Quoted Printable Encoder/Decoder

Quoted-Printable is a content transfer encoding that uses printable ASCII characters to transmit 8-bit data over a 7-bit data path or for systems that are not 8-bit clean. It's commonly used in email systems for sending messages with international characters.

• Email message bodies with international characters (MIME encoding)
• Transmission of text with special characters through legacy systems
• Making binary data readable and editable in text editors
• Email headers for non-ASCII characters (slightly different format)
• Preserving text formatting in email messages

Quoted Printable encoding follows these basic rules:

• Printable ASCII characters (values 33 to 126, except 61) are represented as themselves
• Non-printable characters are represented by an equals sign (=) followed by the character's hexadecimal ASCII value
• The equals sign (=) itself is encoded as =3D
• Lines longer than 76 characters are broken by inserting a "soft line break" (= at the end of a line)
• Space (32) and tab (9) characters can be represented as themselves, but not at the end of a line

Quoted Printable is part of the MIME (Multipurpose Internet Mail Extensions) standard, which is defined in RFC 2045. It's used alongside other encodings like Base64 to ensure email messages with attachments or special characters can be reliably transmitted across different email systems.

Advantages:

• Human-readable for text that's mostly ASCII
• Efficient for text with few non-ASCII characters
• Preserves line breaks and formatting

Limitations:

• Less efficient than Base64 for binary data or text with many special characters
• More complex to implement correctly compared to some other encodings
• Has specific rules for line breaks and whitespace handling