From cppreference.com
template<>structhash<std::filesystem::path>;(since C++17)The template specialization of
for
allows users to obtain hash values of
.
The operator() of this specialization is noexcept. For every
value p, std::hash<std::filesystem::path>{}(p) is equal to std::filesystem::hash_value(p).
This specialization was absent from the C++17 standard publication, see
.
Example
Run this code
#include<cassert>#include<cstddef>#include<filesystem>#include<iomanip>#include<iostream>#include<unordered_set>namespacefs=std::filesystem;voidshow_hash(fs::pathconst&p){std::cout<<std::hex<<std::uppercase<<std::setw(16)<<std::hash<fs::path>{}(p)<<" : "<<p<<'\n';}intmain(){autotmp1=fs::path{"/tmp"};autotmp2=fs::path{"/tmp/../tmp"};assert(!(tmp1==tmp2));assert(fs::equivalent(tmp1,tmp2));show_hash(tmp1);show_hash(tmp2);for(autos:{"/a///b","/a//b","/a/c","...","..",".",""})show_hash(s);std::unordered_set<fs::path,std::hash<fs::path>>dirs{"/bin","/bin","/lib","/lib","/opt","/opt","/tmp","/tmp/../tmp"};for(fs::pathconst&p:dirs)std::cout<<p<<' ';std::cout<<'\n';}Possible output:
6050C47ADB62DFE5 : "/tmp" 62795A58B69AD90A : "/tmp/../tmp" FF302110C9991974 : "/a///b" FF302110C9991974 : "/a//b" FD6167277915D464 : "/a/c" C42040F82CD8B542 : "..." D2D30154E0B78BBC : ".." D18C722215ED0530 : "." 0 : "" "/tmp/../tmp" "/opt" "/lib" "/tmp" "/bin" See also
(C++11)
hash function object
(class template)
(C++17)
calculates a hash value for a path object
(function)