using System;
using System.IO;

/* 
 * Reference arithmetic coding
 * Copyright (c) Project Nayuki
 * 
 * https://www.nayuki.io/page/reference-arithmetic-coding
 * https://github.com/nayuki/Reference-arithmetic-coding
 */



/// <summary>
/// Decompression application using static arithmetic coding.
/// <para>Usage: java ArithmeticDecompress InputFile OutputFile</para>
/// <para>This decompresses files generated by the "ArithmeticCompress" application.</para>
/// </summary>
public class ArithmeticDecompress
{

//JAVA TO C# CONVERTER WARNING: Method 'throws' clauses are not available in C#:
//ORIGINAL LINE: public static void main(String[] args) throws java.io.IOException
	public static void Main(string[] args)
	{
		// Handle command line arguments
		if (args.Length != 2)
		{
			Console.Error.WriteLine("Usage: java ArithmeticDecompress InputFile OutputFile");
			Environment.Exit(1);
			return;
		}
		string inputFile = args[0]; // new File(args[0]);
		string outputFile = args[1]; //new File(args[1]);

		// Perform file decompression
		using( BitInputStream @in = new BitInputStream(new BufferedStream(new FileStream(inputFile, FileMode.Open, FileAccess.Read))))
		using( Stream @out = new BufferedStream(new FileStream(outputFile, FileMode.Create, FileAccess.Write) ) ) 
		{

			FrequencyTable freqs = readFrequencies(@in);
			decompress( freqs, @in, @out );

		}
	}


	// To allow unit testing, this method is package-private instead of private.
//JAVA TO C# CONVERTER WARNING: Method 'throws' clauses are not available in C#:
//ORIGINAL LINE: static FrequencyTable readFrequencies(BitInputStream in) throws java.io.IOException
	internal static FrequencyTable readFrequencies(BitInputStream @in)
	{
		int[] freqs = new int[257];
		for (int i = 0; i < 256; i++)
		{
			freqs[i] = readInt(@in, 32);
		}
		freqs[256] = 1; // EOF symbol
		return new SimpleFrequencyTable(freqs);
	}


	// To allow unit testing, this method is package-private instead of private.
//JAVA TO C# CONVERTER WARNING: Method 'throws' clauses are not available in C#:
//ORIGINAL LINE: static void decompress(FrequencyTable freqs, BitInputStream in, java.io.OutputStream out) throws java.io.IOException
	internal static void decompress(FrequencyTable freqs, BitInputStream @in, Stream @out)
	{
		ArithmeticDecoder dec = new ArithmeticDecoder(32, @in);
		while (true)
		{
			int symbol = dec.read(freqs);
			if (symbol == 256) // EOF symbol
			{
				break;
			}
			@out.WriteByte((byte)symbol);
		}
	}


	// Reads an unsigned integer of the given bit width from the given stream.
//JAVA TO C# CONVERTER WARNING: Method 'throws' clauses are not available in C#:
//ORIGINAL LINE: private static int readInt(BitInputStream in, int numBits) throws java.io.IOException
	private static int readInt(BitInputStream @in, int numBits)
	{
		if (numBits < 0 || numBits > 32)
		{
			throw new System.ArgumentException();
		}

		int result = 0;
		for (int i = 0; i < numBits; i++)
		{
			result = (result << 1) | @in.readNoEof(); // Big endian
		}
		return result;
	}

}