Initial version of bencode module.

1 files changed, 55 insertions, 0 deletions

diff --git a/bencode.erl b/bencode.erl
new file mode 100644
index 0000000..aaf737e
--- /dev/null
+++ b/bencode.erl
@@ -0,0 +1,55 @@
+
+-module(bencode).
+
+-export([bdecode/1]).
+
+-import(string, [substr/2, substr/3, to_integer/1, chr/2]).
+
+%% String
+bdecode([Char | _Rest] = Str) when Char >= $0, Char =< $9 ->
+    ColIdx = chr(Str, $:),
+    IntStr = substr(Str, 1, ColIdx-1),
+    {Len, _} = to_integer(IntStr),
+    Result = substr(Str, ColIdx+1, Len),
+    Rest = substr(Str, ColIdx+Len+1),
+    {{string, Result}, Rest};
+
+%% Int
+bdecode([Char | Rest]) when Char == $i ->
+    End = chr(Rest, $e),
+    {Result, _} = to_integer(substr(Rest, 1, End-1)),
+    {{int, Result}, substr(Rest, End+1)};
+
+%% List
+bdecode([Char | Rest]) when Char == $l ->
+    {List, Rem} = dolist(Rest),
+    {{list, List}, Rem};
+
+%% Dict
+bdecode([Char | Rest]) when Char == $d ->
+    {Dict, Rem} = dodict(Rest),
+    {{dict, Dict}, Rem}.
+
+
+dolist(Str) ->
+    dolist(Str, []).
+
+dolist([Char | Rest], List) when Char == $e ->
+    {List, Rest};
+
+dolist(Str, List) ->
+    {Result, Rest} = bdecode(Str),
+    dolist(Rest, lists:append(List, [Result])).
+
+
+dodict(Str) ->
+    dodict(Str, dict:new()).
+
+dodict([Char | Rest], Dict) when Char == $e ->
+    {Dict, Rest};
+
+dodict(Str, Dict) ->
+    {{string, Key}, Rest} = bdecode(Str),
+    {Val, Rest2} = bdecode(Rest),
+    dodict(Rest2, dict:store(Key, Val, Dict)).
+