Improve String matcher handling of case sensitivity

The old implementation of String matchers worked by making a, potentially
lower-cased, copy of both the constructor arg, and the arg to `match` calls.

The new implementation does not make copies, and instead does per-character
lowering if needed. This is a win in **most** cases, with two exceptions:

1) Case-insensitive `Equals` between long strings. The old implementation
   is easy to autovectorize by the compiler, which wins over the extra copy
   with sufficiently long inputs.
2) Case-insensitive `ContainsSubstring` with inputs that trigger the worst
   case complexity of O(m*n) of the naive implementation.

The latter is fixable with some elbow grease by implementing a proper
string search algorithm, but the former is a cost we have to live with.

0 files changed, 0 insertions, 0 deletions