Opened 9 years ago
Last modified 5 years ago
#9480 new Patches
make_permissions slower then it needs to be
| Reported by: | Owned by: | Beman Dawes | |
|---|---|---|---|
| Milestone: | To Be Determined | Component: | filesystem |
| Version: | Boost Development Trunk | Severity: | Optimization |
| Keywords: | filesystem make_permissions | Cc: | a.dorr@… |
Description
in libs\filesystem\src\operations.cpp the make_permissions calls path::extension four times, which accounts for pretty much 100% of the cpu cycles outside the OS call of the directory iterators increment function. A better approach would be to get the extension string once and reuse it four times. Even better would be to find the last '.' in the filename and avoid the extra std::string construction.
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;
std::string ext = p.extension().string(); if (BOOST_FILESYSTEM_STRICMP(ext.c_str(), ".exe") == 0
BOOST_FILESYSTEM_STRICMP(ext.c_str(), ".com") == 0 BOOST_FILESYSTEM_STRICMP(ext.c_str(), ".bat") == 0 BOOST_FILESYSTEM_STRICMP(ext.c_str(), ".cmd") == 0) prms |= fs::owner_exe | fs::group_exe | fs::others_exe;
return prms;
}
Or for extra performance (avoids construction of one std::string for the extension at the price of extra nasty code):
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;
const std::string& path_str = p.string(); if (path_str.size() >= 4) {
const char* ext = path_str.c_str() + path_str.size() - 4; if (BOOST_FILESYSTEM_STRICMP(ext, ".exe") == 0
BOOST_FILESYSTEM_STRICMP(ext, ".com") == 0 BOOST_FILESYSTEM_STRICMP(ext, ".bat") == 0 BOOST_FILESYSTEM_STRICMP(ext, ".cmd") == 0) prms |= fs::owner_exe | fs::group_exe | fs::others_exe;
} return prms;
}
Change History (4)
comment:1 by , 9 years ago
| Summary: | make_permissions slower then it needs to me → make_permissions slower then it needs to be |
|---|
follow-up: 3 comment:2 by , 8 years ago
comment:3 by , 6 years ago
Replying to Daniel Krügler <daniel.kruegler@…>:
Ticket #10731 suggests some further improvements
Based on that patch suggestion in ticket #10731 I have created a pull request via the github project:
https://github.com/boostorg/filesystem/pull/41/commits/755766a0536df599ac0280428defad03dac92cfc
Please consider this request, it also solves the code conversion problem described in ticket #10731.
comment:4 by , 5 years ago
This issue should be marked as resolved by accepting the pull request
https://github.com/boostorg/filesystem/commit/0e831d5c2d9c5a7baed75cfe2fb914daaf4a6182
for Boost version 1.64.
Ticket #10731 suggests some further improvements