From: Pavel Vozenilek (pavel_vozenilek_at_[hidden])
Date: 2004-11-22 17:00:54
"Ion Gaztañaga" wrote:
> first rough version of shared memory library
1. The HTML documentation does't allow
to change font in browser.
2. End of document can be marked so it doesn't
look like cut in half during transmission.
3. docs 3.2:
"Boost Shmem provides some STL containers"
"Boost Shmem provides some STL compliant containers"
4. Example in 3.2: the "alignement" parameter in
segment.create() isn't found in code.
5. Example in 4.2:
("MyType instance", /*name of the object*/
10 /*number of elements*/,
false /*if previously present, return error*/,
0 /*ctor first argument*/,
0 /*ctor second argument*/);
a. What does t mean "return error" here? Exception?
b. Wouldn't it be better to split the function into
two, one which allow to overwrite, second which
This would get rid of boolean parameter which
is always hard to understand w/o context.
c. Could the syntax be like:
so it looks more like operator new?
Current signature feels very prone to bugs.
std::pair< MyType *, std::size_t> res =
segment.find_named_new< MyType > ("MyType instance");
Why do I need the "size"? Doesn't a type have
always the same size regardless? Isn't
sizeof(MyType) == res.second
6. Could you use namespace shmem_detail or so
instead of "detal" to avoid possible clashes?
a) file name should be shmem_exceptions.hpp or so
b) does it make sense to have common base
for both exceptions there?
8. offset_ptr.hpp: full_offset_ptr class
a) using char as de-facto bool class has usually
no practical advantage and may be actually slowe.
b) The flag could be eliminated completely.
If m_offset == 0 it is NULL pointer and
no data allocated in shmem will starts
on the beginning. This would also eliminate
need for min_offset_ptr.
c) swap() could be added and other operators.
9. Maybe the protection of mutext from shared ptr
lib could be worked around so the code
duplication would be eliminated. Even if it
is dirty it would be worth.
10. The example in 4.3 uses very dirty C-like
approach with casts. Cannot it be rewritten
in C++ way with overloaded new?
11. Some source files use Unix line ends,
some DOS line ends. Just bit strange.
12. The simple algorithm to find fitting memory
block may not be adequate for high-performance
apps (who are most likely to use shared
13. Can be be possible to identify named objects
with something else than C string? Say
wchar_t* or numeral or other templated type?
14. What I would like to see:
a) avoiding shmem specific containers/mutexes/etc
as much as possible.
b) ability to "equalize" shared memory features
between operating systems. E.g. Windows
deletes shared memory when no one is using it,
Unix keeps it until destroyed explicitly.
I would like to have both approaches on
both platforms (handled possibly by exec()ing
In addition, Shmem should provide platform
specific access to its internals,
e.g. to Win32 handles to allow security settings.
c) support for inheritance in shmem using object
factories, e.g. like one in Classloader
d) support for "transactions": I would like to
be able to add/modify/remove objects in shared
memory and made all changes visible to other
process in one moment. This would save me
one more IPC channel to signal readiness of data.
If possible the library should provide several
levels of isolation. Long lasting
transactions could be also considered.
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