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;
	}

}