This project provides a custom implementation of a Base64 encoder and decoder in C#. The code includes methods for encoding byte arrays to Base64 strings, decoding Base64 strings back to byte arrays, and validating Base64 strings.

INFO: The readme is AI generated. The code itself is selfmade ...

• Custom Charset Dictionary: Uses a _charset dictionary to map byte values to Base64 characters, presented in a table-like format for better readability.

• Encoding: The Encode method converts a byte array into a Base64 encoded string.

• Decoding: The Decode and TryDecode methods convert a Base64 encoded string back into a byte array. TryDecode returns a boolean indicating success or failure, while Decode throws an exception if the input is invalid.

• Validation: The IsValid method checks if a given string is a valid Base64 encoded string.

using System.Text;
using FSC;

while (true)
{
    Console.Write("Input: \t");
    string text = Console.ReadLine() ?? string.Empty;

    byte[] bytes = Encoding.UTF8.GetBytes(text);
    Console.Write("Output: \t");
    Console.WriteLine(Base64.Encode(bytes));
    Console.WriteLine();
}

using System.Text;
using FSC;

while (true)
{
    Console.Write("Input: \t");
    string text = Console.ReadLine() ?? string.Empty;
    byte[] bytes = Base64.Decode(text);
    Console.Write("Output: \t");
    Console.WriteLine(Encoding.UTF8.GetString(bytes));
    Console.WriteLine();
}

Console.WriteLine($"IsValid Base64: {Base64.IsValid("ABC")} == TRUE");
Console.WriteLine($"IsValid Base64: {Base64.IsValid("XYZ")} == TRUE");
Console.WriteLine($"IsValid Base64: {Base64.IsValid("...")}  == FALSE");
Console.WriteLine($"IsValid Base64: {Base64.IsValid("/\\")}  == FALSE");
Console.WriteLine($"IsValid Base64: {Base64.IsValid("123")}  == TRUE");
Console.WriteLine($"IsValid Base64: {Base64.IsValid("mno")}  == TRUE");
Console.WriteLine($"IsValid Base64: {Base64.IsValid("==")}  == FALSE");
Console.WriteLine($"IsValid Base64: {Base64.IsValid("Hallo==")}  == TRUE");
Console.WriteLine($"IsValid Base64: {Base64.IsValid("")}  == FALSE");
Console.WriteLine($"IsValid Base64: {Base64.IsValid(null)}  == FALSE");
Console.WriteLine($"IsValid Base64: {Base64.IsValid(string.Empty)}  == FALSE");

• Fields:

  • _charset: A Dictionary<byte, char> representing the Base64 character set in a table-like structure for better readability.
  • PADDING: A constant char representing the padding character '='.

• Methods:

  • Encode(byte[] bytes): Encodes a byte array into a Base64 string.
  • Decode(string str): Decodes a Base64 string into a byte array.
  • TryDecode(string str, out byte[] bytes): Tries to decode a Base64 string, returning a boolean indicating success.
  • IsValid(string str): Validates whether a string is a valid Base64 encoded string.
  • GetCharsetBytes(char c): Retrieves the byte value corresponding to a Base64 character from the _charset dictionary.

• Encoding Process:

  • The input byte array is processed in chunks of 3 bytes (24 bits).
  • These 24 bits are divided into four 6-bit groups.
  • Each 6-bit group is mapped to a Base64 character using the _charset dictionary.
  • If the input length is not a multiple of 3, padding characters are added to the result.

• Decoding Process:

  • The input Base64 string is processed in chunks of 4 characters.
  • Padding characters are removed before processing.
  • Each character is converted back to its 6-bit value using GetCharsetBytes.
  • The 6-bit values are combined to reconstruct the original bytes.

• Validation:

  • The IsValid method checks for null or empty strings, verifies that padding is correctly placed, and ensures all characters are within the Base64 character set.

• This implementation avoids using built-in Base64 methods to provide a deeper understanding of how Base64 encoding and decoding work.

• The use of a dictionary for the character set enhances readability and mimics a table structure, making it easier to understand the mapping between bytes and characters.

• Exception handling is implemented in the Decode method to handle invalid Base64 strings gracefully.

This code is provided as-is without any warranty. You are free to use and modify it for your own projects.