fp-idn

fp-idn is a lightweight Pascal library for encoding and decoding Internationalized Domain Names (IDN) using the Punycode algorithm. Designed to be compatible with FreePascal and Lazarus projects.

Features

• ✅ Pure FreePascal implementation (no dependencies)
• 🌍 Supports full round-trip conversion between Unicode and Punycode
• 🔤 Includes domain-level IDN handling with subdomain support
• 🧪 Comes with comprehensive test coverage using FPCUnit

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Units

• fppunycode.pas: Core Punycode encode/decode functions
• fpidn.pas: Domain-level IDN wrapper functions (IDNToUnicode, UnicodeToIDN)
• test_idn_n_punycode.pas: Unit tests for both units
• test_idn_n_punycode_property.pas: Property-based tests
• fpidn_rt.lpk: Lazarus run-time package bundling the IDN units

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Usage

Convert UTF-8 to Punycode

uses fppunycode;

var
  puny: string;
begin
  puny := UTF8ToPunycode('тест'); // -> b1abfaa5a0a
end;

Convert domain name using IDN unit

uses fpidn;

var
  encoded, decoded: string;
begin
  encoded := UnicodeToIDN('пример.рф');
  decoded := IDNToUnicode(encoded);
end;

Demo console application

A small console demonstration is located in examples/demo_console. Open the demo_console.lpi project in Lazarus or build it with lazbuild:

lazbuild examples/demo_console/demo_console.lpi
./demo_console

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Build & Run Tests

Before running the scripts below make sure the FreePascal compiler is installed. If it is not available in your PATH, set the FPC environment variable to the full path of the fpc executable.

Windows

Run the batch script:

build_tests.bat

Linux/macOS

Run the shell script:

./build_tests.sh

You will see FPCUnit test output with full results in XML and console form.

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Build & Run Benchmarks

The repository also includes simple performance benchmarks for fppunycode and fpidn. They output results to the console and save them to benchmarks/results.csv.

Windows

Run the batch script:

build_benchmarks.bat

Linux/macOS

Run the shell script:

./build_benchmarks.sh

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Requirements

• FreePascal 3.0+ (ensure fpc is accessible or set the FPC environment variable)
• Optional: Lazarus IDE for integration in GUI-based tools

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License

MIT License — free to use in personal and commercial projects.

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Author

Developed by @al-muhandis

Inspired by the need for lightweight, native Punycode support in FreePascal-based applications.