std::hash<std::filesystem::path>
Defined in header <filesystem> |
||
|---|---|---|
template<> struct hash<std::filesystem::path>; |
(since C++17) |
The template specialization of std::hash for std::filesystem::path allows users to obtain hash values of std::filesystem::path.
The operator() of this specialization is noexcept. For every std::filesystem::path value p, std::hash<std::filesystem::path>{}(p) is equal to std::filesystem::hash_value(p).
Example
#include <cassert>
#include <cstddef>
#include <iomanip>
#include <iostream>
#include <filesystem>
#include <unordered_set>
namespace fs = std::filesystem;
void show_hash(fs::path const& p)
{
std::cout << std::hex << std::uppercase << std::setw(16)
<< std::hash<fs::path>{}(p) << " : " << p << '\n';
}
int main()
{
auto tmp1 = fs::path{"/tmp"};
auto tmp2 = fs::path{"/tmp/../tmp"};
assert( ! (tmp1 == tmp2) );
assert( fs::equivalent(tmp1, tmp2) );
show_hash( tmp1 );
show_hash( tmp2 );
for (auto s : {"/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::path const& p: dirs) { std::cout << p << ' '; }
}
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) |
| calculates a hash value for a path object (function) |
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https://en.cppreference.com/w/cpp/filesystem/path/hash
