Re: Lua Socket

[Diego Nehab <diego@...>]

Hi,

> Now you mention it, here's a related feature request
> for the next LuaSocket. For line-by-line reading, allow
> an additional numeric parameter for the max no of
> bytes to read. Return at EOL or after max bytes,
> whichever comes first. This avoids the need for yet
> another (Lua) level of buffering whilst preventing
> badly behaved line-based TCP clients (some Outlooks
> spring to mind) which send more data than the RFC
> allows, and possibly very much more. (Have seen
> Outlook/Exchange msgs with 'lines' 2MB long or more.)

I have actually thought about implementing this one. I even
wrote partial support for it in the form of a "*<n>l" or
"*<n>a" patterns, where <n> gives the maximum size. The functions would
return "truncated" if the maximum size
was reached before the end of the pattern.

But then I noticed that any serious server would be doing
non-blocking I/O anyways (which already returns partial
results).  At this point, it becomes trivial to check the
size of the accumulated pattern within the reading loop, and
abort if needed.

> Another featurette which could be considered as a
> generic version of your patch is to have a single char to
> specify the EOL char (you would just use a
> zero byte). Reason for this is the occasions when
> you want to know exactly what line of chars was sent
> in a line-oriented protocol. The current definition of
> a line is very convenient but does not allow exact
> reconstruction of the input data (since CRs just before
> LFs get silently eaten), so you can't, for example,
> use line oriented LuaSocket reads to write a mail server
> with  a 'strict EOL enforcement' -- lone LFs not
> allowed -- option) and simply strip the CRs yourself.

I try to cover most of the use cases, but I am usually avoid
introducing to too much complexity into the library. I know,
each request seems simple, but once they pile up, things
become untreatable. Are there many protocols that behave
like this? Examples would be helpful.

Regards,
Diego