4256db48c0
Also move MOZ_MUST_USE before function declarations' specifiers and return type. While clang and gcc's attribute((warn_unused_result)) can appear before, between, or after function specifiers and return types, the [[nodiscard]] attribute must precede the function specifiers. And removed a few unneded `#include "mozilla/Attributes.h"`. Differential Revision: https://phabricator.services.mozilla.com/D69755
98 lines
4.0 KiB
C++
98 lines
4.0 KiB
C++
/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=8 sts=2 et sw=2 tw=80: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef ProfileBufferIndex_h
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#define ProfileBufferIndex_h
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#include "mozilla/Attributes.h"
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#include <cstddef>
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#include <cstdint>
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namespace mozilla {
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// Generic index into a Profiler buffer, mostly for internal usage.
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// Intended to appear infinite (it should effectively never wrap).
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// 0 (zero) is reserved as nullptr-like value; it may indicate failure result,
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// or it may point at the earliest available block.
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using ProfileBufferIndex = uint64_t;
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// Externally-opaque class encapsulating a block index, i.e. a
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// ProfileBufferIndex that is guaranteed to point at the start of a Profile
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// buffer block (until it is destroyed, but then that index cannot be reused and
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// functions should gracefully handle expired blocks).
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// Users may get these from Profile buffer functions, to later access previous
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// blocks; they should avoid converting and operating on their value.
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class ProfileBufferBlockIndex {
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public:
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// Default constructor with internal 0 value, for which Profile buffers must
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// guarantee that it is before any valid entries; All public APIs should
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// fail gracefully, doing and/or returning Nothing.
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ProfileBufferBlockIndex() : mBlockIndex(0) {}
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// Implicit conversion from literal `nullptr` to internal 0 value, to allow
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// convenient init/reset/comparison with 0 index.
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MOZ_IMPLICIT ProfileBufferBlockIndex(std::nullptr_t) : mBlockIndex(0) {}
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// Explicit conversion to bool, works in `if` and other tests.
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// Only returns false for default `ProfileBufferBlockIndex{}` value.
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explicit operator bool() const { return mBlockIndex != 0; }
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// Comparison operators. Default `ProfileBufferBlockIndex{}` value is always
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// the lowest.
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[[nodiscard]] bool operator==(const ProfileBufferBlockIndex& aRhs) const {
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return mBlockIndex == aRhs.mBlockIndex;
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}
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[[nodiscard]] bool operator!=(const ProfileBufferBlockIndex& aRhs) const {
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return mBlockIndex != aRhs.mBlockIndex;
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}
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[[nodiscard]] bool operator<(const ProfileBufferBlockIndex& aRhs) const {
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return mBlockIndex < aRhs.mBlockIndex;
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}
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[[nodiscard]] bool operator<=(const ProfileBufferBlockIndex& aRhs) const {
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return mBlockIndex <= aRhs.mBlockIndex;
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}
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[[nodiscard]] bool operator>(const ProfileBufferBlockIndex& aRhs) const {
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return mBlockIndex > aRhs.mBlockIndex;
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}
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[[nodiscard]] bool operator>=(const ProfileBufferBlockIndex& aRhs) const {
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return mBlockIndex >= aRhs.mBlockIndex;
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}
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// Explicit conversion to ProfileBufferIndex, mostly used by internal Profile
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// buffer code.
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[[nodiscard]] ProfileBufferIndex ConvertToProfileBufferIndex() const {
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return mBlockIndex;
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}
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// Explicit creation from ProfileBufferIndex, mostly used by internal
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// Profile buffer code.
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[[nodiscard]] static ProfileBufferBlockIndex CreateFromProfileBufferIndex(
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ProfileBufferIndex aIndex) {
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return ProfileBufferBlockIndex(aIndex);
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}
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private:
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// Private to prevent easy construction from any value. Use
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// `CreateFromProfileBufferIndex()` instead.
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// The main reason for this indirection is to make it harder to create these
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// objects, because only the profiler code should need to do it. Ideally, this
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// class should be used wherever a block index should be stored, but there is
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// so much code that uses `uint64_t` that it would be a big task to change
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// them all. So for now we allow conversions to/from numbers, but it's as ugly
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// as possible to make sure it doesn't get too common; and if one day we want
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// to tackle a global change, it should be easy to find all these locations
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// thanks to the explicit conversion functions.
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explicit ProfileBufferBlockIndex(ProfileBufferIndex aBlockIndex)
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: mBlockIndex(aBlockIndex) {}
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ProfileBufferIndex mBlockIndex;
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};
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} // namespace mozilla
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#endif // ProfileBufferIndex_h
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