This patch goes in the right direction, but has several problems IMO:

- it reads a complete chunk for just one more byte
- the re-read should be disabled when lineends are not translated
these two are minor annoyance and can be easily corrected, but:

- there is no limit to the re-read; it can exhaust the memory if the
source is a big file with many \r (like a Mac text file)

- How does this behave if the underlying stream has not yet available
data (a socket, a terminal, or an opened file): will the re-read block
at the 129th byte until more data is available? If so, it is annoying
for a simple call to read(1).

I will try to write these test cases if you want.