gecko-dev/xpcom/string/nsStringFlags.h
Nicholas Nethercote 9e0714dd26 Bug 1403506 - Remove nsTFixedString<T>. r=erahm.
(patch is actually r=erahm,mystor)

nsTFixedString<T> is only used as a base class for nsTAutoStringN<T, N>, so
this patch merges the former into the latter, cutting some code and simplifying
the string class hierarchy.

Because the "Fixed" name is now gone, the patch also renames
StringDataFlags::FIXED as INLINE and ClassDataFlags::FIXED as INLINE.

The patch also removes nsFixed[C]String and ns_auto_[c]string! from Rust code
because nsAutoString can't be implemented directly in Rust due to its move
semantics. There were only two uses of ns_auto_string! outside of tests so this
seems like a minor loss.

MozReview-Commit-ID: 8ntximghiut

--HG--
extra : rebase_source : f36edbae0553adcfee356fb8b311097ff7424786
2017-09-27 20:19:33 +10:00

77 lines
3.1 KiB
C++

/* -*- 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.
//
// "shared buffer" A shared buffer is one that the string class
// allocates. When it allocates a shared 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:
//
// SHARED, 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.
//
// SHARED, 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 SHARED, OWNED, and INLINE.
TERMINATED = 1 << 0, // IsTerminated returns true
VOIDED = 1 << 1, // IsVoid returns true
SHARED = 1 << 2, // mData points to a heap-allocated, shared buffer
OWNED = 1 << 3, // mData points to a heap-allocated, raw buffer
INLINE = 1 << 4, // mData points to a writable, inline buffer
LITERAL = 1 << 5 // mData points to a string literal; DataFlags::TERMINATED will also be set
};
// bits for mClassFlags
enum class StringClassFlags : uint16_t
{
INLINE = 1 << 0, // |this|'s buffer is inline
NULL_TERMINATED = 1 << 1 // |this| requires its buffer is null-terminated
};
MOZ_MAKE_ENUM_CLASS_BITWISE_OPERATORS(StringDataFlags)
MOZ_MAKE_ENUM_CLASS_BITWISE_OPERATORS(StringClassFlags)
} // namespace detail
} // namespace mozilla
#endif