Encoding1257 1.0.0

Encoding1257

A high-performance managed implementation of Windows-1257 (Baltic) encoding for .NET.

Overview

Windows-1257 is a legacy character encoding used primarily for Baltic languages (Lithuanian, Latvian, Estonian). While this encoding has been largely superseded by Unicode (UTF-8/UTF-16) for modern applications, it's still needed for:

• Legacy System Integration: Working with older systems and databases that store data in Windows-1257
• File Format Compatibility: Reading and writing files created by legacy applications
• Data Migration: Converting historical data from Windows-1257 to modern encodings
• Interoperability: Communicating with systems that still use this encoding

This library provides a fast, managed implementation of the Windows-1257 encoding that integrates seamlessly with .NET's System.Text.Encoding infrastructure.

Note: For new projects, consider using UTF-8 encoding unless you specifically need Windows-1257 compatibility.

Features

• High Performance: Optimized implementation with aggressive inlining and efficient lookup tables
• Zero-Allocation Operations: When using buffer-based methods (GetBytes/GetChars with pre-allocated buffers), no heap allocations occur
• Source Generation: Uses Roslyn source generators to generate optimal encoding/decoding tables at compile time
• Zero Dependencies: Pure .NET implementation with no external dependencies
• Thread Safe: Singleton pattern ensures safe usage across multiple threads
• Full .NET Integration: Inherits from System.Text.Encoding for seamless integration

Installation

Install the package from NuGet:

dotnet add package Encoding1257

Usage

Basic Usage

using Encoding1257;
using System.Text;

// Get the Windows-1257 encoding instance
var encoding = Windows1257.Instance;

// Encode a string to bytes
string text = "Vilnius yra Lietuvos sostinė";
byte[] bytes = encoding.GetBytes(text);

// Decode bytes back to string
string decoded = encoding.GetString(bytes);

Integration with System.Text.Encoding

// Register with Encoding.RegisterProvider if needed
Encoding.RegisterProvider(Win1257EncodingProvider.Instance)

// Use like any other encoding
Encoding encoding = Encoding.GetEncoding(1257);
var encoder = encoding.GetEncoder();
var decoder = encoding.GetDecoder();

Working with Streams

using var stream = new FileStream("file.txt", FileMode.Open);
using var reader = new StreamReader(stream, Windows1257.Instance);
string content = reader.ReadToEnd();

Architecture

This project consists of three main components:

1. Encoding1257 (Main Library)

• Contains the Windows1257 encoding implementation
• Uses source generation for optimal performance
• Provides the public API

2. Encoding1257.CodeGen (Source Generator)

• Roslyn-based source generator
• Generates Unicode ↔ Windows-1257 mapping tables at compile time
• Creates optimized lookup methods

3. Encoding1257.Benchmark (Performance Testing)

• BenchmarkDotNet-based performance tests
• Measures encoding/decoding performance
• Validates performance improvements

Performance

The library is designed for high performance with the following optimizations:

• Compile-time code generation: Mapping tables are generated at compile time
• Aggressive inlining: Critical methods use MethodImplOptions.AggressiveInlining
• Efficient lookups: Direct array indexing for byte-to-char conversion
• Optimized Unicode mapping: Generated switch statements for char-to-byte conversion

Benchmark Results (Apple M2)

Results for .NET 9.0 on Apple M2

Character Support

Windows-1257 supports all standard ASCII characters (0x00-0x7F) plus additional characters for Baltic languages:

• Lithuanian characters: ą, č, ę, ė, į, š, ų, ū, ž and their uppercase variants
• Latvian characters: ā, č, ē, ģ, ī, ķ, ļ, ņ, š, ū, ž and their uppercase variants
• Estonian characters: ä, ö, ü, õ and their uppercase variants
• Common European characters: €, „, ", –, —, etc.

Requirements

• C# 13.0 language features

Contributing

Contributions are welcome! Please feel free to submit issues and pull requests.

Development Setup

1. Clone the repository
2. Build the solution: dotnet build
3. Run tests: dotnet test
4. Run benchmarks: dotnet run --project Encoding1257.Benchmark -c Release

License

This project is licensed under the MIT License. See the LICENSE file for details.

Acknowledgments

• Character mapping based on the official Windows-1257 specification
• Performance optimizations inspired by .NET's built-in encoding implementations