procedure Decode(
    const AIn: string; 
    const AStartPos: Integer = 1; 
    const ABytes: Integer = -1
); override;

DecodeToStream is an overridden procedure in TIdDecoderQuotedPrintable that implements the decoding algorithm for the Quoted-Printable encoding scheme. DecodeToStream converts the Quoted-Printable value in AIn to it's original un-encoded form, and stores the result in the Stream ADest. 

AIn contains a value in the format generated by TIdEncoderQuotedPrintable.Encode. DecodeToStream will remove any trailing whitespace in AIn before performing the decoding algorithm, in accordance with RFC 2045. If AIn is an empty string (''), DecodeToStream performs no processing and exits from the method. 

ADest is a TStream descendant that will receive the un-encoded value of AIn.