using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.IO;

namespace ReadFile
{
	public partial class Form1 : Form
	{
		public Form1()
		{
			InitializeComponent();
		}

		private void Form1_Load(object sender, EventArgs e)
		{
			Test();
		}
		public void Test()
		{
			// Use default replacement fallback for invalid encoding.
			//UnicodeEncoding enc = new UnicodeEncoding(true, false, false);
			UTF8Encoding enc = new UTF8Encoding();
			// Define a string with various Unicode characters.
			string str1 = "AB YZ 19 DEGREE \xb0 BULLET \x95 \uD800\udc05 \u00e4";
			str1 += "Unicode characters. \u00a9 \u010C s \u0062\u0308";
			Console.WriteLine("Created original string...\n");

			// Convert string to byte array.                     
			byte[] bytes = enc.GetBytes(str1);

			FileStream fs = File.Create(@".\characters.bin");
			BinaryWriter bw = new BinaryWriter(fs);
			bw.Write(bytes);
			bw.Close();

			// Read bytes from file.
			FileStream fsIn = File.OpenRead(@".\characters.bin");
			BinaryReader br = new BinaryReader(fsIn);

			const int count = 10;            // Number of bytes to read at a time. 
			byte[] bytesRead = new byte[10]; // Buffer (byte array).
			int read;                        // Number of bytes actually read. 
			string str2 = String.Empty;      // Decoded string.

			// Try using Encoding object for all operations.
			do
			{
				read = br.Read(bytesRead, 0, count);
				str2 += enc.GetString(bytesRead, 0, read);
			} while (read == count);
			br.Close();
			Console.WriteLine("Decoded string using UnicodeEncoding.GetString()...");
			CompareForEquality(str1, str2);
			Console.WriteLine();

			// Use Decoder for all operations.
			fsIn = File.OpenRead(@".\characters.bin");
			br = new BinaryReader(fsIn);
			Decoder decoder = enc.GetDecoder();
			char[] chars = new char[50];
			int index = 0;                   // Next character to write in array.
			int written = 0;                 // Number of chars written to array.
			do
			{
				read = br.Read(bytesRead, 0, count);
				if (index + decoder.GetCharCount(bytesRead, 0, read) - 1 >= chars.Length)
					Array.Resize(ref chars, chars.Length + 50);

				written = decoder.GetChars(bytesRead, 0, read, chars, index);
				index += written;
			} while (read == count);
			br.Close();
			// Instantiate a string with the decoded characters.
			string str3 = new String(chars, 0, index);
			Console.WriteLine("Decoded string using UnicodeEncoding.Decoder.GetString()...");
			CompareForEquality(str1, str3);
		}

		private static void CompareForEquality(string original, string decoded)
		{
			bool result = original.Equals(decoded);
			Console.WriteLine("original = decoded: {0}",
												original.Equals(decoded, StringComparison.Ordinal));
			if (!result)
			{
				Console.WriteLine("Code points in original string:{0}",original);
				foreach (var ch in original)
					Console.Write("{0} ", Convert.ToUInt16(ch).ToString("X4"));
				Console.WriteLine();

				Console.WriteLine("Code points in decoded string:{0}",decoded);
				foreach (var ch in decoded)
					Console.Write("{0} ", Convert.ToUInt16(ch).ToString("X4"));
				Console.WriteLine();
			}
		}
		// The example displays the following output:
		//    Created original string...
		//    
		//    Decoded string using UnicodeEncoding.GetString()...
		//    original = decoded: False
		//    Code points in original string:
		//    0041 0042 0020 0059 005A 0020 0031 0039 0020 D800 DC05 0020 00E4 0055 006E 0069 0063 006F
		//    0064 0065 0020 0063 0068 0061 0072 0061 0063 0074 0065 0072 0073 002E 0020 00A9 0020 010C
		//    0020 0073 0020 0062 0308
		//    Code points in decoded string:
		//    0041 0042 0020 0059 005A 0020 0031 0039 0020 FFFD FFFD 0020 00E4 0055 006E 0069 0063 006F
		//    0064 0065 0020 0063 0068 0061 0072 0061 0063 0074 0065 0072 0073 002E 0020 00A9 0020 010C
		//    0020 0073 0020 0062 0308
		//    
		//    Decoded string using UnicodeEncoding.Decoder.GetString()...
		//    original = decoded: True
	}
}