Working on chapter 7 exercises.

pe/chapter7.erl

@@ -0,0 +1,52 @@
+-module(chapter7).
+-export([breverse/1, term_to_packet/1, packet_to_term/1, reverse_byte/1,
+	 reverse_bits/1, reverse_bitlist/1, test/0]).
+
+%% Exercises
+%% 1. Write a function that reverses the order of bytes in a binary.
+breverse(Bin) ->
+    binary:list_to_bin(lists:reverse(binary:bin_to_list(Bin))).
+
+%% 2. Write a function term_to_packet(Term) -> Packet that returns a
+%%    binary consisting of a 4-byte length header N followed by N
+%%    bytes of data produced by calling term_to_binary(Term).
+
+%% Need to packetize
+term_to_packet(Term) ->
+    BinaryTerm = erlang:term_to_binary(Term),
+    Length = erlang:byte_size(BinaryTerm),
+    <<Length:32, BinaryTerm:Length/bytes>>.
+    
+%% 3. Write the inverse function packet_to_term(Packet) -> Term that
+%%    is the inverse of the previous function.
+packet_to_term(<<Length:32, BinaryTerm:Length/bytes>>) ->
+    erlang:binary_to_term(BinaryTerm).
+
+packet_test(Term) ->
+    Term = packet_to_term(term_to_packet(Term)).
+
+%% 4. Write some tests in the style of Adding Tests to Your Code, on
+%%    page 46, to test that the previous two functions can correctly
+%%    encode terms into packets and recover the original terms by
+%%    decoding the packets.
+test() ->
+    Squared = fun (X) -> X * X end,
+    packet_test(Squared),
+    packet_test(32),
+    packet_test(<<"Goodbye, Joe.">>),
+    <<0:7, 1:1>> = reverse_byte(<<1:1, 0:7>>).
+
+%% 5. Write a function to reverse the bits in a binary.
+reverse_byte(<<A:1, B:1, C:1, D:1, E:1, F:1, G:1, H:1>>) ->
+    <<H:1,G:1,F:1,E:1,D:1,C:1,B:1,A:1>>;
+reverse_byte(<<>>) -> <<>>.
+
+reverse_bitlist([]) -> [];
+reverse_bitlist([H|T]) ->
+    [reverse_byte(H) || reverse_bitlist(T)].
+
+reverse_bits(Binary) ->
+    erlang:list_to_binary(reverse_bitlist(erlang:binary_to_list(Binary))).
+
+
+