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'.

llvm-svn: 273034
diff --git a/libcxx/test/support/filesystem_test_helper.hpp b/libcxx/test/support/filesystem_test_helper.hpp
new file mode 100644
index 0000000..5434590
--- /dev/null
+++ b/libcxx/test/support/filesystem_test_helper.hpp
@@ -0,0 +1,370 @@
+#ifndef FILESYSTEM_TEST_HELPER_HPP
+#define FILESYSTEM_TEST_HELPER_HPP
+
+#include <experimental/filesystem>
+#include <cassert>
+#include <cstdio> // for printf
+#include <string>
+#include <fstream>
+#include <random>
+
+namespace fs = std::experimental::filesystem;
+
+// static test helpers
+
+#ifndef LIBCXX_FILESYSTEM_STATIC_TEST_ROOT
+#warning "STATIC TESTS DISABLED"
+#else // LIBCXX_FILESYSTEM_STATIC_TEST_ROOT
+
+namespace StaticEnv {
+
+inline fs::path makePath(fs::path const& p) {
+    static const fs::path env_path = LIBCXX_FILESYSTEM_STATIC_TEST_ROOT;
+    return env_path / p;
+}
+
+static const fs::path Root = LIBCXX_FILESYSTEM_STATIC_TEST_ROOT;
+
+static const fs::path TestFileList[] = {
+        makePath("empty_file"),
+        makePath("non_empty_file"),
+        makePath("dir1/file1"),
+        makePath("dir1/file2")
+};
+const std::size_t TestFileListSize = sizeof(TestFileList) / sizeof(fs::path);
+
+static const fs::path TestDirList[] = {
+        makePath("dir1"),
+        makePath("dir1/dir2"),
+        makePath("dir1/dir2/dir3")
+};
+const std::size_t TestDirListSize = sizeof(TestDirList) / sizeof(fs::path);
+
+static const fs::path File          = TestFileList[0];
+static const fs::path Dir           = TestDirList[0];
+static const fs::path Dir2          = TestDirList[1];
+static const fs::path Dir3          = TestDirList[2];
+static const fs::path SymlinkToFile = makePath("symlink_to_empty_file");
+static const fs::path SymlinkToDir  = makePath("symlink_to_dir");
+static const fs::path BadSymlink    = makePath("bad_symlink");
+static const fs::path DNE           = makePath("DNE");
+static const fs::path EmptyFile     = TestFileList[0];
+static const fs::path NonEmptyFile  = TestFileList[1];
+static const fs::path CharFile      = "/dev/null"; // Hopefully this exists
+
+static const fs::path DirIterationList[] = {
+    makePath("dir1/dir2"),
+    makePath("dir1/file1"),
+    makePath("dir1/file2")
+};
+const std::size_t DirIterationListSize = sizeof(DirIterationList)
+                                        / sizeof(fs::path);
+
+static const fs::path DirIterationListDepth1[] = {
+    makePath("dir1/dir2/afile3"),
+    makePath("dir1/dir2/dir3"),
+    makePath("dir1/dir2/symlink_to_dir3"),
+    makePath("dir1/dir2/file4"),
+};
+
+static const fs::path RecDirIterationList[] = {
+    makePath("dir1/dir2"),
+    makePath("dir1/file1"),
+    makePath("dir1/file2"),
+    makePath("dir1/dir2/afile3"),
+    makePath("dir1/dir2/dir3"),
+    makePath("dir1/dir2/symlink_to_dir3"),
+    makePath("dir1/dir2/file4"),
+    makePath("dir1/dir2/dir3/file5")
+};
+
+static const fs::path RecDirFollowSymlinksIterationList[] = {
+    makePath("dir1/dir2"),
+    makePath("dir1/file1"),
+    makePath("dir1/file2"),
+    makePath("dir1/dir2/afile3"),
+    makePath("dir1/dir2/dir3"),
+    makePath("dir1/dir2/file4"),
+    makePath("dir1/dir2/dir3/file5"),
+    makePath("dir1/dir2/symlink_to_dir3"),
+    makePath("dir1/dir2/symlink_to_dir3/file5"),
+};
+
+} // namespace StaticEnv
+
+#endif // LIBCXX_FILESYSTEM_STATIC_TEST_ROOT
+
+#ifndef LIBCXX_FILESYSTEM_DYNAMIC_TEST_ROOT
+#warning LIBCXX_FILESYSTEM_DYNAMIC_TEST_ROOT must be defined
+#else // LIBCXX_FILESYSTEM_DYNAMIC_TEST_ROOT
+
+#ifndef LIBCXX_FILESYSTEM_DYNAMIC_TEST_HELPER
+#error LIBCXX_FILESYSTEM_DYNAMIC_TEST_HELPER must be defined
+#endif
+
+struct scoped_test_env
+{
+    scoped_test_env() : test_root(random_env_path())
+        { fs_helper_run(fs_make_cmd("init_test_directory", test_root)); }
+
+    ~scoped_test_env()
+        { fs_helper_run(fs_make_cmd("destroy_test_directory", test_root)); }
+
+    scoped_test_env(scoped_test_env const &) = delete;
+    scoped_test_env & operator=(scoped_test_env const &) = delete;
+
+    fs::path make_env_path(std::string p) { return sanitize_path(p); }
+
+    std::string sanitize_path(std::string raw) {
+        assert(raw.find("..") == std::string::npos);
+        std::string const& root = test_root.native();
+        if (root.compare(0, root.size(), raw, 0, root.size()) != 0) {
+            assert(raw.front() != '\\');
+            fs::path tmp(test_root);
+            tmp /= raw;
+            return std::move(const_cast<std::string&>(tmp.native()));
+        }
+        return raw;
+    }
+
+    std::string create_file(std::string filename, std::size_t size = 0) {
+        filename = sanitize_path(std::move(filename));
+        std::string out_str(size, 'a');
+        {
+            std::ofstream out(filename.c_str());
+            out << out_str;
+        }
+        return filename;
+    }
+
+    std::string create_dir(std::string filename) {
+        filename = sanitize_path(std::move(filename));
+        fs_helper_run(fs_make_cmd("create_dir", filename));
+        return filename;
+    }
+
+    std::string create_symlink(std::string source, std::string to) {
+        source = sanitize_path(std::move(source));
+        to = sanitize_path(std::move(to));
+        fs_helper_run(fs_make_cmd("create_symlink", source, to));
+        return to;
+    }
+
+    std::string create_hardlink(std::string source, std::string to) {
+        source = sanitize_path(std::move(source));
+        to = sanitize_path(std::move(to));
+        fs_helper_run(fs_make_cmd("create_hardlink", source, to));
+        return to;
+    }
+
+    std::string create_fifo(std::string file) {
+        file = sanitize_path(std::move(file));
+        fs_helper_run(fs_make_cmd("create_fifo", file));
+        return file;
+    }
+
+  // OS X and FreeBSD doesn't support socket files so we shouldn't even
+  // allow tests to call this unguarded.
+#if !defined(__FreeBSD__) && !defined(__APPLE__)
+    std::string create_socket(std::string file) {
+        file = sanitize_path(std::move(file));
+        fs_helper_run(fs_make_cmd("create_socket", file));
+        return file;
+    }
+#endif
+
+    fs::path const test_root;
+
+private:
+    static char to_hex(int ch) {
+        return ch < 10 ? static_cast<char>('0' + ch)
+                       : static_cast<char>('a' + (ch - 10));
+    }
+
+    static char random_hex_char() {
+        static std::mt19937 rd { std::random_device{}() };
+        static std::uniform_int_distribution<int> mrand{0, 15};
+        return to_hex( mrand(rd) );
+    }
+
+    static std::string unique_path_suffix() {
+        std::string model = "test.%%%%%%";
+        for (auto & ch :  model) {
+            if (ch == '%') ch = random_hex_char();
+        }
+        return model;
+    }
+
+    // This could potentially introduce a filesystem race with other tests
+    // running at the same time, but oh well, it's just test code.
+    static inline fs::path random_env_path() {
+        static const char* env_path = LIBCXX_FILESYSTEM_DYNAMIC_TEST_ROOT;
+        fs::path p = fs::path(env_path) / unique_path_suffix();
+        assert(p.parent_path() == env_path);
+        return p;
+    }
+
+    static inline std::string make_arg(std::string const& arg) {
+        return "'" + arg + "'";
+    }
+
+    static inline std::string make_arg(std::size_t arg) {
+        return std::to_string(arg);
+    }
+
+    template <class T>
+    static inline std::string
+    fs_make_cmd(std::string const& cmd_name, T const& arg) {
+        return cmd_name + "(" + make_arg(arg) + ")";
+    }
+
+    template <class T, class U>
+    static inline std::string
+    fs_make_cmd(std::string const& cmd_name, T const& arg1, U const& arg2) {
+        return cmd_name + "(" + make_arg(arg1) + ", " + make_arg(arg2) + ")";
+    }
+
+    static inline void fs_helper_run(std::string const& raw_cmd) {
+        // check that the fs test root in the enviroment matches what we were
+        // compiled with.
+        static bool checked = checkDynamicTestRoot();
+        std::string cmd = LIBCXX_FILESYSTEM_DYNAMIC_TEST_HELPER;
+        cmd += " \"" + raw_cmd + "\"";
+        int ret = std::system(cmd.c_str());
+        assert(ret == 0);
+    }
+
+    static bool checkDynamicTestRoot() {
+        char* fs_root = std::getenv("LIBCXX_FILESYSTEM_DYNAMIC_TEST_ROOT");
+        if (!fs_root) {
+            std::printf("ERROR: LIBCXX_FILESYSTEM_DYNAMIC_TEST_ROOT must be a defined "
+                         "environment variable when running the test.\n");
+            std::abort();
+        }
+        if (std::string(fs_root) != LIBCXX_FILESYSTEM_DYNAMIC_TEST_ROOT) {
+            std::printf("ERROR: LIBCXX_FILESYSTEM_DYNAMIC_TEST_ROOT enviroment variable"
+                        " must have the same value as when the test was compiled.\n");
+            std::printf("   Current Value:  '%s'\n", fs_root);
+            std::printf("   Expected Value: '%s'\n", LIBCXX_FILESYSTEM_DYNAMIC_TEST_ROOT);
+            std::abort();
+        }
+        return true;
+    }
+
+};
+
+#endif // LIBCXX_FILESYSTEM_DYNAMIC_TEST_ROOT
+
+// Misc test types
+
+#define CONCAT2(LHS, RHS) LHS##RHS
+#define CONCAT(LHS, RHS) CONCAT2(LHS, RHS)
+#define MKSTR(Str) {Str, CONCAT(L, Str), CONCAT(u, Str), CONCAT(U, Str)}
+
+struct MultiStringType {
+  const char* s;
+  const wchar_t* w;
+  const char16_t* u16;
+  const char32_t* u32;
+
+  operator const char* () const { return s; }
+  operator const wchar_t* () const { return w; }
+  operator const char16_t* () const { return u16; }
+  operator const char32_t* () const { return u32; }
+};
+
+const MultiStringType PathList[] = {
+        MKSTR(""),
+        MKSTR(" "),
+        MKSTR("//"),
+        MKSTR("."),
+        MKSTR(".."),
+        MKSTR("foo"),
+        MKSTR("/"),
+        MKSTR("/foo"),
+        MKSTR("foo/"),
+        MKSTR("/foo/"),
+        MKSTR("foo/bar"),
+        MKSTR("/foo/bar"),
+        MKSTR("//net"),
+        MKSTR("//net/foo"),
+        MKSTR("///foo///"),
+        MKSTR("///foo///bar"),
+        MKSTR("/."),
+        MKSTR("./"),
+        MKSTR("/.."),
+        MKSTR("../"),
+        MKSTR("foo/."),
+        MKSTR("foo/.."),
+        MKSTR("foo/./"),
+        MKSTR("foo/./bar"),
+        MKSTR("foo/../"),
+        MKSTR("foo/../bar"),
+        MKSTR("c:"),
+        MKSTR("c:/"),
+        MKSTR("c:foo"),
+        MKSTR("c:/foo"),
+        MKSTR("c:foo/"),
+        MKSTR("c:/foo/"),
+        MKSTR("c:/foo/bar"),
+        MKSTR("prn:"),
+        MKSTR("c:\\"),
+        MKSTR("c:\\foo"),
+        MKSTR("c:foo\\"),
+        MKSTR("c:\\foo\\"),
+        MKSTR("c:\\foo/"),
+        MKSTR("c:/foo\\bar"),
+        MKSTR("//"),
+        MKSTR("/finally/we/need/one/really/really/really/really/really/really/really/long/string")
+};
+const unsigned PathListSize = sizeof(PathList) / sizeof(MultiStringType);
+
+template <class Iter>
+Iter IterEnd(Iter B) {
+  using VT = typename std::iterator_traits<Iter>::value_type;
+  for (; *B != VT{}; ++B)
+    ;
+  return B;
+}
+
+template <class CharT>
+const CharT* StrEnd(CharT const* P) {
+    return IterEnd(P);
+}
+
+template <class CharT>
+std::size_t StrLen(CharT const* P) {
+    return StrEnd(P) - P;
+}
+
+// Testing the allocation behavior of the code_cvt functions requires
+// *knowing* that the allocation was not done by "path::__str_".
+// This hack forces path to allocate enough memory.
+inline void PathReserve(fs::path& p, std::size_t N) {
+  auto const& native_ref = p.native();
+  const_cast<std::string&>(native_ref).reserve(N);
+}
+
+template <class Iter1, class Iter2>
+bool checkCollectionsEqual(
+    Iter1 start1, Iter1 const end1
+  , Iter2 start2, Iter2 const end2
+  )
+{
+    while (start1 != end1 && start2 != end2) {
+        if (*start1 != *start2) {
+            return false;
+        }
+        ++start1; ++start2;
+    }
+    return (start1 == end1 && start2 == end2);
+}
+
+// We often need to test that the error_code was cleared if no error occurs
+// this function returns a error_code which is set to an error that will
+// never be returned by the filesystem functions.
+inline std::error_code GetTestEC() {
+    return std::make_error_code(std::errc::address_family_not_supported);
+}
+
+#endif /* FILESYSTEM_TEST_HELPER_HPP */