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Subject: Re: [boost] RFC: interest in Unicode codecs?
From: Stewart, Robert (Robert.Stewart_at_[hidden])
Date: 2009-07-21 08:42:12

Sebastian Redl wrote:
> Phil Endecott wrote:
> > Eric Niebler wrote:
> >> I believe that as of C++03, std::string is required to have
> >> contiguous storage. The null-termination is another thing.
> >> The only guarantee is that the char* returned by c_str() is
> >> required to be null terminated. No such guarantee is made
> >> for the sequence traversed by std::string's iterators.
> >> Dereferencing the end iterator is verboten.
> >
> > Here is an outline of a zero-overhead wrapper for std::string
> > that I hope guarantees that *end() == 0:
> >
> > struct string_with_zero_beyond_end: std::string {
> > typedef const char* const_iterator;
> > const_iterator begin() const { return c_str(); }
> > const_iterator end() const { return c_str() + length(); }
> > };
> Not zero-overhead if the string implementation is one (of the
> non-existent ones) that doesn't store the NUL internally.

Worse: you'd be returning iterators to what may well be a
temporary array of characters. The result of calling c_str()
need not refer to the internal storage of the string.

There's also the issue of deriving from a concrete class so that
slicing will revert to std::string::begin()/end().

Then there's also the little problem of std::string implementations
that don't use raw pointers for iterators, particularly those in
a checked STL.

Rob Stewart robert.stewart_at_[hidden]
Software Engineer, Core Software using std::disclaimer;
Susquehanna International Group, LLP

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