зеркало из https://github.com/mozilla/gecko-dev.git
Bug 1494515 - Rework the comments about static atoms. r=froydnj
nsGkAtoms.h has a big comment explaining how static atom definitions get expanded by macros. This comment was very useful when there were multiple sources of static atoms and their definitions used macros a lot. But bug 1482782 combined all the static atom sources into nsGkAtoms and removed a lot of macro use. So now the comment is now something of a hindrance, duplicating quite a bit of the code (and not entirely accurately). This commit removes the big comment, and moves the still-useful parts inline with the code. This makes things much easier to follow. This commit also reformats some of the remaining macros so they are easier to read. --HG-- extra : rebase_source : 4377be2fa0edc4ea1f592985ded89acbb76fb104
This commit is contained in:
Nicholas Nethercote
Родитель
d2ed7ef067
Коммит
dd61fd6ccf
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@ -13,8 +13,17 @@ NS_RegisterStaticAtoms(const nsStaticAtom* aAtoms, size_t aAtomsLen);
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namespace mozilla {
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namespace detail {
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// Because this is `constexpr` it ends up in read-only memory where it can be
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// shared between processes.
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extern constexpr GkAtoms gGkAtoms = {
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// The initialization of each atom's string.
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//
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// Expansion of the example GK_ATOM entries in nsGkAtoms.h:
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//
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// u"a",
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// u"bb",
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// u"ccc",
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//
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#define GK_ATOM(name_, value_, hash_, type_, atom_type_) \
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u"" value_,
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#include "nsGkAtomList.h"
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@ -25,13 +34,30 @@ extern constexpr GkAtoms gGkAtoms = {
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// Note that |value_| is an 8-bit string, and so |sizeof(value_)| is equal
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// to the number of chars (including the terminating '\0'). The |u""| prefix
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// converts |value_| to a 16-bit string.
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#define GK_ATOM(name_, value_, hash_, type_, atom_type_) \
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nsStaticAtom(u"" value_, \
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sizeof(value_) - 1, \
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hash_, \
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offsetof(GkAtoms, \
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mAtoms[static_cast<size_t>(GkAtoms::Atoms::name_)]) - \
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offsetof(GkAtoms, name_##_string)),
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//
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// Expansion of the example GK_ATOM entries in nsGkAtoms.h:
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//
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// nsStaticAtom(
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// u"a", 1, 0x01234567,
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// offsetof(GkAtoms, mAtoms[static_cast<size_t>(GkAtoms::Atoms::a)]) -
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// offsetof(GkAtoms, a_string)),
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//
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// nsStaticAtom(
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// u"bb", 2, 0x12345678,
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// offsetof(GkAtoms, mAtoms[static_cast<size_t>(GkAtoms::Atoms::bb)]) -
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// offsetof(GkAtoms, bb_string)),
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//
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// nsStaticAtom(
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// u"ccc", 3, 0x23456789,
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// offsetof(GkAtoms, mAtoms[static_cast<size_t>(GkAtoms::Atoms::ccc)]) -
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// offsetof(GkAtoms, ccc_string)),
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//
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#define GK_ATOM(name_, value_, hash_, type_, atom_type_) \
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nsStaticAtom( \
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u"" value_, sizeof(value_) - 1, hash_, \
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offsetof(GkAtoms, \
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mAtoms[static_cast<size_t>(GkAtoms::Atoms::name_)]) - \
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offsetof(GkAtoms, name_##_string)),
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#include "nsGkAtomList.h"
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#undef GK_ATOM
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}
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@ -43,10 +69,33 @@ extern constexpr GkAtoms gGkAtoms = {
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const nsStaticAtom* const nsGkAtoms::sAtoms = mozilla::detail::gGkAtoms.mAtoms;
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// Definition of the pointer to the static atom.
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#define GK_ATOM(name_, value_, hash_, type_, atom_type_) \
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type_* nsGkAtoms::name_ = const_cast<type_*>(static_cast<const type_*>( \
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&mozilla::detail::gGkAtoms.mAtoms[ \
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static_cast<size_t>(mozilla::detail::GkAtoms::Atoms::name_)]));
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//
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// Expansion of the example GK_ATOM entries in nsGkAtoms.h:
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//
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// nsStaticAtom* nsGkAtoms::a =
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// const_cast<nsStaticAtom*>(
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// static_cast<const nsStaticAtom*>(
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// &mozilla::detail::gGkAtoms.mAtoms[
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// static_cast<size_t>(mozilla::detail::GkAtoms::Atoms::a)]));
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//
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// nsICSSPseudoElement* nsGkAtoms::bb =
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// const_cast<nsICSSPseudoElement*>(
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// static_cast<const nsICSSPseudoElement*>(
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// &mozilla::detail::gGkAtoms.mAtoms[
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// static_cast<size_t>(mozilla::detail::GkAtoms::Atoms::bb)]));
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//
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// nsICSSAnonBoxPseudo* nsGkAtoms::ccc =
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// const_cast<nsICSSAnonBoxPseudo*>(
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// static_cast<const nsICSSAnonBoxPseudo*>(
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// &mozilla::detail::gGkAtoms.mAtoms[
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// static_cast<size_t>(mozilla::detail::GkAtoms::Atoms::ccc)]));
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//
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#define GK_ATOM(name_, value_, hash_, type_, atom_type_) \
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type_* nsGkAtoms::name_ = \
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const_cast<type_*>( \
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static_cast<const type_*>( \
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&mozilla::detail::gGkAtoms.mAtoms[ \
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static_cast<size_t>(mozilla::detail::GkAtoms::Atoms::name_)]));
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#include "nsGkAtomList.h"
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#undef GK_ATOM
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@ -43,119 +43,15 @@
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//
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// nsGkAtoms below defines static atoms in a way that satisfies these
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// constraints. It uses nsGkAtomList.h, which defines the names and values of
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// the atoms.
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// the atoms. nsGkAtomList.h is generated by StaticAtoms.py and has entries
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// that look like this:
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//
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// nsGkAtomList.h is generated by StaticAtoms.py and has entries that look
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// like this:
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// GK_ATOM(a, "a", 0x01234567, nsStaticAtom, Atom)
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// GK_ATOM(bb, "bb", 0x12345678, nsICSSPseudoElement, PseudoElementAtom)
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// GK_ATOM(ccc, "ccc", 0x23456789, nsICSSAnonBoxPseudo, InheritingAnonBoxAtom)
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//
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// GK_ATOM(one, "one", 0x01234567, nsStaticAtom, Atom)
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// GK_ATOM(two, "two", 0x12345678, nsICSSPseudoElement, PseudoElementAtom)
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// GK_ATOM(three, "three", 0x23456789, nsICSSAnonBoxPseudo, InheritingAnonBoxAtom)
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//
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// After macro expansion, the atom definitions look like the following:
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//
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// ====> nsGkAtoms.h <====
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//
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// namespace mozilla {
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// namespace detail {
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//
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// struct GkAtoms
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// {
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// // The declaration of each atom's string.
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// const char16_t one_string[sizeof("one")];
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// const char16_t two_string[sizeof("two")];
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// const char16_t three_string[sizeof("three")];
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//
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// // The enum value for each atom.
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// enum class Atoms {
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// one_,
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// two_,
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// three_,
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// AtomsCount
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// };
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//
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// const nsStaticAtom mAtoms[static_cast<size_t>(Atoms::AtomsCount)];
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// };
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//
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// } // namespace detail
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// } // namespace mozilla
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//
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// // This class holds the pointers to the individual atoms.
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// class nsGkAtoms
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// {
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// private:
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// // This is a useful handle to the array of atoms, used below and also
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// // possibly by Rust code.
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// static const nsStaticAtom* const sAtoms;
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//
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// // The number of atoms, used below.
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// static constexpr size_t sAtomsLen =
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// static_cast<size_t>(detail::MyAtoms::Atoms::AtomsCount);
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//
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// public:
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// // These types are not `nsStaticAtom* const`, etc. -- even though these
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// // atoms are immutable -- because they are often passed to functions with
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// // `nsAtom*` parameters, i.e. that can be passed both dynamic and
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// // static.
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// static nsStaticAtom* one;
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// static nsICSSPseudoElement* two;
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// static nsICSSAnonBoxPseudo* three;
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// };
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//
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// ====> nsGkAtoms.cpp <====
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//
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// namespace mozilla {
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// namespace detail {
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//
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// // Need to suppress some MSVC warning weirdness with WrappingMultiply().
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// MOZ_PUSH_DISABLE_INTEGRAL_CONSTANT_OVERFLOW_WARNING
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// // Because this is `constexpr` it ends up in read-only memory where it can
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// // be shared between processes.
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// static constexpr GkAtoms gGkAtoms = {
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// // The initialization of each atom's string.
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// u"one",
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// u"two",
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// u"three",
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// {
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// // The initialization of the atoms themselves.
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// nsStaticAtom(
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// u"one", 3,
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// 0x01234567,
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// offsetof(GkAtoms, mAtoms[static_cast<size_t>(GkAtoms::Atoms::one)]) -
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// offsetof(GkAtoms, one_string)),
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// nsStaticAtom(
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// u"two", 3,
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// 0x12345678,
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// offsetof(GkAtoms, mAtoms[static_cast<size_t>(GkAtoms::Atoms::two)]) -
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// offsetof(GkAtoms, two_string)),
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// nsStaticAtom(
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// u"three", 3,
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// 0x23456789,
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// offsetof(GkAtoms, mAtoms[static_cast<size_t>(GkAtoms::Atoms::three)]) -
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// offsetof(GkAtoms, three_string)),
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// }
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// };
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// MOZ_POP_DISABLE_INTEGRAL_CONSTANT_OVERFLOW_WARNING
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//
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// } // namespace detail
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// } // namespace mozilla
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//
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// const nsStaticAtom* const nsGkAtoms::sAtoms =
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// mozilla::detail::gGkAtoms.mAtoms;
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//
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// // Definition of the pointer to the static atom.
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// nsStaticAtom* nsGkAtoms::one =
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// const_cast<nsStaticAtom*>(static_cast<const nsStaticAtom*>(
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// &detail::gGkAtoms.mAtoms[
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// static_cast<size_t>(detail::GkAtoms::Atoms::one)]);
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// nsICSSPseudoElement* nsGkAtoms::two =
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// const_cast<nsICSSPseudoElement*>(static_cast<const nsICSSPseudoElement*>(
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// &detail::gGkAtoms.mAtoms[
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// static_cast<size_t>(detail::GkAtoms::Atoms::two)]);
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// nsICSSAnonBoxPseudo* nsGkAtoms::three =
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// const_cast<nsICSSAnonBoxPseudo*>(static_cast<const nsICSSAnonBoxPseudo*>(
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// &detail::gGkAtoms.mAtoms[
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// static_cast<size_t>(detail::GkAtoms::Atoms::three)]);
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// Comments throughout this file and nsGkAtoms.cpp show how these entries get
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// expanded by macros.
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// Trivial subclasses of nsStaticAtom so that function signatures can require
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// an atom from a specific atom list.
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@ -176,15 +72,22 @@ DEFINE_STATIC_ATOM_SUBCLASS(nsICSSPseudoElement)
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namespace mozilla {
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namespace detail {
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// This `detail` class contains the atom strings and the atom objects.
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// Because they are together in a class, the mStringOffset field of the
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// atoms will be small and can be initialized at compile time.
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// This `detail` class contains the atom strings and the atom objects. Because
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// they are together in a class, the `mStringOffset` field of the atoms will be
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// small and can be initialized at compile time.
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//
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// A `detail` namespace is used because the things within it aren't directly
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// referenced by external users of these static atoms.
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struct GkAtoms
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{
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// The declaration of each atom's string.
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//
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// Expansion of the example GK_ATOM entries from above:
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//
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// const char16_t a_string[sizeof("a")];
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// const char16_t bb_string[sizeof("bb")];
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// const char16_t ccc_string[sizeof("ccc")];
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//
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#define GK_ATOM(name_, value_, hash_, type_, atom_type_) \
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const char16_t name_##_string[sizeof(value_)];
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#include "nsGkAtomList.h"
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@ -192,6 +95,12 @@ struct GkAtoms
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// The enum value for each atom.
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enum class Atoms {
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// Expansion of the example GK_ATOM entries above:
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//
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// a,
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// bb,
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// ccc,
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//
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#define GK_ATOM(name_, value_, hash_, type_, atom_type_) \
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name_,
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#include "nsGkAtomList.h"
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@ -205,10 +114,15 @@ struct GkAtoms
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} // namespace detail
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} // namespace mozilla
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// This class holds the pointers to the individual atoms.
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class nsGkAtoms
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{
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private:
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// This is a useful handle to the array of atoms, used below and also
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// possibly by Rust code.
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static const nsStaticAtom* const sAtoms;
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// The number of atoms, used below.
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static constexpr size_t sAtomsLen =
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static_cast<size_t>(mozilla::detail::GkAtoms::Atoms::AtomsCount);
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@ -223,6 +137,12 @@ public:
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// The declaration of the pointer to each static atom.
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//
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// Expansion of the example GK_ATOM entries above:
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//
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// static nsStaticAtom* a;
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// static nsICSSPseudoElement* bb;
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// static nsICSSAnonBoxPseudo* ccc;
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//
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// XXX: Eventually this should be combined with its definition and the
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// pointer should be made `constexpr`. See bug 1449787.
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#define GK_ATOM(name_, value_, hash_, type_, atom_type_) \
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