159 lines
4 KiB
C++
159 lines
4 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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