bf3516e81e
In modern C++, static constexpr member variables are automatically inline (aka weak) so the template trick is not needed. This also avoid duplication and reduces the amount of parsed code. No impact on generated binary (actually: smaller debuginfo, close to identical binary). Differential Revision: https://phabricator.services.mozilla.com/D247825
160 lines
4.0 KiB
C++
160 lines
4.0 KiB
C++
/* -*- Mode: C++; tab-width: 8; 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 nsID_h__
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#define nsID_h__
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#include <string.h>
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#include "nscore.h"
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#define NSID_LENGTH 39
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#ifndef XPCOM_GLUE_AVOID_NSPR
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class nsIDToCString;
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#endif
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/**
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* A "unique identifier". This is modeled after OSF DCE UUIDs.
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*/
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struct nsID {
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uint32_t m0;
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uint16_t m1;
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uint16_t m2;
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uint8_t m3[8];
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/**
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* Create a new random UUID.
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* GenerateUUIDInPlace() is fallible, whereas GenerateUUID() will abort in
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* the unlikely case that the OS RNG returns an error.
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*/
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[[nodiscard]] static nsresult GenerateUUIDInPlace(nsID& aId);
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static nsID GenerateUUID();
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/**
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* Ensures everything is zeroed out.
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*/
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void Clear();
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/**
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* Equivalency method. Compares this nsID with another.
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* @return true if they are the same, false if not.
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*/
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inline bool Equals(const nsID& aOther) const {
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// At the time of this writing, modern compilers (namely Clang) inline this
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// memcmp call into a single SIMD operation on x86/x86-64 architectures (as
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// long as we compare to zero rather than returning the full integer return
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// value), which is measurably more efficient to any manual comparisons we
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// can do directly.
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#if defined(__x86_64__) || defined(__i386__)
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return !memcmp(this, &aOther, sizeof *this);
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#else
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// However, on ARM architectures, compilers still tend to generate a direct
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// memcmp call, which we'd like to avoid.
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return (((uint32_t*)&m0)[0] == ((uint32_t*)&aOther.m0)[0]) &&
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(((uint32_t*)&m0)[1] == ((uint32_t*)&aOther.m0)[1]) &&
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(((uint32_t*)&m0)[2] == ((uint32_t*)&aOther.m0)[2]) &&
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(((uint32_t*)&m0)[3] == ((uint32_t*)&aOther.m0)[3]);
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#endif
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}
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inline bool operator==(const nsID& aOther) const { return Equals(aOther); }
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/**
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* nsID Parsing method. Turns a {xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx}
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* string into an nsID
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*/
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bool Parse(const char* aIDStr);
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#ifndef XPCOM_GLUE_AVOID_NSPR
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/**
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* nsID string encoder. Returns a managed string in
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* {xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx} format.
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*/
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nsIDToCString ToString() const;
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/**
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* nsID string encoder. Builds a string in
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* {xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx} format, into a char[NSID_LENGTH]
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* buffer provided by the caller (for instance, on the stack).
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*/
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void ToProvidedString(char (&aDest)[NSID_LENGTH]) const;
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#endif // XPCOM_GLUE_AVOID_NSPR
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// Infallibly duplicate an nsID. Must be freed with free().
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nsID* Clone() const;
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};
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#ifndef XPCOM_GLUE_AVOID_NSPR
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/**
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* A stack helper class to convert a nsID to a string. Useful
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* for printing nsIDs. For example:
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* nsID aID = ...;
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* printf("%s", nsIDToCString(aID).get());
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*/
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class nsIDToCString {
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public:
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explicit nsIDToCString(const nsID& aID) {
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aID.ToProvidedString(mStringBytes);
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}
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const char* get() const { return mStringBytes; }
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protected:
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char mStringBytes[NSID_LENGTH];
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};
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#endif
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/*
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* Class IDs
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*/
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typedef nsID nsCID;
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// Define an CID
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#define NS_DEFINE_CID(_name, _cidspec) const nsCID _name = _cidspec
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#define NS_DEFINE_NAMED_CID(_name) static const nsCID k##_name = _name
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#define REFNSCID const nsCID&
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/**
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* An "interface id" which can be used to uniquely identify a given
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* interface.
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*/
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typedef nsID nsIID;
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/**
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* A macro shorthand for <tt>const nsIID&<tt>
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*/
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#define REFNSIID const nsIID&
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/**
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* A macro to add a static constexpr kIID variable.
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*/
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#define NS_INLINE_DECL_STATIC_IID(the_iid) \
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static constexpr nsIID kIID NS_HIDDEN = the_iid;
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/**
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* A macro to build the static const CID accessor method
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*/
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#define NS_DEFINE_STATIC_CID_ACCESSOR(the_cid) \
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static const nsID& GetCID() { \
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static constexpr nsID cid = the_cid; \
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return cid; \
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}
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#define NS_GET_IID(T) (T::kIID)
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#endif
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