String buffers that automatically get flushed at every line return.
create ~eol f
Create a new line buffer where f will be called once on every line.
Eol is the endline character (it's possible to use a Linebuffer to
process null separated strings )
flush b
Flushes any pending output to the callback function.
This causes unfinished newlines to be flushed out so adding
more characters after flushing might result in there looking as though
there are more lines than there really were.
add_substring b s ofs len
takes len
characters from offset ofs
in
string s
and appends them at the end of the buffer b
.