From e69ac5f3714c9284e9b162b4560942a29d7c8107 Mon Sep 17 00:00:00 2001
From: alisdair sullivan <alisdairsullivan@yahoo.ca>
Date: Wed, 4 Apr 2012 20:46:41 -0700
Subject: [PATCH] detect utf8 bom and ignore if present

---
 priv/test_cases/bom.json |  1 +
 priv/test_cases/bom.test |  3 +++
 src/jsx_decoder.erl      | 26 +++++++++++++++++++++++++-
 3 files changed, 29 insertions(+), 1 deletion(-)
 create mode 100644 priv/test_cases/bom.json
 create mode 100644 priv/test_cases/bom.test

diff --git a/priv/test_cases/bom.json b/priv/test_cases/bom.json
new file mode 100644
index 0000000..ad47dbb
--- /dev/null
+++ b/priv/test_cases/bom.json
@@ -0,0 +1 @@
+[]
\ No newline at end of file
diff --git a/priv/test_cases/bom.test b/priv/test_cases/bom.test
new file mode 100644
index 0000000..75b9d3e
--- /dev/null
+++ b/priv/test_cases/bom.test
@@ -0,0 +1,3 @@
+{name, "byte order mark"}.
+{jsx, [start_array, end_array, end_json]}.
+{json, "bom.json"}.
diff --git a/src/jsx_decoder.erl b/src/jsx_decoder.erl
index 4e64bec..a362638 100644
--- a/src/jsx_decoder.erl
+++ b/src/jsx_decoder.erl
@@ -29,7 +29,7 @@
 -spec decoder(Handler::module(), State::any(), Opts::jsx:opts()) -> jsx:decoder().
 
 decoder(Handler, State, Opts) ->
-    fun(JSON) -> value(JSON, {Handler, Handler:init(State)}, [], jsx_utils:parse_opts(Opts)) end.
+    fun(JSON) -> start(JSON, {Handler, Handler:init(State)}, [], jsx_utils:parse_opts(Opts)) end.
 
 
 -include("jsx_opts.hrl").
@@ -128,6 +128,30 @@ decoder(Handler, State, Opts) ->
 -define(end_seq(Seq), unicode:characters_to_binary(lists:reverse(Seq))).
 
 
+start(<<16#ef, Rest/binary>>, Handler, Stack, Opts) ->
+    maybe_bom(Rest, Handler, Stack, Opts);
+start(<<>>, Handler, Stack, Opts) ->
+    ?incomplete(start, <<>>, Handler, Stack, Opts);
+start(Bin, Handler, Stack, Opts) ->
+    value(Bin, Handler, Stack, Opts).
+
+
+maybe_bom(<<16#bb, Rest/binary>>, Handler, Stack, Opts) ->
+    definitely_bom(Rest, Handler, Stack, Opts);
+maybe_bom(<<>>, Handler, Stack, Opts) ->
+    ?incomplete(maybe_bom, <<>>, Handler, Stack, Opts);
+maybe_bom(Bin, Handler, Stack, Opts) ->
+    ?error([Bin, Handler, Stack, Opts]).
+
+
+definitely_bom(<<16#bf, Rest/binary>>, Handler, Stack, Opts) ->
+    value(Rest, Handler, Stack, Opts);
+definitely_bom(<<>>, Handler, Stack, Opts) ->
+    ?incomplete(definitely_bom, <<>>, Handler, Stack, Opts);
+definitely_bom(Bin, Handler, Stack, Opts) ->
+    ?error([Bin, Handler, Stack, Opts]).
+
+
 value(<<?doublequote, Rest/binary>>, Handler, Stack, Opts) ->
     string(Rest, Handler, [?new_seq()|Stack], Opts);
 value(<<?singlequote, Rest/binary>>, Handler, Stack, Opts = #opts{single_quoted_strings=true}) ->