Re: Reading LAST line from text file without iterating through the file?

On 2/23/2011 10:59 AM, Robin Wenger wrote:


     Others have mentioned using RandomAccess to work backward from the
end of the file until you find the penultimate line-ending. This can
work, but it can also fail. Consider a file with context-sensitive
encoding, for example, where the meaning of a byte depends on the values
of bytes that precede it. If you read an isolated byte of value 91 from
such a file, without knowing whether it's a free-standing character or a
part of a multi-byte sequence or possibly preceded by a "shift-out," you
won't know what that byte value means.

     One strategy is to estimate a typical line length of N characters,
seek to 100*N (say) bytes before the end, and start reading from
there. A nice feature of most multi-byte encoding schemes is that they
tend to self-synchronize: You may get misinterpreted garbage for a
while, but things are likely to get back on track eventually. If you
want to get fancy you can apply reasonability tests to what you (think
you've) read, and restart at END-1000*N if things seem unreasonable.

--
Eric Sosman
esosman@ieee-dot-org.invalid