ConfigScript

Overview

This is a grammar in ANTLR for a config markup language, similar to OGRE Scripts:

// This is a comment
object_keyword "Example/ObjectName"
{
    attribute_name "some value"

    list_of_strings_attribute [
        "item #1" "item #2"
        "item #3" "item #4" "item #5"
    ]

    object_keyword2 "Nested Object"
    {
        other_attribute 1 2 3
        /* block comment */
    }
}

This repo includes a parser implementation in C++, so grammar is spiced up with the C++-specific actions.

Building

First, generate the C++ sources for the grammar parser using ANTLR 4.13.0 JAR:

java -jar antlr-4.13.0-complete.jar -o gen_parser -Dlanguage=Cpp ConfigScript.g4

NOTE: it is important to keep ANTLR4 generator version in sync with what is provided by the vcpkg.

Run CMake specifying vcpkg as a toolchain:

cmake -B build -S . -DCMAKE_TOOLCHAIN_FILE="[path to vcpkg]/scripts/buildsystems/vcpkg.cmake"

Then, build the project:

cmake --build build

Usage

First, add the necessary headers to your code:

#include "parser.hpp"

Parse the code:

const auto configSource = R"(
// This is a comment
my_object_1 "Example/ObjectName" // <--- this can not be just Example/ObjectName (no quotes)
{
    some_attribute "some value"

    list_of_strings_attribute [
        "item #1" "item #2"
        "item #3" "item #4" "item #5"
    ]

    my_object_2 "Nested Object"
    {
        other_attribute 1 2 3
        // and so on..
        /* block comment */
    }
}
)";

// parse the source
auto config = ConfigScript::Parser::parse(configSource);

The config variable would then contain a list (std::vector) of top-level objects from the config.

To access the top-level object properties, use

std::map<std::string, ConfigScript::PropertyType> properties = config[0].properties;

ConfigScripr::PropertyType is an alias for std::variant containing all possible value types:

• int and float vectors of 2, 3 or 4 components: Vec2i, Vec3i, Vec4i, Vec2f, Vec3f, Vec4f
• std::string
• bool
• int
• float
• lists of strings (std::vector<std::string>)
• objects, represented as

  ConfigScript::Object {
    std::string name;
    std::string classifier;
    std::map<std::string, ConfigScript::PropertyType> properties;
  }

Since PropertyType is alias for std::variant, you would have to cast it to whatever it is underneath in order to access a specific property value:

auto property1 = std::get<std::string>(propertyValue1); // string values
auto property2 = std::get<ConfigScript::Vec3f>(propertyValue2); // 4-component float vector

Objects can have a classifier, which is a string following the object name:

object_name "object classifier"
{
  // properties
}