haki

%%%-------------------------------------------------------------------
%%% @doc Using the syntax compiler has an over head of creating an AST
%%%      and having the compiler to lint/expand records/optimize.
%%%      Moreover, building an AST and compiling has a huge overhead on
%%%      memory, if the data is large.
%%%
%%%      However for the most usecases of this library you are caching
%%%      a literal value, so if we hack the ASM file on the fly it should
%%%      produce a decent module that can be then compiled and loaded.
%%% @end
%%%-------------------------------------------------------------------
-module(haki_asm_compiler).

-behavior(haki_compiler).

-include("internal.hrl").
-include("types.hrl").

-export([
    compile/3
]).

-spec compile(cache_module_name(), cache_value(), cache_options()) -> compile_ret().
compile(ModName, Val, _Options) ->
    ModNameB = atom_to_binary(ModName, utf8),

    FileName = atom_to_list(ModName) ++ ".S",
    {ok, File} = file:open(FileName, [write]),

    ValB = io_lib:format(<<"~p~n">>, [Val]),
    Asm = asm_template(ModNameB, ValB),
    ?timed(file, file:write(File, Asm)),
    ok = file:close(File),

    Compile = compile:file(FileName, ?COMPILER_OPTS ++ [from_asm]),

    case Compile of
        {ok, Module, Bin} ->
            code:soft_purge(Module),
            F = atom_to_list(ModName) ++ ".erl",
            {module, Module} = code:load_binary(Module, F, Bin),

            file:delete(FileName),

            {ok, Bin};
        Error ->
            error_logger:error_msg("[hakicache_asm_compiler] - Could not build module: ~p", [Error]),

            Error
    end.

-spec asm_template(binary(), binary()) -> binary().
asm_template(ModName, BinaryVal) ->
    Template = [
        %% Header
        <<"{module, ", ModName/binary, "}.  %% version = 0\n">>,
        <<"{exports, [{get,0},{info,0},{module_info,0},{module_info,1}]}.\n">>,
        <<"{attributes, []}.\n">>,
        <<"{labels, 7}.\n">>,

        %% Get
        <<"{function, get, 0, 2}.\n">>,
        <<"{label, 1}.\n">>,
        <<"{func_info,{atom,", ModName/binary, "},{atom,get},0}.\n">>,
        <<"{label, 2}.\n">>,
        [<<"{move,{literal,">>, BinaryVal, <<"},{x,0}}.\n">>],
        <<"return.\n">>,

        %% Module Info
        <<"{function, module_info, 0, 6}.\n">>,
        <<"{label,3}.\n">>,
        <<"{func_info,{atom,", ModName/binary, "},{atom,module_info},0}.\n">>,
        <<"{label,4}.\n">>,
        <<"{move,{atom,", ModName/binary, "},{x,0}}.\n">>,
        <<"{call_ext_only,1,{extfunc,erlang,get_module_info,1}}.\n">>,

        <<"{function, module_info, 1, 8}.\n">>,
        <<"{label,5}.\n">>,
        <<"{func_info,{atom,", ModName/binary, "},{atom,module_info},1}.\n">>,
        <<"{label,6}.\n">>,
        <<"{move,{x,0},{x,1}}.\n">>,
        <<"{move,{atom,", ModName/binary, "},{x,0}}.\n">>,
        <<"{call_ext_only,2,{extfunc,erlang,get_module_info,2}}.\n">>
    ],

    iolist_to_binary(Template).