Adding column names functionality

c_src/esqlite3_nif.c

@@ -59,6 +59,7 @@ typedef enum {
      cmd_prepare,
      cmd_bind,
      cmd_step,
+     cmd_column_names,
      cmd_close,
      cmd_stop
 } command_type;
@@ -381,6 +382,13 @@ do_step(ErlNifEnv *env, sqlite3_stmt *stmt)
      if(rc == SQLITE_ROW) 
 	  return make_row(env, stmt);
 
+     return make_error_tuple(env, "unexpected_return_value");
+}
+
+static ERL_NIF_TERM
+do_column_names(ErlNifEnv *env, sqlite3_stmt *stmt)
+{
+     fprintf(stderr, "Called column names\n");
      return _atom_ok;
 }
 
@@ -414,6 +422,8 @@ evaluate_command(esqlite_command *cmd, esqlite_connection *conn)
 	  return do_step(cmd->env, cmd->stmt);
      case cmd_bind:
 	  return do_bind(cmd->env, conn->db, cmd->stmt, cmd->arg);
+     case cmd_column_names:
+	  return do_column_names(cmd->env, cmd->stmt);
      case cmd_close:
 	  return do_close(cmd->env, conn, cmd->arg);
      default:
@@ -682,6 +692,48 @@ esqlite_step(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[])
      return _atom_ok;
 }
 
+/*
+ * Step to a prepared statement
+ */
+static ERL_NIF_TERM 
+esqlite_column_names(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[])
+{
+     esqlite_statement *stmt;
+     esqlite_command *cmd = NULL;
+     ErlNifPid pid;
+
+     if(argc != 3) 
+	  return enif_make_badarg(env);
+     if(!enif_get_resource(env, argv[0], esqlite_statement_type, (void **) &stmt))
+	  return enif_make_badarg(env);
+     if(!enif_is_ref(env, argv[1])) 
+	  return make_error_tuple(env, "invalid_ref");
+     if(!enif_get_local_pid(env, argv[2], &pid)) 
+	  return make_error_tuple(env, "invalid_pid"); 
+
+     if(!stmt->statement) 
+	  return make_error_tuple(env, "no_prepared_statement");
+
+     cmd = command_create();
+     if(!cmd) 
+	  return make_error_tuple(env, "command_create_failed");
+
+     cmd->type = cmd_column_names;
+     cmd->ref = enif_make_copy(cmd->env, argv[1]);
+     cmd->pid = pid;
+     cmd->stmt = stmt->statement;
+
+     if(!stmt->connection) 
+	  return make_error_tuple(env, "no_connection");
+     if(!stmt->connection->commands)
+	  return make_error_tuple(env, "no_command_queue");
+
+     if(!queue_push(stmt->connection->commands, cmd)) 
+	  return make_error_tuple(env, "command_push_failed");
+
+     return _atom_ok;
+}
+
 /*
  * Close the database
  */
@@ -750,6 +802,7 @@ static ErlNifFunc nif_funcs[] = {
      {"step", 3, esqlite_step},
      // {"esqlite_bind", 3, esqlite_bind_named},
      {"bind", 4, esqlite_bind},
+     {"column_names", 3, esqlite_column_names},
      {"close", 3, esqlite_close}
 };
 

src/esqlite3.erl

@@ -71,7 +71,8 @@ foreach(F, Sql, Connection) ->
 %%
 foreach_s(F, Statement) ->    
     case try_step(Statement, 0) of
-	'$done' -> ok;
+	'$done' -> 
+	    ok;
 	Row when is_tuple(Row) ->
 	    F(Row),
 	    foreach_s(F, Statement)
@@ -82,7 +83,7 @@ map_s(F, Statement) ->
     case try_step(Statement, 0) of
 	'$done' ->
 	    [];
-	Row -> 
+	Row when is_tuple(Row) -> 
 	    [F(Row) | map_s(F, Statement)]
     end.
 
@@ -95,11 +96,13 @@ do_steps(Statement) ->
 	    [Row | do_steps(Statement)]
     end.  
 
+%% Try the step, when the database is busy, 
 try_step(_Statement, Tries) when Tries > 5 ->
     throw(too_many_tries);
 try_step(Statement, Tries) ->
     case esqlite3:step(Statement) of
 	'$busy' -> 
+	    timer:sleep(100 * Tries),
 	    try_step(Statement, Tries + 1);
 	Something -> 
 	    Something

src/esqlite3_nif.erl

@@ -27,6 +27,7 @@
 	 prepare/4,
 	 step/3,
 	 bind/4,
+	 column_names/3,
 	 close/3
 ]).
 
@@ -70,16 +71,22 @@ prepare(_Db, _Ref, _Dest, _Sql) ->
 
 %% @doc
 %%
-%% @spec step(connection(), reference(), pid()) -> ok | {error, message()}
+%% @spec step(statement(), reference(), pid()) -> ok | {error, message()}
 step(_Stmt, _Ref, _Dest) ->
     exit(nif_library_not_loaded).
 
 %% @doc Bind parameters to a prepared statement. 
 %%
-%% @spec bind(connection(), reference(), pid(), []) -> ok | {error, message()} 
+%% @spec bind(statement(), reference(), pid(), []) -> ok | {error, message()} 
 bind(_Stmt, _Ref, _Dest, _Args) ->
     exit(nif_library_not_loaded).
 
+%% @doc Retrieve the column names of the prepared statement
+%%
+%% @spec column_names(statement(), reference(), pid()) -> {ok, tuple()} | {error, message()} 
+column_names(_Stmt, _Ref, _Dest) ->
+    exit(nif_library_not_loaded).
+
 %% @doc Close the connection.
 %%
 %% @spec close(connection(), reference(), pid()) -> ok | {error, message()}

test/esqlite_test.erl

@@ -74,6 +74,21 @@ bind_test() ->
 
     ok.
 
+column_names_test() ->
+    {ok, Db} = esqlite3:open(":memory:"),
+    ok = esqlite3:exec("begin;", Db),
+    ok = esqlite3:exec("create table test_table(one varchar(10), two int);", Db),
+    ok = esqlite3:exec(["insert into test_table values(", "\"hello1\"", ",", "10" ");"], Db),
+    ok = esqlite3:exec("commit;", Db),
+
+    {ok, Stmt} = esqlite3:prepare("select * from test_table", Db),
+    
+    test = esqlite3:column_names(Stmt),
+    
+    ok.
+
+    
+
 foreach_test() ->
     {ok, Db} = esqlite3:open(":memory:"),
     ok = esqlite3:exec("begin;", Db),
@@ -93,7 +108,7 @@ foreach_test() ->
 		end
 	end,
     
-    esqlite3:foreach(F, "select * from test_table", Db),
+    esqlite3:foreach(F, "select * from test_table;", Db),
     
     10 = get("hello1"),
     11 = get("hello2"),