Re: [Boost-users] Serializing a char *

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Basilevs

1 Sep 2008 1 Sep '08

3:12 a.m.

On Sat, Aug 30, 2008 at 11:12 AM, Robert Ramey wrote:

...

I'm suspecting that there is a confusion about how to seriailzation a pointer to a null terminated string. It's natural to want to do something like

char *p; ... p = "jsdkfjads" ... ar & p;

because the library syntax encourages one to think that way.

But in this case, one would want

save(... int i = strlen(p); ar << i; ar << binary_object(i, p); }

load(... int i; ar >> i; ar >> binary_object(i,p); }

How do we deal with the trailing null? In this example trailing null is not saved, and it is a good thing, but shouldn't we add it after loading?

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Robert Ramey

1 Sep 1 Sep

4 p.m.

New subject: Serializing a char *

This example should probably be ar << binary_object(i + 1, p); // etc Robert Ramey Basilevs wrote:

...

On Sat, Aug 30, 2008 at 11:12 AM, Robert Ramey wrote:

...
I'm suspecting that there is a confusion about how to seriailzation a pointer to a null terminated string. It's natural to want to do something like

char *p; ... p = "jsdkfjads" ... ar & p;

because the library syntax encourages one to think that way.

But in this case, one would want

save(... int i = strlen(p); ar << i; ar << binary_object(i, p); }

load(... int i; ar >> i; ar >> binary_object(i,p); }

How do we deal with the trailing null? In this example trailing null is not saved, and it is a good thing, but shouldn't we add it after loading?

Diane

3 Sep 3 Sep

12:03 a.m.

New subject: Serializing a char *

Robert Ramey writes:

...

This example should probably be

ar << binary_object(i + 1, p); // etc

Robert Ramey

Basilevs wrote:

...
On Sat, Aug 30, 2008 at 11:12 AM, Robert Ramey wrote:

...
I'm suspecting that there is a confusion about how to seriailzation a pointer to a null terminated string. It's natural to want to do something like

char *p; ... p = "jsdkfjads" ... ar & p;

because the library syntax encourages one to think that way.

But in this case, one would want

save(... int i = strlen(p); ar << i; ar << binary_object(i, p); }

load(... int i; ar >> i; ar >> binary_object(i,p); }

How do we deal with the trailing null? In this example trailing null is not saved, and it is a good thing, but shouldn't we add it after loading?

Thank you for laying this out, it is exactly what I need. Is there a way to do this in a free serialize function rather than requiring save & load functions? I would like to write a serialize function for each of my structures up through the hierarchy, and it looks to me like if I write save/load functions for a structure in the middle then I will have to continue with that all the way through to the top. So I would like to be able to handle the null terminated string within the serialize function if that's possible. Thanks, Diane

Robert Ramey

2:40 a.m.

New subject: Serializing a char *

Diane wrote:

...

looks to me like if I write save/load functions for a structure in the middle then I will have to continue with that all the way through to the top.

Not at all true. serialize is called at each point. If ..SPLIT is used then a standard serial.ize function is inserted whch calls save/load for that (and only that) structure. Robert Ramey

Diane

4 Sep 4 Sep

2:11 a.m.

New subject: Serializing a char *

Robert Ramey writes:

...

Not at all true. serialize is called at each point. If ..SPLIT is used then a standard serial.ize function is inserted whch calls save/load for that (and only that) structure.

Robert Ramey

Awesome, thanks! I found a similar piece of code in greg_serialize.hpp that I'm trying to work from, but I get compile errors even if I'm not doing anything in save/load: error: call of overloaded `serialize(boost::archive::text_iarchive&, MYSTRSTRUCT&, const boost::serialization::version_type&)' is ambiguous Is there any chance you can spot what I'm doing wrong in my code? typedef struct MYSTRSTRUCT { char *chstar; } MYSTRSTRUCT; BOOST_SERIALIZATION_SPLIT_FREE(MYSTRSTRUCT) template<class Archive> inline void serialize(Archive & ar, MYSTRSTRUCT & d, const unsigned int file_version) { split_free(ar, d, file_version); } template<class Archive> void save(Archive & ar, const MYSTRSTRUCT & d, unsigned int /* version */) { int i = strlen(d.chstar); } template<class Archive> void load(Archive & ar, MYSTRSTRUCT & d, unsigned int /*version*/) { int i; } And then it's used in serialize() for the struct that contains a MYSTRSTRUCT: ar & it.strstruct Here's the full compiler output: boost_1_36_0/boost/serialization/serialization.hpp: In function `void boost::serialization::serialize_adl(Archive&, T&, unsigned int) [with Archive = boost::archive::text_iarchive, T = MYSTRSTRUCT]': boost_1_36_0/boost/archive/detail/iserializer.hpp:152: instantiated from `void boost::archive::detail::iserializer::load_object_data(boost::archive::detail::basic_iarchive&, void*, unsigned int) const [with Archive = boost::archive::text_iarchive, T = MYSTRSTRUCT]' serialize4.cpp:80: instantiated from here boost_1_36_0/boost/serialization/serialization.hpp:133: error: call of overloaded `serialize(boost::archive::text_iarchive&, MYSTRSTRUCT&, const boost::serialization::version_type&)' is ambiguous boost_1_36_0/boost/serialization/serialization.hpp:73: note: candidates are: void boost::serialization::serialize(Archive&, T&, unsigned int) [with Archive = boost::archive::text_iarchive, T = MYSTRSTRUCT] serialize4.cpp:337: note: void boost::serialization::serialize(Archive&, MYSTRSTRUCT&, unsigned int) [with Archive = boost::archive::text_iarchive] serialize4.cpp:345: note: void serialize(Archive&, MYSTRSTRUCT&, unsigned int) [with Archive = boost::archive::text_iarchive] boost_1_36_0/boost/serialization/serialization.hpp: In function `void boost::serialization::serialize_adl(Archive&, T&, unsigned int) [with Archive = boost::archive::text_oarchive, T = MYSTRSTRUCT]': boost_1_36_0/boost/archive/detail/oserializer.hpp:144: instantiated from `void boost::archive::detail::oserializer::save_object_data(boost::archive::detail::basic_oarchive&, const void* const [with Archive = boost::archive::text_oarchive, T = MYSTRSTRUCT]' serialize4.cpp:80: instantiated from here boost_1_36_0/boost/serialization/serialization.hpp:133: error: call of overloaded `serialize(boost::archive::text_oarchive&, MYSTRSTRUCT&, const boost::serialization::version_type&)' is ambiguous boost_1_36_0/boost/serialization/serialization.hpp:73: note: candidates are: void boost::serialization::serialize(Archive&, T&, unsigned int) [with Archive = boost::archive::text_oarchive, T = MYSTRSTRUCT] serialize4.cpp:337: note: void boost::serialization::serialize(Archive&, MYSTRSTRUCT&, unsigned int) [with Archive = boost::archive::text_oarchive] serialize4.cpp:345: note: void serialize(Archive&, MYSTRSTRUCT&, unsigned int) [with Archive = boost::archive::text_oarchive] Thanks, Diane

Robert Ramey

5:22 a.m.

New subject: Serializing a char *

Look at the definition of the macros .. SPLIT_FREE. It defines a serialization function in terms of save/load. So defining your own serializaton function is redundant (and ambiguous) Robert Ramey Diane wrote:

...

Robert Ramey writes:

...
Not at all true. serialize is called at each point. If ..SPLIT is used then a standard serial.ize function is inserted whch calls save/load for that (and only that) structure.

Robert Ramey

Awesome, thanks!

I found a similar piece of code in greg_serialize.hpp that I'm trying to work from, but I get compile errors even if I'm not doing anything in save/load:

error: call of overloaded `serialize(boost::archive::text_iarchive&, MYSTRSTRUCT&, const boost::serialization::version_type&)' is ambiguous

Is there any chance you can spot what I'm doing wrong in my code?

typedef struct MYSTRSTRUCT { char *chstar; } MYSTRSTRUCT;

BOOST_SERIALIZATION_SPLIT_FREE(MYSTRSTRUCT)

template<class Archive> inline void serialize(Archive & ar, MYSTRSTRUCT & d, const unsigned int file_version) { split_free(ar, d, file_version); }

template<class Archive> void save(Archive & ar, const MYSTRSTRUCT & d, unsigned int /* version */) { int i = strlen(d.chstar); }

template<class Archive> void load(Archive & ar, MYSTRSTRUCT & d, unsigned int /*version*/) { int i; }

And then it's used in serialize() for the struct that contains a MYSTRSTRUCT: ar & it.strstruct

Here's the full compiler output: boost_1_36_0/boost/serialization/serialization.hpp: In function `void boost::serialization::serialize_adl(Archive&, T&, unsigned int) [with Archive = boost::archive::text_iarchive, T = MYSTRSTRUCT]': boost_1_36_0/boost/archive/detail/iserializer.hpp:152: instantiated from `void boost::archive::detail::iserializer
...
...
...
load_object_data(boost::archive::detail::basic_iarchive&, void*, unsigned int) const [with Archive = boost::archive::text_iarchive, T = MYSTRSTRUCT]' serialize4.cpp:80: instantiated from here boost_1_36_0/boost/serialization/serialization.hpp:133: error: call of overloaded `serialize(boost::archive::text_iarchive&, MYSTRSTRUCT&, const boost::serialization::version_type&)' is ambiguous boost_1_36_0/boost/serialization/serialization.hpp:73: note: candidates are: void boost::serialization::serialize(Archive&, T&, unsigned int) [with Archive = boost::archive::text_iarchive, T = MYSTRSTRUCT] serialize4.cpp:337: note: void boost::serialization::serialize(Archive&, MYSTRSTRUCT&, unsigned int) [with Archive = boost::archive::text_iarchive] serialize4.cpp:345: note: void serialize(Archive&, MYSTRSTRUCT&, unsigned int) [with Archive = boost::archive::text_iarchive] boost_1_36_0/boost/serialization/serialization.hpp: In function `void boost::serialization::serialize_adl(Archive&, T&, unsigned int) [with Archive = boost::archive::text_oarchive, T = MYSTRSTRUCT]': boost_1_36_0/boost/archive/detail/oserializer.hpp:144: instantiated from `void boost::archive::detail::oserializer
Thanks, Diane

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Basilevs
Diane
Robert Ramey