[Boost-users] How to convert std::string into basic_string

[manish4gupta]

#include <boost/interprocess/managed_shared_memory.hpp>
#include <boost/interprocess/allocators/allocator.hpp>
#include <boost/interprocess/containers/map.hpp>

How to convert std::string into boost string. I am doing some benchmarking
by inserting the std::string value instead of char_string(ypedef of
basic_string) but i am getting error message.

#include <boost/interprocess/containers/vector.hpp>
#include <boost/interprocess/containers/string.hpp>
#include <iostream>

using namespace boost::interprocess;

//Typedefs of allocators and containers
typedef managed_shared_memory::segment_manager
segment_manager_t;
typedef allocator<void, segment_manager_t>
void_allocator;
typedef allocator<int, segment_manager_t>
int_allocator;
typedef vector<int, int_allocator>
int_vector;
typedef allocator<int_vector, segment_manager_t>
int_vector_allocator;
typedef vector<int_vector, int_vector_allocator>
int_vector_vector;
typedef allocator<char, segment_manager_t>
char_allocator;
typedef basic_string<char, std::char_traits<char>, char_allocator>
char_string;

class complex_data
{
int id_;
char_string char_string_;
int_vector_vector int_vector_vector_;

public:
//Since void_allocator is convertible to any other allocator<T>, we can
simplify
//the initialization taking just one allocator for all inner containers.
complex_data(int id, const char *name, const void_allocator &void_alloc)
: id_(id), char_string_(name, void_alloc),
int_vector_vector_(void_alloc)
{}
//Other members...
};

//Definition of the map holding a string as key and complex_data as mapped
type
typedef std::pair<const char_string, int>
map_value_type;
typedef std::pair<char_string, int>
movable_to_map_value_type;
typedef allocator<map_value_type, segment_manager_t>
map_value_type_allocator;
typedef map< char_string, int
, std::less<char_string>, map_value_type_allocator>
complex_map_type;

int main ()
{
//Remove shared memory on construction and destruction
struct shm_remove
{
shm_remove() { shared_memory_object::remove("MySharedMemory"); }
~shm_remove(){ shared_memory_object::remove("MySharedMemory"); }
} remover;

//Create shared memory
managed_shared_memory segment(create_only,"MySharedMemory", 65536);

//An allocator convertible to any allocator<T, segment_manager_t> type
void_allocator alloc_inst (segment.get_segment_manager());

//Construct the shared memory map and fill it
complex_map_type *mymap = segment.construct<complex_map_type>
//(object name), (first ctor parameter, second ctor parameter)
("MyMap")(std::less<char_string>(), alloc_inst);
string s = "hello";
char y = (char_string)s;

for(int i = 0; i < 100; ++i)
{
char_string key_object(alloc_inst);
map_value_type value(key_object, i);
mymap->insert(value);
}
return 0;
}

error: no matching function for call to
‘boost::interprocess_container::basic_string<char, std::char_traits<char>,
boost::interprocess::allocator<char,
boost::interprocess::segment_manager<char,
boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family,
boost::interprocess::offset_ptr<void>, 0u>, boost::interprocess::iset_index>
> >::basic_string(boost::interprocess_container::string&)’
/usr/include/boost/interprocess/containers/container/string.hpp:591: note:
candidates are: boost::interprocess_container::basic_string<CharT, Traits,
Alloc>::basic_string(typename A::size_type, CharT, const A&) [with CharT =
char, Traits = std::char_traits<char>, A =
boost::interprocess::allocator<char,
boost::interprocess::segment_manager<char,
boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family,
boost::interprocess::offset_ptr<void>, 0u>, boost::interprocess::iset_index>
>]
/usr/include/boost/interprocess/containers/container/string.hpp:584: note:
boost::interprocess_container::basic_string<CharT, Traits,
Alloc>::basic_string(const CharT*, const A&) [with CharT = char, Traits =
std::char_traits<char>, A = boost::interprocess::allocator<char,
boost::interprocess::segment_manager<char,
boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family,
boost::interprocess::offset_ptr<void>, 0u>, boost::interprocess::iset_index>
>]
/usr/include/boost/interprocess/containers/container/string.hpp:577: note:
boost::interprocess_container::basic_string<CharT, Traits,
Alloc>::basic_string(const CharT*, typename A::size_type, const A&) [with
CharT = char, Traits = std::char_traits<char>, A =
boost::interprocess::allocator<char,
boost::interprocess::segment_manager<char,
boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family,
boost::interprocess::offset_ptr<void>, 0u>, boost::interprocess::iset_index>
>]
/usr/include/boost/interprocess/containers/container/string.hpp:564: note:
boost::interprocess_container::basic_string<CharT, Traits,
Alloc>::basic_string(const
boost::interprocess_container::basic_string<CharT, Traits, Alloc>&, typename
A::size_type, typename A::size_type, const A&) [with CharT = char, Traits =
std::char_traits<char>, A = boost::interprocess::allocator<char,
boost::interprocess::segment_manager<char,
boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family,
boost::interprocess::offset_ptr<void>, 0u>, boost::interprocess::iset_index>
>]
/usr/include/boost/interprocess/containers/container/string.hpp:557: note:
boost::interprocess_container::basic_string<CharT, Traits,
Alloc>::basic_string(boost::interprocess::rv<boost::interprocess_container::basic_string<CharT,
Traits, Alloc> >&) [with CharT = char, Traits = std::char_traits<char>, A =
boost::interprocess::allocator<char,
boost::interprocess::segment_manager<char,
boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family,
boost::interprocess::offset_ptr<void>, 0u>, boost::interprocess::iset_index>
>]
/usr/include/boost/interprocess/containers/container/string.hpp:548: note:
boost::interprocess_container::basic_string<CharT, Traits,
Alloc>::basic_string(const
boost::interprocess_container::basic_string<CharT, Traits, Alloc>&) [with
CharT = char, Traits = std::char_traits<char>, A =
boost::interprocess::allocator<char,
boost::interprocess::segment_manager<char,
boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family,
boost::interprocess::offset_ptr<void>, 0u>, boost::interprocess::iset_index>
>]
/usr/include/boost/interprocess/containers/container/string.hpp:539: note:
boost::interprocess_container::basic_string<CharT, Traits,
Alloc>::basic_string(const A&) [with CharT = char, Traits =
std::char_traits<char>, A = boost::interprocess::allocator<char,
boost::interprocess::segment_manager<char,
boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family,
boost::interprocess::offset_ptr<void>, 0u>, boost::interprocess::iset_index>
>]
/usr/include/boost/interprocess/containers/container/string.hpp:532: note:
boost::interprocess_container::basic_string<CharT, Traits,
Alloc>::basic_string(boost::interprocess_container::basic_string<CharT,
Traits, Alloc>::reserve_t, size_t, const A&) [with CharT = char, Traits =
std::char_traits<char>, A = boost::interprocess::allocator<char,
boost::interprocess::segment_manager<char,
boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family,
boost::interprocess::offset_ptr<void>, 0u>, boost::interprocess::iset_index>
>]

Thanks in advance.

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[Mathias Gaunard]

manish4gupta wrote:

> How to convert std::string into boost string. I am doing some benchmarking
> by inserting the std::string value instead of char_string(ypedef of
> basic_string) but i am getting error message.

To convert between two different types of basic_string, you need to use
the constructor that takes two iterators.

[manish4gupta]

Is this that constructor...
basic_string& assign(InputIter first, InputIter last)
{
//Dispatch depending on integer/iterator
const bool aux_boolean = containers_detail::is_convertible<InputIter,
std::size_t>::value;
typedef containers_detail::bool_<aux_boolean> Result;
return this->priv_assign_dispatch(first, last, Result());
}

I am new to boost-interprocess. I don't know much about this. Any example
converting the std:: string/c-string into boost basic_string will help me. I
will be really thankful to you.

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_______________________________________________

[Christoph Gysin]

>   char y = (char_string)s;

That doesn't make any sense. The rest of the example compiles fine here.

Chris
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[Christoph Gysin]

> I am new to boost-interprocess. I don't know much about this. Any example
> converting the std:: string/c-string into boost basic_string will help me. I
> will be really thankful to you.

basic_string is not boost, it's plain STL.

from <string>:

typedef basic_string<char> string;

To assign two different basic_strings:

std::string s = "foobar";
std::basic_string<wchar_t> ws(s.begin(), s.end());

Chris
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[manish4gupta]

This is ok but i have to convert string into boost string. if i use the
method as suggested.

string s = "hello";
std::basic_string<wchar_t> ts(s.begin(), s.end());
char_string y = ts;

I am getting the following error.

run.cpp: In function ‘int main()’:
run.cpp:63: error: conversion from ‘std::basic_string<wchar_t,
std::char_traits<wchar_t>, std::allocator<wchar_t> >’ to non-scalar type

‘boost::interprocess_container::basic_string<char, std::char_traits<char>,
boost::interprocess:allocator<char,
boost::interprocess::segment_manager<char,
:boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family,
boost::interprocess::offset_ptr<void>, 0u>, boost::interprocess::iset_index>

> >’ requested

from <string>:

typedef basic_string<char> string;

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[Igor R]

> This is ok but i have to convert string into boost string.

You mean Boost.Interprocess string.

std::string s1("test");

char_string s2(s1.begin(), s1.end());
or:
char_string s2(s1.c_str());

[manish4gupta]

I have tried both but i am getting the following error message

In constructor ‘boost::interprocess_container::basic_string<CharT, Traits,

Alloc>::basic_string(const CharT*, const A&) [with CharT = char, Traits =

std::char_traits<char>, A = boost::interprocess::allocator<char,

boost::interprocess::segment_manager<char,
boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family,
boost::interprocess::offset_ptr<void>, 0u>, boost::interprocess::iset_index>

>]’:
run.cpp:63: error: no matching function for call to
‘boost::interprocess::allocator<char,

boost::interprocess::segment_manager<char,
boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family,
boost::interprocess::offset_ptr<void>, 0u>, boost::interprocess::iset_index>

>::allocator()’
/usr/include/boost/interprocess/allocators/allocator.hpp:129: note:
candidates are: boost::interprocess::allocator<T,
SegmentManager>::allocator(const boost::interprocess::allocator<T,
SegmentManager>&) [with T = char, SegmentManager =

boost::interprocess::segment_manager<char,
boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family,
boost::interprocess::offset_ptr<void>, 0u>,

boost::interprocess::iset_index>]
/usr/include/boost/interprocess/allocators/allocator.hpp:124: note:
boost::interprocess::allocator<T,
SegmentManager>::allocator(SegmentManager*) [with T = char, SegmentManager =

boost::interprocess::segment_manager<char,
boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family,
boost::interprocess::offset_ptr<void>, 0u>,

boost::interprocess::iset_index>]

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[Roland Bock]

Hi,

can you please send a small but complete sample code of what you are
trying (a bunch of includes and a main function, not more than a few lines)?

Regards,

Roland

[Christoph Gysin]

> This is ok but i have to convert string into boost string. if i use the
> method as suggested.
>
> string s = "hello";

> char_string y = ts;

You probably want this:

char_string cs(s.c_str(), alloc_inst);

[manish4gupta]

I am trying to store the index file (keyword , position) where keyword is
string while position is long. But before doing that i am doing some
benchmarking for the given code in which map is created as key, value.
Where key is char_string (typedef of basic_string) but when i read the data
using C++, it will be string. So my intention is to convert string into
char_string. For that i am testing to convert std:: string s = "test" into
char_string. But getting the error message. Please do help me.

#include <boost/interprocess/managed_shared_memory.hpp>
#include <boost/interprocess/allocators/allocator.hpp>
#include <boost/interprocess/containers/map.hpp>

using namespace boost::interprocess;

std::string s1("test");
char_string s2(s1.c_str());

for(int i = 0; i < 100; ++i)
{
char_string key_object(alloc_inst);
map_value_type value(key_object, i);
mymap->insert(value);
}
return 0;
}

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[manish4gupta]

Thanks it works.....
But after loading into the map when i try to get the value how can i do the
reverse.i.e converting char_string into string

std::string s = "test"; // OK
char_string cs(s.c_str(), alloc_inst); // OK and thanks
string y = (char_string) cs; // pblm

error message
run.cpp:63: error: conversion from ‘char_string’ to non-scalar type

‘boost::interprocess_container::basic_string<char, std::char_traits<char>,

std::allocator<char> >’ requested

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[Roland Bock]

manish4gupta wrote:
> I am trying to store the index file (keyword , position) where keyword is
> string while position is long. But before doing that i am doing some
> benchmarking for the given code in which map is created as key, value.
> Where key is char_string (typedef of basic_string) but when i read the data
> using C++, it will be string. So my intention is to convert string into
> char_string. For that i am testing to convert std:: string s = "test" into
> char_string. But getting the error message. Please do help me.

Hi,

sorry, but that is not even close to a minimal example.

Your problem is somewhere here (as you stated in another mail):

std::string s = "test"; // OK
char_string cs(s.c_str(), alloc_inst); // OK and thanks
string y = (char_string) cs; // pblm

Is you could send a sample program with just these lines in the main
function and the required includes/typedefs.

Nothing more. Lets focus on the problem, please.

Regards,

Roland

[Christoph Gysin]

> But after loading into the map when i try to get the value how can i do the
> reverse.i.e converting char_string into string
>
> std::string s = "test";             // OK
> char_string cs(s.c_str(), alloc_inst);   // OK and thanks
> string y = (char_string) cs;               // pblm

string y(cs.c_str());

[manish4gupta]

Thank you very much. Now it works as suggested.

Regards

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