Implements BIT(N) <--> bitstring() of length N

doc/overview.edoc

@@ -54,6 +54,11 @@ connecting to and interacting with a MySQL server.
       <td>`<<"foo">>, "bar"'</td>
     </tr>
     <tr>
+      <td>BIT(N)</td>
+      <td>`bitstring()'</td>
+      <td>`<<255, 6:3>>'</td>
+    </tr>
+    <tr>
       <td>FLOAT, DOUBLE</td>
       <td>`float()'</td>
       <td>`3.14'</td>
@@ -105,7 +110,7 @@ Notes:
     seconds, we use a float for the seconds part. (These are unusual and were
     added to MySQL in version 5.6.4.)</li>
   <li id="vn4">Since `TIME' can be outside the `calendar:time()' interval, we use
-    the format as returned by calendar:seconds_to_daystime/1 for `TIME'
+    the format as returned by `calendar:seconds_to_daystime/1' for `TIME'
     values.</li>
 </ol>
 

src/mysql_protocol.erl

@@ -405,9 +405,9 @@ decode_text(#col{type = T}, Text)
     %% As of MySQL 5.6.21 we receive SET and ENUM values as STRING, i.e. we
     %% cannot convert them to atom() or sets:set(), etc.
     Text;
-decode_text(#col{type = ?TYPE_BIT, length = _Length}, Text) ->
-    %% TODO: Convert to <<_:Length/bitstring>>
-    Text;
+decode_text(#col{type = ?TYPE_BIT, length = Length}, Text) ->
+    %% Convert to <<_:Length/bitstring>>
+    decode_bitstring(Text, Length);
 decode_text(#col{type = ?TYPE_DATE},
             <<Y:4/binary, "-", M:2/binary, "-", D:2/binary>>) ->
     {binary_to_integer(Y), binary_to_integer(M), binary_to_integer(D)};
@@ -543,8 +543,7 @@ decode_binary(#col{type = T}, Data)
   when T == ?TYPE_STRING; T == ?TYPE_VARCHAR; T == ?TYPE_VAR_STRING;
        T == ?TYPE_ENUM; T == ?TYPE_SET; T == ?TYPE_LONG_BLOB;
        T == ?TYPE_MEDIUM_BLOB; T == ?TYPE_BLOB; T == ?TYPE_TINY_BLOB;
-       T == ?TYPE_GEOMETRY; T == ?TYPE_BIT; T == ?TYPE_DECIMAL;
-       T == ?TYPE_NEWDECIMAL ->
+       T == ?TYPE_GEOMETRY; T == ?TYPE_DECIMAL; T == ?TYPE_NEWDECIMAL ->
     %% As of MySQL 5.6.21 we receive SET and ENUM values as STRING, i.e. we
     %% cannot convert them to atom() or sets:set(), etc.
     lenenc_str(Data);
@@ -598,6 +597,10 @@ decode_binary(#col{type = ?TYPE_FLOAT},
     Factor = math:pow(10, floor(6 - math:log10(abs(Value)))),
     RoundedValue = round(Value * Factor) / Factor,
     {RoundedValue, Rest};
+decode_binary(#col{type = ?TYPE_BIT, length = Length}, Data) ->
+    {Binary, Rest} = lenenc_str(Data),
+    %% Convert to <<_:Length/bitstring>>
+    {decode_bitstring(Binary, Length), Rest};
 decode_binary(#col{type = ?TYPE_DATE}, <<Length, Data/binary>>) ->
     %% Coded in the same way as DATETIME and TIMESTAMP below, but returned in
     %% a simple triple.
@@ -701,6 +704,10 @@ encode_param(Value) when is_integer(Value), Value < 0 ->
     end;
 encode_param(Value) when is_float(Value) ->
     {<<?TYPE_DOUBLE, 0>>, <<Value:64/float-little>>};
+encode_param(Value) when is_bitstring(Value) ->
+    Binary = encode_bitstring(Value),
+    EncLength = lenenc_int_encode(byte_size(Binary)),
+    {<<?TYPE_VAR_STRING, 0>>, <<EncLength/binary, Binary/binary>>};
 encode_param(Set) when is_tuple(Set), element(1, Set) == set ->
     %% For convenience; encode only. When decoding, a set is returned as binary.
     Binary = set_to_binary(Set),
@@ -747,6 +754,17 @@ encode_param({D, {H, M, 0.0}}) ->
 
 %% -- Value representation in both the text and binary protocols --
 
+%% @doc Convert to `<<_:Length/bitstring>>'
+decode_bitstring(Binary, Length) ->
+    PaddingLength = bit_size(Binary) - Length,
+    <<_:PaddingLength/bitstring, Bitstring:Length/bitstring>> = Binary,
+    Bitstring.
+
+encode_bitstring(Bitstring) ->
+    Size = bit_size(Bitstring),
+    PaddingSize = byte_size(Bitstring) * 8 - Size,
+    <<0:PaddingSize, Bitstring:Size/bitstring>>.
+
 %% @doc Converts a set of atoms (or binaries) to a comma-separated binary.
 set_to_binary(Set) ->
     List = [if is_atom(X) -> atom_to_binary(X, utf8); is_binary(X) -> X end
@@ -940,7 +958,7 @@ decode_text_test() ->
                    ?TYPE_INT24, ?TYPE_YEAR]),
 
     %% BIT
-    <<217>> = decode_text(#col{type = ?TYPE_BIT}, <<217>>),
+    <<217>> = decode_text(#col{type = ?TYPE_BIT, length = 8}, <<217>>),
 
     %% Floating point and decimal numbers
     lists:foreach(fun (T) ->

test/mysql_tests.erl

@@ -62,7 +62,7 @@ query_test_() ->
              fun binary_protocol/1,
              fun float_rounding/1,
              fun int/1,
-             %fun bit/1,
+             fun bit/1,
              fun time/1,
              fun microseconds/1]}}.
 
@@ -210,7 +210,7 @@ bit(Pid) ->
     ok = mysql:query(Pid, "CREATE TABLE bits (b BIT(11))"),
     write_read_text_binary(Pid, <<16#ff, 0:3>>, <<"b'11111111000'">>,
                            <<"bits">>, <<"b">>),
-    write_read_text_binary(Pid, <<16#7f, 2:3>>, <<"b'01111111110'">>,
+    write_read_text_binary(Pid, <<16#7f, 6:3>>, <<"b'01111111110'">>,
                            <<"bits">>, <<"b">>),
     ok = mysql:query(Pid, "DROP TABLE bits").