std::hash<std::filesystem::path>

 

C++

编译器支持

自立实现与有宿主实现

语言

标准库

标准库标头

具名要求

功能特性测试宏(C++20)

语言支持库

概念库(C++20)

诊断库

内存管理库

元编程库(C++11)

通用工具库

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范围库(C++20)

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文本处理库

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日期和时间库

输入/输出库

文件系统库(C++17)

并发支持库(C++11)

执行控制库(C++26)

技术规范

符号索引

外部库

 

文件系统库

类
filesystem::path filesystem::filesystem_error filesystem::directory_entry filesystem::directory_iterator filesystem::recursive_directory_iterator    filesystem::file_status filesystem::space_info	filesystem::file_type filesystem::file_time_type filesystem::perms filesystem::perm_options filesystem::copy_options filesystem::directory_options
函数
filesystem::absolute filesystem::canonicalfilesystem::weakly_canonical filesystem::relativefilesystem::proximate filesystem::copy filesystem::copy_file filesystem::copy_symlink filesystem::create_directory filesystem::create_directories filesystem::create_hard_link filesystem::create_symlink filesystem::create_directory_symlink filesystem::current_path filesystem::temp_directory_path	filesystem::exists filesystem::equivalent filesystem::file_size filesystem::hard_link_count filesystem::last_write_time filesystem::permissions filesystem::read_symlink filesystem::remove filesystem::remove_all filesystem::rename filesystem::resize_file filesystem::space filesystem::status filesystem::symlink_status
文件类型
filesystem::is_block_file filesystem::is_character_file filesystem::is_directory filesystem::is_empty filesystem::status_known	filesystem::is_fifo filesystem::is_other filesystem::is_regular_file filesystem::is_socket filesystem::is_symlink

 

std::filesystem::path

成员类型
成员常量
path::native_formatpath::generic_formatpath::auto_format
成员函数
path::path path::~path path::operator= path::assign path::appendpath::operator/= path::concatpath::operator+= path::clear path::make_preferred path::remove_filename path::replace_filename path::replace_extension    path::swap path::compare path::beginpath::end	path::c_strpath::nativepath::operator string_type path::stringpath::u8stringpath::u16stringpath::u32stringpath::wstring path::generic_stringpath::generic_u8stringpath::generic_u16stringpath::generic_u32stringpath::generic_wstring path::lexically_normalpath::lexically_relativepath::lexically_proximate
路径分解
path::root_name path::root_directory path::root_path path::relative_path path::parent_path path::filename path::stem path::extension path::empty	path::has_root_pathpath::has_root_namepath::has_root_directorypath::has_relative_pathpath::has_parent_pathpath::has_filenamepath::has_stempath::has_extension path::is_absolutepath::is_relative
非成员函数
operator==operator!=operator<operator<=operator>operator>=operator<=> (C++20 前)(C++20 前)(C++20 前)(C++20 前)(C++20 前)(C++20)	operator/ operator<<operator>> swap(std::filesystem::path) hash_value u8path
辅助类
hash<std::filesystem::path>	formatter<std::filesystem::path> (C++26)

 

在标头 <filesystem> 定义
template<> struct hash<std::filesystem::path>;		(C++17 起)

std::hash 对 std::filesystem::path 的模板特化允许用户获得 std::filesystem::path 的散列值。

此特化的 operator() 为 noexcept。对每个 std::filesystem::path 值 p，std::hash<std::filesystem::path>{}(p) 等于 std::filesystem::hash_value(p)。

在 C++17 标准出版中缺少这个特化，参见 LWG 问题 3657。

示例

运行此代码

#include <cassert>#include <cstddef>#include <filesystem>#include <iomanip>#include <iostream>#include <unordered_set>namespace fs = std::filesystem;   void show_hash(fs::pathconst& 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::pathconst& p : dirs)std::cout<< p <<' ';std::cout<<'\n';}

可能的输出：

6050C47ADB62DFE5 : "/tmp" 62795A58B69AD90A : "/tmp/../tmp" FF302110C9991974 : "/a///b" FF302110C9991974 : "/a//b" FD6167277915D464 : "/a/c" C42040F82CD8B542 : "..." D2D30154E0B78BBC : ".." D18C722215ED0530 : "." 0 : "" "/tmp/../tmp" "/opt" "/lib" "/tmp" "/bin"

参阅

hash (C++11)	散列函数对象 (类模板)
hash_value	计算路径对象的散列值 (函数)