A 64-character string specifying the regular Base64 alphabet.

The type for decoders.

The type for input sources. With a `Manual source the client must provide input with src.

src d s j l provides d with l bytes to read, starting at j in s. This byte range is read by calls to decode with d until `Await is returned. To signal the end of input, call the function with l = 0.

decoder src is a decoder that inputs from src.

decode d is:

• `Await if d has a `Manual input source and awaits for more input. The client must use src to provide it.
• `End if the end of input was reached
• `Malformed bytes if the bytes sequence is malformed according to the decoded base64 encoding scheme. If you are interested in a best-effort decoding, you can still continue to decode after an error until the decode synchronizes again on valid bytes.
• `Flush data if a data sequence value was decoded.
• `Wrong_padding if decoder retrieve a wrong padding at the end of the input.

Note. Repeated invocation always eventually returns `End, even in case of errors.

decoder_byte_count d is the number of characters already decoded on d (included malformed ones). This is the last decode's end output offset counting from beginning of the stream.

decoder_src d is d's input source.

decoder_dangerous d returns true if encoded input does not respect the 80-columns rule. If your are interested in a best-effort decoding you can still continue to decode even if decoder_dangerous d returns true. Nothing grow automatically internally in this state.

The type for output destinations. With a `Manual destination the client must provide output storage with dst.

The type for Quoted-Printable encoder.

encoder dst is an encoder for quoted-printable that outputs to dst.

encode e v: is

• `Partial iff e has a `Manual destination and needs more output storage. The client must use dst to provide a new buffer and then call encode with `Await until `Ok is returned.
• `Ok when the encoder is ready to encode a new `Char, `Line_break or `End

For `Manual destination, encoding `End always return `Partial, the client should continue as usual with `Await until `Ok is returned at which point dst_rem encoder is guaranteed to be the sode of the last provided buffer (i.e. nothing was written).

Raises. Invalid_argument if a `Char, `Line_break or `End is encoded after a `Partial encode.

encoder_dst encoder is encoder's output destination.

dst e s j l provides e with l bytes to write, starting at j in s. This byte range is written by calls to encode with e until `Partial is returned. Use dst_rem to know the remaining number of non-written free bytes in s.

dst_rem e is the remaining number of non-written, free bytes in the last buffer provided with dst.