Encodes fragmented input to an output

It is equivalent to use an Encoder with multiple calls to [Encoder::append()] than to first concatenate all the input and then use [Encoding::encode_append()]. In particular, this function will not introduce padding or wrapping between inputs.

Examples

// This is a bit inconvenient but we can't take a long-term reference to data_encoding::BASE64
// because it's a constant. We need to use a static which has an address instead. This will be
// fixed in version 3 of the library.
static BASE64: data_encoding::Encoding = data_encoding::BASE64;
let mut output = String::new();
let mut encoder = BASE64.new_encoder(&mut output);
encoder.append(b"hello");
encoder.append(b"world");
encoder.finalize();
assert_eq!(output, BASE64.encode(b"helloworld"));