Initial version of bencode module.

3 files changed, 124 insertions, 0 deletions

diff --git a/Makefile b/Makefile
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+++ b/Makefile
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+
+EUNITPATH=/home/ssmith/software/eunit-1.1
+
+ERLC=erlc
+ERLFLAGS=-I$(EUNITPATH)/inc 
+
+SRC=bencode.erl tests.erl
+BEAM=$(SRC:.erl=.beam)
+
+all: $(BEAM)
+
+%.beam : %.erl
+	$(ERLC) $(ERLFLAGS) $<
+
+test: $(BEAM)
+	erl -noshell -pa $(EUNITPATH)/ebin -s tests -s init stop
+
+clean:
+	rm -f $(BEAM) *~
diff --git a/bencode.erl b/bencode.erl
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+++ b/bencode.erl
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+
+-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)).
+    
diff --git a/tests.erl b/tests.erl
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+++ b/tests.erl
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+
+-module(tests).
+
+-include("eunit.hrl").
+
+-export([start/0, 
+	 test_int1/0, test_int2/0, test_int3/0, test_int4/0, 
+	 test_string1/0, test_string2/0, 
+	 test_list1/0, test_list2/0, test_list3/0, test_list4/0, test_list5/0, 
+	 test_dict1/0]).
+
+%% Integer decoding tests
+test_int1() ->
+    ?match({{int, 999}, []}, bencode:bdecode("i999e")).
+test_int2() ->
+    ?match({{int, 0}, []}, bencode:bdecode("i0e")).
+test_int3() ->
+    ?match({{int, 123}, "abc"}, bencode:bdecode("i123eabc")).
+test_int4() ->
+    ?match({{int, -10}, []}, bencode:bdecode("i-10e")).
+
+%% String decoding tests
+test_string1() ->
+    ?match({{string, ""}, []}, bencode:bdecode("0:")).
+test_string2() ->
+    ?match({{string, "abcde"}, []}, bencode:bdecode("5:abcde")).
+
+%% List decoding tests
+test_list1() ->
+    ?match({{list, []}, []}, bencode:bdecode("le")).
+test_list2() ->
+    ?match({{list, [{int,1}]}, []}, bencode:bdecode("li1ee")).
+test_list3() ->
+    ?match({{list, [{int,1}]}, []}, bencode:bdecode("li1ee")).
+test_list4() ->
+    ?match({{list, [{int,1}, {int,2}]}, []}, bencode:bdecode("li1ei2ee")).
+test_list5() ->
+    ?match({{list, [{int,1},
+		    {list, [{int, 2}, {int, 3}]}]},
+	   []}, 
+	   bencode:bdecode("li1eli2ei3eee")).
+
+%% Dict decoding tests
+test_dict1() ->
+    {{dict, Dict}, []} = bencode:bdecode("d3:agei25e4:eyes4:bluee"),
+    ?match([{"age", {int, 25}}, {"eyes", {string, "blue"}}], dict:to_list(Dict)).
+
+%% Entry point
+start() ->
+    eunit:run([tests], {prefix, "test_"}).