Improve processing of SQLITE_NULL

null-atom can be configured on configure or make stage. For example
./configure --enable-null-atom=undefined && make

Emakefile

@@ -1,3 +1,3 @@
-{'src/sqlite3_lib.erl',[debug_info,{outdir,"ebin"}]}.
+{'src/sqlite3_lib.erl',[debug_info,{outdir,"ebin"}, {d, 'NULL_ATOM', 'xxx'}]}.
 {'src/sqlite3.erl',[debug_info,{outdir,"ebin"}]}.
 {'src/sqlite3_test.erl',[debug_info,{outdir,"ebin"}]}.

Emakefile.in

@@ -0,0 +1,3 @@
+{'src/sqlite3_lib.erl',[debug_info,{outdir,"ebin"}, {d, 'NULL_ATOM', '@NULL_ATOM@'}]}.
+{'src/sqlite3.erl',[debug_info,{outdir,"ebin"}]}.
+{'src/sqlite3_test.erl',[debug_info,{outdir,"ebin"}]}.

Makefile.in

@@ -1,4 +1,5 @@
 ERL=@ERL@
+ERLC=@ERLC@
 ERL_KERNEL=@ERLANG_LIB_DIR_kernel@
 ERL_STDLIB=@ERLANG_LIB_DIR_stdlib@
 ERL_CRYPTO=@ERLANG_LIB_DIR_crypto@

configure.ac

@@ -41,6 +41,15 @@ AC_ERLANG_CHECK_LIB(compiler)
 AC_ERLANG_CHECK_LIB(hipe)
 AC_ERLANG_CHECK_LIB(syntax_tools)
 
+AC_ARG_ENABLE([null-atom], 
+              [AC_HELP_STRING([--enable-null-atom=atom],
+                              [Set to configure null-atom, default 'null'])],
+              [ ac_null_atom=$enableval ],
+              [ ac_null_atom=null ])
+
+NULL_ATOM="$ac_null_atom"
+AC_SUBST([NULL_ATOM])
 AC_CONFIG_FILES([Makefile
+                 Emakefile
                  priv/Makefile])
 AC_OUTPUT

priv/Makefile.in

@@ -4,7 +4,7 @@ GCC=gcc
 LDFLAGS=-shared -L/usr/lib -lsqlite3 -undefined -fPIC -lerl_interface -L$(ERL_INTERFACE)/lib -lei
 SRCS=sqlite3_drv.c sqlite3_drv.h
 OUTPUT=sqlite3_drv.so
-CFLAGS=-o ../ebin/${OUTPUT} -I$(ERL_ROOT)/usr/include/ -I$(ERL_INTERFACE)/include/ 
+CFLAGS=-o ../ebin/${OUTPUT} -I$(ERL_ROOT)/usr/include/ -I$(ERL_INTERFACE)/include/ -DNULL_ATOM=@NULL_ATOM@
 
 all: ../ebin/${OUTPUT}
 

priv/sqlite3_drv.c

@@ -65,10 +65,12 @@ static ErlDrvData start(ErlDrvPort port, char* cmd) {
   retval->db = db;
   retval->key = 42; //FIXME: Just a magic number, make real key
 
+#define STR_(ARG) #ARG
+#define STR(ARG) STR_(ARG)
   retval->atom_error = driver_mk_atom ("error");
   retval->atom_columns = driver_mk_atom ("columns");
   retval->atom_rows = driver_mk_atom ("rows");
-  retval->atom_null = driver_mk_atom ("null");
+  retval->atom_null = driver_mk_atom (STR (NULL_ATOM));
   retval->atom_id = driver_mk_atom ("id");
   retval->atom_ok = driver_mk_atom ("ok");
   retval->atom_unknown_cmd = driver_mk_atom ("uknown_command");

src/sqlite3_lib.erl

@@ -50,12 +50,11 @@ col_type("DATE") ->
 %%--------------------------------------------------------------------
 -spec(write_value_sql/1::(any()) -> string()).
 write_value_sql(Values) ->
-    StrValues = lists:map(fun(X) when is_integer(X) ->
-				  integer_to_list(X);
-			     (X) when is_float(X) ->
-				  float_to_list(X);
-			     (X) ->
-				  io_lib:format("'~s'", [X])
+    StrValues = lists:map(fun
+          (X) when is_integer(X) -> integer_to_list(X);
+          (X) when is_float(X)   -> float_to_list(X);
+          (?NULL_ATOM)           -> 'null';
+          (X)                    -> io_lib:format("'~s'", [X])
 			  end, Values),
     string:join(StrValues, ",").