92 lines
2.6 KiB
C++
92 lines
2.6 KiB
C++
/* This file provides a variant of std::istringstream that doesn't
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copy its string argument. This is useful for large strings. The
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caller must ensure that the string object is not destroyed while
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it's referenced by this object. */
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#pragma once
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#include <string>
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#include <iostream>
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template <class CharT, class Traits = std::char_traits<CharT>, class Allocator = std::allocator<CharT>>
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class basic_istringbuf_nocopy : public std::basic_streambuf<CharT, Traits>
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{
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public:
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typedef std::basic_string<CharT, Traits, Allocator> string_type;
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typedef typename std::basic_streambuf<CharT, Traits>::off_type off_type;
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typedef typename std::basic_streambuf<CharT, Traits>::pos_type pos_type;
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typedef typename std::basic_streambuf<CharT, Traits>::int_type int_type;
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typedef typename std::basic_streambuf<CharT, Traits>::traits_type traits_type;
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private:
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const string_type & s;
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off_type off;
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public:
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basic_istringbuf_nocopy(const string_type & s) : s{s}, off{0}
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{
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}
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private:
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pos_type seekoff(off_type off, std::ios_base::seekdir dir, std::ios_base::openmode which)
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{
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if (which & std::ios_base::in) {
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this->off = dir == std::ios_base::beg
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? off
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: (dir == std::ios_base::end
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? s.size() + off
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: this->off + off);
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}
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return pos_type(this->off);
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}
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pos_type seekpos(pos_type pos, std::ios_base::openmode which)
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{
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return seekoff(pos, std::ios_base::beg, which);
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}
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std::streamsize showmanyc()
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{
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return s.size() - off;
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}
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int_type underflow()
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{
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if (typename string_type::size_type(off) == s.size())
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return traits_type::eof();
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return traits_type::to_int_type(s[off]);
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}
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int_type uflow()
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{
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if (typename string_type::size_type(off) == s.size())
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return traits_type::eof();
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return traits_type::to_int_type(s[off++]);
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}
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int_type pbackfail(int_type ch)
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{
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if (off == 0 || (ch != traits_type::eof() && ch != s[off - 1]))
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return traits_type::eof();
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return traits_type::to_int_type(s[--off]);
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}
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};
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template <class CharT, class Traits = std::char_traits<CharT>, class Allocator = std::allocator<CharT>>
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class basic_istringstream_nocopy : public std::basic_iostream<CharT, Traits>
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{
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typedef basic_istringbuf_nocopy<CharT, Traits, Allocator> buf_type;
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buf_type buf;
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public:
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basic_istringstream_nocopy(const typename buf_type::string_type & s) :
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std::basic_iostream<CharT, Traits>(&buf), buf(s) {};
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};
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typedef basic_istringstream_nocopy<char> istringstream_nocopy;
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