hi guys!
I want to use boost::interprocess to store some resources (strings) into
`bi::map` that uses `bi::managed_mapped_file` so
I can put the resources in the map once, take the file, and distribute
it with the program.
the problem is that I cannot calculate the required size in advance, so
I want to use `bi::managed_mapped_file::grow ()` before inserting
another element into the map.
but it doesn't work as i expected, at some point i get exception:
what(): boost::interprocess::bad_alloc
I know the length of the key string and the length of the value string,
how can I find out the size by which I must `grow()` before inserting
another element into the map?
now my code looks like this:
#include
#include
#include
#include
#include <iostream>
int main () {
namespace bi = boost::interprocess;
using segment_manager_t = bi::managed_mapped_file::segment_manager;
using void_allocator = bi::allocator;
using char_allocator = bi::allocator;
using char_string = bi::basic_string;
using map_value_type = std::pair;
using map_value_type_allocator = bi::allocator;
using map_type = bi::map, map_value_type_allocator>;
static const char *mapfname = "map.dat";
bi::managed_mapped_file mmfile(bi::open_or_create, mapfname, 1024);
{
void_allocator alloc_inst(mmfile.get_segment_manager());
map_type *mymap =
mmfile.find_or_construct("MyMap")(alloc_inst);
assert(mymap);
for ( int i = 0; i < 100; ++i ) {
std::string s = std::to_string(i);
char_string key(s.c_str(), alloc_inst);
char_string value(s.c_str(), alloc_inst);
// bi::managed_mapped_file::grow(mapfname, ???);
<<<<<<<<<<<<<<<<<<<<<<
mymap->emplace(std::move(key), std::move(value));
}
}
bi::managed_mapped_file::shrink_to_fit(mapfname);
return 0;
}
(or: https://wandbox.org/permlink/jtTOzlMh16ZS8jG6)
any ideas?
best!
