|
SerializationArchive Concept |
class oarchive : ...
{
...
public:
// called to save objects
template<class T>
oarchive & operator<<(const T & t);
template<class T>
oarchive & operator&(T & t){
return *this << t;
}
void save_binary(const void *address, std::size_t count);
template<class T>
register_type(T * t = NULL);
unsigned int library_version() const;
struct is_saving {
typedef mpl::bool_<true> type;
BOOST_STATIC_CONSTANT(bool, value=true);
};
struct is_loading {
typedef mpl::bool_<false> type;
BOOST_STATIC_CONSTANT(bool, value=false);
};
...
};
The template parameter T
must correspond to a type which
models the Serializable concept.
template<class T>
oarchive & operator<<(const T & t);
template<class T>
oarchive & operator&(T & t);
Appends an object of type T to the archive. The object may be
serialize
function has been defined.
void save_binary(const void *address, std::size_t count);
count
bytes found at
address
.
template<class T>
register_type(T * t = NULL);
unsigned int library_version() const;
is_saving::type = mpl::bool<true>;
is_saving::value= true;
is_loading::type = mpl::bool<false>;
is_loading::value= false;
class iarchive : ...
{
...
public:
// called to load objects
template<class T>
iarchive & operator>>(T & t);
template<class T>
iarchive & operator&(T & t){
return *this >> t;
}
void delete_created_pointers();
void load_binary(void *address, std::size_t count);
template<class T>
register_type(T * t = NULL);
reset_object_address(void * old_address, void * new_address);
unsigned int library_version() const;
struct is_saving {
typedef mpl::bool_<false> type;
BOOST_STATIC_CONSTANT(bool, value=false);
};
struct is_loading {
typedef mpl::bool_<true> type;
BOOST_STATIC_CONSTANT(bool, value=true);
};
...
};
} //namespace archive
) //namespace boost
T
must correspond to a type which
models the Serializable concept.
template<class T>
iarchive & operator>>(T & t);
template<class T>
iarchive & operator&(T & t);
Retrieves an object of type T from the archive. The object may be
serialize
function has been defined.
void load_binary(void *address, std::size_t count);
count
bytes and stores
them in memory starting at address
.
void delete_created_pointers();
template<class T>
register_type(T * t = NULL);
void reset_object_address(void * new_address, void * old_address);
In such cases, reset_object_address should be invoked to communicate the final address of the last item loaded. This permits the internal tables to be correctly maintained in these special case.
unsigned int library_version() const;
is_saving::type = mpl::bool<false>;
is_saving::value= false;
is_loading::type = mpl::bool<true>;
is_loading::value= true;
The existence of the <<
and >>
suggest
a relationship between archives and C++ i/o streams. Archives are not
C++ i/o streams. All the archives included with this system take a stream
as an argument in the constructor and that stream is used for output or input.
However, this is not a requirement of the serialization functions or the
archive interface. It just turns out that the archives written so far have
found it useful to base their implementation on streams.
// a portable text archive
boost::archive::text_oarchive(ostream &s) // saving
boost::archive::text_iarchive(istream &s) // loading
// a portable text archive using a wide character stream
boost::archive::text_woarchive(wostream &s) // saving
boost::archive::text_wiarchive(wistream &s) // loading
// a non-portable native binary archive
boost::archive::binary_oarchive(ostream &s) // saving
boost::archive::binary_iarchive(istream &s) // loading
// a portable XML archive
boost::archive::xml_oarchive(ostream &s) // saving
boost::archive::xml_iarchive(istream &s) // loading
// a portable XML archive which uses wide characters - use for utf-8 output
boost::archive::xml_woarchive(wostream &s) // saving
boost::archive::xml_wiarchive(wistream &s) // loading
All of these archives implement the same inteface. Hence, it should suffice to describe only one
of them in detail. For this purpose we will use the text archive.
namespace boost {
namespace archive {
enum archive_flags {
no_header = 1, // suppress archive header info
no_codecvt = 2, // suppress alteration of codecvt facet
no_xml_tag_checking = 4 // suppress checking of xml tags - igored on saving
};
} // archive
} // boost
namespace boost {
namespace archive {
template<class OStream>
class text_oarchive : ...
{
...
public:
... // implementation of Archive concept
oarchive(OStream & os, unsigned int flags = 0);
~oarchive();
};
} // archive
} // boost
OStream
basic_istream<char>
oarchive(OStream & os, unsigned int flags = 0);
stream
as
an argument and optional flags. For most applications there will be no need to use flags.
Flags are defined by enum archive_flags
enumerator.
Multiple flags can be combined with the |
operator.
By default, archives prepend
output with initial data which helps identify them as archives produced by this system.
This permits a more graceful handling of the case where an attempt is made to load an archive
from an invalid file format. In addition to this, each type of archive might have
its own information. For example, native binary archives include information about
sizes of native types and endianess to gracefully handle the case where it has been
erroneously assumed that such an archive is portable across platforms. In some cases,
where this extra overhead might be considered objectionable, it can be suppressed with the
no_header
flag.
In some cases, an archive may alter (and later restore)
the codecvt facet of the stream locale. To suppress this action,
include the no_codecvt
flag.
XML archives contain nested tags signifying the start and end of data fields.
These tags are normally checked for agreement with the object name when
data is loaded. If a mismatch occurs an exception is thrown. It's possible
that this may not be desired behavior. To suppress this checking of XML
tags, use no_xml_tag_checking
flag.
~oarchive();
namespace boost {
namespace archive {
template<class IStream>
class text_iarchive : ...
{
...
public:
... // implementation of Archive concept
iarchive(IStream & is, unsigned int flags = 0);
~iarchive();
};
} //namespace archive
) //namespace boost
IStream
basic_ostream<char>
iarchive(IStream & is, unsigned int flags = 0);
stream
as
an argument and optional flags. If flags are used, they should be the same
as those used when the archive was created. Function and usage of flags is described
above.
~iarchive();
xml_w?archive
) renders it output as UTF-8 which can
handle any wide character without loss of information.
std::string
data is converted from multi-byte format to wide
character format using the current
locale
. Hence this version should give a fair rendering of all
C++ data for all cases. This could result in some unexpected behavior.
Suppose an std::string
is created with the locale
character
set to hebrew characters. On output this is converted to wide characters.
On input however, there could be a problem if the locale
is
not set the same as when the archive is created.
The normal character version (xml_?archive
) renders
std::string
output without any conversion. Though this may work
fine for serialization, it may create difficulties if the XML archive is used
for some other purpose.
© Copyright Robert Ramey 2002-2004. Distributed under the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)