young wrote:

I have 2 functions for read files list in one directory. One uses Win32 and one uses boost:

void GetFilesWin32(std::string dir) { std::vectorstd::string vFiles; std::string f = dir + "*.*"; std::string file; WIN32_FIND_DATA findFileData; HANDLE h = FindFirstFile(f.c_str(), &findFileData); if(h != INVALID_HANDLE_VALUE) { do { if((findFileData.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY) != FILE_ATTRIBUTE_DIRECTORY) { file = findFileData.cFileName; vFiles.push_back( file); } } while( FindNextFile( h, &findFileData) != 0); } FindClose(h); }

void GetFilesBoost(std::string dir) { namespace fs = boost::filesystem; std::vectorstd::string vFiles; fs::path path(dir); fs::directory_iterator end_dir; for(fs::directory_iterator it(path); it != end_dir; it++) { if(!(fs::is_directory(it->status()))) { vFiles.push_back(it->path().filename().string()); } } }

Boost takes 1.00 ms while Win32 taks 0.15 ms for same directory. Why?

How about trying out the profiling facilites available with your development system. I"ve used both the ones available with gcc and recent versions of VC IDE and found them very useful for answering such questions. Robert Ramey

I have 2 functions for read files list in one directory. One uses Win32 and one uses boost:

FWIW, directory_iterator_increment() look like this: void directory_iterator_increment(directory_iterator& it, system::error_code* ec) { BOOST_ASSERT_MSG(it.m_imp.get(), "attempt to increment end iterator"); BOOST_ASSERT_MSG(it.m_imp->handle != 0, "internal program error"); path::string_type filename; file_status file_stat, symlink_file_stat; system::error_code temp_ec; for (;;) { temp_ec = dir_itr_increment(it.m_imp->handle, # if defined(BOOST_POSIX_API) it.m_imp->buffer, # endif filename, file_stat, symlink_file_stat); if (temp_ec) // happens if filesystem is corrupt, such as on a damaged optical disc { path error_path(it.m_imp->dir_entry.path().parent_path()); // fix ticket #5900 it.m_imp.reset(); if (ec == 0) BOOST_FILESYSTEM_THROW( filesystem_error("boost::filesystem::directory_iterator::operator++", error_path, error_code(BOOST_ERRNO, system_category()))); ec->assign(BOOST_ERRNO, system_category()); return; } else if (ec != 0) ec->clear(); if (it.m_imp->handle == 0) // eof, make end { it.m_imp.reset(); return; } if (!(filename[0] == dot // !(dot or dot-dot) && (filename.size()== 1 || (filename[1] == dot && filename.size()== 2)))) { it.m_imp->dir_entry.replace_filename( filename, file_stat, symlink_file_stat); return; } } } ...and the inner dir_itr_increment() function involves the following: perms make_permissions(const path& p, DWORD attr) { perms prms = fs::owner_read | fs::group_read | fs::others_read; if ((attr & FILE_ATTRIBUTE_READONLY) == 0) prms |= fs::owner_write | fs::group_write | fs::others_write; if (BOOST_FILESYSTEM_STRICMP(p.extension().string().c_str(), ".exe") == 0 || BOOST_FILESYSTEM_STRICMP(p.extension().string().c_str(), ".com") == 0 || BOOST_FILESYSTEM_STRICMP(p.extension().string().c_str(), ".bat") == 0 || BOOST_FILESYSTEM_STRICMP(p.extension().string().c_str(), ".cmd") == 0) prms |= fs::owner_exe | fs::group_exe | fs::others_exe; return prms; } ...where each of the 4 comparisons invokes conversion from wchar_t* to std::string. So, there's obviously a lot of overhead, but the question is whether it's really a bottleneck in a real-life application.