From 1b0138061361d0d9cb3708141f5c1347e2e48bc8 Mon Sep 17 00:00:00 2001
From: Eric Merritt <ericbmerritt@gmail.com>
Date: Sun, 16 Sep 2012 13:11:41 -0500
Subject: [PATCH] compilation utilities for the implementors

Signed-off-by: Jordan Wilberding <diginux@gmail.com>
---
 src/ec_compile.erl | 107 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 107 insertions(+)
 create mode 100644 src/ec_compile.erl

diff --git a/src/ec_compile.erl b/src/ec_compile.erl
new file mode 100644
index 0000000..482bdb3
--- /dev/null
+++ b/src/ec_compile.erl
@@ -0,0 +1,107 @@
+%%%-------------------------------------------------------------------
+%%% @author Eric Merritt <>
+%%% @copyright (C) 2011, Erlware, LLC.
+%%% @doc
+%%%  These are various utility functions to help with compiling and
+%%%  decompiling erlang source. They are mostly useful to the
+%%%  language/parse transform implementor.
+%%% @end
+%%%-------------------------------------------------------------------
+-module(ec_compile).
+
+-export([beam_to_erl_source/2,
+         erl_source_to_core_ast/1,
+         erl_source_to_erl_ast/1,
+         erl_source_to_asm/1,
+         erl_string_to_core_ast/1,
+         erl_string_to_erl_ast/1,
+         erl_string_to_asm/1]).
+
+%%%===================================================================
+%%% API
+%%%===================================================================
+
+%% @doc decompile a beam file that has been compiled with +debug_info
+%% into a erlang source file
+%%
+%% @param BeamFName the name of the beamfile
+%% @param ErlFName the name of the erlang file where the generated
+%% source file will be output. This should *not* be the same as the
+%% source file that created the beamfile unless you want to overwrite
+%% it.
+-spec beam_to_erl_source(string(), string()) -> ok | term().
+beam_to_erl_source(BeamFName, ErlFName) ->
+  case beam_lib:chunks(BeamFName, [abstract_code]) of
+    {ok, {_, [{abstract_code, {raw_abstract_v1,Forms}}]}} ->
+      Src =
+        erl_prettypr:format(erl_syntax:form_list(tl(Forms))),
+        {ok, Fd} = file:open(ErlFName, [write]),
+        io:fwrite(Fd, "~s~n", [Src]),
+        file:close(Fd);
+    Error ->
+       Error
+  end.
+
+%% @doc compile an erlang source file into a Core Erlang AST
+%%
+%% @param Path - The path to the erlang source file
+-spec erl_source_to_core_ast(file:filename()) -> CoreAst::term().
+erl_source_to_core_ast(Path) ->
+    {ok, Contents} = file:read_file(Path),
+    erl_string_to_core_ast(binary_to_list(Contents)).
+
+%% @doc compile an erlang source file into an Erlang AST
+%%
+%% @param Path - The path to the erlang source file
+-spec erl_source_to_erl_ast(file:filename()) -> ErlangAst::term().
+erl_source_to_erl_ast(Path) ->
+    {ok, Contents} = file:read_file(Path),
+    erl_string_to_erl_ast(binary_to_list(Contents)).
+
+%% @doc compile an erlang source file into erlang terms that represent
+%% the relevant ASM
+%%
+%% @param Path - The path to the erlang source file
+-spec erl_source_to_asm(file:filename()) -> ErlangAsm::term().
+erl_source_to_asm(Path) ->
+    {ok, Contents} = file:read_file(Path),
+    erl_string_to_asm(binary_to_list(Contents)).
+
+%% @doc compile a string representing an erlang expression into an
+%% Erlang AST
+%%
+%% @param StringExpr - The path to the erlang source file
+-spec erl_string_to_erl_ast(string()) -> ErlangAst::term().
+erl_string_to_erl_ast(StringExpr) ->
+    Forms0 =
+        lists:foldl(fun(<<>>, Acc) ->
+                            Acc;
+                       (<<"\n\n">>, Acc) ->
+                            Acc;
+                       (El, Acc) ->
+                            {ok, Tokens, _} =
+                                erl_scan:string(binary_to_list(El)
+                                                ++ "."),
+                            [Tokens | Acc]
+                    end, [], re:split(StringExpr, "\\.\n")),
+    %% No need to reverse. This will rereverse for us
+    lists:foldl(fun(Form, Forms) ->
+                        {ok, ErlAST} = erl_parse:parse_form(Form),
+                        [ErlAST | Forms]
+                end, [], Forms0).
+
+%% @doc compile a string representing an erlang expression into a
+%% Core Erlang AST
+%%
+%% @param StringExpr - The path to the erlang source file
+-spec erl_string_to_core_ast(string()) -> CoreAst::term().
+erl_string_to_core_ast(StringExpr) ->
+    compile:forms(erl_string_to_erl_ast(StringExpr), [to_core]).
+
+%% @doc compile a string representing an erlang expression into a term
+%% that represents the ASM
+%%
+%% @param StringExpr - The path to the erlang source file
+-spec erl_string_to_asm(string()) -> ErlangAsm::term().
+erl_string_to_asm(StringExpr) ->
+    compile:forms(erl_string_to_erl_ast(StringExpr), ['S']).