Add Filesystem TS -- Complete

Add the completed std::experimental::filesystem implementation and tests.
The implementation supports C++11 or newer.

The TS is built as part of 'libc++experimental.a'. Users of the TS need to
manually link this library. Building and testing the TS can be disabled using
the CMake option '-DLIBCXX_ENABLE_FILESYSTEM=OFF'.

Currently 'libc++experimental.a' is not installed by default. To turn on the
installation of the library use '-DLIBCXX_INSTALL_EXPERIMENTAL_LIBRARY=ON'.


git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@273034 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 1402 insertions, 0 deletions

diff --git a/src/experimental/filesystem/directory_iterator.cpp b/src/experimental/filesystem/directory_iterator.cpp
new file mode 100644
index 000000000..059c4124a
--- /dev/null
+++ b/src/experimental/filesystem/directory_iterator.cpp
@@ -0,0 +1,256 @@
+#include "experimental/filesystem"
+#include <dirent.h>
+#include <errno.h>
+
+_LIBCPP_BEGIN_NAMESPACE_EXPERIMENTAL_FILESYSTEM
+
+namespace { namespace detail {
+
+inline error_code capture_errno() {
+    _LIBCPP_ASSERT(errno, "Expected errno to be non-zero");
+    return error_code{errno, std::generic_category()};
+}
+
+template <class ...Args>
+inline bool capture_error_or_throw(std::error_code* user_ec,
+                                   const char* msg, Args&&... args)
+{
+    std::error_code my_ec = capture_errno();
+    if (user_ec) {
+        *user_ec = my_ec;
+        return true;
+    }
+    __libcpp_throw(filesystem_error(msg, std::forward<Args>(args)..., my_ec));
+    return false;
+}
+
+template <class ...Args>
+inline bool set_or_throw(std::error_code& my_ec,
+                               std::error_code* user_ec,
+                               const char* msg, Args&&... args)
+{
+    if (user_ec) {
+        *user_ec = my_ec;
+        return true;
+    }
+    __libcpp_throw(filesystem_error(msg, std::forward<Args>(args)..., my_ec));
+    return false;
+}
+
+typedef path::string_type string_type;
+
+
+inline string_type posix_readdir(DIR *dir_stream, error_code& ec) {
+    struct dirent* dir_entry_ptr = nullptr;
+    errno = 0; // zero errno in order to detect errors
+    if ((dir_entry_ptr = ::readdir(dir_stream)) == nullptr) {
+        ec = capture_errno();
+        return {};
+    } else {
+        ec.clear();
+        return dir_entry_ptr->d_name;
+    }
+}
+
+}}                                                       // namespace detail
+
+using detail::set_or_throw;
+
+class __dir_stream {
+public:
+    __dir_stream() = delete;
+    __dir_stream& operator=(const __dir_stream&) = delete;
+
+    __dir_stream(__dir_stream&& other) noexcept
+        : __stream_(other.__stream_), __root_(std::move(other.__root_)),
+          __entry_(std::move(other.__entry_))
+    {
+        other.__stream_ = nullptr;
+    }
+
+
+    __dir_stream(const path& root, directory_options opts, error_code& ec)
+        : __stream_(nullptr),
+          __root_(root)
+    {
+        if ((__stream_ = ::opendir(root.c_str())) == nullptr) {
+            ec = detail::capture_errno();
+            const bool allow_eacess =
+                bool(opts & directory_options::skip_permission_denied);
+            if (allow_eacess && ec.value() == EACCES)
+                ec.clear();
+            return;
+        }
+        advance(ec);
+    }
+
+    ~__dir_stream() noexcept
+      { if (__stream_) close(); }
+
+    bool good() const noexcept { return __stream_ != nullptr; }
+
+    bool advance(error_code &ec) {
+        while (true) {
+            auto str = detail::posix_readdir(__stream_,  ec);
+            if (str == "." || str == "..") {
+                continue;
+            } else if (ec || str.empty()) {
+                close();
+                return false;
+            } else {
+                __entry_.assign(__root_ / str);
+                return true;
+            }
+        }
+    }
+private:
+    std::error_code close() noexcept {
+        std::error_code m_ec;
+        if (::closedir(__stream_) == -1)
+           m_ec = detail::capture_errno();
+        __stream_ = nullptr;
+        return m_ec;
+    }
+
+    DIR * __stream_{nullptr};
+public:
+    path __root_;
+    directory_entry __entry_;
+};
+
+// directory_iterator
+
+directory_iterator::directory_iterator(const path& p, error_code *ec,
+                                       directory_options opts)
+{
+    std::error_code m_ec;
+    __imp_ = make_shared<__dir_stream>(p, opts, m_ec);
+    if (ec) *ec = m_ec;
+    if (!__imp_->good()) {
+        __imp_.reset();
+        if (m_ec)
+            set_or_throw(m_ec, ec,
+                         "directory_iterator::directory_iterator(...)", p);
+    }
+}
+
+directory_iterator& directory_iterator::__increment(error_code *ec)
+{
+    _LIBCPP_ASSERT(__imp_, "Attempting to increment an invalid iterator");
+    std::error_code m_ec;
+    if (!__imp_->advance(m_ec)) {
+        __imp_.reset();
+        if (m_ec)
+            set_or_throw(m_ec, ec, "directory_iterator::operator++()");
+    } else {
+        if (ec) ec->clear();
+    }
+    return *this;
+
+}
+
+directory_entry const& directory_iterator::__deref() const {
+    _LIBCPP_ASSERT(__imp_, "Attempting to dereference an invalid iterator");
+    return __imp_->__entry_;
+}
+
+// recursive_directory_iterator
+
+struct recursive_directory_iterator::__shared_imp {
+  stack<__dir_stream> __stack_;
+  directory_options   __options_;
+};
+
+recursive_directory_iterator::recursive_directory_iterator(const path& p,
+    directory_options opt, error_code *ec)
+    : __imp_(nullptr), __rec_(true)
+{
+    std::error_code m_ec;
+    __dir_stream new_s(p, opt, m_ec);
+    if (m_ec) set_or_throw(m_ec, ec, "recursive_directory_iterator", p);
+    if (m_ec || !new_s.good()) return;
+
+    __imp_ = _VSTD::make_shared<__shared_imp>();
+    __imp_->__options_ = opt;
+    __imp_->__stack_.push(_VSTD::move(new_s));
+}
+
+void recursive_directory_iterator::__pop(error_code* ec)
+{
+    _LIBCPP_ASSERT(__imp_, "Popping the end iterator");
+    __imp_->__stack_.pop();
+    if (__imp_->__stack_.size() == 0) {
+        __imp_.reset();
+        if (ec) ec->clear();
+    } else {
+        __advance(ec);
+    }
+}
+
+directory_options recursive_directory_iterator::options() const {
+    return __imp_->__options_;
+}
+
+int recursive_directory_iterator::depth() const {
+    return __imp_->__stack_.size() - 1;
+}
+
+const directory_entry& recursive_directory_iterator::__deref() const {
+    return __imp_->__stack_.top().__entry_;
+}
+
+recursive_directory_iterator&
+recursive_directory_iterator::__increment(error_code *ec)
+{
+    if (recursion_pending()) {
+        if (__try_recursion(ec) || (ec && *ec))
+            return *this;
+    }
+    __rec_ = true;
+    __advance(ec);
+    return *this;
+}
+
+void recursive_directory_iterator::__advance(error_code* ec) {
+    const directory_iterator end_it;
+    auto& stack = __imp_->__stack_;
+    std::error_code m_ec;
+    while (stack.size() > 0) {
+        if (stack.top().advance(m_ec)) {
+            if (ec) ec->clear();
+            return;
+        }
+        if (m_ec) break;
+        stack.pop();
+    }
+    __imp_.reset();
+    if (m_ec)
+        set_or_throw(m_ec, ec, "recursive_directory_iterator::operator++()");
+}
+
+bool recursive_directory_iterator::__try_recursion(error_code *ec) {
+
+    bool rec_sym =
+        bool(options() & directory_options::follow_directory_symlink);
+    auto& curr_it = __imp_->__stack_.top();
+
+    if (is_directory(curr_it.__entry_.status()) &&
+        (!is_symlink(curr_it.__entry_.symlink_status()) || rec_sym))
+    {
+        std::error_code m_ec;
+        __dir_stream new_it(curr_it.__entry_.path(), __imp_->__options_, m_ec);
+        if (new_it.good()) {
+            __imp_->__stack_.push(_VSTD::move(new_it));
+            return true;
+        }
+        if (m_ec) {
+            __imp_.reset();
+            set_or_throw(m_ec, ec,
+                               "recursive_directory_iterator::operator++()");
+        }
+    }
+    return false;
+}
+
+
+_LIBCPP_END_NAMESPACE_EXPERIMENTAL_FILESYSTEM
diff --git a/src/experimental/filesystem/operations.cpp b/src/experimental/filesystem/operations.cpp
new file mode 100644
index 000000000..7d382d104
--- /dev/null
+++ b/src/experimental/filesystem/operations.cpp
@@ -0,0 +1,754 @@
+//===--------------------- filesystem/ops.cpp -----------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "experimental/filesystem"
+#include "iterator"
+#include "fstream"
+#include "type_traits"
+#include "random"  /* for unique_path */
+#include "cstdlib"
+#include "climits"
+
+#include <unistd.h>
+#include <sys/stat.h>
+#include <sys/statvfs.h>
+#include <fcntl.h>  /* values for fchmodat */
+#if defined(__APPLE__)
+#include <sys/time.h> // for ::utimes as used in __last_write_time
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_EXPERIMENTAL_FILESYSTEM
+
+filesystem_error::~filesystem_error() {}
+
+
+//                       POSIX HELPERS
+
+namespace detail { namespace  {
+
+using value_type = path::value_type;
+using string_type = path::string_type;
+
+
+
+inline std::error_code capture_errno() {
+    _LIBCPP_ASSERT(errno, "Expected errno to be non-zero");
+    std::error_code m_ec(errno, std::generic_category());
+    return m_ec;
+}
+
+void set_or_throw(std::error_code const& m_ec, std::error_code* ec,
+                  const char* msg, path const& p = {}, path const& p2 = {})
+{
+    if (ec) {
+        *ec = m_ec;
+    } else {
+        string msg_s("std::experimental::filesystem::");
+        msg_s += msg;
+        __libcpp_throw(filesystem_error(msg_s, p, p2, m_ec));
+    }
+}
+
+void set_or_throw(std::error_code* ec, const char* msg,
+                  path const& p = {}, path const& p2 = {})
+{
+    return set_or_throw(capture_errno(), ec, msg, p, p2);
+}
+
+perms posix_get_perms(const struct ::stat & st) noexcept {
+    return static_cast<perms>(st.st_mode) & perms::mask;
+}
+
+::mode_t posix_convert_perms(perms prms) {
+    return static_cast< ::mode_t>(prms & perms::mask);
+}
+
+file_status create_file_status(std::error_code& m_ec, path const& p,
+                               struct ::stat& path_stat,
+                               std::error_code* ec)
+{
+    if (ec) *ec = m_ec;
+    if (m_ec && (m_ec.value() == ENOENT || m_ec.value() == ENOTDIR)) {
+        return file_status(file_type::not_found);
+    }
+    else if (m_ec) {
+        set_or_throw(m_ec, ec, "posix_stat", p);
+        return file_status(file_type::none);
+    }
+    // else
+
+    file_status fs_tmp;
+    auto const mode = path_stat.st_mode;
+    if      (S_ISLNK(mode))  fs_tmp.type(file_type::symlink);
+    else if (S_ISREG(mode))  fs_tmp.type(file_type::regular);
+    else if (S_ISDIR(mode))  fs_tmp.type(file_type::directory);
+    else if (S_ISBLK(mode))  fs_tmp.type(file_type::block);
+    else if (S_ISCHR(mode))  fs_tmp.type(file_type::character);
+    else if (S_ISFIFO(mode)) fs_tmp.type(file_type::fifo);
+    else if (S_ISSOCK(mode)) fs_tmp.type(file_type::socket);
+    else                     fs_tmp.type(file_type::unknown);
+
+    fs_tmp.permissions(detail::posix_get_perms(path_stat));
+    return fs_tmp;
+}
+
+file_status posix_stat(path const & p, struct ::stat& path_stat,
+                       std::error_code* ec)
+{
+    std::error_code m_ec;
+    if (::stat(p.c_str(), &path_stat) == -1)
+        m_ec = detail::capture_errno();
+    return create_file_status(m_ec, p, path_stat, ec);
+}
+
+file_status posix_stat(path const & p, std::error_code* ec) {
+    struct ::stat path_stat;
+    return posix_stat(p, path_stat, ec);
+}
+
+file_status posix_lstat(path const & p, struct ::stat & path_stat,
+                        std::error_code* ec)
+{
+    std::error_code m_ec;
+    if (::lstat(p.c_str(), &path_stat) == -1)
+        m_ec = detail::capture_errno();
+    return create_file_status(m_ec, p, path_stat, ec);
+}
+
+file_status posix_lstat(path const & p, std::error_code* ec) {
+    struct ::stat path_stat;
+    return posix_lstat(p, path_stat, ec);
+}
+
+bool stat_equivalent(struct ::stat& st1, struct ::stat& st2) {
+    return (st1.st_dev == st2.st_dev && st1.st_ino == st2.st_ino);
+}
+
+//                           DETAIL::MISC
+
+
+bool copy_file_impl(const path& from, const path& to, perms from_perms,
+                    std::error_code *ec)
+{
+    std::ifstream in(from.c_str(), std::ios::binary);
+    std::ofstream out(to.c_str(),  std::ios::binary);
+
+    if (in.good() && out.good()) {
+        using InIt = std::istreambuf_iterator<char>;
+        using OutIt = std::ostreambuf_iterator<char>;
+        InIt bin(in);
+        InIt ein;
+        OutIt bout(out);
+        std::copy(bin, ein, bout);
+    }
+    if (out.fail() || in.fail()) {
+        set_or_throw(make_error_code(errc::operation_not_permitted),
+                     ec, "copy_file", from, to);
+        return false;
+    }
+    __permissions(to, from_perms, ec);
+    // TODO what if permissions fails?
+    return true;
+}
+
+}} // end namespace detail
+
+using detail::set_or_throw;
+
+path __canonical(path const & orig_p, const path& base, std::error_code *ec)
+{
+    path p = absolute(orig_p, base);
+    char buff[PATH_MAX + 1];
+    char *ret;
+    if ((ret = ::realpath(p.c_str(), buff)) == nullptr) {
+        set_or_throw(ec, "canonical", orig_p, base);
+        return {};
+    }
+    if (ec) ec->clear();
+    return {ret};
+}
+
+void __copy(const path& from, const path& to, copy_options options,
+            std::error_code *ec)
+{
+    const bool sym_status = bool(options &
+        (copy_options::create_symlinks | copy_options::skip_symlinks));
+
+    const bool sym_status2 = bool(options &
+        copy_options::copy_symlinks);
+
+    std::error_code m_ec;
+    struct ::stat f_st = {};
+    const file_status f = sym_status || sym_status2
+                                     ? detail::posix_lstat(from, f_st, &m_ec)
+                                     : detail::posix_stat(from,  f_st, &m_ec);
+    if (m_ec)
+        return set_or_throw(m_ec, ec, "copy", from, to);
+
+    struct ::stat t_st = {};
+    const file_status t = sym_status ? detail::posix_lstat(to, t_st, &m_ec)
+                                     : detail::posix_stat(to, t_st, &m_ec);
+
+    if (not status_known(t))
+        return set_or_throw(m_ec, ec, "copy", from, to);
+
+    if (!exists(f) || is_other(f) || is_other(t)
+        || (is_directory(f) && is_regular_file(t))
+        || detail::stat_equivalent(f_st, t_st))
+    {
+        return set_or_throw(make_error_code(errc::function_not_supported),
+                            ec, "copy", from, to);
+    }
+
+    if (ec) ec->clear();
+
+    if (is_symlink(f)) {
+        if (bool(copy_options::skip_symlinks & options)) {
+            // do nothing
+        } else if (not exists(t)) {
+            __copy_symlink(from, to, ec);
+        } else {
+            set_or_throw(make_error_code(errc::file_exists),
+                         ec, "copy", from, to);
+        }
+        return;
+    }
+    else if (is_regular_file(f)) {
+        if (bool(copy_options::directories_only & options)) {
+            // do nothing
+        }
+        else if (bool(copy_options::create_symlinks & options)) {
+            __create_symlink(from, to, ec);
+        }
+        else if (bool(copy_options::create_hard_links & options)) {
+            __create_hard_link(from, to, ec);
+        }
+        else if (is_directory(t)) {
+            __copy_file(from, to / from.filename(), options, ec);
+        } else {
+            __copy_file(from, to, options, ec);
+        }
+        return;
+    }
+    else if (is_directory(f)) {
+        if (not bool(copy_options::recursive & options) &&
+            bool(copy_options::__in_recursive_copy & options))
+        {
+            return;
+        }
+
+        if (!exists(t)) {
+            // create directory to with attributes from 'from'.
+            __create_directory(to, from, ec);
+            if (ec && *ec) { return; }
+        }
+        directory_iterator it = ec ? directory_iterator(from, *ec)
+                                   : directory_iterator(from);
+        if (ec && *ec) { return; }
+        std::error_code m_ec;
+        for (; it != directory_iterator(); it.increment(m_ec)) {
+            if (m_ec) return set_or_throw(m_ec, ec, "copy", from, to);
+            __copy(it->path(), to / it->path().filename(),
+                   options | copy_options::__in_recursive_copy, ec);
+            if (ec && *ec) { return; }
+        }
+    }
+}
+
+
+bool __copy_file(const path& from, const path& to, copy_options options,
+                 std::error_code *ec)
+{
+    if (ec) ec->clear();
+
+    std::error_code m_ec;
+    auto from_st = detail::posix_stat(from, &m_ec);
+    if (not is_regular_file(from_st)) {
+        if (not m_ec)
+            m_ec = make_error_code(errc::not_supported);
+        set_or_throw(m_ec, ec, "copy_file", from, to);
+        return false;
+    }
+
+    auto to_st = detail::posix_stat(to, &m_ec);
+    if (!status_known(to_st)) {
+        set_or_throw(m_ec, ec, "copy_file", from, to);
+        return false;
+    }
+
+    const bool to_exists = exists(to_st);
+    if (to_exists && bool(copy_options::skip_existing & options)) {
+        return false;
+    }
+    else if (to_exists && bool(copy_options::update_existing & options)) {
+        auto from_time = __last_write_time(from, ec);
+        if (ec && *ec) { return false; }
+        auto to_time = __last_write_time(to, ec);
+        if (ec && *ec) { return false; }
+        if (from_time <= to_time) {
+            return false;
+        }
+        return detail::copy_file_impl(from, to, from_st.permissions(), ec);
+    }
+    else if (!to_exists || bool(copy_options::overwrite_existing & options)) {
+        return detail::copy_file_impl(from, to, from_st.permissions(), ec);
+    }
+    else {
+        set_or_throw(make_error_code(errc::file_exists), ec, "copy", from, to);
+        return false;
+    }
+}
+
+void __copy_symlink(const path& existing_symlink, const path& new_symlink,
+                    std::error_code *ec)
+{
+    const path real_path(__read_symlink(existing_symlink, ec));
+    if (ec && *ec) { return; }
+    // NOTE: proposal says you should detect if you should call
+    // create_symlink or create_directory_symlink. I don't think this
+    // is needed with POSIX
+    __create_symlink(real_path, new_symlink, ec);
+}
+
+
+bool __create_directories(const path& p, std::error_code *ec)
+{
+    std::error_code m_ec;
+    auto const st = detail::posix_stat(p, &m_ec);
+    if (!status_known(st)) {
+        set_or_throw(m_ec, ec, "create_directories", p);
+        return false;
+    }
+    else if (is_directory(st)) {
+        if (ec) ec->clear();
+        return false;
+    }
+    else if (exists(st)) {
+        set_or_throw(make_error_code(errc::file_exists),
+                     ec, "create_directories", p);
+        return false;
+    }
+
+    const path parent = p.parent_path();
+    if (!parent.empty()) {
+        const file_status parent_st = status(parent, m_ec);
+        if (not status_known(parent_st)) {
+            set_or_throw(m_ec, ec, "create_directories", p);
+            return false;
+        }
+        if (not exists(parent_st)) {
+            __create_directories(parent, ec);
+            if (ec && *ec) { return false; }
+        }
+    }
+    return __create_directory(p, ec);
+}
+
+bool __create_directory(const path& p, std::error_code *ec)
+{
+    if (ec) ec->clear();
+    if (::mkdir(p.c_str(), static_cast<int>(perms::all)) == 0)
+        return true;
+    if (errno != EEXIST || !is_directory(p))
+        set_or_throw(ec, "create_directory", p);
+    return false;
+}
+
+bool __create_directory(path const & p, path const & attributes,
+                        std::error_code *ec)
+{
+    struct ::stat attr_stat;
+    std::error_code mec;
+    auto st = detail::posix_stat(attributes, attr_stat, &mec);
+    if (!status_known(st)) {
+        set_or_throw(mec, ec, "create_directory", p, attributes);
+        return false;
+    }
+    if (ec) ec->clear();
+    if (::mkdir(p.c_str(), attr_stat.st_mode) == 0)
+        return true;
+    if (errno != EEXIST || !is_directory(p))
+        set_or_throw(ec, "create_directory", p, attributes);
+    return false;
+}
+
+void __create_directory_symlink(path const & from, path const & to,
+                                std::error_code *ec){
+    if (::symlink(from.c_str(), to.c_str()) != 0)
+        set_or_throw(ec, "create_directory_symlink", from, to);
+    else if (ec)
+        ec->clear();
+}
+
+void __create_hard_link(const path& from, const path& to, std::error_code *ec){
+    if (::link(from.c_str(), to.c_str()) == -1)
+        set_or_throw(ec, "create_hard_link", from, to);
+    else if (ec)
+        ec->clear();
+}
+
+void __create_symlink(path const & from, path const & to, std::error_code *ec) {
+
+    if (::symlink(from.c_str(), to.c_str()) == -1)
+        set_or_throw(ec, "create_symlink", from, to);
+    else if (ec)
+        ec->clear();
+}
+
+path __current_path(std::error_code *ec) {
+    auto size = ::pathconf(".", _PC_PATH_MAX);
+    _LIBCPP_ASSERT(size >= 0, "pathconf returned a 0 as max size");
+
+    auto buff = std::unique_ptr<char[]>(new char[size + 1]);
+    char* ret;
+    if ((ret = ::getcwd(buff.get(), static_cast<size_t>(size))) == nullptr) {
+        set_or_throw(ec, "current_path");
+        return {};
+    }
+    if (ec) ec->clear();
+    return {buff.get()};
+}
+
+void __current_path(const path& p, std::error_code *ec) {
+    if (::chdir(p.c_str()) == -1)
+        set_or_throw(ec, "current_path", p);
+    else if (ec)
+        ec->clear();
+}
+
+bool __equivalent(const path& p1, const path& p2, std::error_code *ec)
+{
+    std::error_code ec1, ec2;
+    struct ::stat st1 = {};
+    struct ::stat st2 = {};
+    auto s1 = detail::posix_stat(p1.native(), st1, &ec1);
+    auto s2 = detail::posix_stat(p2.native(), st2, &ec2);
+
+    if ((!exists(s1) && !exists(s2)) || (is_other(s1) && is_other(s2))) {
+        set_or_throw(make_error_code(errc::not_supported), ec,
+                     "equivalent", p1, p2);
+        return false;
+    }
+    if (ec) ec->clear();
+    return (st1.st_dev == st2.st_dev && st1.st_ino == st2.st_ino);
+}
+
+
+std::uintmax_t __file_size(const path& p, std::error_code *ec)
+{
+    std::error_code m_ec;
+    struct ::stat st;
+    file_status fst = detail::posix_stat(p, st, &m_ec);
+    if (!exists(fst) || !is_regular_file(fst)) {
+        if (!m_ec)
+            m_ec = make_error_code(errc::not_supported);
+        set_or_throw(m_ec, ec, "file_size", p);
+        return static_cast<uintmax_t>(-1);
+    }
+    // is_regular_file(p) == true
+    if (ec) ec->clear();
+    return static_cast<std::uintmax_t>(st.st_size);
+}
+
+std::uintmax_t __hard_link_count(const path& p, std::error_code *ec)
+{
+    std::error_code m_ec;
+    struct ::stat st;
+    detail::posix_stat(p, st, &m_ec);
+    if (m_ec) {
+        set_or_throw(m_ec, ec, "hard_link_count", p);
+        return static_cast<std::uintmax_t>(-1);
+    }
+    if (ec) ec->clear();
+    return static_cast<std::uintmax_t>(st.st_nlink);
+}
+
+
+bool __fs_is_empty(const path& p, std::error_code *ec)
+{
+    if (ec) ec->clear();
+    std::error_code m_ec;
+    struct ::stat pst;
+    auto st = detail::posix_stat(p, pst, &m_ec);
+    if (is_directory(st))
+        return directory_iterator(p) == directory_iterator{};
+    else if (is_regular_file(st))
+        return static_cast<std::uintmax_t>(pst.st_size) == 0;
+    // else
+    set_or_throw(m_ec, ec, "is_empty", p);
+    return false;
+}
+
+
+file_time_type __last_write_time(const path& p, std::error_code *ec)
+{
+    using Clock = file_time_type::clock;
+    std::error_code m_ec;
+    struct ::stat st;
+    detail::posix_stat(p, st, &m_ec);
+    if (m_ec) {
+        set_or_throw(m_ec, ec, "last_write_time", p);
+        return file_time_type::min();
+    }
+    if (ec) ec->clear();
+    return Clock::from_time_t(static_cast<std::time_t>(st.st_mtime));
+}
+
+
+void __last_write_time(const path& p, file_time_type new_time,
+                       std::error_code *ec)
+{
+    using namespace std::chrono;
+    std::error_code m_ec;
+
+#if defined(__APPLE__)
+    // FIXME: Use utimensat when it becomes available on OS X.
+    // This implementation has a race condition between determining the
+    // last access time and attempting to set it to the same value using
+    // ::utimes
+    using Clock = file_time_type::clock;
+    struct ::stat st;
+    file_status fst = detail::posix_stat(p, st, &m_ec);
+    if (m_ec && !status_known(fst)) {
+        set_or_throw(m_ec, ec, "last_write_time", p);
+        return;
+    }
+    auto write_dur = new_time.time_since_epoch();
+    auto write_sec = duration_cast<seconds>(write_dur);
+    auto access_dur = Clock::from_time_t(st.st_atime).time_since_epoch();
+    auto access_sec = duration_cast<seconds>(access_dur);
+    struct ::timeval tbuf[2];
+    tbuf[0].tv_sec = access_sec.count();
+    tbuf[0].tv_usec = duration_cast<microseconds>(access_dur - access_sec).count();
+    tbuf[1].tv_sec = write_sec.count();
+    tbuf[1].tv_usec = duration_cast<microseconds>(write_dur - write_sec).count();
+    if (::utimes(p.c_str(), tbuf) == -1) {
+        m_ec = detail::capture_errno();
+    }
+#else
+    auto dur_since_epoch = new_time.time_since_epoch();
+    auto sec_since_epoch = duration_cast<seconds>(dur_since_epoch);
+    auto ns_since_epoch = duration_cast<nanoseconds>(dur_since_epoch - sec_since_epoch);
+    struct ::timespec tbuf[2];
+    tbuf[0].tv_sec = 0;
+    tbuf[0].tv_nsec = UTIME_OMIT;
+    tbuf[1].tv_sec = sec_since_epoch.count();
+    tbuf[1].tv_nsec = ns_since_epoch.count();
+    if (::utimensat(AT_FDCWD, p.c_str(), tbuf, 0) == -1) {
+        m_ec = detail::capture_errno();
+    }
+#endif
+    if (m_ec)
+        set_or_throw(m_ec, ec, "last_write_time", p);
+    else if (ec)
+        ec->clear();
+}
+
+
+void __permissions(const path& p, perms prms, std::error_code *ec)
+{
+
+    const bool resolve_symlinks = bool(perms::resolve_symlinks & prms);
+    const bool add_perms = bool(perms::add_perms & prms);
+    const bool remove_perms = bool(perms::remove_perms & prms);
+
+    _LIBCPP_ASSERT(!(add_perms && remove_perms),
+                   "Both add_perms and remove_perms are set");
+
+    std::error_code m_ec;
+    file_status st = detail::posix_lstat(p, &m_ec);
+    if (m_ec) return set_or_throw(m_ec, ec, "permissions", p);
+
+    const bool set_sym_perms = is_symlink(st) && !resolve_symlinks;
+
+    if ((resolve_symlinks && is_symlink(st)) && (add_perms || remove_perms)) {
+        st = detail::posix_stat(p, &m_ec);
+        if (m_ec) return set_or_throw(m_ec, ec, "permissions", p);
+    }
+
+    prms = prms & perms::mask;
+    if (add_perms)
+        prms |= st.permissions();
+    else if (remove_perms)
+        prms = st.permissions() & ~prms;
+    auto real_perms = detail::posix_convert_perms(prms);
+
+# if defined(AT_SYMLINK_NOFOLLOW) && defined(AT_FDCWD)
+    const int flags = set_sym_perms ? AT_SYMLINK_NOFOLLOW : 0;
+    if (::fchmodat(AT_FDCWD, p.c_str(), real_perms, flags) == -1) {
+# else
+    if (set_sym_perms)
+        return set_or_throw(make_error_code(errc::operation_not_supported),
+                            ec, "permissions", p);
+    if (::chmod(p.c_str(), real_perms) == -1) {
+# endif
+        return set_or_throw(ec, "permissions", p);
+    }
+    if (ec) ec->clear();
+}
+
+
+path __read_symlink(const path& p, std::error_code *ec) {
+    char buff[PATH_MAX + 1];
+    std::error_code m_ec;
+    ::ssize_t ret;
+    if ((ret = ::readlink(p.c_str(), buff, PATH_MAX)) == -1) {
+        set_or_throw(ec, "read_symlink", p);
+        return {};
+    }
+    _LIBCPP_ASSERT(ret <= PATH_MAX, "TODO");
+    _LIBCPP_ASSERT(ret > 0, "TODO");
+    if (ec) ec->clear();
+    buff[ret] = 0;
+    return {buff};
+}
+
+
+bool __remove(const path& p, std::error_code *ec) {
+    if (ec) ec->clear();
+    if (::remove(p.c_str()) == -1) {
+        set_or_throw(ec, "remove", p);
+        return false;
+    }
+    return true;
+}
+
+namespace {
+
+std::uintmax_t remove_all_impl(path const & p, std::error_code& ec)
+{
+    const auto npos = static_cast<std::uintmax_t>(-1);
+    const file_status st = __symlink_status(p, &ec);
+    if (ec) return npos;
+     std::uintmax_t count = 1;
+    if (is_directory(st)) {
+        for (directory_iterator it(p, ec); !ec && it != directory_iterator();
+             it.increment(ec)) {
+            auto other_count = remove_all_impl(it->path(), ec);
+            if (ec) return npos;
+            count += other_count;
+        }
+        if (ec) return npos;
+    }
+    if (!__remove(p, &ec)) return npos;
+    return count;
+}
+
+} // end namespace
+
+std::uintmax_t __remove_all(const path& p, std::error_code *ec) {
+    std::error_code mec;
+    auto count = remove_all_impl(p, mec);
+    if (mec) {
+        set_or_throw(mec, ec, "remove_all", p);
+        return static_cast<std::uintmax_t>(-1);
+    }
+    if (ec) ec->clear();
+    return count;
+}
+
+void __rename(const path& from, const path& to, std::error_code *ec) {
+    if (::rename(from.c_str(), to.c_str()) == -1)
+        set_or_throw(ec, "rename", from, to);
+    else if (ec)
+        ec->clear();
+}
+
+void __resize_file(const path& p, std::uintmax_t size, std::error_code *ec) {
+    if (::truncate(p.c_str(), static_cast<long>(size)) == -1)
+        set_or_throw(ec, "resize_file", p);
+    else if (ec)
+        ec->clear();
+}
+
+space_info __space(const path& p, std::error_code *ec) {
+    space_info si;
+    struct statvfs m_svfs;
+    if (::statvfs(p.c_str(), &m_svfs) == -1)  {
+        set_or_throw(ec, "space", p);
+        si.capacity = si.free = si.available =
+            static_cast<std::uintmax_t>(-1);
+        return si;
+    }
+    if (ec) ec->clear();
+    // Multiply with overflow checking.
+    auto do_mult = [&](std::uintmax_t& out, fsblkcnt_t other) {
+      out = other * m_svfs.f_frsize;
+      if (out / other != m_svfs.f_frsize || other == 0)
+          out = static_cast<std::uintmax_t>(-1);
+    };
+    do_mult(si.capacity, m_svfs.f_blocks);
+    do_mult(si.free, m_svfs.f_bfree);
+    do_mult(si.available, m_svfs.f_bavail);
+    return si;
+}
+
+file_status __status(const path& p, std::error_code *ec) {
+    return detail::posix_stat(p, ec);
+}
+
+file_status __symlink_status(const path& p, std::error_code *ec) {
+    return detail::posix_lstat(p, ec);
+}
+
+path __system_complete(const path& p, std::error_code *ec) {
+    if (ec) ec->clear();
+    return absolute(p, current_path());
+}
+
+path __temp_directory_path(std::error_code *ec) {
+    const char* env_paths[] = {"TMPDIR", "TMP", "TEMP", "TEMPDIR"};
+    const char* ret = nullptr;
+    for (auto & ep : env_paths)  {
+        if ((ret = std::getenv(ep)))
+            break;
+    }
+    path p(ret ? ret : "/tmp");
+    std::error_code m_ec;
+    if (is_directory(p, m_ec)) {
+        if (ec) ec->clear();
+        return p;
+    }
+    if (!m_ec || m_ec == make_error_code(errc::no_such_file_or_directory))
+        m_ec = make_error_code(errc::not_a_directory);
+    set_or_throw(m_ec, ec, "temp_directory_path");
+    return {};
+}
+
+// An absolute path is composed according to the table in [fs.op.absolute].
+path absolute(const path& p, const path& base) {
+    auto root_name = p.root_name();
+    auto root_dir = p.root_directory();
+
+    if (!root_name.empty() && !root_dir.empty())
+      return p;
+
+    auto abs_base = base.is_absolute() ? base : absolute(base);
+
+    /* !has_root_name && !has_root_dir */
+    if (root_name.empty() && root_dir.empty())
+    {
+      return abs_base / p;
+    }
+    else if (!root_name.empty()) /* has_root_name && !has_root_dir */
+    {
+      return  root_name / abs_base.root_directory()
+              /
+              abs_base.relative_path() / p.relative_path();
+    }
+    else /* !has_root_name && has_root_dir */
+    {
+      if (abs_base.has_root_name())
+        return abs_base.root_name() / p;
+      // else p is absolute,  return outside of block
+    }
+    return p;
+}
+
+_LIBCPP_END_NAMESPACE_EXPERIMENTAL_FILESYSTEM
diff --git a/src/experimental/filesystem/path.cpp b/src/experimental/filesystem/path.cpp
new file mode 100644
index 000000000..9c72abd7c
--- /dev/null
+++ b/src/experimental/filesystem/path.cpp
@@ -0,0 +1,392 @@
+//===--------------------- filesystem/path.cpp ----------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+#include "experimental/filesystem"
+#include "experimental/string_view"
+#include "utility"
+
+_LIBCPP_BEGIN_NAMESPACE_EXPERIMENTAL_FILESYSTEM
+
+_LIBCPP_CONSTEXPR path::value_type path::preferred_separator;
+
+
+namespace { namespace parser
+{
+
+using string_type = string_view;
+using value_type = path::value_type;
+
+using string_view_pair = pair<string_view, string_view>;
+
+// status reporting
+constexpr size_t npos = static_cast<size_t>(-1);
+
+inline bool good(size_t pos) { return pos != npos; }
+
+// lexical elements
+constexpr value_type preferred_separator = path::preferred_separator;
+constexpr value_type const * preferred_separator_str = "/";
+constexpr value_type const * dot = ".";
+
+// forward //
+bool is_separator(string_type const &, size_t);
+bool is_root_name(const string_type&, size_t);
+bool is_root_directory(string_type const &, size_t);
+bool is_trailing_separator(string_type const &, size_t);
+
+size_t start_of(string_type const &, size_t);
+size_t end_of(string_type const &, size_t);
+
+size_t root_name_start(const string_type& s);
+size_t root_name_end(const string_type&);
+
+size_t root_directory_start(string_type const &);
+size_t root_directory_end(string_type const &);
+
+string_view_pair separate_filename(string_type const &);
+string_view extract_raw(string_type const &, size_t);
+string_view extract_preferred(string_type const &, size_t);
+
+inline bool is_separator(const string_type& s, size_t pos) {
+    return (pos < s.size() && s[pos] == preferred_separator);
+}
+
+inline bool is_root_name(const string_type& s, size_t pos) {
+  return good(pos) && pos == 0 ? root_name_start(s) == pos : false;
+}
+
+inline bool is_root_directory(const string_type& s, size_t pos) {
+    return good(pos) ? root_directory_start(s) == pos : false;
+}
+
+inline bool is_trailing_separator(const string_type& s, size_t pos) {
+    return (pos < s.size() && is_separator(s, pos) &&
+            end_of(s, pos) == s.size()-1 &&
+            !is_root_directory(s, pos) && !is_root_name(s, pos));
+}
+
+size_t start_of(const string_type& s, size_t pos) {
+    if (pos >= s.size()) return npos;
+    bool in_sep = (s[pos] == preferred_separator);
+    while (pos - 1 < s.size() &&
+        (s[pos-1] == preferred_separator) == in_sep)
+    { --pos; }
+    if (pos == 2 && !in_sep && s[0] == preferred_separator &&
+        s[1] == preferred_separator)
+    { return 0; }
+    return pos;
+}
+
+size_t end_of(const string_type& s, size_t pos) {
+    if (pos >= s.size()) return npos;
+    // special case for root name
+    if (pos == 0 && is_root_name(s, pos)) return root_name_end(s);
+    bool in_sep = (s[pos] == preferred_separator);
+    while (pos + 1 < s.size() && (s[pos+1] == preferred_separator) == in_sep)
+    { ++pos; }
+    return pos;
+}
+
+inline size_t root_name_start(const string_type& s) {
+    return good(root_name_end(s)) ? 0 : npos;
+}
+
+size_t root_name_end(const string_type& s) {
+    if (s.size() < 2 || s[0] != preferred_separator
+        || s[1] != preferred_separator) {
+        return npos;
+    }
+    if (s.size() == 2) {
+        return 1;
+    }
+    size_t index = 2; // current position
+    if (s[index] == preferred_separator) {
+        return npos;
+    }
+    while (index + 1 < s.size() && s[index+1] != preferred_separator) {
+        ++index;
+    }
+    return index;
+}
+
+size_t root_directory_start(const string_type& s) {
+    size_t e = root_name_end(s);
+    if (!good(e))
+    return is_separator(s, 0) ? 0 : npos;
+    return is_separator(s, e + 1) ? e + 1 : npos;
+}
+
+size_t root_directory_end(const string_type& s) {
+    size_t st = root_directory_start(s);
+    if (!good(st)) return npos;
+    size_t index = st;
+    while (index + 1 < s.size() && s[index + 1] == preferred_separator)
+      { ++index; }
+    return index;
+}
+
+string_view_pair separate_filename(string_type const & s) {
+    if (s == "." || s == ".." || s.empty()) return string_view_pair{s, ""};
+    auto pos = s.find_last_of('.');
+    if (pos == string_type::npos) return string_view_pair{s, string_view{}};
+    return string_view_pair{s.substr(0, pos), s.substr(pos)};
+}
+
+inline string_view extract_raw(const string_type& s, size_t pos) {
+    size_t end_i = end_of(s, pos);
+    if (!good(end_i)) return string_view{};
+    return string_view(s).substr(pos, end_i - pos + 1);
+}
+
+string_view extract_preferred(const string_type& s, size_t pos) {
+    string_view raw = extract_raw(s, pos);
+    if (raw.empty())
+        return raw;
+    if (is_trailing_separator(s, pos))
+        return string_view{dot};
+    if (is_separator(s, pos) && !is_root_name(s, pos))
+        return string_view(preferred_separator_str);
+    return raw;
+}
+
+}} // namespace parser
+
+
+////////////////////////////////////////////////////////////////////////////////
+//                            path_view_iterator
+////////////////////////////////////////////////////////////////////////////////
+namespace {
+
+struct path_view_iterator {
+  const string_view __s_;
+  size_t __pos_;
+
+  explicit path_view_iterator(string_view const& __s) : __s_(__s), __pos_(__s_.empty() ? parser::npos : 0) {}
+  explicit path_view_iterator(string_view const& __s, size_t __p) : __s_(__s), __pos_(__p) {}
+
+  string_view operator*() const {
+    return parser::extract_preferred(__s_, __pos_);
+  }
+
+  path_view_iterator& operator++() {
+    increment();
+    return *this;
+  }
+
+  path_view_iterator& operator--() {
+    decrement();
+    return *this;
+  }
+
+  void increment() {
+    if (__pos_ == parser::npos) return;
+    while (! set_position(parser::end_of(__s_, __pos_)+1))
+        ;
+    return;
+  }
+
+  void decrement() {
+    if (__pos_ == 0) {
+      set_position(0);
+    }
+    else if (__pos_ == parser::npos) {
+      auto const str_size = __s_.size();
+      set_position(parser::start_of(
+          __s_, str_size != 0 ? str_size - 1 : str_size));
+    } else {
+      while (!set_position(parser::start_of(__s_, __pos_-1)))
+        ;
+    }
+  }
+
+  bool set_position(size_t pos) {
+    if (pos >= __s_.size()) {
+      __pos_ = parser::npos;
+    } else {
+      __pos_ = pos;
+    }
+    return valid_iterator_position();
+  }
+
+  bool valid_iterator_position() const {
+    if (__pos_ == parser::npos) return true; // end position is valid
+    return (!parser::is_separator      (__s_, __pos_) ||
+          parser::is_root_directory    (__s_, __pos_) ||
+          parser::is_trailing_separator(__s_, __pos_) ||
+          parser::is_root_name         (__s_, __pos_));
+  }
+
+  bool is_end() const { return __pos_ == parser::npos; }
+
+  inline bool operator==(path_view_iterator const& __p) {
+      return __pos_ == __p.__pos_;
+  }
+};
+
+path_view_iterator pbegin(path const& p) {
+    return path_view_iterator(p.native());
+}
+
+path_view_iterator pend(path const& p) {
+    path_view_iterator __p(p.native());
+    __p.__pos_ = parser::npos;
+    return __p;
+}
+
+} // end namespace
+///////////////////////////////////////////////////////////////////////////////
+//                            path definitions
+///////////////////////////////////////////////////////////////////////////////
+
+path & path::replace_extension(path const & replacement)
+{
+    path p = extension();
+    if (not p.empty()) {
+      __pn_.erase(__pn_.size() - p.native().size());
+    }
+    if (!replacement.empty()) {
+        if (replacement.native()[0] != '.') {
+            __pn_ += ".";
+        }
+        __pn_.append(replacement.__pn_);
+    }
+    return *this;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+// path.decompose
+
+string_view path::__root_name() const
+{
+    return parser::is_root_name(__pn_, 0)
+      ? parser::extract_preferred(__pn_, 0)
+      : string_view{};
+}
+
+string_view path::__root_directory() const
+{
+    auto start_i = parser::root_directory_start(__pn_);
+    if(!parser::good(start_i)) {
+        return {};
+    }
+    return parser::extract_preferred(__pn_, start_i);
+}
+
+string_view path::__relative_path() const
+{
+    if (empty()) {
+        return {__pn_};
+    }
+    auto end_i = parser::root_directory_end(__pn_);
+    if (not parser::good(end_i)) {
+        end_i = parser::root_name_end(__pn_);
+    }
+    if (not parser::good(end_i)) {
+        return {__pn_};
+    }
+    return string_view(__pn_).substr(end_i+1);
+}
+
+string_view path::__parent_path() const
+{
+    if (empty() || pbegin(*this) == --pend(*this)) {
+        return {};
+    }
+    auto end_it = --(--pend(*this));
+    auto end_i = parser::end_of(__pn_, end_it.__pos_);
+    return string_view(__pn_).substr(0, end_i+1);
+}
+
+string_view path::__filename() const
+{
+    return empty() ? string_view{} : *--pend(*this);
+}
+
+string_view path::__stem() const
+{
+    return parser::separate_filename(__filename()).first;
+}
+
+string_view path::__extension() const
+{
+    return parser::separate_filename(__filename()).second;
+}
+
+////////////////////////////////////////////////////////////////////////////
+// path.comparisons
+int path::__compare(const value_type* __s) const {
+    path_view_iterator thisIter(this->native());
+    path_view_iterator sIter(__s);
+    while (!thisIter.is_end() && !sIter.is_end()) {
+        int res = (*thisIter).compare(*sIter);
+        if (res != 0) return res;
+        ++thisIter; ++sIter;
+    }
+    if (thisIter.is_end() && sIter.is_end())
+        return 0;
+    if (thisIter.is_end())
+        return -1;
+    return 1;
+}
+
+////////////////////////////////////////////////////////////////////////////
+// path.nonmembers
+size_t hash_value(const path& __p) _NOEXCEPT {
+  path_view_iterator thisIter(__p.native());
+  struct HashPairT {
+    size_t first;
+    size_t second;
+  };
+  HashPairT hp = {0, 0};
+  std::hash<string_view> hasher;
+  std::__scalar_hash<decltype(hp)> pair_hasher;
+  while (!thisIter.is_end()) {
+    hp.second = hasher(*thisIter);
+    hp.first = pair_hasher(hp);
+    ++thisIter;
+  }
+  return hp.first;
+}
+
+////////////////////////////////////////////////////////////////////////////
+// path.itr
+path::iterator path::begin() const
+{
+    path_view_iterator pit = pbegin(*this);
+    iterator it;
+    it.__path_ptr_ = this;
+    it.__pos_ = pit.__pos_;
+    it.__elem_.__assign_view(*pit);
+    return it;
+}
+
+path::iterator path::end() const
+{
+    iterator it{};
+    it.__path_ptr_ = this;
+    it.__pos_ = parser::npos;
+    return it;
+}
+
+path::iterator& path::iterator::__increment() {
+  path_view_iterator it(__path_ptr_->native(), __pos_);
+  it.increment();
+  __pos_ = it.__pos_;
+  __elem_.__assign_view(*it);
+  return *this;
+}
+
+path::iterator& path::iterator::__decrement() {
+  path_view_iterator it(__path_ptr_->native(), __pos_);
+  it.decrement();
+  __pos_ = it.__pos_;
+  __elem_.__assign_view(*it);
+  return *this;
+}
+
+_LIBCPP_END_NAMESPACE_EXPERIMENTAL_FILESYSTEM