1 files changed, 38 insertions, 0 deletions
diff --git a/mfbt/Utf8.cpp b/mfbt/Utf8.cpp
new file mode 100644
index 0000000000..1a10c7a011
--- /dev/null
+++ b/mfbt/Utf8.cpp
@@ -0,0 +1,38 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/Maybe.h"
+#include "mozilla/TextUtils.h"
+#include "mozilla/Types.h"
+#include "mozilla/Utf8.h"
+
+#include <stddef.h>
+#include <stdint.h>
+
+MFBT_API bool mozilla::detail::IsValidUtf8(const void* aCodeUnits,
+                                           size_t aCount) {
+  const auto* s = reinterpret_cast<const unsigned char*>(aCodeUnits);
+  const auto* const limit = s + aCount;
+
+  while (s < limit) {
+    unsigned char c = *s++;
+
+    // If the first byte is ASCII, it's the only one in the code point.  Have a
+    // fast path that avoids all the rest of the work and looping in that case.
+    if (IsAscii(c)) {
+      continue;
+    }
+
+    Maybe<char32_t> maybeCodePoint =
+        DecodeOneUtf8CodePoint(Utf8Unit(c), &s, limit);
+    if (maybeCodePoint.isNothing()) {
+      return false;
+    }
+  }
+
+  MOZ_ASSERT(s == limit);
+  return true;
+}