vendor tsgo

tools/tsgo/internal/nativepath/realpath_darwin.go

@@ -0,0 +1,66 @@
+package nativepath
+
+import (
+	"path/filepath"
+	"sync"
+	"unsafe"
+
+	"golang.org/x/sys/unix"
+)
+
+// On macOS, we use open + fcntl(F_GETPATH) to resolve the canonical path in
+// O(1) syscalls instead of Go's filepath.EvalSymlinks which does an lstat per
+// path component — O(depth).
+//
+// How it works:
+//   - open(path, O_EVTONLY|O_NONBLOCK|O_CLOEXEC) follows all symlinks and gives
+//     us a lightweight fd. O_EVTONLY is macOS's event-only descriptor — it
+//     doesn't require read permission (similar to Linux's O_PATH) but still
+//     references the vnode. O_NONBLOCK prevents blocking on FIFOs.
+//   - fcntl(fd, F_GETPATH, buf) asks the kernel for the canonical path of the
+//     open file descriptor, written into a MAXPATHLEN buffer.
+//
+// unix.FcntlInt takes an int arg, so call it through a uintptr-escaping wrapper
+// to keep the buffer pointer valid until fcntl returns.
+
+var hasFGetPath = sync.OnceValue(func() bool {
+	// Verify that F_GETPATH is supported by this kernel version.
+	var buf [unix.PathMax]byte
+	fd, err := unix.Open(".", unix.O_EVTONLY|unix.O_NONBLOCK|unix.O_CLOEXEC, 0)
+	if err != nil {
+		return false
+	}
+	defer unix.Close(fd)
+	_, err = fcntlGetPath(fd, &buf)
+	return err == nil
+})
+
+func fcntlGetPath(fd int, buf *[unix.PathMax]byte) (int, error) {
+	return ignoringEINTR(func() (int, error) {
+		return fcntlGetPathPtr(uintptr(fd), uintptr(unsafe.Pointer(&buf[0])))
+	})
+}
+
+//go:uintptrescapes
+func fcntlGetPathPtr(fd uintptr, buf uintptr) (int, error) {
+	return unix.FcntlInt(fd, unix.F_GETPATH, int(buf))
+}
+
+func Realpath(path string) (string, error) {
+	if !hasFGetPath() {
+		return filepath.EvalSymlinks(path)
+	}
+
+	fd, err := unix.Open(path, unix.O_EVTONLY|unix.O_NONBLOCK|unix.O_CLOEXEC, 0)
+	if err != nil {
+		return "", err
+	}
+	defer unix.Close(fd)
+
+	var buf [unix.PathMax]byte
+	if _, err := fcntlGetPath(fd, &buf); err != nil {
+		return "", err
+	}
+
+	return unix.ByteSliceToString(buf[:]), nil
+}