Fix paths on Windows

lib/std/fs.zig

@@ -1168,8 +1168,9 @@ pub const Dir = struct {
     /// Asserts that the path parameter has no null bytes.
     pub fn openDir(self: Dir, sub_path: []const u8, args: OpenDirOptions) OpenError!Dir {
         if (builtin.os.tag == .windows) {
-            const sub_path_w = try os.windows.sliceToPrefixedFileW(sub_path);
-            return self.openDirW(sub_path_w.span().ptr, args);
+            const nt_path = try os.windows.NtPath.init((try os.windows.utf8ToWPathSpace(sub_path)).span());
+            defer nt_path.deinit();
+            return self.openDirWindows(std.fs.path.isAbsoluteWindows(sub_path), nt_path.str, args);
         } else if (builtin.os.tag == .wasi) {
             return self.openDirWasi(sub_path, args);
         } else {
@@ -1223,8 +1224,7 @@ pub const Dir = struct {
     /// Same as `openDir` except the parameter is null-terminated.
     pub fn openDirZ(self: Dir, sub_path_c: [*:0]const u8, args: OpenDirOptions) OpenError!Dir {
         if (builtin.os.tag == .windows) {
-            const sub_path_w = try os.windows.cStrToPrefixedFileW(sub_path_c);
-            return self.openDirW(sub_path_w.span().ptr, args);
+            return self.openDir(std.mem.spanZ(sub_path_c), args);
         }
         const symlink_flags: u32 = if (args.no_follow) os.O_NOFOLLOW else 0x0;
         if (!args.iterate) {
@@ -1235,15 +1235,13 @@ pub const Dir = struct {
         }
     }
 
-    /// Same as `openDir` except the path parameter is WTF-16 encoded, NT-prefixed.
+    /// Same as `openDir` except the path parameter is WTF-16 encoded.
     /// This function asserts the target OS is Windows.
     pub fn openDirW(self: Dir, sub_path_w: [*:0]const u16, args: OpenDirOptions) OpenError!Dir {
         const w = os.windows;
-        // TODO remove some of these flags if args.access_sub_paths is false
-        const base_flags = w.STANDARD_RIGHTS_READ | w.FILE_READ_ATTRIBUTES | w.FILE_READ_EA |
-            w.SYNCHRONIZE | w.FILE_TRAVERSE;
-        const flags: u32 = if (args.iterate) base_flags | w.FILE_LIST_DIRECTORY else base_flags;
-        return self.openDirAccessMaskW(sub_path_w, flags, args.no_follow);
+        const nt_path = try w.NtPath.init(sub_path_w);
+        defer nt_path.deinit();
+        return self.openDirWindows(std.fs.path.isAbsoluteWindowsW(sub_path_w), nt_path.str, args);
     }
 
     /// `flags` must contain `os.O_DIRECTORY`.
@@ -1264,37 +1262,28 @@ pub const Dir = struct {
         return Dir{ .fd = fd };
     }
 
-    fn openDirAccessMaskW(self: Dir, sub_path_w: [*:0]const u16, access_mask: u32, no_follow: bool) OpenError!Dir {
+    fn openDirWindows(self: Dir, is_absolute: bool, nt_path: os.windows.UNICODE_STRING, args: OpenDirOptions) OpenError!Dir {
         const w = os.windows;
 
+        // TODO remove some of these flags if args.access_sub_paths is false
+        const base_flags = w.STANDARD_RIGHTS_READ | w.FILE_READ_ATTRIBUTES | w.FILE_READ_EA |
+            w.SYNCHRONIZE | w.FILE_TRAVERSE;
+        const access_mask: u32 = if (args.iterate) base_flags | w.FILE_LIST_DIRECTORY else base_flags;
+
         var result = Dir{
             .fd = undefined,
         };
 
-        const path_len_bytes = @intCast(u16, mem.lenZ(sub_path_w) * 2);
-        var nt_name = w.UNICODE_STRING{
-            .Length = path_len_bytes,
-            .MaximumLength = path_len_bytes,
-            .Buffer = @intToPtr([*]u16, @ptrToInt(sub_path_w)),
-        };
+        var adjusted_nt_path = if (is_absolute) nt_path else try w.toRelativeNtPath(nt_path);
         var attr = w.OBJECT_ATTRIBUTES{
             .Length = @sizeOf(w.OBJECT_ATTRIBUTES),
-            .RootDirectory = if (path.isAbsoluteWindowsW(sub_path_w)) null else self.fd,
+            .RootDirectory = if (is_absolute) null else self.fd,
             .Attributes = 0, // Note we do not use OBJ_CASE_INSENSITIVE here.
-            .ObjectName = &nt_name,
+            .ObjectName = &adjusted_nt_path,
             .SecurityDescriptor = null,
             .SecurityQualityOfService = null,
         };
-        if (sub_path_w[0] == '.' and sub_path_w[1] == 0) {
-            // Windows does not recognize this, but it does work with empty string.
-            nt_name.Length = 0;
-        }
-        if (sub_path_w[0] == '.' and sub_path_w[1] == '.' and sub_path_w[2] == 0) {
-            // If you're looking to contribute to zig and fix this, see here for an example of how to
-            // implement this: https://git.midipix.org/ntapi/tree/src/fs/ntapi_tt_open_physical_parent_directory.c
-            @panic("TODO opening '..' with a relative directory handle is not yet implemented on Windows");
-        }
-        const open_reparse_point: w.DWORD = if (no_follow) w.FILE_OPEN_REPARSE_POINT else 0x0;
+        const open_reparse_point: w.DWORD = if (args.no_follow) w.FILE_OPEN_REPARSE_POINT else 0x0;
         var io: w.IO_STATUS_BLOCK = undefined;
         const rc = w.ntdll.NtCreateFile(
             &result.fd,

lib/std/fs/test.zig

@@ -79,8 +79,17 @@ test "openDirAbsolute" {
         break :blk try fs.realpathAlloc(&arena.allocator, relative_path);
     };
 
-    var dir = try fs.openDirAbsolute(base_path, .{});
-    defer dir.close();
+    {
+        var dir = try fs.openDirAbsolute(base_path, .{});
+        defer dir.close();
+    }
+
+    for ([_][]const u8 { ".", ".." }) |sub_path| {
+        const dir_path = try fs.path.join(&arena.allocator, &[_][]const u8 { base_path, sub_path });
+        defer arena.allocator.free(dir_path);
+        var dir = try fs.openDirAbsolute(dir_path, .{});
+        defer dir.close();
+    }
 }
 
 test "readLinkAbsolute" {

lib/std/os/windows.zig

@@ -1528,6 +1528,16 @@ pub const PathSpace = struct {
     }
 };
 
+/// Decode a utf8 encoded path to a "wide character" path.  Returns the path by value via PathSpace
+/// which can accomodate paths up to `PATH_MAX_WIDE` characters long.
+pub fn utf8ToWPathSpace(utf8_path: []const u8) !PathSpace {
+    // TODO https://github.com/ziglang/zig/issues/2765
+    var path_space : PathSpace = undefined;
+    path_space.len = try std.unicode.utf8ToUtf16Le(&path_space.data, utf8_path);
+    path_space.data[path_space.len] = 0;
+    return path_space;
+}
+
 /// Same as `sliceToPrefixedFileW` but accepts a pointer
 /// to a null-terminated path.
 pub fn cStrToPrefixedFileW(s: [*:0]const u8) !PathSpace {
@@ -1569,6 +1579,48 @@ pub fn sliceToPrefixedFileW(s: []const u8) !PathSpace {
     return path_space;
 }
 
+/// Convert `dos_path` to an NT path that can be passed to Nt* functions like NtCreateFile.
+pub const NtPath = struct {
+    str: UNICODE_STRING,
+    pub fn init(dos_path: [*:0]const u16) !NtPath {
+        var str : UNICODE_STRING = undefined;
+        const status = ntdll.RtlDosPathNameToNtPathName_U_WithStatus(dos_path, &str, null, null);
+        if (status != .SUCCESS) return unexpectedStatus(status);
+        return NtPath { .str = str };
+    }
+    // TODO: not sure if the path is guaranteed to be NULL-terminted
+    pub fn span(self: NtPath) []const u16 {
+        return self.str.Buffer[0 .. self.str.Length / 2];
+    }
+    pub fn deinit(self: NtPath) void {
+        if (TRUE != kernel32.HeapFree(kernel32.GetProcessHeap().?, 0, self.str.Buffer)) {
+            std.debug.panic("in NtPath, HeapFree failed with {}\n", .{kernel32.GetLastError()});
+        }
+    }
+};
+
+/// return the relative path of `nt_path` based on CWD
+pub fn toRelativeNtPath(nt_path: UNICODE_STRING) !UNICODE_STRING {
+    const cwd_nt_path = try NtPath.init(&[_:0]u16 {'.'});
+    defer cwd_nt_path.deinit();
+    const cwd_span = cwd_nt_path.span();
+    std.debug.assert(mem.startsWith(u16, unicodeSpan(nt_path), cwd_span));
+    std.debug.assert(nt_path.Buffer[cwd_span.len] == '\\');
+    return unicodeSubstring(nt_path, @intCast(c_ushort, cwd_span.len + 1));
+}
+
+pub fn unicodeSpan(str: UNICODE_STRING) []u16 {
+    return str.Buffer[0..str.Length/2];
+}
+pub fn unicodeSubstring(str: UNICODE_STRING, char_offset: c_ushort) UNICODE_STRING {
+    std.debug.assert(char_offset * 2 <= str.Length);
+    return .{
+        .Buffer = str.Buffer + char_offset,
+        .MaximumLength = str.MaximumLength - (char_offset*2),
+        .Length = str.Length - (char_offset*2),
+    };
+}
+
 /// Assumes an absolute path.
 pub fn wToPrefixedFileW(s: []const u16) !PathSpace {
     // TODO https://github.com/ziglang/zig/issues/2765
@@ -1637,3 +1689,9 @@ pub fn unexpectedStatus(status: NTSTATUS) std.os.UnexpectedError {
     }
     return error.Unexpected;
 }
+
+test "" {
+    if (builtin.os.tag == .windows) {
+        _ = @import("windows/test.zig");
+    }
+}

lib/std/os/windows/ntdll.zig

@@ -113,3 +113,10 @@ pub extern "NtDll" fn NtWaitForKeyedEvent(
 ) callconv(WINAPI) NTSTATUS;
 
 pub extern "NtDll" fn RtlSetCurrentDirectory_U(PathName: *UNICODE_STRING) callconv(WINAPI) NTSTATUS;
+
+pub extern "NtDll" fn RtlDosPathNameToNtPathName_U_WithStatus(
+  DosFileName: [*:0]const WCHAR,
+  NtFileName: *UNICODE_STRING,
+  FilePath: ?*[*:0]WCHAR,
+  cd: ?*CURDIR,
+) callconv(WINAPI) NTSTATUS;

lib/std/os/windows/test.zig

@@ -0,0 +1,30 @@
+// SPDX-License-Identifier: MIT
+// Copyright (c) 2015-2020 Zig Contributors
+// This file is part of [zig](https://ziglang.org/), which is MIT licensed.
+// The MIT license requires this copyright notice to be included in all copies
+// and substantial portions of the software.
+const std = @import("../../std.zig");
+const builtin = @import("builtin");
+const windows = std.os.windows;
+const mem = std.mem;
+const testing = std.testing;
+const expect = testing.expect;
+
+fn testNtPath(input: []const u8, expected: []const u8) !void {
+    const input_w = try std.unicode.utf8ToUtf16LeWithNull(testing.allocator, input);
+    defer testing.allocator.free(input_w);
+    const expected_w = try std.unicode.utf8ToUtf16LeWithNull(testing.allocator, expected);
+    defer testing.allocator.free(expected_w);
+
+    const nt_path = try windows.NtPath.init(input_w);
+    defer nt_path.deinit();
+    const relative_path = try windows.toRelativeNtPath(nt_path.str);
+    expect(mem.eql(u16, windows.unicodeSpan(relative_path), expected_w));
+}
+
+test "NtPath" {
+    try testNtPath("a", "a");
+    try testNtPath("a\\b", "a\\b");
+    try testNtPath("a\\.\\b", "a\\b");
+    try testNtPath("a\\..\\b", "b");
+}