This patch adds a series of fallible methods for the rust ns[C]String
bindings, as well as the `set_length` method, which is the same as the
`SetLength` method in C++. `set_length` is marked as unsafe.
The decision was made to make the fallible methods seperate from the
infallible methods, and to use seperate Rust->C++ bindings for each of
them, rather than only binding the fallible bindings, and unwrapping
them in rust-land. This is to try to match the C++ API as closely as
possible, and to ensure that the behavior matches.
MozReview-Commit-ID: FkSomkFUFGD
This adds an SSE2 optimized path for UTF-16 strings that can be trivially
converted to UTF-8 (they contain no characters > 0X7F). It has a
speedup for the case where many of the leading characters are < 0X80 and
should have the same performance in the worst-case scenario where the first
character is > 0X7F.
StringBeginsWith (resp. StringEndsWith) takes a defaulted
nsStringComparator object for doing comparisons. The flexibility this
affords is great, but the cost is not: nsStringComparator has virtual
methods, so initializing that defaulted object (at every callsite)
requires a temporary object whose vtable must be initialized.
Since the overwhemingly common case is to use the default comparator
anyway, we should not use defaulted arguments and instead provide the
default comparator/user-provided comparator cases as separate overloads.
This change eliminates the virtual call for the majority of callsites
and reduces codesize as well.
This patch handles most of the call sites for these allocations except
for a few where I added TODO comments with some information. Handling
those places may require reworking lots of code, so I prefer to not do
that here.
