%%% See accompanying file LICENSE or visit the Thrift site at:
%%% http://developers.facebook.com/thrift/
+%%%
+%%% dox:
+%%%
+%%% C++ <-> Erlang
+%%% classes modules
+%%% class b : public a a:super() -> b.
+%%%
+
-module(oop).
--export([get/2, set/3, call/2, call/3, inspect/1, start_new/2, is_object/1, class/1]).
+-export([start_new/2, get/2, set/3, call/2, call/3, inspect/1, class/1, is_object/1]).
+-export([call1/3]). %% only for thrift_oop_server ... don't use it
-export([behaviour_info/1]).
-include("thrift.hrl").
-include("oop.hrl").
+%% state for the call loop
+-record(cstate, {
+ obj, %% the current object (on which we want to invoke MFA)
+ module, %% the current module we're considering
+ func, %% the method name (i.e. the function we're trying to invoke in Module)
+ args, %% the arguments, the first of which is Obj
+ tried, %% a (backwards) list of modules we've tried
+ first_obj %% the original object
+ }).
+
%%%
%%% behavior definition
%%%
-behaviour_info(callbacks) ->
- [
- {attr, 4},
- {super, 0}
- ];
-behaviour_info(_) ->
+behaviour_info(callbacks) ->
+ [ {attr, 4},
+ {super, 0}
+ ];
+behaviour_info(_) ->
undefined.
-%%
-
--define(TRIED, lists:reverse([TryModule|TriedRev])).
-
-%% no super attr defined
--define(NOSUPEROBJ, exit({missing_attr_super, {inspect(Obj), ?TRIED}})).
-
--define(NOMETHOD, exit({missing_method, {Method, inspect(Obj), tl(Args), ?TRIED}})).
-
--define(NOATTR, exit({missing_attr, {hd(tl(Args)), inspect(FirstObj), ?TRIED}})).
-
--define(NOATTR_SET, exit({missing_attr, {Field, inspect(Obj), ".." %% TODO: give a backtrace
- }})).
-
+%%%
+%%% public interface
+%%%
-%%% get(Obj, Field) -> term()
-%%% looks up Field in Obj or its ancestor objects
+%% TODO: voids take only ok as return?
+start_new(none=Resv, _) ->
+ error_logger:format("can't instantiate ~p: class name is a reserved word", [Resv]),
+ error;
+start_new(Class, Args) ->
+ {ok, Pid} = gen_server:start_link(thrift_oop_server, {Class, Args}, []),
+ Pid.
+%% get(Obj, Field) -> term()
+%% looks up Field in Obj or its ancestor objects
get(Obj, Field) ->
call(Obj, attr, [get, Field, get]).
set(Obj, Field, Value) -> %% TODO: could be tail-recursive
Module = ?CLASS(Obj),
- try
- Module:attr(Obj, set, Field, Value)
- catch
- error:Kind when Kind == undef; Kind == function_clause ->
- case get_superobject(Obj) of
+ case apply_if_defined(Module, attr, [Obj, set, Field, Value]) of
+ {ok, V} -> V;
+ undef ->
+ case get_superobject(Obj) of
{ ok, Superobj } ->
- Super1 = set(Superobj, Field, Value),
- try
- Module:attr(Obj, set, super, Super1)
- catch %% TODO(cpiro): remove check
- X -> exit({burnsauce, X})
- end;
- none ->
- ?NOATTR_SET
+ Superobj1 = set(Superobj, Field, Value),
+ Module:attr(Obj, set, super, Superobj1);
+ undef ->
+ error(missing_attr_set, Field, Obj)
end
end.
-%%% C++ <-> Erlang
-%%% classes modules
-%%% class b : public a a:super() -> b.
-%%%
+%%
+%% ** dynamic method dispatch **
+%%
+%% calls Module:Func(*Args) if it exists
+%% if not, Module <- Module:super() and try again recursively
+%%
+%% Module:attr(*Args) is handled specially:
+%% Obj needs to be replaced with Obj's "superobject"
+%%
+call(Obj, Func) ->
+ call(Obj, Func, []).
+
+call(Obj, Func, ArgsProper) ->
+ %% error_logger:info_msg("call called: Obj=~p Func=~p ArgsProper=~p", [inspect(Obj), Func, ArgsProper]),
+ case call1(Obj, Func, ArgsProper) of
+ {ok, Value} -> Value;
+ {error, Kind, S1} -> error(Kind, S1)
+ end.
-get_superobject(Obj) ->
- try
- {ok, (?CLASS(Obj)):attr(Obj, get, super, get)}
- catch
- error:Kind when Kind == undef; Kind == function_clause ->
- none
+call1(Obj, Func, ArgsProper) ->
+ S = #cstate{
+ obj = Obj,
+ module = ?CLASS(Obj),
+ func = Func,
+ args = [Obj|ArgsProper], %% prepend This to args
+ tried = [],
+ first_obj = Obj
+ },
+ call1(S).
+
+call1(S = #cstate{obj=Obj, module=Module, func=Func, args=Args}) ->
+ %% error_logger:info_msg("call1~n obj=~p~n MFA=~p, ~p, ~p", [inspect(Obj), Module, Func, Args]),
+ %% io:format("call ~p~n", [Module]),
+ case apply_if_defined(Module, Func, Args) of
+ {ok, Value} -> {ok, Value};
+ undef -> call1_try_super(S)
end.
-is_object(Obj) when is_tuple(Obj) ->
- try
- (?CLASS(Obj)):super(), %% if it's an object its first element will be a class name, and it'll have super/0
- true
- catch
- error:Kind when Kind == undef; Kind == function_clause ->
- false
+call1_try_super(S = #cstate{func=attr, module=Module, tried=Tried}) ->
+ case Module:super() of
+ none -> {error, missing_attr, S};
+ Superclass -> call1_try_super_attr(Superclass, S)
end;
-is_object(_) ->
- false.
-
-call(Obj, Method, ArgsProper) ->
- %% error_logger:info_msg("call called: Obj=~p Method=~p ArgsProper=~p", [inspect(Obj), Method, ArgsProper]),
- Args = [Obj|ArgsProper], %% prepend This to args
- TryModule = ?CLASS(Obj),
- call_loop(Obj, Method, Args, TryModule, [], Obj).
-
-call(Obj, Method) ->
- call(Obj, Method, []).
-
-call_loop(Obj, Method, Args, TryModule, TriedRev, FirstObj) ->
- try
- %% error_logger:info_msg("call_loop~n ~p~n ~p~n ~p~n ~p", [inspect(Obj), Method, Args, TryModule]),
- apply(TryModule, Method, Args)
- catch
- error:Kind when Kind == undef; Kind == function_clause ->
- case { TryModule:super(), Method } of
- { none, attr } ->
- ?NOATTR;
-
- { none, _ } ->
- ?NOMETHOD;
-
- { Superclass, attr } ->
- %% look for attrs in the "super object"
-
- case get_superobject(Obj) of
- {ok, Superobj} when (TryModule == ?CLASS(Obj)) ->
- %% replace This with Superobj
- NewArgs = [Superobj|tl(Args)],
- call_loop(Superobj, Method, NewArgs,
- Superclass, [TryModule|TriedRev], FirstObj);
-
- {ok, _Superobj} -> % failed guard TODO(cpiro): removeme
- exit(oh_noes);
-
- none -> ?NOSUPEROBJ
- end;
-
- { SuperClass, _ } ->
- call_loop(Obj, Method, Args,
- SuperClass, [TryModule|TriedRev], FirstObj)
- end
+call1_try_super(S = #cstate{func=Func, module=Module, tried=Tried}) ->
+ case Module:super() of
+ none -> {error, missing_method, S};
+ Superclass ->
+ S1 = S#cstate{
+ module = Superclass,
+ tried = [Module|Tried]
+ },
+ call1(S1)
+ end.
+
+call1_try_super_attr(Superclass, S = #cstate{obj=Obj, module=Module, args=Args, tried=Tried}) ->
+ %% look for attrs in the "super object"
+ case get_superobject(Obj) of
+ undef -> {error, missing_superobj, S};
+ {ok, Superobj} when Module == ?CLASS(Obj) ->
+ %% replace This with Superobj
+ S1 = S#cstate{
+ obj = Superobj,
+ args = [Superobj|tl(Args)],
+ module = Superclass,
+ tried = [Module|Tried]
+ },
+ call1(S1)
end.
-
-class(Obj) when is_tuple(Obj) ->
- case is_object(Obj) of
- true ->
- ?CLASS(Obj);
- false ->
- none
- end;
-class(_) ->
- none.
%% careful: not robust against records beginning with a class name
%% (note: we can't just guard with is_record(?CLASS(Obj), Obj) since we
try
case is_object(Obj) of
true ->
- DeepList = inspect_loop(Obj, "#<"),
+ DeepList = inspect1(Obj, "#<"),
lists:flatten(DeepList);
false ->
thrift_utils:sformat("~p", [Obj])
%% _:E -> thrift_utils:sformat("~p", [Obj])
end.
-inspect_loop(Obj, Str) ->
+inspect1(Obj, Str) ->
Class = ?CLASS(Obj),
Inspect = Class:inspect(Obj),
Current = atom_to_list(Class) ++ ": " ++ Inspect,
case get_superobject(Obj) of
- { ok, Superobj } ->
- inspect_loop(Superobj, Str ++ Current ++ " | ");
- none ->
+ {ok, Superobj} ->
+ inspect1(Superobj, Str ++ Current ++ " | ");
+ undef ->
Str ++ Current ++ ">"
end.
-%% TODO: voids take only ok as return?
-start_new(none=Resv, _) ->
- error_logger:format("can't instantiate ~p: class name is a reserved word", [Resv]),
- error;
-start_new(Class, Args) ->
- {ok, Pid} = gen_server:start_link(thrift_oop_server, {Class, Args}, []),
- Pid.
+%% class(Obj) -> atom() = Class
+%% | none
+class(Obj) when is_tuple(Obj) ->
+ %% if it's an object its first element will be a class name, and it'll have super/0
+ case apply_if_defined(?CLASS(Obj), super, []) of
+ {ok, V} -> V;
+ undef -> none
+ end;
+class(_) -> none.
+
+%% is the tuple/record an object?
+%% is_object(Obj) = bool()
+is_object(Obj) when is_tuple(Obj) ->
+ case class(Obj) of
+ none -> false;
+ _ -> true
+ end;
+is_object(_) -> false.
+
+%%%
+%%% private helpers
+%%%
+
+%% apply_if_defined(MFA) -> {ok, apply(MFA)}
+%% | undef
+%% this could be worth some money
+apply_if_defined(M, F, A) ->
+ apply_if_defined({M,F,A}).
+
+apply_if_defined({M,F,A} = MFA) ->
+ try
+ %% io:format("apply ~p ~p ~p~n", [M,F,A]),
+ {ok, apply(M, F, A)}
+ catch
+ error:Kind when Kind == undef; Kind == function_clause ->
+ case erlang:get_stacktrace() of
+ %% the first stack call should match MFA when `apply' fails because the function is undefined
+ %% they won't match if the function is currently running and an error happens in the middle
+ [MFA|_] -> undef; % trapped successfully
+ ST ->
+ io:format("DONIT THE EXIT THING ~p~n", [Kind]),
+ exit({Kind, ST}) % some unrelated error, re-exit
+ end
+ end.
+
+get_superobject(Obj) ->
+ apply_if_defined(?CLASS(Obj), attr, [Obj, get, super, get]).
+
+%%%
+%%% errors
+%%%
+
+tried(S = #cstate{module=Module, tried=Tried}) ->
+ lists:reverse([Module|Tried]).
+
+error(missing_superobj, S = #cstate{obj=Obj}) ->
+ exit({missing_superobj, {inspect(Obj), tried(S)}});
+error(missing_method, S = #cstate{obj=Obj, func=Func, args=Args}) ->
+ exit({missing_method, {Func, inspect(Obj), tl(Args), tried(S)}});
+error(missing_attr, S = #cstate{args=Args, first_obj=FirstObj}) ->
+ exit({missing_attr, {hd(tl(Args)), inspect(FirstObj), tried(S)}}).
+
+error(missing_attr_set, Field, Obj) ->
+ BT = "..", %% TODO: give a backtrace
+ exit({missing_attr, {Field, inspect(Obj), BT}}).
Code Review / common / thrift.git / commitdiff
