diff --git a/services/files/util.cc b/services/files/util.cc
new file mode 100644
index 0000000..d2af8cb
--- /dev/null
+++ b/services/files/util.cc
@@ -0,0 +1,103 @@
+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "services/files/util.h"
+
+#include <errno.h>
+#include <fcntl.h>
+#include <sys/stat.h>
+#include <time.h>
+
+#include <limits>
+
+#include "base/logging.h"
+#include "base/strings/string_util.h"
+#include "mojo/public/cpp/bindings/string.h"
+
+namespace mojo {
+namespace files {
+
+Error IsPathValid(const String& path) {
+  DCHECK(!path.is_null());
+  if (!base::IsStringUTF8(path.get()))
+    return ERROR_INVALID_ARGUMENT;
+  if (path.size() > 0 && path[0] == '/')
+    return ERROR_PERMISSION_DENIED;
+  return ERROR_OK;
+}
+
+Error IsWhenceValid(Whence whence) {
+  return (whence == WHENCE_FROM_CURRENT || whence == WHENCE_FROM_START ||
+          whence == WHENCE_FROM_END)
+             ? ERROR_OK
+             : ERROR_UNIMPLEMENTED;
+}
+
+Error IsOffsetValid(int64_t offset) {
+  return (offset >= std::numeric_limits<off_t>::min() &&
+          offset <= std::numeric_limits<off_t>::max())
+             ? ERROR_OK
+             : ERROR_OUT_OF_RANGE;
+}
+
+Error ErrnoToError(int errno_value) {
+  // TODO(vtl)
+  return ERROR_UNKNOWN;
+}
+
+int WhenceToStandardWhence(Whence whence) {
+  DCHECK_EQ(IsWhenceValid(whence), ERROR_OK);
+  switch (whence) {
+    case WHENCE_FROM_CURRENT:
+      return SEEK_CUR;
+    case WHENCE_FROM_START:
+      return SEEK_SET;
+    case WHENCE_FROM_END:
+      return SEEK_END;
+  }
+  NOTREACHED();
+  return 0;
+}
+
+Error TimespecToStandardTimespec(const Timespec* in, struct timespec* out) {
+  if (!in) {
+    out->tv_sec = 0;
+    out->tv_nsec = UTIME_OMIT;
+    return ERROR_OK;
+  }
+
+  static_assert(sizeof(int64_t) >= sizeof(time_t), "whoa, time_t is huge");
+  if (in->seconds < std::numeric_limits<time_t>::min() ||
+      in->seconds > std::numeric_limits<time_t>::max())
+    return ERROR_OUT_OF_RANGE;
+
+  if (in->nanoseconds < 0 || in->nanoseconds >= 1000000000)
+    return ERROR_INVALID_ARGUMENT;
+
+  out->tv_sec = static_cast<time_t>(in->seconds);
+  out->tv_nsec = static_cast<long>(in->nanoseconds);
+  return ERROR_OK;
+}
+
+Error TimespecOrNowToStandardTimespec(const TimespecOrNow* in,
+                                      struct timespec* out) {
+  if (!in) {
+    out->tv_sec = 0;
+    out->tv_nsec = UTIME_OMIT;
+    return ERROR_OK;
+  }
+
+  if (in->now) {
+    if (!in->timespec.is_null())
+      return ERROR_INVALID_ARGUMENT;
+    out->tv_sec = 0;
+    out->tv_nsec = UTIME_NOW;
+    return ERROR_OK;
+  }
+
+  return TimespecToStandardTimespec(in->timespec.get(), out);
+}
+
+}  // namespace files
+}  // namespace mojo