On Jul 19, 2005, at 12:55 PM, William A. Rowe, Jr. wrote:
Greg and a few others voiced interest in moving from null-term
strings to counted strings for a future version of Apache.
This was too broad a scope change to make it into 2.0, of course,
and was dropped on the floor for the time being.
I'm wondering today; what metadata interests us in an ap_string_t
prefix header? I have a hunch that a short, 65536, is enough
to map most data we want to handle in one chunk; brigades are
better for handling large sets of data. Of course we could push
that to an int, or size_t, but there would be a small memory
penalty. It might be overcome by cpu-specific optimized int
or size_t handling behavior, since the assembly code wouldn't
need to truncate short values.
Perhaps, both bytes allocated/used, in order to play optimized
games with string allocation. Perhaps, a refcount? (This
doesn't play well with pool allocations, obviously.)
But the byte count clearly isn't enough. I'm thinking of;
encoding; is this data URI escaped or un-escaped?
tainted; is it raw? or has it been untainted with
context-specific validity checks?
charset; is this native? (e.g. EBCDIC). utf-8?
opaque or otherwise a specific set?
What else interests us within an 'ap_string_t' header, that
would help eliminate bugs within httpd? A random trailing
short following the string, in a 'string debug' mode, to
detect buffer overflows? Something similar to detect
underflows?
Open to all ideas.
This may be a bit more radical than you were hoping for, but...
I like the idea of using a reference-counted, non-null-terminated
string type for 3.x.
More generally, it would be great to have overflow detection
on all arrays.
And although I like the performance benefits of the pool memory
allocators, I remember how tricky it was to debug some of the
pool and bucket lifetime problems that we encountered during
the development of 2.0 (especially in filters). All things considered,
I don't think I'd mind the overhead of a garbage collection thread.
Thus I can't help but wonder: Would 3.0 be a good time to consider
trying a Java-based httpd?
Brian
