The JSONPointer implementation requires that we escape "~"  and "/" as "~0" and "~1" respectively. Our current implementation incorrectly evaluates "~000" as "~".  Instead, it should evaluate to "~00". 

Existing tests in json_pointer_test.cpp incorrectly expect this behaviour as well, so the tests should be updated: https://github.com/10gen/mongo/blob/master/src/mongo/db/matcher/schema/json_pointer_test.cpp#L70

As an example, consider a document:

{ a: { "b~0":

} }

With the current implementation, it would not be possible to specify a jsonpointer to "b~0" since the escaped string would be: "/a/b~00" which in our impl. would be evaluated as "/a/b~" instead of "/a/b~0"