Compression decoders read from one input stream (an io_reader called src) and write to an output stream (an io_writer called dst). Wuffs' implementations have one key method: decode_io_writer, named after the operation (decoding) and the type of the destination (an io_writer). It incrementally decompresses the source data.
This method is a coroutine, and does not require either all of the input or all of the output to fit in a single contiguous buffer. It can suspend with the $short_read or $short_write statuses when the src buffer needs re-filling or the dst buffer needs flushing. For an example, look at the example/zcat program, which uses fixed size buffers, but reads arbitrarily long compressed input from stdin and writes arbitrarily long decompressed output to stdout.
TODO: standardize the various dictionary APIs, after Wuffs v0.2 is released.
See also the general remarks on Wuffs' standard library.