On 2015-12-31 05:29, Alex Rousskov wrote:
On 12/30/2015 03:42 AM, Kinkie wrote:
reserveSpace(n) is actually just
reserveCapacity(n+length()); what about simply getting rid of
reserveSpace and rename reserveCapacity to reserve? Minimum surprise
here for users here.
I will use reductio ad absurdum to highlight what I perceive as a flaw
in your question:
C++ is just assembly language with a few keywords and curly braces
added. What about getting rid of those keywords and curly braces and
just using pure assembly? Minimum surprise for users!
By the considerations I use to judge whether a helper submission is
suitable assembly is one language that could indeed pass for acceptance.
It would probably fail on the readability, and code safety
considerations. But that depends on the specific helper design. The
language itself is portable enough not to be a reason for rejection in
itself.
Yes, you can remove protections, but that usually results in a
different
kind of surprises -- the ones you want to avoid the most. I am pretty
sure that given a statistically significant sample, the amount of buggy
code calling reserve(length() + n) would be significantly larger than
the amount of buggy code code calling reserveSpace(n).
Maybe I'm missing something over the last few days discussion, but why
does reserve(length() + n) imply bugs?
I was of the understanding that this proposal was to make that the
right/only way to reserve ?
I wouldn't call them "tightly integrated" but simply
"bundled". What I'm trying to do is to make them more readable, secure
and adaptable first by using c++ in place of the c-with-thin-c++-paint
they currently are coded as. Making them more maintainable, hopefully
robust and readable is the main goal. In fact, as we can assume that
they will be used as reference by others writing their own helpers,
it's in everyone's best interests if they are as readable and compact
as possible.
If your goals are readability and adaptability combined with the ease
of
distribution, a scripting language may work [much] better than C++.
Let's consider mempools for instance. Having a build-time, static,
mechanism which can prevent linking against mempools is IMO tricky and
fragile;
Lets not. Except to confirm that the bundled C/C++ helpers are not and
will not depend on mempools or any other src/ code.
Enforcing that dependency separation is a major reason why I moved the
helpers/ directory to build before src/ all those years ago in the first
place.
Further enforcing the split and reducing the remaining build issues is
part of why I moved the mempools from include/lib to src/mem/ more
recently.
It is difficult to argue efficiently with fuzzy characteristics like
"tricky" and "fragile", but I think that making SBuf available without
mempools is better than making SBuf-driven algorithms generic. The
alternatives (such as generics) are not necessarily trickier or more
fragile, but nevertheless worse overall.
Nod. If anyone is looking at using heavyweight components of Squid (like
mempools, SBuf etc) in the helpers then it is probably a situation where
the helper is not a helper but a new mode of operation for Squid
workers.
For example; Diskers ride that line of distinction - having a relatively
small scope of operations (Store) but that scope is a heavyweight
component. As compared to the diskd helper which does similar tasks but
with simpler components.
Let me restrict the scope to "the C-ish and C++ helpers we bundle"
It could have been worse. Imagine us bundling helpers written in
assembly. After you reject that image as obviously absurd, I hope you
will notice a funny aftertaste questions lingering for a few seconds:
Why are we bundling *C++* helpers? If we continue to bundle C++
helpers,
what does it say about our true goals with regard to bundled helper
qualities? Are we after ease of writing? Ease of reading? Ease of
adapting? Ease of maintaining? Ease of bundling? Performance?
Since Squid is (or should be) using standard encodings, I suspect
there
are libraries and modules (for various programming languages) that
already provide appropriate encoding support. We would not have to
maintain any of those implementations.
There are. However:
Please note that I was only talking about "libraries and modules" to
use
with _helpers_, not with Squid proper.
- the ones I could find seem to be quite generic, we have different
needs in different contexts
This item is too general to agree or disagree with.
- impedence mismatch. These are either C or use std::string; this
generally means two more data-copies if we wish to use SBuf (or
std::string with a custom allocator)
I lost you here. If helpers wish to use SBuf, then they do not need 3rd
party libraries and Squid does not need to make its SBuf algorithms
generic. If helpers do not wish to use SBuf, then 3rd party libraries
do
not introduce any extra copies (from SBufs).
Nod. IMO, the need for a third-party RFC1738/3986 coder library is
primarily for the helpers, not Squid itself. We already have this
adequate coder logic for Squid internals. Moving the helpers to a
third-party library we can then adapt our custom logic for better
suiting SBuf etc.
This both helps with simplifying the helpers dependency on Squid code
and eases third-party helpers being written as they no longer have to
cut-n-paste our rfc1738 code.
So, if you found a FOSS library that provides RFC1738/3986 encoding and
supports std:string please look at adopting it for the helpers/ code.
- finding one which is generally available on all OSes we care about
seems not trivial.
Agreed. We can add portability or ease of deployment to the bundled
helper criteria. It is a topic on its own!
Portability is already one of the main criteria for bundled helpers. But
just important, not critical. What is critical is being able to detect
the OS environments where they will fail to execute or build and avoid
auto-enabling them.
However, let's assume that our ultimate goal[1] is to ship fast,
production-quality helpers that are built without external
dependencies
(i.e., built using Squid libraries) and that Squid code is (or will
be)
using SBuf for most string and buffering operations.
Quality helpers are likely to need a variety of string and buffering
operations. Which of the following approaches is better long-term?
A. Support a growing number of templated algorithms while making SBuf
API more and more interchangeable with std::string (while at the same
time providing a growing number of SBuf methods for raw buffer
operations).
B. Make SBufs and SBuf-driven algorithms easily available in helpers
by
making SBuf storage/memory backing (and any other current
dependencies
on Squid core) easily replaceable with something that does not need
any
integration with Squid core.
To me, option B looks like the right overall direction.
Could be, but we'd then need to redesign mempools to be stub-able, or
templatize SBuf with an allocator and isolate it from mempools (I
focus on these as these are the dependency bringing in most baggage.
I hope there are better ways to get B because, IIRC, SBufs do not know
[much] about mempools. I am oversimplifying, but I suspect that
separating SBufs from needless hard-coded dependencies requires not
much
more than providing a memAllocString() and memFreeString() function
implementations that do not depend on memory pools. After a bit of
cleanup, it would be just a matter of linking with the right object
file
(Squid gets trueMem.o while helpers get fakeMem.o) or internal library.
Given the fact that we won't probably require many common algorithms,
I believe that A is not a bad an option as you do.
Glad you at least agree that A is bad. I know that is not enough to
stop
you from implementing it, but I still hope that you will try to do B
instead.
Both A and B are bad.
I prefer C; ensuring helper code is a simple as possible with as few
dependencies - *particularly* from the complex code within src/.
IMHO, our primary goal with these helpers is to provide good quality
demo code for others to use as template for writing their own. With
secondary goal of acting as a source of some ready-made helpers for
common installation needs.
That places code readability (not quite quality), stand-alone
simplicity, and performance/speed fir the first goal above language or
portability. Though the latter two are still high importance as they
pertain to the second goal.
The C++ nature of the helpers is due to our personal preferences for
coding that way (more experienced dev attention and code quality etc)
combined with the bundling providing a guarantee of C++ compiler being
available (portability), nothing more.
Amos
_______________________________________________
squid-dev mailing list
[email protected]
http://lists.squid-cache.org/listinfo/squid-dev
