generate_hello_world.cpp

// AI Generated 2026 Ryan P. Nicholl  <rnicholl@protonmail.com>
// SPDX-License-Identifier: Apache-2.0
 
#include <rpnx/cortado/builders.hpp>
#include <rpnx/cortado/jar.hpp>
 
#include <cstddef>
#include <cstdint>
#include <exception>
#include <filesystem>
#include <fstream>
#include <iostream>
#include <span>
#include <stdexcept>
#include <string>
#include <utility>
#include <vector>
 
int main(int argument_count, char** argument_values)
{
    try
    {
        if (argument_count > 2)
        {
            std::cerr << "usage: rpnx_cortado_generate_hello_world [output-directory]\n";
            return 2;
        }
 
        std::filesystem::path const output_directory = argument_count == 2 ? std::filesystem::path(argument_values[1]) : std::filesystem::current_path();
        std::filesystem::create_directories(output_directory);
 
        rpnx::cortado::class_file_builder builder("HelloWorld", "java/lang/Object", {0, 52});
        rpnx::cortado::code_builder main_code;
        main_code.getstatic("java/lang/System", "out", "Ljava/io/PrintStream;").ldc_string("hello world").invokevirtual("java/io/PrintStream", "println", "(Ljava/lang/String;)V").append< rpnx::cortado::opcode::return_ >();
        static_cast< void >(builder.add_method("main", "([Ljava/lang/String;)V", rpnx::cortado::method_access_flags::is_public | rpnx::cortado::method_access_flags::is_static, main_code));
 
        rpnx::cortado::code_builder choose_code;
        rpnx::cortado::label const false_result = choose_code.new_label();
        choose_code.iload({0}).branch< rpnx::cortado::opcode::ifeq >(false_result).append< rpnx::cortado::opcode::iconst_1 >().append< rpnx::cortado::opcode::ireturn >();
        choose_code.bind(false_result).append< rpnx::cortado::opcode::iconst_0 >().append< rpnx::cortado::opcode::ireturn >();
        static_cast< void >(builder.add_method("choose", "(Z)I", rpnx::cortado::method_access_flags::is_public | rpnx::cortado::method_access_flags::is_static, choose_code));
        rpnx::cortado::class_file const hello_world_class = builder.build();
 
        std::vector< std::byte > const class_bytes = rpnx::cortado::serialize_class_file(hello_world_class);
        std::string const manifest_text = "Manifest-Version: 1.0\nMain-Class: HelloWorld\n\n";
        std::vector< std::byte > manifest_bytes;
        manifest_bytes.reserve(manifest_text.size());
        for (char const character : manifest_text)
        {
            manifest_bytes.push_back(static_cast< std::byte >(static_cast< std::uint8_t >(character)));
        }
 
        rpnx::cortado::jar_file hello_world_jar;
        hello_world_jar.entries.push_back(rpnx::cortado::jar_entry{.name = "META-INF/MANIFEST.MF", .data = std::move(manifest_bytes), .compression = rpnx::cortado::compression_method::stored, .flags = rpnx::cortado::jar_entry_flags::utf8_names, .modification_date = rpnx::cortado::zip_dos_date{0x0021}});
        hello_world_jar.entries.push_back(rpnx::cortado::jar_entry{.name = "HelloWorld.class", .data = class_bytes, .compression = rpnx::cortado::compression_method::deflated, .flags = rpnx::cortado::jar_entry_flags::utf8_names, .modification_date = rpnx::cortado::zip_dos_date{0x0021}});
        std::vector< std::byte > const jar_bytes = rpnx::cortado::serialize_jar(hello_world_jar);
 
        auto write_binary_file = [](std::filesystem::path const& path, std::span< std::byte const > bytes)
        {
            std::ofstream output(path, std::ios::binary | std::ios::trunc);
            if (!output)
            {
                throw std::runtime_error("could not open " + path.string());
            }
            for (std::byte const byte : bytes)
            {
                output.put(static_cast< char >(std::to_integer< std::uint8_t >(byte)));
            }
            if (!output)
            {
                throw std::runtime_error("could not write " + path.string());
            }
        };
 
        std::filesystem::path const class_path = output_directory / "HelloWorld.class";
        std::filesystem::path const jar_path = output_directory / "hello-world.jar";
        write_binary_file(class_path, class_bytes);
        write_binary_file(jar_path, jar_bytes);
        std::cout << "wrote " << class_path << '\n';
        std::cout << "wrote " << jar_path << '\n';
        return 0;
    }
    catch (std::exception const& error)
    {
        std::cerr << "rpnx_cortado_generate_hello_world: " << error.what() << '\n';
        return 1;
    }
}