pkt: parse want and have lines

src/geef_pkt.erl

@@ -1,6 +1,10 @@
 -module(geef_pkt).
 
--export([line/1]).
+-export([line/1, parse/1]).
+
+-include("geef_records.hrl").
+
+-define(SHA_LEN, 40).
 
 -spec line(iolist()) -> iolist().
 line(Text) ->
@@ -8,3 +12,29 @@ line(Text) ->
     Len = 4 + iolist_size(Text) + 1,
     Prefix = io_lib:format("~4.16.0b", [Len]),
     [Prefix, Text, "\n"].
+
+-spec parse(iolist()) -> {{want | have, geef_oid()}, binary()}.
+parse(In0) ->
+    In = iolist_to_binary(In0),
+    <<BLen:4/binary, Rest/binary>> = In,
+    Len = binary_to_integer(BLen, 16),
+    case Len of
+	0 ->
+	    flush;
+	_ ->
+	    parse_pkt(Rest, Len - 4)
+    end.
+
+parse_pkt(In, Len) when size(In) < Len ->
+    {error, ebufs};
+parse_pkt(In, Len0) ->
+    Len1 = Len0 - 5, % "want " | "have "
+    case In of
+	<<"want ", Sha:?SHA_LEN/binary, Rest0/binary>> ->
+	    Pkt = {want, geef_oid:parse(Sha)};
+	<<"have ", Sha:?SHA_LEN/binary, Rest0/binary>> ->
+	    Pkt = {have, geef_oid:parse(Sha)}
+    end,
+    Len2 = Len1 - ?SHA_LEN, % get rid of the LF if we have it
+    <<_:Len2/binary, Rest/binary>> = Rest0,
+    {Pkt, Rest}.