%%
%% %CopyrightBegin%
%% 
%% Copyright Ericsson AB 1999-2012. All Rights Reserved.
%% 
%% The contents of this file are subject to the Erlang Public License,
%% Version 1.1, (the "License"); you may not use this file except in
%% compliance with the License. You should have received a copy of the
%% Erlang Public License along with this software. If not, it can be
%% retrieved online at http://www.erlang.org/.
%% 
%% Software distributed under the License is distributed on an "AS IS"
%% basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
%% the License for the specific language governing rights and limitations
%% under the License.
%% 
%% %CopyrightEnd%
%%
-module(erts_debug).

%% Low-level debugging support. EXPERIMENTAL!

-export([size/1,df/1,df/2,df/3]).

%% This module contains the following *experimental* BIFs:
%%   disassemble/1
%%   breakpoint/2
%%   same/2
%%   flat_size/1

%% size(Term)
%%  Returns the size of Term in actual heap words. Shared subterms are
%%  counted once.  Example: If A = [a,b], B =[A,A] then size(B) returns 8,
%%  while flat_size(B) returns 12.

-spec size(term()) -> non_neg_integer().

size(Term) ->
    {Sum,_} = size(Term, gb_trees:empty(), 0),
    Sum.

size([H|T]=Term, Seen0, Sum0) ->
    case remember_term(Term, Seen0) of
	seen -> {Sum0,Seen0};
	Seen1 ->
	    {Sum,Seen} = size(H, Seen1, Sum0+2),
	    size(T, Seen, Sum)
    end;
size(Tuple, Seen0, Sum0) when is_tuple(Tuple) ->
    case remember_term(Tuple, Seen0) of
	seen -> {Sum0,Seen0};
	Seen ->
	    Sum = Sum0 + 1 + tuple_size(Tuple),
	    tuple_size(1, tuple_size(Tuple), Tuple, Seen, Sum)
    end;
size(Fun, Seen0, Sum) when is_function(Fun) ->
    case remember_term(Fun, Seen0) of
	seen -> {Sum,Seen0};
	Seen -> fun_size(Fun, Seen, Sum)
    end;
size(Term, Seen0, Sum) ->
    case erts_debug:flat_size(Term) of
	0 -> {Sum,Seen0};
	Sz ->
	    case remember_term(Term, Seen0) of
		seen -> {Sum,Seen0};
		Seen -> {Sum+Sz,Seen}
	    end
    end.

tuple_size(I, Sz, _, Seen, Sum) when I > Sz ->
    {Sum,Seen};
tuple_size(I, Sz, Tuple, Seen0, Sum0) ->
    {Sum,Seen} = size(element(I, Tuple), Seen0, Sum0),
    tuple_size(I+1, Sz, Tuple, Seen, Sum).

fun_size(Fun, Seen, Sum) ->
    case erlang:fun_info(Fun, type) of
	{type,external} ->
	    {Sum + erts_debug:flat_size(Fun),Seen};
	{type,local} ->
	    Sz = erts_debug:flat_size(fun() -> ok end),
	    {env,Env} = erlang:fun_info(Fun, env),
	    fun_size_1(Env, Seen, Sum+Sz+length(Env))
    end.

fun_size_1([H|T], Seen0, Sum0) ->
    {Sum,Seen} = size(H, Seen0, Sum0),
    fun_size_1(T, Seen, Sum);
fun_size_1([], Seen, Sum) -> {Sum,Seen}.
	    
remember_term(Term, Seen) ->
    case gb_trees:lookup(Term, Seen) of
	none -> gb_trees:insert(Term, [Term], Seen);
	{value,Terms} ->
	    case is_term_seen(Term, Terms) of
		false -> gb_trees:update(Term, [Term|Terms], Seen);
		true -> seen
	    end
    end.

-spec is_term_seen(term(), [term()]) -> boolean().

is_term_seen(Term, [H|T]) ->
    case erts_debug:same(Term, H) of
	true -> true;
	false -> is_term_seen(Term, T)
    end;
is_term_seen(_, []) -> false.

%% df(Mod)              -- Disassemble Mod to file Mod.dis.
%% df(Mod, Func)        -- Disassemble Mod:Func/Any to file Mod_Func.dis.
%% df(Mod, Func, Arity) -- Disassemble Mod:Func/Arity to file Mod_Func_Arity.dis.

-type df_ret() :: 'ok' | {'error', {'badopen', module()}} | {'undef', module()}.

-spec df(module()) -> df_ret().

df(Mod) when is_atom(Mod) ->
    try Mod:module_info(functions) of
	Fs0 when is_list(Fs0) ->
	    Name = lists:concat([Mod, ".dis"]),
	    Fs = [{Mod,Func,Arity} || {Func,Arity} <- Fs0],
	    dff(Name, Fs)
    catch _:_ -> {undef,Mod}
    end.

-spec df(module(), atom()) -> df_ret().

df(Mod, Func) when is_atom(Mod), is_atom(Func) ->
    try Mod:module_info(functions) of
	Fs0 when is_list(Fs0) ->
	    Name = lists:concat([Mod, "_", Func, ".dis"]),
	    Fs = [{Mod,Func1,Arity} || {Func1,Arity} <- Fs0, Func1 =:= Func],
	    dff(Name, Fs)
    catch _:_ -> {undef,Mod}
    end.

-spec df(module(), atom(), arity()) -> df_ret().

df(Mod, Func, Arity) when is_atom(Mod), is_atom(Func) ->
    try Mod:module_info(functions) of
	Fs0 when is_list(Fs0) ->
	    Name = lists:concat([Mod, "_", Func, "_", Arity, ".dis"]),
	    Fs = [{Mod,Func1,Arity1} || {Func1,Arity1} <- Fs0,
					Func1 =:= Func, Arity1 =:= Arity],
	    dff(Name, Fs)
    catch _:_ -> {undef,Mod}
    end.

dff(File, Fs) when is_pid(File), is_list(Fs) ->
    lists:foreach(fun(Mfa) ->
			  disassemble_function(File, Mfa),
			  io:nl(File)
		  end, Fs);
dff(Name, Fs) when is_list(Name) ->
    case file:open(Name, [write]) of
	{ok,F} ->
	    try
		dff(F, Fs)
	    after
		file:close(F)
	    end;
	{error,Reason} ->
	    {error,{badopen,Reason}}
    end.

disassemble_function(File, {_,_,_}=MFA) ->
    cont_dis(File, erts_debug:disassemble(MFA), MFA).

cont_dis(_, false, _) -> ok;
cont_dis(File, {Addr,Str,MFA}, MFA) ->
    io:put_chars(File, binary_to_list(Str)),
    cont_dis(File, erts_debug:disassemble(Addr), MFA);
cont_dis(_, {_,_,_}, _) -> ok.