Hello everyone!
Bug 1377351 landed on central recently, and adds move assignment operators
and constructors to ns[C]String. These operators attempt to re-use
allocations when possible and can reduce the cost of copying strings around.
This could be used in some situations to improve assignment to nsString
fields in structs, for example, this call will avoid allocating & using
reference counts in more situations than the equivalent code using `const
nsAString&`:
void
SetFoo(nsAString&& aFoo)
{
mFoo.Assign(Move(aFoo));
}
In addition, this can be used to save some work when returning using an
outparameter:
void
GetFoo(nsAString& aOut)
{
// Somehow get a string value we want to return
nsString returnValue = ...;
aOut.Assign(Move(returnValue));
}
After using one of these move assignment operators, the original string
will be truncated. This functionality is also exposed to rust code through
the `take_from` method.
Consider moving ns[C]String values in the future when assigning to avoid
unnecessary work.
Nika
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