Question

I’m writing a latency-sensitive app which reads a text file upon initialisation. I have profiled and re-written all my algorithms such that 85% of my execution time is from the lines:

boost::interprocess::file_mapping file(Path, read_only);
boost::interprocess::mapped_region data(file, read_only);

I am writing this on windows- is there any faster way to map a file into memory? Portability is not a concern.

Answer 1

You could just use the native functions of Win32, but I think you won’t save alot, because boost will not add alot of overhead:

OFSTRUCT ofStruct;
ofStruct.cBytes=sizeof (OFSTRUCT);
HANDLE file=(HANDLE)OpenFile(fileName, &ofStruct, OF_READ); 
if (file==INVALID_HANDLE_VALUE) 
  handle errors
else {
  HANDLE map=CreateFileMapping(file, NULL, PAGE_READONLY, 0, 0, 0);
  if (map==INVALID_HANDLE_VALUE) 
    handle errors
  else {
    const char *p=(const char *)MapViewOfFile(map, FILE_MAP_READ, 0, 0, 0));
    if (p) {
      // enjoy using p to read access file contents.
    }
    // close all that handles now...
  }