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#### Unicode Iterators

##### Synopsis

    #include <boost/regex/pending/unicode_iterator.hpp>

    template <class BaseIterator, class U16Type = ::boost::uint16_t>
    class u32_to_u16_iterator;

    template <class BaseIterator, class U32Type = ::boost::uint32_t>
    class u16_to_u32_iterator;

    template <class BaseIterator, class U8Type = ::boost::uint8_t>
    class u32_to_u8_iterator;

    template <class BaseIterator, class U32Type = ::boost::uint32_t>
    class u8_to_u32_iterator;

    template <class BaseIterator>
    class utf16_output_iterator;

    template <class BaseIterator>
    class utf8_output_iterator;

##### Description

This header contains a selection of iterator adaptors that make a sequence of characters in one encoding "look like" a read-only sequence of characters in another encoding.

    template <class BaseIterator, class U16Type = ::boost::uint16_t>
    class u32_to_u16_iterator
    {
       u32_to_u16_iterator();
       u32_to_u16_iterator(BaseIterator start_position);

       // Other standard BidirectionalIterator members here...
    };

A Bidirectional iterator adapter that makes an underlying sequence of UTF32 characters look like a (read-only) sequence of UTF16 characters. The UTF16 characters are encoded in the platforms native byte order.

    template <class BaseIterator, class U32Type = ::boost::uint32_t>
    class u16_to_u32_iterator
    {
       u16_to_u32_iterator();
       u16_to_u32_iterator(BaseIterator start_position);
       u16_to_u32_iterator(BaseIterator start_position, BaseIterator start_range, BaseIterator end_range);

       // Other standard BidirectionalIterator members here...
    };

A Bidirectional iterator adapter that makes an underlying sequence of UTF16 characters (in the platforms native byte order) look like a (read-only) sequence of UTF32 characters.

The three-arg constructor of this class takes the start and end of the underlying sequence as well as the position to start iteration from. This constructor validates that the underlying sequence has validly encoded endpoints: this prevents accidently incrementing/decrementing past the end of the underlying sequence as a result of invalid UTF16 code sequences at the endpoints of the underlying range.

    template <class BaseIterator, class U8Type = ::boost::uint8_t>
    class u32_to_u8_iterator
    {
       u32_to_u8_iterator();
       u32_to_u8_iterator(BaseIterator start_position);

       // Other standard BidirectionalIterator members here...
    };

A Bidirectional iterator adapter that makes an underlying sequence of UTF32 characters look like a (read-only) sequence of UTF8 characters.

    template <class BaseIterator, class U32Type = ::boost::uint32_t>
    class u8_to_u32_iterator
    {
       u8_to_u32_iterator();
       u8_to_u32_iterator(BaseIterator start_position);
       u8_to_u32_iterator(BaseIterator start_position, BaseIterator start_range, BaseIterator end_range);

       // Other standard BidirectionalIterator members here...
    };

A Bidirectional iterator adapter that makes an underlying sequence of UTF8 characters look like a (read-only) sequence of UTF32 characters.

The three-arg constructor of this class takes the start and end of the underlying sequence as well as the position to start iteration from. This constructor validates that the underlying sequence has validly encoded endpoints: this prevents accidently incrementing/decrementing past the end of the underlying sequence as a result of invalid UTF8 code sequences at the endpoints of the underlying range.

    template <class BaseIterator>
    class utf16_output_iterator
    {
       utf16_output_iterator(const BaseIterator& b);
       utf16_output_iterator(const utf16_output_iterator& that);
       utf16_output_iterator& operator=(const utf16_output_iterator& that);

       // Other standard OutputIterator members here...
    };

Simple OutputIterator adapter - accepts UTF32 values as input, and forwards them to BaseIterator b as UTF16. Both UTF32 and UTF16 values are in native byte order.

    template <class BaseIterator>
    class utf8_output_iterator
    {
       utf8_output_iterator(const BaseIterator& b);
       utf8_output_iterator(const utf8_output_iterator& that);
       utf8_output_iterator& operator=(const utf8_output_iterator& that);

       // Other standard OutputIterator members here...
    };

Simple OutputIterator adapter - accepts UTF32 values as input, and forwards them to BaseIterator b as UTF8. The UTF32 input values must be in native byte order.