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Bug 1276669 - part 10 - remove dynamic->static atom transmutation code; r=erahm

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Good riddance to some sketchy code.
This commit is contained in:
Nathan Froyd 2017-01-26 15:43:38 -05:00
parent 141f9b249d
commit ad51ed8360
1 changed files with 0 additions and 42 deletions
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42
xpcom/ds/nsAtomTable.cpp
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@ -121,45 +121,11 @@ private:
public:
NS_DECL_THREADSAFE_ISUPPORTS
NS_DECL_NSIATOM
void TransmuteToStatic(nsStringBuffer* aStringBuffer);
};
class StaticAtom final : public nsIAtom
{
// This is the function that calls the private constructor.
friend void DynamicAtom::TransmuteToStatic(nsStringBuffer*);
// This constructor must only be used in conjunction with placement new on an
// existing DynamicAtom (in DynamicAtom::TransmuteToStatic()) in order to
// transmute that DynamicAtom into a StaticAtom. The constructor does four
// notable things.
// - Overwrites the vtable pointer (implicitly).
// - Inverts mIsStatic.
// - Zeroes the refcount (via the nsIAtom constructor). Having a zero refcount
// doesn't matter because StaticAtom's AddRef/Release methods don't consult
// the refcount.
// - Releases the existing heap-allocated string buffer (explicitly),
// replacing it with the static string buffer (which must contain identical
// chars).
explicit StaticAtom(nsStringBuffer* aStaticBuffer)
{
static_assert(sizeof(DynamicAtom) >= sizeof(StaticAtom),
"can't safely transmute a smaller object to a bigger one");
// We must be transmuting an existing DynamicAtom.
MOZ_ASSERT(!mIsStatic);
mIsStatic = true;
char16_t* staticString = static_cast<char16_t*>(aStaticBuffer->Data());
MOZ_ASSERT(nsCRT::strcmp(staticString, mString) == 0);
nsStringBuffer* dynamicBuffer = nsStringBuffer::FromData(mString);
mString = staticString;
dynamicBuffer->Release();
}
public:
// This is the normal constructor.
StaticAtom(nsStringBuffer* aStringBuffer, uint32_t aLength, uint32_t aHash)
{
mLength = aLength;
@ -260,14 +226,6 @@ StaticAtom::SizeOfIncludingThis(MallocSizeOf aMallocSizeOf)
return n;
}
// See the comment on the private StaticAtom constructor for details of how
// this works.
void
DynamicAtom::TransmuteToStatic(nsStringBuffer* aStringBuffer)
{
new (this) StaticAtom(aStringBuffer);
}
//----------------------------------------------------------------------
/**