Serialize sdt::map without boost

[leolio24]

Can I serialize STL map<string, string> at once to a binary file and read back from the same?

[Disch]

Not in 1 step... but you can write a common routine to do it.

Simply write the number of entries ( get with size() ), then iterate through the map ( using begin() and end() ) and write the key/value pairs to the file.

[leolio24]

thank you!

[leolio24]

I'm sorry but I have another question...

I did my "store routine" :

void store (fstream &stream) {
map<string,string>::iterator it;

stream.write ((char*)&name, sizeof (string));
stream.write ((char*)&basecalls, sizeof (string));
stream.write ((char*)&quality, sizeof (string));
for (it=directionPosition.begin(); it!=directionPosition.end(); it++) {
stream.write ((char*)&(it->first), sizeof(string));
stream.write ((char*)&(it->second), sizeof(string));
}
}

and it seems to work, but I really don't know how I can retrieve my data in my binary file...because I can't do a "for" loop, cause I don't know how many entries I have...Could you help me?

About the first three elements it's not a problem I can do this :

void retrieve (fstream &stream) {
stream.read ((char*)&name, sizeof(string));
stream.read ((char*)&basecalls, sizeof(string));
stream.read ((char*)&quality, sizeof(string));
}

[jsmith]

That's not going to work. string is a class containing pointers. You can't write the pointers to the file (well, you can, but it is useless).

Write the number of elements in the map to the file first.

[leolio24]

thanks.

But if it isn't a good idea to write string (pointers) into the file, I can't see what I have to do...

maybe my store method could be just like this ?

void store (fstream &stream) {
   stream.write ((char*)&size, sizeof (int)); //map size
   stream.write ((char*)&MyObject, sizeof (Object));
}

?

and for retrieve my object, I take the size and then loop on size, taking out values ?

[jsmith]

To write a string object, you will need to

string str;   // String to write
size_t strSz( str.length() );

stream.write( &strSz, sizeof( strSz ) );
stream.write( str.c_str(), strSz );

ie, write the length of the C-string first, then write the data.