1 files changed, 95 insertions, 0 deletions
diff --git a/xpcom/string/nsStringFlags.h b/xpcom/string/nsStringFlags.h
new file mode 100644
index 0000000000..d0ba05c8db
--- /dev/null
+++ b/xpcom/string/nsStringFlags.h
@@ -0,0 +1,95 @@
+/* -*- 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/. */
+
+#ifndef nsStringFlags_h
+#define nsStringFlags_h
+
+#include <stdint.h>
+#include "mozilla/TypedEnumBits.h"
+
+namespace mozilla {
+namespace detail {
+// NOTE: these flags are declared public _only_ for convenience inside
+// the string implementation.  And they are outside of the string
+// class so that the type is the same for both narrow and wide
+// strings.
+
+// bits for mDataFlags
+enum class StringDataFlags : uint16_t {
+  // Some terminology:
+  //
+  //   "dependent buffer"    A dependent buffer is one that the string class
+  //                         does not own.  The string class relies on some
+  //                         external code to ensure the lifetime of the
+  //                         dependent buffer.
+  //
+  //   "refcounted buffer"   A refcounted buffer is one that the string class
+  //                         allocates.  When it allocates a refcounted string
+  //                         buffer, it allocates some additional space at
+  //                         the beginning of the buffer for additional
+  //                         fields, including a reference count and a
+  //                         buffer length.  See nsStringHeader.
+  //
+  //   "adopted buffer"      An adopted buffer is a raw string buffer
+  //                         allocated on the heap (using moz_xmalloc)
+  //                         of which the string class subsumes ownership.
+  //
+  // Some comments about the string data flags:
+  //
+  //   REFCOUNTED, OWNED, and INLINE are all mutually exlusive.  They
+  //   indicate the allocation type of mData.  If none of these flags
+  //   are set, then the string buffer is dependent.
+  //
+  //   REFCOUNTED, OWNED, or INLINE imply TERMINATED.  This is because
+  //   the string classes always allocate null-terminated buffers, and
+  //   non-terminated substrings are always dependent.
+  //
+  //   VOIDED implies TERMINATED, and moreover it implies that mData
+  //   points to char_traits::sEmptyBuffer.  Therefore, VOIDED is
+  //   mutually exclusive with REFCOUNTED, OWNED, and INLINE.
+  //
+  //   INLINE requires StringClassFlags::INLINE to be set on the type.
+
+  // IsTerminated returns true
+  TERMINATED = 1 << 0,
+
+  // IsVoid returns true
+  VOIDED = 1 << 1,
+
+  // mData points to a heap-allocated, shareable, refcounted buffer
+  REFCOUNTED = 1 << 2,
+
+  // mData points to a heap-allocated, raw buffer
+  OWNED = 1 << 3,
+
+  // mData points to a writable, inline buffer
+  INLINE = 1 << 4,
+
+  // mData points to a string literal; DataFlags::TERMINATED will also be set
+  LITERAL = 1 << 5,
+
+  // used to check for invalid flags -- all bits above the last item
+  INVALID_MASK = (uint16_t) ~((LITERAL << 1) - 1)
+};
+
+// bits for mClassFlags
+enum class StringClassFlags : uint16_t {
+  // |this|'s buffer is inline, and requires the type to be binary-compatible
+  // with nsTAutoStringN
+  INLINE = 1 << 0,
+  // |this| requires its buffer is null-terminated
+  NULL_TERMINATED = 1 << 1,
+  // used to check for invalid flags -- all bits above the last item
+  INVALID_MASK = (uint16_t) ~((NULL_TERMINATED << 1) - 1)
+};
+
+MOZ_MAKE_ENUM_CLASS_BITWISE_OPERATORS(StringDataFlags)
+MOZ_MAKE_ENUM_CLASS_BITWISE_OPERATORS(StringClassFlags)
+
+}  // namespace detail
+}  // namespace mozilla
+
+#endif