Question

I have a program that reads data from a file line-by-line. I would like to copy some substring of that line in to a map as below:

std::map< DWORD, std::string > my_map;
DWORD index;         // populated with some data
char buffer[ 1024 ]; // populated with some data
char* element_begin; // points to some location in buffer
char* element_end;   // points to some location in buffer > element_begin

my_map.insert( std::make_pair( index, std::string( element_begin, element_end ) ) );

This std::map<>::insert() operation takes a long time (It doubles the file parsing time). Is there a way to make this a less expensive operation?

Thanks,
PaulH

Edit: to be more specific, I want to know that I’m doing the minimum number of copy operations to get the data from the file in to the map.

Answer 1

To answer your supplementary question slightly. Try changing the map temporarily to a vector of strings, and then time it inserting a fixed string value into the vector For example:

vector <string> v;
string s( "foobar" );

your insert loop:
   v.push_back( s );

That should give you a lower bound of what is possible regarding speed.

Also, you should time things with all optimisations turned on (if you are not already doing so). This can make a suprising difference to many Standard Library operations.