214 lines
8.6 KiB
C++
214 lines
8.6 KiB
C++
// This file is part of the uSTL library, an STL implementation.
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//
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// Copyright (c) 2005 by Mike Sharov <msharov@users.sourceforge.net>
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// This file is free software, distributed under the MIT License.
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//
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// This file contains stream iterators that read and write UTF-8 encoded
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// characters. The encoding is defined as follows:
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//
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// U-00000000 - U-0000007F: 0xxxxxxx
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// U-00000080 - U-000007FF: 110xxxxx 10xxxxxx
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// U-00000800 - U-0000FFFF: 1110xxxx 10xxxxxx 10xxxxxx
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// U-00010000 - U-001FFFFF: 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
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// U-00200000 - U-03FFFFFF: 111110xx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
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// U-04000000 - U-7FFFFFFF: 1111110x 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
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// U-80000000 - U-FFFFFFFF: 11111110 100000xx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
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#pragma once
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#include "uiterator.h"
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namespace ustl {
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//----------------------------------------------------------------------
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typedef uint8_t utf8subchar_t; ///< Type for the encoding subcharacters.
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//----------------------------------------------------------------------
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inline size_t Utf8Bytes (wchar_t v) __attribute__((const));
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inline size_t Utf8Bytes (const wchar_t* first, const wchar_t* last) __attribute__((pure));
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inline size_t Utf8SequenceBytes (wchar_t c) __attribute__((const));
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//----------------------------------------------------------------------
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/// Returns the number of bytes required to UTF-8 encode \p v.
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inline size_t Utf8Bytes (wchar_t v)
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{
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if (uint32_t(v) < 128)
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return 1;
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size_t n;
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#if __x86__
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uint32_t r = 0;
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asm ("bsr\t%2, %%eax\n\t"
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"add\t$4, %0\n\t"
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"div\t%3":"=a"(n),"+d"(r):"r"(v),"c"(5));
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#else
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static const uint32_t c_Bounds[7] = { 0x0000007F, 0x000007FF, 0x0000FFFF, 0x001FFFFF, 0x03FFFFFF, 0x7FFFFFFF, 0xFFFFFFFF };
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for (n = 0; c_Bounds[n++] < uint32_t(v););
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#endif
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return n;
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}
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/// Measures the size of a wchar_t array in UTF-8 encoding.
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inline size_t Utf8Bytes (const wchar_t* first, const wchar_t* last)
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{
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size_t bc = 0;
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for (; first < last; ++first)
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bc += Utf8Bytes(*first);
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return bc;
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}
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/// Returns the number of bytes in a UTF-8 sequence that starts with \p c.
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inline size_t Utf8SequenceBytes (wchar_t c) // a wchar_t to keep c in a full register
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{
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// Count the leading bits. Header bits are 1 * nBytes followed by a 0.
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// 0 - single byte character. Take 7 bits (0xFF >> 1)
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// 1 - error, in the middle of the character. Take 6 bits (0xFF >> 2)
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// so you will keep reading invalid entries until you hit the next character.
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// >2 - multibyte character. Take remaining bits, and get the next bytes.
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// All errors are ignored, since the user can not correct them.
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//
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wchar_t mask = 0x80;
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size_t nBytes = 0;
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for (; c & mask; ++nBytes)
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mask >>= 1;
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return nBytes ? nBytes : 1; // A sequence is always at least 1 byte.
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}
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//----------------------------------------------------------------------
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/// \class utf8in_iterator utf8.h ustl.h
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/// \ingroup IteratorAdaptors
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///
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/// \brief An iterator adaptor to character containers for reading UTF-8 encoded text.
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///
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/// For example, you can copy from ustl::string to ustl::vector<wchar_t> with
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/// copy (utf8in (str.begin()), utf8in (str.end()), back_inserter(wvect));
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/// There is no error handling; if the reading frame slips you'll get extra
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/// characters, one for every misaligned byte. Although it is possible to skip
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/// to the start of the next character, that would result in omitting the
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/// misformatted character and the one after it, making it very difficult to
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/// detect by the user. It is better to write some strange characters and let
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/// the user know his file is corrupted. Another problem is overflow on bad
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/// encodings (like a 0xFF on the end of a string). This is checked through
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/// the end-of-string nul character, which will always be there as long as
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/// you are using the string class.
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///
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template <typename Iterator, typename WChar = wchar_t>
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class utf8in_iterator {
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public:
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typedef typename iterator_traits<Iterator>::value_type value_type;
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typedef typename iterator_traits<Iterator>::difference_type difference_type;
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typedef typename iterator_traits<Iterator>::pointer pointer;
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typedef typename iterator_traits<Iterator>::reference reference;
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typedef input_iterator_tag iterator_category;
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public:
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explicit utf8in_iterator (const Iterator& is) : _i (is), _v (0) { Read(); }
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utf8in_iterator (const utf8in_iterator& i) : _i (i._i), _v (i._v) {}
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inline const utf8in_iterator& operator= (const utf8in_iterator& i) { _i = i._i; _v = i._v; return *this; }
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inline Iterator base (void) const { return _i - (Utf8Bytes(_v) - 1); }
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/// Reads and returns the next value.
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inline WChar operator* (void) const { return _v; }
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inline utf8in_iterator& operator++ (void) { ++_i; Read(); return *this; }
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inline utf8in_iterator operator++ (int) { utf8in_iterator old (*this); operator++(); return old; }
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inline utf8in_iterator& operator+= (uoff_t n) { while (n--) operator++(); return *this; }
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inline utf8in_iterator operator+ (uoff_t n) { utf8in_iterator v (*this); return v += n; }
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inline bool operator== (const utf8in_iterator& i) const { return _i == i._i; }
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inline bool operator< (const utf8in_iterator& i) const { return _i < i._i; }
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difference_type operator- (const utf8in_iterator& i) const;
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private:
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void Read (void);
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private:
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Iterator _i;
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WChar _v;
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};
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/// Steps to the next character and updates current returnable value.
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template <typename Iterator, typename WChar>
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void utf8in_iterator<Iterator,WChar>::Read (void)
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{
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const utf8subchar_t c = *_i;
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size_t nBytes = Utf8SequenceBytes (c);
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_v = c & (0xFF >> nBytes); // First byte contains bits after the header.
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while (--nBytes && *++_i) // Each subsequent byte has 6 bits.
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_v = (_v << 6) | (*_i & 0x3F);
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}
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/// Returns the distance in characters (as opposed to the distance in bytes).
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template <typename Iterator, typename WChar>
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typename utf8in_iterator<Iterator,WChar>::difference_type
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utf8in_iterator<Iterator,WChar>::operator- (const utf8in_iterator<Iterator,WChar>& last) const
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{
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difference_type dist = 0;
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for (Iterator first (last._i); first < _i; ++dist)
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first = advance (first, Utf8SequenceBytes (*first));
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return dist;
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}
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//----------------------------------------------------------------------
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/// \class utf8out_iterator utf8.h ustl.h
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/// \ingroup IteratorAdaptors
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///
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/// \brief An iterator adaptor to character containers for writing UTF-8 encoded text.
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///
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template <typename Iterator, typename WChar = wchar_t>
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class utf8out_iterator {
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public:
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typedef typename iterator_traits<Iterator>::value_type value_type;
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typedef typename iterator_traits<Iterator>::difference_type difference_type;
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typedef typename iterator_traits<Iterator>::pointer pointer;
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typedef typename iterator_traits<Iterator>::reference reference;
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typedef output_iterator_tag iterator_category;
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public:
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explicit utf8out_iterator (const Iterator& os) : _i (os) {}
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utf8out_iterator (const utf8out_iterator& i) : _i (i._i) {}
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inline const Iterator& base (void) const { return _i; }
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/// Writes \p v into the stream.
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utf8out_iterator& operator= (WChar v);
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inline utf8out_iterator& operator* (void) { return *this; }
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inline utf8out_iterator& operator++ (void) { return *this; }
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inline utf8out_iterator& operator++ (int) { return *this; }
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inline bool operator== (const utf8out_iterator& i) const { return _i == i._i; }
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inline bool operator< (const utf8out_iterator& i) const { return _i < i._i; }
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private:
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Iterator _i;
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};
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/// Writes \p v into the stream.
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template <typename Iterator, typename WChar>
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utf8out_iterator<Iterator,WChar>& utf8out_iterator<Iterator,WChar>::operator= (WChar v)
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{
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const size_t nBytes = Utf8Bytes (v);
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if (nBytes > 1) {
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// Write the bits 6 bits at a time, except for the first one,
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// which may be less than 6 bits.
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wchar_t shift = nBytes * 6;
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*_i++ = ((v >> (shift -= 6)) & 0x3F) | (0xFF << (8 - nBytes));
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while (shift)
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*_i++ = ((v >> (shift -= 6)) & 0x3F) | 0x80;
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} else // If only one byte, there is no header.
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*_i++ = v;
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return *this;
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}
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//----------------------------------------------------------------------
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/// Returns a UTF-8 adaptor writing to \p i. Useful in conjuction with back_insert_iterator.
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template <typename Iterator>
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inline utf8out_iterator<Iterator> utf8out (Iterator i)
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{
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return utf8out_iterator<Iterator> (i);
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}
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/// Returns a UTF-8 adaptor reading from \p i.
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template <typename Iterator>
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inline utf8in_iterator<Iterator> utf8in (Iterator i)
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{
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return utf8in_iterator<Iterator> (i);
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}
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//----------------------------------------------------------------------
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} // namespace ustl
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