CompiledExpr FieldExpr::compile()
{
if (this->protected_data->internal_type == 0)
{
std::string compiled_value(
get_field_name() + " == '" + this->protected_data->value + "'");
return CompiledExpr(get_compiled_expr_type(), compiled_value.c_str());
}
else if (this->protected_data->internal_type == 1)
{
return CompiledExpr(get_compiled_expr_type(),
this->protected_data->function->compile(get_field_name().c_str()));
}
}
std::string QueryCompiler::compile(Query& query_to_compile, std::string result_var_name)
{
ConnectiveExpr* expression_to_compile = query_to_compile.get_expr();
// The final script.
std::string script;
// Keeps first lines of the function (mainly, result variables initialization).
std::ostringstream function_header_stream;
// Keeps condition of tags.
std::ostringstream tags_stream;
// Keeps condition of other fields.
std::ostringstream fields_stream;
// Keeps sequence of `$r'.
std::ostringstream result;
compile_states::States current_state = compile_states::GROUP_AFTER_GROUP;
// Compiling expressions to CompiledExprs.
std::list<CompiledExpr> compiled_list = expression_to_compile->compile();
// Iterating over CompiledExprs to create a Jx9 script.
std::list<CompiledExpr>::iterator iterator = compiled_list.begin();
CompiledExpr* first_element = &*iterator;
++iterator;
CompiledExpr* second_element = &*iterator;
// Initializing data.
CompileStateData data(first_element, second_element,
&function_header_stream,
&tags_stream, &fields_stream, &result);
++iterator;
for (;iterator != compiled_list.end(); ++iterator)
{
current_state = state_table[current_state](data);
data.current_expr = &*data.next_expr;
data.next_expr = &*iterator;
}
// Last two elements in the list.
current_state = state_table[current_state](data);
// The last element.
data.current_expr = &*data.next_expr;
CompiledExpr nope_element = CompiledExpr(compiled_expr::NOPE, "");
data.next_expr = &nope_element;
current_state = state_table[current_state](data);
// Creating filter function.
script += "$filter_func = function($record) { ";
// Header of the function.
if (function_header_stream.tellp() != 0)
{
script += function_header_stream.str();
}
// Appending tags conditions, if there's any.
if (tags_stream.tellp() != 0)
{
script += " " + tags_stream.str() +" }";
}
script += " " + fields_stream.str();
script += " return " + result.str() + ";";
script += " }; ";
// Applying filter on database's records, and putting the result in the
// result variable.
script += "$" + result_var_name + " = db_fetch_all('files', $filter_func);";
return script;
}
