Add readlink smoke test

lib/std/os.zig

@@ -2355,6 +2355,8 @@ pub const ReadLinkError = error{
     FileNotFound,
     SystemResources,
     NotDir,
+    InvalidUtf8,
+    BadPathName,
     /// Windows-only.
     UnsupportedSymlinkType,
 } || UnexpectedError;
@@ -2366,7 +2368,7 @@ pub fn readlink(file_path: []const u8, out_buffer: []u8) ReadLinkError![]u8 {
         @compileError("readlink is not supported in WASI; use readlinkat instead");
     } else if (builtin.os.tag == .windows) {
         const file_path_w = try windows.sliceToPrefixedFileW(file_path);
-        return readlinkW(file_path_w.span().ptr, out_buffer);
+        return readlinkW(file_path_w.span(), out_buffer);
     } else {
         const file_path_c = try toPosixPath(file_path);
         return readlinkZ(&file_path_c, out_buffer);
@@ -2377,11 +2379,11 @@ pub const readlinkC = @compileError("deprecated: renamed to readlinkZ");
 
 /// Windows-only. Same as `readlink` except `file_path` is null-terminated, WTF16 encoded.
 /// See also `readlinkZ`.
-pub fn readlinkW(file_path: [*:0]const u16, out_buffer: []u8) ReadLinkError![]u8 {
+pub fn readlinkW(file_path: []const u16, out_buffer: []u8) ReadLinkError![]u8 {
     const handle = windows.OpenFile(file_path, .{
         .access_mask = 0,
-        .creation = c.FILE_OPEN_REPARSE_POINT | c.FILE_LIST_DIRECTORY,
-        .io_mode = 0,
+        .creation = windows.FILE_OPEN_REPARSE_POINT | windows.FILE_LIST_DIRECTORY,
+        .io_mode = std.io.default_mode,
     }) catch |err| {
         switch (err) {
             error.IsDir => unreachable,
@@ -2390,28 +2392,32 @@ pub fn readlinkW(file_path: [*:0]const u16, out_buffer: []u8) ReadLinkError![]u8
             error.PipeBusy => unreachable,
             error.PathAlreadyExists => unreachable,
             error.WouldBlock => unreachable,
-            else => return err,
+            else => |e| return e,
         }
     };
     var reparse_buf: [windows.MAXIMUM_REPARSE_DATA_BUFFER_SIZE]u8 = undefined;
     _ = try windows.DeviceIoControl(handle, windows.FSCTL_GET_REPARSE_POINT, null, reparse_buf[0..], null);
-    const reparse_struct = @bitCast(windows._REPARSE_DATA_BUFFER, reparse_buf[0..@sizeOf(windows._REPARSE_DATA_BUFFER)]);
+    const reparse_struct = mem.bytesAsValue(windows._REPARSE_DATA_BUFFER, reparse_buf[0..@sizeOf(windows._REPARSE_DATA_BUFFER)]);
     switch (reparse_struct.ReparseTag) {
-        windows.IO_REPARSE_TAG_SYMLINK => {},
-        windows.IO_REPARSE_TAG_MOUNT_POINT => {},
+        windows.IO_REPARSE_TAG_SYMLINK => {
+            std.debug.warn("got symlink!", .{});
+        },
+        windows.IO_REPARSE_TAG_MOUNT_POINT => {
+            std.debug.warn("got mount point!", .{});
+        },
         else => |value| {
-            std.debug.print("unsupported symlink type: {}", value);
+            std.debug.warn("unsupported symlink type: {}", .{value});
             return error.UnsupportedSymlinkType;
         },
     }
-    @compileError("TODO implement readlink for Windows");
+    @panic("Oh no!");
 }
 
 /// Same as `readlink` except `file_path` is null-terminated.
 pub fn readlinkZ(file_path: [*:0]const u8, out_buffer: []u8) ReadLinkError![]u8 {
     if (builtin.os.tag == .windows) {
         const file_path_w = try windows.cStrToPrefixedFileW(file_path);
-        return readlinkW(file_path_w.span().ptr, out_buffer);
+        return readlinkW(file_path_w.span(), out_buffer);
     }
     const rc = system.readlink(file_path, out_buffer.ptr, out_buffer.len);
     switch (errno(rc)) {

lib/std/os/test.zig

@@ -17,6 +17,7 @@ const AtomicRmwOp = builtin.AtomicRmwOp;
 const AtomicOrder = builtin.AtomicOrder;
 const tmpDir = std.testing.tmpDir;
 const Dir = std.fs.Dir;
+const ArenaAllocator = std.heap.ArenaAllocator;
 
 test "fstatat" {
     // enable when `fstat` and `fstatat` are implemented on Windows
@@ -40,6 +41,36 @@ test "fstatat" {
     expectEqual(stat, statat);
 }
 
+test "readlink" {
+    if (builtin.os.tag == .wasi) return error.SkipZigTest;
+
+    var tmp = tmpDir(.{});
+    defer tmp.cleanup();
+
+    // create file
+    try tmp.dir.writeFile("file.txt", "nonsense");
+
+    // get paths
+    // TODO: use Dir's realpath function once that exists
+    var arena = ArenaAllocator.init(testing.allocator);
+    defer arena.deinit();
+
+    const base_path = blk: {
+        const relative_path = try fs.path.join(&arena.allocator, &[_][]const u8{ "zig-cache", "tmp", tmp.sub_path[0..]});
+        break :blk try fs.realpathAlloc(&arena.allocator, relative_path);
+    };
+    const target_path = try fs.path.join(&arena.allocator, &[_][]const u8{"file.txt"});
+    const symlink_path = try fs.path.join(&arena.allocator, &[_][]const u8{"symlinked"});
+
+    // create symbolic link by path
+    try os.symlink(target_path, symlink_path);
+
+    // now, read the link and verify
+    var buffer: [fs.MAX_PATH_BYTES]u8 = undefined;
+    const given = try os.readlink(symlink_path, buffer[0..]);
+    expect(mem.eql(u8, symlink_path, given));
+}
+
 test "readlinkat" {
     // enable when `readlinkat` and `symlinkat` are implemented on Windows
     if (builtin.os.tag == .windows) return error.SkipZigTest;

lib/std/os/windows/bits.zig

@@ -488,7 +488,7 @@ pub const FILE_OPEN_BY_FILE_ID = 0x00002000;
 pub const FILE_OPEN_FOR_BACKUP_INTENT = 0x00004000;
 pub const FILE_NO_COMPRESSION = 0x00008000;
 pub const FILE_RESERVE_OPFILTER = 0x00100000;
-pub const FILE_TRANSACTED_MODE = 0x00200000;
+pub const FILE_OPEN_REPARSE_POINT = 0x00200000;
 pub const FILE_OPEN_OFFLINE_FILE = 0x00400000;
 pub const FILE_OPEN_FOR_FREE_SPACE_QUERY = 0x00800000;