September 2011 - Boost - lists.preview.boost.org

[Review] Boost.Endian - template requirements and scope
by Vicente J. Botet Escriba 10 Sep '11

10 Sep '11

Hi, I have not found the requiremenst of the endian class template parapeter T and conversion functions. What are they? Could them be added to the documentation? I have not found a tutorial on how to use the endian conversions. Could you give an example that shows how easy is to use them with UDT? Collections of UDT? Could the user overload the conversion functions for UDT? While the predefined endian types are useful I guess that the user could instantiate the endian class with a UDT, isn't it? Could you post a working example and add it to the documentation? The scope of Boost.Endian is integer types. Aren't floating point types and endianness related? If the scope of the library is limited to integers, maybe Integer.Endian could be a better name? Best, Vicente

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[proto] proto::as_child potentially unsafe?
by John Maddock 09 Sep '11

09 Sep '11

Following the guide here: http://www.boost.org/doc/libs/1_47_0/doc/html/proto/users_guide.html#boost_… I fell into a nasty trap: as_child stores it's argument as a reference, and as far as I can tell there is no way to force it to store by value, unless you apply deep_copy to the whole expression tree (not just the one child created with as_child). I found this when trying to protoize a function that looked like: template <class Exp> some-return-type foo(const Exp&, int i); In which the value "i" was returned as a reference to a value on the stack which then went out of scope :-( Even if the function has a signature such as: template <class Exp> some-return-type foo(const Exp&, const int& i); There is still a potential trap, because you don't know where "i" came from and when it will go out of scope - OK so the result of the expression will *usually* be calculated before that happens - but you never know. IMO I think this trap needs better documenting, because the section in question (and text preceding it) read to me "as if" arguments to as_child were stored by value. I'm sure I'm reading that wrong.... but you know ;-) John.

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[Endian] Proposed endian integer types
by Phil Endecott 09 Sep '11

09 Sep '11

Dear All, I have had a quick look at the proposed endian::big|littleN_t types. A couple of comments: - I was expecting to find that these types would use the conversion functions that I've already looked at at the lowest level, so that optimisations made to those functions would be useful here too. But instead, these classes seem to use their own byte-shuffling code. This seems like an odd design. - I'm not convinced that these types cause the conversion to happen at the optimum time. For example: struct file_header { big32_t n_things; .... }; int main() { file_header h; h.n_things = 0; while (....) { ++h.n_things; .... } write(h); .... } Here the conversion is happening twice every time that n_things is incremented. It would be better to instead do the conversion once, just before the file_header is written. The same thing applies in reverse when reading from a file. (Surely this is the most common use-case?) I have been wondering if there is a better design that can avoid this. If we had some sort of struct introspection, we could store the fields in native byte order and then template <typename T> T external_representation(const T& t) { T res(t); for each field of T { res.field.reorder(); } } ++h.n_things; // cheap write(external_representation(h)); // conversion happens once here. Of course we don't have introspection of structs so we can't do that. Maybe someone else has another idea. Regards, Phil.

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[system] BOOST_ERROR_CODE_HEADER_ONLY undocumented
by Akira Takahashi 09 Sep '11

09 Sep '11

Hi, BOOST_ERROR_CODE_HEADER_ONLY macro is useful, but undocumented. Should not use this macro? And I think should move implementation (`libs/system/src/error_code.cpp`) to `boost/system` if formal provide this macro(example: `boost/chrono/detail/inlined`). Depending on the package manager is not provide below the `libs` directory (example: Portage of Gentoo Linux). Thanks, Akira >>======================== Akira Takahashi mailto:faithandbrave@gmail.com blog: http://d.hatena.ne.jp/faith_and_brave/

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[Review] Boost.Endian
by john filo 08 Sep '11

08 Sep '11

- What is your evaluation of the design? For the original scope (i.e. integers), very good. However, I'd like to see additional support for float, double, and user defined types added. Without it, this library isn't very useful to me personally since a large percentage of the values that I have to deal with are either float or double. ---------------------------------------------------------------------- - What is your evaluation of the documentation? Excellent. Is a tutorial section going to be added? I'm not sure one is needed given the existing examples in the rest of the documentation, but the documentation's menu bar implies there will be one. ---------------------------------------------------------------------- - What is your evaluation of the implementation? Very good. At -O2, I was impressed with the performance relative to GCC's builtin byteswap routines. When I first saw the implementation, I honestly didn't think it would perform very well given its complexity compared to a naive implementation (e.g. the version used in the endian::reorder functions). I was pleasantly surprised. I guess that's a testament to the level of optimization compilers are capable of these days. On an Intel Core2, the performance penalty of the uint32 endian<> template and the reorder() function relative to GCC-4.4 builtins (i.e. runtime divided by runtime of builtin) is as follows: endian<> reorder() ------------------------ -O0 5.4 3.0 -O2 2.3 6.5 It seems like the reorder functions could be implemented in terms of the integer types for improved performance (and also maintainability). Something like: template<typename T> inline void reorder(T& x) { x = *reinterpret_cast< endian<endianness::nonnative, T, sizeof(T)/8> *>(&x); } template<typename T> inline void reorder(T source, T& target) { target = *reinterpret_cast< endian<endianness::nonnative, T, sizeof(T)/8> *>(&source); } Obviously the above requires extending the endianess enum with a "nonnative" value. Performance isn't that critical for me, but it does seem like providing platform specific implementations that take advantage of things like GCC's builtin byteswap functions should also be considered to get the performance up even further. Finally, for my last performance related comment, I was surprised to see that the native types had basically exact same performance as the nonnative types. Couldn't the native types be specialized to effectively be a no-op? Would "byteswap" or maybe "swapbytes" be a better name than "reorder"? ---------------------------------------------------------------------- - What is your evaluation of the potential usefulness of the library? For those who deal with non-native endian data, this library is extremely useful. It automatically eliminates a whole class of common programming errors when dealing with such data. ---------------------------------------------------------------------- - Did you try to use the library? With what compiler? Yes; gcc-4.4.3 on Linux ---------------------------------------------------------------------- - Are you knowledgeable about the problem domain? Yes. I've used a similar home-grown library for the past 10 years, and have been looking forward this being added to Boost for a long time. ---------------------------------------------------------------------- > - Do you think the library should be accepted as a Boost library? Absolutely. I'd like to see support for float and double, but even without those additions, I still vote yes.

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Re: [boost] [optional] Thoughts on disallowing assignment for wrapped references.
by Stewart, Robert 08 Sep '11

08 Sep '11

Fernando Cacciola wrote: > > >> optional<T> > >> f() > >> { > >> optional<T> result; > >> // do stuff > >> return result; > >> } > > > > However, in the latter case, there is no loss of generality > > since the above would still be a no-no where T a reference > > type... > > Or did I miss something in your response? > > You totally missed his point. Indeed. > In Robert's example, it is easy to see--or should be easy to > see--that the fact that the optional<T> is being returned is > secondary, perhaps even irrelevant, to the point he is making > His point is about the shortcoming of lacking assignment, not > about object lifetimes (and BTW, is the same point Nevin and > I made earlier). I wouldn't go quite that far... > Perhaps a less distracting example would be: > > optional<T> o ; > > switch ( cond ) > { > case a : o = foo1(); break ; > case b : o = foo2(); break ; > case c : o = foo3(); break ; > case e : o = foo4(); break ; > case e : o = foo5(); break ; > > default : // o remains uninitialized > } > > Notice that is quite possible to encounter the above example > in real-life, as it is common that a variable remains > uninitialized in the default case of a switch (or, for that > matter, in any branch of a complex conditional). > > In fact, I even wonder if that example couldn't be considered > as the canonical use case for optional<>'s assignment > operation. The one thing you overlook in your example is that there are reasonable alternatives to using optional within a local scope. However, when returning a value from a function, ownership must be transferred to the caller, which reduces the safe options. Regardless, disallowing assignment for reference types which, in effect, "reseats a reference," is surprising in too many cases. A new, non-assignable optional type might gain traction, but removing assignment from optional<T&> is not acceptable. _____ Rob Stewart robert.stewart(a)sig.com Software Engineer using std::disclaimer; Dev Tools & Components Susquehanna International Group, LLP http://www.sig.com ________________________________ IMPORTANT: The information contained in this email and/or its attachments is confidential. If you are not the intended recipient, please notify the sender immediately by reply and immediately delete this message and all its attachments. Any review, use, reproduction, disclosure or dissemination of this message or any attachment by an unintended recipient is strictly prohibited. Neither this message nor any attachment is intended as or should be construed as an offer, solicitation or recommendation to buy or sell any security or other financial instrument. Neither the sender, his or her employer nor any of their respective affiliates makes any warranties as to the completeness or accuracy of any of the information contained herein or that this message or any of its attachments is free of viruses.

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Boost.Endian comments
by tymofey 08 Sep '11

08 Sep '11

This is not a full review, but rather a few comments on the implementation of reorder(x) functions. What you are doing is casting pointers around and assigning individual bytes, which might not really effective: inline void reorder(int64_t source, int64_t& target) { const char* s (reinterpret_cast<const char*>(&source)); char * t (reinterpret_cast<char*>(&target) + sizeof(target) - 1); *t = *s; *--t = *++s; *--t = *++s; *--t = *++s; *--t = *++s; *--t = *++s; *--t = *++s; *--t = *++s; } it does eight increments, eight decrements, one addition, one substraction and eight assignments. maybe something like: inline void reorder(int64_t source, int64_t& target) { target = ((source << 0x38) & 0xFF00000000000000) | ((source << 0x28) & 0x00FF000000000000) | ((source << 0x18) & 0x0000FF0000000000) | ((source << 0x08) & 0x000000FF00000000) | ((source >> 0x08) & 0x00000000FF000000) | ((source >> 0x18) & 0x0000000000FF0000) | ((source >> 0x28) & 0x000000000000FF00) | ((source >> 0x38) & 0x00000000000000FF); } would be more efficient?

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[Boost.spirit] How to use the Json/Spirit example found on codeproject site
by Demetrio Car 08 Sep '11

08 Sep '11

I am new in C++. I came from C# and Java world. I tried the example http://www.codeproject.com/KB/recipes/JSON_Spirit.aspx) and it`s working perfectly when I used that in Microsoft Visual Studio 2010. But, I expended two days and I couldn't do the same in Eclipse Indigo over Linux Ubuntu. I installed Boost in my Linux, included it in my project and some boost`s command (example BOOST_FOREACH) are working perfectly. But, I can't run the example I downloaded from codeproject and I believe that it's happening because I don't know how properly include libraries in Eclipse. I was able to include Boost and Curl because I followed some tutorials, but I don't know exactly what I have done. And, now, I couldn't run the codeproject example in Eclipse/linux as I've done in Visual Studio. If someone has already used this codeproject example on Eclipse/Linux and could give some suggestion about make the example work on Eclipse/Linux, it will be nice as well.

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[serialization] or [spirit] JSON Archives
by Fernando Pelliccioni 08 Sep '11

08 Sep '11

Hi, After experimenting with Spirit.Qi to make a JSON parser, I had the need for a serializer. First, I thought I could serialize my model of JSON (json:: value, json: object, etc.), but that was not compatible with boost::serialization. I am currently writing a ARCHIVE for Boost Serialization, but I'm finding some problems in order to implement JSON correctly. The question is, does anyone know about some files to Boost Serialization already finished? I've seen the Archive made by Esteve Fernandez, but do not serve my purpose, because I just need JSON. I would like to develop a JSON parser which in turn is a compatible Boost Serialization serializer . Any ideas? Thanks and regards, Fernando Pelliccioni.

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[integer] Type-safe and bounded integers with compile-time checking
by Leif Linderstam 07 Sep '11

07 Sep '11

Hi all, There are some integer libraries out there that improve on the fundamental integers; Boost.Integer, ACCU BoundedInt, part of The Boost Constrained Value library, and probably many other. They add the ability to specify an integer based on a range, they add bounds checking at runtime, or a combination of both. What I have not found yet though is a library that checks bounds at compile time. Me personally I would like to have the compiler check as much as possible. For instance, the compiler would complain about an assignment if the target's range is not a superset of the source's, unless an explicit conversion is made. Does anyone know of a library supporting this? If there is no such library I hope there is an interest in one and that this post will start a discussion about how it best can be done. The motivation for this kind of library is that its usage helps show the intent of the developer, and it can point out faults that otherwise even an extensive test suite might miss. That it forces the developer to thoroughly think about value ranges in computations I also regard as a point in favour. What about the type-safe part in the subject of this post? Even though most mistakes will be caught by the bounds checking, I believe there are situations where one wants to clearly state that an integer represents one specific concept and nothing else, for instance a numeric identifier. So I would like this kind of library to also support a kind of type-safety. I am not sure that that is the correct term for it, but what I mean is that when one declares a bounded integer it should be possible to state that it can not mix with other bounded integers regardless if the bounds are compatible. As I have been thinking about this for years now I of course have a lot of ideas on how to implement this. As a starting point for a discussion I would like to present some basic parts of what I have come up with. The integer type is declared as follows: template< typename Range, typename Tune = fast > struct integer; It takes a range type instead of taking the bounds directly. It also has a tuning parameter which is used when selecting the fundamental integer type to use for storage. The idea of having a separate range type is that it can be used for other types, see the array type below. The range type then: template< intmax_t Lower, intmax_t Upper, typename TypesafetyTag = defaultTypesafety > struct range_c; The bounds is no surprise, but here I add the type-safety part. I am not quit sure about this approach because the bounds and the type-safety mechanisms are orthogonal, but it works together quite well in practice I believe. Maybe it should not be named "range" but something else. The type-safety mechanism is fairly simple; two integers must have the same tag to be part of the same expression (unless a type-safety conversion is used). This means that they cannot be mixed with fundamental integers either. The default type-safety tag is special in that it allows for a mix with fundamental integers except that there is no implicit conversion or assignment to fundamental integers (this would otherwise provide a loophole). In practice fundamental integers do not work that well with the static bounded integers though, because most often the range is too big. Another type that seems fairly obvious is a static array (similar to Boost.Array): template< typename Range > struct array; The array of course is just as large as needed for the range. As subscript parameter it only accepts bounded integers with compatible ranges, i.e. with subset bounds and equal type-safety tag. Contrary to what is normal in C++ the array is not necessarily zero-based, it starts at the lower bound of the array. There is much more of course, for instance that the range type should take types instead of integers as bounds, but this post is getting too long already. As said before I hope this is going to be the start of a fruitful discussion. Sincerely, Leif Linderstam

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[Boost][GSoC] Checks summary
by Pierre Talbot 07 Sep '11

07 Sep '11

Hello all, The Google summer of code gave me the opportunity to learn a lot, but overall I started to build another little part of the open-source world. This was a great experience for me. I'd like to thank my mentor, Paul A. Bristow for all the help he bestowed, Google and all the Boost members who gave me their opinions or advice. During this summer, I've started to build the foundation of a new library. It's only a prototype for the time being but I hope make it useful and powerful soon. The name of this library is "Checks", it currently implements one kind of check function: those used for catching human errors. For example, the famous ISBN has a check digit computed with all the characters. It exists few algorithms and a lot of number are based on well-known algorithm. This library should offer useful extending possibilities because there are so many that we can't implement every type of checks for a Boost library. I've implemented and written the following contents : * Basic check algorithms ( Luhn, Mod11, Verhoeff, ...). * Start to write a test suite that should facilitate the measurement of efficiency of the check algorithms (number of alterations, transposition, ... detected). * Write some sanity tests for the functions implemented (using Boot.Test). * Documented the functions already written and start a "global" documentation of the parameters that affect the efficiency of each algorithms. This library is absolutely not finished but can be used for simple verification or computation of check digit. I would like to improve and even-fuller-document this library before a Boost review. The code, tests and documentation can be found at https://svn.boost.org/svn/boost/sandbox/SOC/2011/checks/ and here are a direct links to the documentation in html https://svn.boost.org/svn/boost/sandbox/SOC/2011/checks/libs/checks/doc/htm… and as a single pdf file https://svn.boost.org/svn/boost/sandbox/SOC/2011/checks/libs/checks/doc/che… (Sadly the Doxygen comments documenting the (many) template parameters are not displayed correctly in the C++ reference section (due to a buglet in the toolchain), so for now you may need to consult the header files to read the C++/Doxygen \tparam comments. Meanwhile, you can also consult the Standalone Doxygen documentation at https://svn.boost.org/svn/boost/sandbox/SOC/2011/checks/libs/checks/doc/dox… Or you can rebuild the Standalone Doxygen documentation using the Doxywizard and https://svn.boost.org/svn/boost/sandbox/SOC/2011/checks/libs/checks/doc/dox… If you have any comments or suggestions, please do not hesitate to contact me. Cordially, Pierre Talbot.

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Re: [boost] [interest] URL (John Ratcliffe)
by john＠firecrest.eclipse.co.uk 07 Sep '11

07 Sep '11

From: Dean Michael Berris Date: Tue, 6 Sep 2011 22:34:19 +1000 > This project (cpp-netlib) is already submitted for review to Boost, > but is still under heavy development. I've already had some offline > arrangements for a review manager, but now it's a matter of scheduling > for when the formal review should be held. > Needless to say it follows much of the Boost conventions and rely > mostly entirely on Boost libraries. And if I'm brave enough I just > might think about submitting the library interfaces to the ISO C++ > Committee through the Library Working Group. :D > I hope this clarifies things. Yes thanks. I noticed the boost namespace and wondered. It looks and sounds well advanced. I would like to get involved but is there anything a new hand can contribute at this stage? Cheers John Links: ------ [1] mailto:mikhailberis@gmail.com

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Intel TBB or Microsoft PPL like Boost library
by Brendon Costa 07 Sep '11

07 Sep '11

Are there any libraries for boost proposed, accepted or in progress that are similar to the Intel Threaded Building Blocks library or the Microsoft Parallel Patterns Library? I did not see any in the official library list and dont remember hearing about any in this mailing list. Such a library could be very useful (well I could use it right now :-) )

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Re: [boost] [Submission] RawMemory
by Joe Mucchiello 07 Sep '11

07 Sep '11

For a library designed to deal with the weirdness of binary file formats, I'm surprised it does not support 24-bit integers of arbitrary alignment/sign. > uint32_t x = raw_memory <uint32_t, big_endian>::peek (&vbBuffer [5]); Do you also support a non-template "endianness" parameter? Sometimes you don't know the endian-style of the file until you open it and read some value out of it. Joe

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[chrono] Build Jamfile missing three source files
by Beman Dawes 06 Sep '11

06 Sep '11

--- c:\temp\Jamfile.v2-revBASE.svn000.tmp.v2 2011-09-06 15:23:30.000000000 -0400 +++ c:\boost\trunk\libs\chrono\build\Jamfile.v2 2011-09-06 15:23:19.000000000 -0400 @@ -74,16 +74,16 @@ <toolset>gcc-3.4.4:<linkflags>--enable-auto-import <toolset>gcc-4.3.4:<linkflags>--enable-auto-import <toolset>gcc-mingw-4.4.0:<linkflags>--enable-auto-import <toolset>gcc-mingw-4.5.0:<linkflags>--enable-auto-import ; -SOURCES = chrono thread_clock process_cpu_clocks ; +SOURCES = chrono thread_clock process_cpu_clocks run_timer run_timer_static process_clock ; lib boost_chrono : $(SOURCES).cpp : <link>shared:<define>BOOST_ALL_DYN_LINK=1 # tell source we're building dll's <link>static:<define>BOOST_All_STATIC_LINK=1 # tell source we're building static lib's ; OK to commit? --Beman

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Re: [boost] [contract] syntax redesign
by Andrzej Krzemienski 06 Sep '11

06 Sep '11

> This use case is different then the above (more compelling). The > issues here is that when programming contracts you quickly start using > extra checks (and especially ==) which add additional requirements on > generic types. For example, in this case T does not have to be > EqualityComparable to program the body but you still want to program > and check the postcondition when T happens to be EqualityComparable. I > have been thinking to solve this issue by providing: > namespace contract { > temlate< typename T> > bool equal(T const& left, T const& right) ... > } > equal will return true if T is not EqualityComparable and left == > right if T is EqualityComparable. That way you can program the > contracts using contract::equal(x, y) without introducing additional > requirements on T at all but still checking the contract conditions > for EqualityComparable types. I will also expand equal to handle > containers (compare all elements of a vector, etc) and I will provide > similar functions for other operations. All of these contract helper > functions will be in a separate header <contract/utility.hpp>. I have > not started to implement this yet. To me, this problem with equality indicates that Boost.Concept already proves useful, as it explores practical aspects of implementing DbC in C++ and its interactions with other C++ features. > BTW, I am also wondering if it would be useful to implement a fully > contracted version of the STL probably in contract::std: > #include <contract/std/vector.hpp> > #include <contract/std/algorithm.hpp> > contract::std::vector<int> v; > contract::std::for_each(v.begin(), v.end(), ...); > I think Boost.Contract can essentially implement most/all of the > interface contracts (preconditions, postconditions, invariants, and > concepts) documented by the SGI: > http://www.sgi.com/tech/stl/<http://www.google.com/url?sa=D&q=http://www.sgi.com/tech/stl/&usg=AFQjCNHIn…> > Would such a contract::std be any useful? This is a fair question. And probably best answered by the authors of contract programming proposal for C++. What ISO C++ Committee did with nearly every new language feature (concepts, auto, noexcept, constexpr, initializer_list) was to also use it in library in order to (i) prove that the future is usable, (ii) give a solid example of how the feature should be used. So, along this reasoning, there are good reasons to do it. I can see, however, also valid reasons against it: Boost only recently approved STL containers library rewrite: Boost.Containers ( http://svn.boost.org/svn/boost/sandbox/move/libs/container/doc/html/index.h…) It already has Boost.PointerContainer (although it serves a different purpose it may be distracting that they are defined and described separately). so now, each time I use a container I will have to decide if I am using std::vector or boost::container::vector. Now if I need to consider a third option boost::contract::stl::vector it really gets hard. And would they all interoperable with one another? Perhaps if the contracts were implemented in Boost.Container, but then... I expect that Boost.Contract syntax may discourage some Boost users, that just want to use (and perhaps debug) Container library. Overwhelming them with the new syntax might discourage them from using Boost.Container. If you implement your containers separately, it is likely that they will just not be used. Difficult to say... Regards, &rzej

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Re: [boost] [interest] URL
by john＠firecrest.eclipse.co.uk 06 Sep '11

06 Sep '11

Hi Glyn Date: Mon, 5 Sep 2011 10:14:28 +0200 From: Glyn Matthews On 4 September 2011 21:36, John Ratcliffe wrote: > Is there any interest in a URL library along the lines of the Java one? > > http://download.oracle.com/**javase/1.5.0/docs/api/java/**net/URL.html [3] > > I'm currently working on a URI class as part of the cpp-netlib project: https://github.com/cpp-netlib [4] The parser already implements RFC 2396 and RFC 2732. There is still a lot of work to be done and, if you're interested, we'd be happy to accept contributions. Thanks for the response. I took a quick look and I am interested. I will take a closer look. What areas need attention? How does this project relate to boost? John Links: ------ [1] mailto:glyn.matthews@gmail.com [2] mailto:john@firecrest.eclipse.co.uk [3] http://download.oracle.com/**javase/1.5.0/docs/api/java/**net/URL.html%3Cht… [4] https://github.com/cpp-netlib

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[Submission] RawMemory
by Adder 06 Sep '11

06 Sep '11

Dear Boost Community, I would like to submit a very modest addition to Boost... It is called "RawMemory": http://adder.iworks.ro/Boost/RawMemory/ <<It supports safe, efficient and portable (all in one) transfer of multi-byte integer values to/from "untyped memory" (also known as "arrays of bytes") (also known as "raw memory"). It handles the little endian and big endian representations and various memory transfer modes (e.g. to support aligned and unaligned data with good performance). Therefore, it can be useful to any application dealing with binary data formats (e.g.: bitmap images, network packets, serialized data structures).>> Thank you so... (-: -- Yours truly, Adder

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painless currying
by Eric Niebler 06 Sep '11

06 Sep '11

After playing around with functional languages, I've come to envy how easy they make it to curry functions. Call a 2-argument function with 1 argument and you get a function that takes 1 argument. Pass another argument and it evaluates the function. Simple. In contrast, C++ users have to use binders, which are not as nice. On a lark, I implemented a wrapper that turns any TR1-style function object into a "curryable" function object (attached). Successive function call invocations bind arguments until enough arguments are bound to invoke the wrapped function. With it you can do the following: curryable<std::plus<int> > p; auto curried = p(1); int i = curried(2); assert(i == 3); Is there any interest in such a thing? -- Eric Niebler BoostPro Computing http://www.boostpro.com

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[serialization] between 32 bit and 64 bit
by Jinqiang Zhang 06 Sep '11

06 Sep '11

I'm using boost.serialization for part of our messaging solution. Now here comes a problem: we want to communicate between 32bit and 64bit, is there a chance that using "text archive" would solve the problem ? jinqiang Zhang

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[endian] comments
by Gordon Woodhull 05 Sep '11

05 Sep '11

Hi Beman, all, Couple of comments after scanning the documentation. It does look like a solid library but the Hello World example in the documentation appears to be out of synch with the code, and with Boost. None of its includes are correct (except iostream). It looks like the operator<= overloading (?) is intended to invoke some binary stream functionality which isn't yet in Boost. Unfortunately I wasn't able to get it to compile because I couldn't find <boost/binary_stream.hpp> anywhere. There appears to be some related detail::binary_data stuff in endian/boost/io/detail/bin_manip.hpp but I couldn't figure out how to connect it. An unrelated comment: on the "conversion functions" page of the documentation, there are some references to "indicated byte ordering" - which confuses me because I don't see where the byte ordering is indicated. Does this mean the ordering which Endian uses internally? Cheers, Gordon

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[variant] Constructible/assignable from anything
by Agustín K-ballo Bergé 05 Sep '11

05 Sep '11

Boost variant has a constructor and an assignment operator that would take just anything. If it cannot be converted to any of its bounded types, it will result in an error within variant's internals. This, mixed with conversion operators, interferes with overload resolution (code that reproduces the issue attached). Would SFINAE'ing out the non-candidate constructors (and assignments) fix this? Agustín K-ballo Bergé.- http://talesofcpp.blogspot.com

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[interest] URL
by John Ratcliffe 05 Sep '11

05 Sep '11

Is there any interest in a URL library along the lines of the Java one? http://download.oracle.com/javase/1.5.0/docs/api/java/net/URL.html John Ratcliffe

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[review] Conversion review starts today
by Gordon Woodhull 04 Sep '11

04 Sep '11

Hi All, The review of Vicente Botet Escriba's Conversion library starts today and ends August 29. The Conversion library manages generic explicit conversion between unrelated types. It can be thought of as a substitute for overloading static_cast, or as an alternative to lexical_cast when conversion via text is unwanted. The code is available here: http://svn.boost.org/svn/boost/sandbox/conversion/ And the documentation is here: http://svn.boost.org/svn/boost/sandbox/conversion/libs/conversion_ext/doc/h… Alternately, you can download a compressed package here: https://github.com/viboes/TBoost.Conversion Reviews may answer the following questions: * What is your evaluation of the design? * What is your evaluation of the implementation? * What is your evaluation of the documentation? * What is your evaluation of the potential usefulness of the library? * Did you try to use the library? With what compiler? Did you have any problems? * How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? * Are you knowledgeable about the problem domain? And finally, every review should answer this question: * Do you think the library should be accepted as a Boost library? Be sure to say this explicitly so that your other comments don't obscure your overall opinion. Of course, "informal reviews" and discussion are also welcome. Cheers, Gordon Woodhull Espen Harlinn

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[serialization] deserializing asynchronously serialized types
by Andrew Hundt 04 Sep '11

04 Sep '11

I have an unusual use case for boost.serialization, and I was wondering if it would be possible to adapt it to my needs: - I have a set of over 100 types, and instances of each are generated asynchronously then serialized to a file in that order. - The most interesting serialized data will be written just before the power is unexpectedly cut. - I need to load in and run on as much data as possible when reading the serialized data back, ignoring incomplete data at the end (due to a power cut). - The basic Boost serialization examples require you to know the type of the next piece of data to be loaded when reading. Since these types are generated asynchronously they are not known in advance. - I need to write the data out immediately when it arrives because of the power issue. - Files will be getting up to around 150GB in size for binary archives, so it can't be marshaled in memory, it needs to be written immediately even if it is redundant. Is there a way to read in that serialized file using the facilities provided in boost.serialization? Here are my current ideas: - I tried using boost.variant, but it loses its will to compile when I increase the typelist limit to around ~60 types on gcc 4.4, and I have more than a hundred. - Use preprocessor metaprogramming to do something equivalent to boost.variant, but I would very much prefer a more pleasant option. - Serialize an index or custom headers indicating the next type to appear - One way of achieving some of these goals is writing one piece at a time using a binary archive to an fstream, with the index mentioned above separating data types. I don't know what aspects of my requirements will prove to be a problem, so if anyone can provide advice that would help me avoid a major pitfall, it would be greatly appreciated. Thanks for your thoughts. Cheers! Andrew Hundt

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