that should only be a problem if stdin is in line-buffered mode, otherwise a single read should return more than enough bytes (assuming i remember how linux pipes work, i'm more familiar with plan9 pipes)
although, it would be nice to have a peek method that tries to look ahead the specified number of bytes, up to a maximum of capacity.
hmm, i'm tempted to draft a PR, trying to remember if a new unstable function requires an RFC, or if it just needs an RFC for stabilization... maybe it still needs an ACP?