined will be returned for keys that are not present.
get_value(K, T) ->
case lookup(K, T) of
{value, {_, V}} ->
expand(V);
none ->
undefined
end.
%% @spec get_primary_value(key(), headers()) -> string() | undefined
%% @doc Return the value of the given header up to the first semicolon using
%% a case insensitive search. undefined will be returned for keys
%% that are not present.
get_primary_value(K, T) ->
case get_value(K, T) of
undefined ->
undefined;
V ->
lists:takewhile(fun (C) -> C =/= $; end, V)
end.
%% @spec lookup(key(), headers()) -> {value, {key(), string()}} | none
%% @doc Return the case preserved key and value for the given header using
%% a case insensitive search. none will be returned for keys that are
%% not present.
lookup(K, T) ->
case gb_trees:lookup(normalize(K), T) of
{value, {K0, V}} ->
{value, {K0, expand(V)}};
none ->
none
end.
%% @spec default(key(), value(), headers()) -> headers()
%% @doc Insert the pair into the headers if it does not already exist.
default(K, V, T) ->
K1 = normalize(K),
V1 = any_to_list(V),
try gb_trees:insert(K1, {K, V1}, T)
catch
error:{key_exists, _} ->
T
end.
%% @spec enter(key(), value(), headers()) -> headers()
%% @doc Insert the pair into the headers, replacing any pre-existing key.
enter(K, V, T) ->
K1 = normalize(K),
V1 = any_to_list(V),
gb_trees:enter(K1, {K, V1}, T).
%% @spec insert(key(), value(), headers()) -> headers()
%% @doc Insert the pair into the headers, merging with any pre-existing key.
%% A merge is done with Value = V0 ++ ", " ++ V1.
insert(K, V, T) ->
K1 = normalize(K),
V1 = any_to_list(V),
try gb_trees:insert(K1, {K, V1}, T)
catch
error:{key_exists, _} ->
{K0, V0} = gb_trees:get(K1, T),
V2 = merge(K1, V1, V0),
gb_trees:update(K1, {K0, V2}, T)
end.
%% Internal API
expand({array, L}) ->
mochiweb_util:join(lists:reverse(L), ", ");
expand(V) ->
V.
merge("set-cookie", V1, {array, L}) ->
{array, [V1 | L]};
merge("set-cookie", V1, V0) ->
{array, [V1, V0]};
merge(_, V1, V0) ->
V0 ++ ", " ++ V1.
normalize(K) when is_list(K) ->
string:to_lower(K);
normalize(K) when is_atom(K) ->
normalize(atom_to_list(K));
normalize(K) when is_binary(K) ->
normalize(binary_to_list(K)).
any_to_list(V) when is_list(V) ->
V;
any_to_list(V) when is_atom(V) ->
atom_to_list(V);
any_to_list(V) when is_binary(V) ->
binary_to_list(V);
any_to_list(V) when is_integer(V) ->
integer_to_list(V).
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