1#ifndef BOOST_ARCHIVE_ITERATORS_TRANSFORM_WIDTH_HPP
2#define BOOST_ARCHIVE_ITERATORS_TRANSFORM_WIDTH_HPP
3
4// MS compatible compilers support #pragma once
5#if defined(_MSC_VER)
6# pragma once
7#endif
8
9/////////1/////////2/////////3/////////4/////////5/////////6/////////7/////////8
10// transform_width.hpp
11
12// (C) Copyright 2002 Robert Ramey - http://www.rrsd.com .
13// Use, modification and distribution is subject to the Boost Software
14// License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
15// http://www.boost.org/LICENSE_1_0.txt)
16
17// See http://www.boost.org for updates, documentation, and revision history.
18
19// iterator which takes elements of x bits and returns elements of y bits.
20// used to change streams of 8 bit characters into streams of 6 bit characters.
21// and vice-versa for implementing base64 encodeing/decoding. Be very careful
22// when using and end iterator. end is only reliable detected when the input
23// stream length is some common multiple of x and y. E.G. Base64 6 bit
24// character and 8 bit bytes. Lowest common multiple is 24 => 4 6 bit characters
25// or 3 8 bit characters
26
27#include <boost/iterator/iterator_adaptor.hpp>
28#include <boost/iterator/iterator_traits.hpp>
29
30#include <algorithm> // std::min
31
32namespace boost {
33namespace archive {
34namespace iterators {
35
36/////////1/////////2/////////3/////////4/////////5/////////6/////////7/////////8
37// class used by text archives to translate char strings to wchar_t
38// strings of the currently selected locale
39template<
40 class Base,
41 int BitsOut,
42 int BitsIn,
43 class CharType = typename boost::iterator_value<Base>::type // output character
44>
45class transform_width :
46 public boost::iterator_adaptor<
47 transform_width<Base, BitsOut, BitsIn, CharType>,
48 Base,
49 CharType,
50 single_pass_traversal_tag,
51 CharType
52 >
53{
54 friend class boost::iterator_core_access;
55 typedef typename boost::iterator_adaptor<
56 transform_width<Base, BitsOut, BitsIn, CharType>,
57 Base,
58 CharType,
59 single_pass_traversal_tag,
60 CharType
61 > super_t;
62
63 typedef transform_width<Base, BitsOut, BitsIn, CharType> this_t;
64 typedef typename iterator_value<Base>::type base_value_type;
65
66 void fill();
67
68 CharType dereference() const {
69 if(!m_buffer_out_full)
70 const_cast<this_t *>(this)->fill();
71 return m_buffer_out;
72 }
73
74 bool equal_impl(const this_t & rhs){
75 if(BitsIn < BitsOut) // discard any left over bits
76 return this->base_reference() == rhs.base_reference();
77 else{
78 // BitsIn > BitsOut // zero fill
79 if(this->base_reference() == rhs.base_reference()){
80 m_end_of_sequence = true;
81 return 0 == m_remaining_bits;
82 }
83 return false;
84 }
85 }
86
87 // standard iterator interface
88 bool equal(const this_t & rhs) const {
89 return const_cast<this_t *>(this)->equal_impl(rhs);
90 }
91
92 void increment(){
93 m_buffer_out_full = false;
94 }
95
96 bool m_buffer_out_full;
97 CharType m_buffer_out;
98
99 // last read element from input
100 base_value_type m_buffer_in;
101
102 // number of bits to left in the input buffer.
103 unsigned int m_remaining_bits;
104
105 // flag to indicate we've reached end of data.
106 bool m_end_of_sequence;
107
108public:
109 // make composable by using templated constructor
110 template<class T>
111 transform_width(T start) :
112 super_t(Base(static_cast< T >(start))),
113 m_buffer_out_full(false),
114 m_buffer_out(0),
115 // To disable GCC warning, but not truly necessary
116 //(m_buffer_in will be initialized later before being
117 //used because m_remaining_bits == 0)
118 m_buffer_in(0),
119 m_remaining_bits(0),
120 m_end_of_sequence(false)
121 {}
122 // intel 7.1 doesn't like default copy constructor
123 transform_width(const transform_width & rhs) :
124 super_t(rhs.base_reference()),
125 m_buffer_out_full(rhs.m_buffer_out_full),
126 m_buffer_out(rhs.m_buffer_out),
127 m_buffer_in(rhs.m_buffer_in),
128 m_remaining_bits(rhs.m_remaining_bits),
129 m_end_of_sequence(false)
130 {}
131};
132
133template<
134 class Base,
135 int BitsOut,
136 int BitsIn,
137 class CharType
138>
139void transform_width<Base, BitsOut, BitsIn, CharType>::fill() {
140 unsigned int missing_bits = BitsOut;
141 m_buffer_out = 0;
142 do{
143 if(0 == m_remaining_bits){
144 if(m_end_of_sequence){
145 m_buffer_in = 0;
146 m_remaining_bits = missing_bits;
147 }
148 else{
149 m_buffer_in = * this->base_reference()++;
150 m_remaining_bits = BitsIn;
151 }
152 }
153
154 // append these bits to the next output
155 // up to the size of the output
156 unsigned int i = (std::min)(a: missing_bits, b: m_remaining_bits);
157 // shift interesting bits to least significant position
158 base_value_type j = m_buffer_in >> (m_remaining_bits - i);
159 // and mask off the un interesting higher bits
160 // note presumption of twos complement notation
161 j &= (1 << i) - 1;
162 // append then interesting bits to the output value
163 m_buffer_out <<= i;
164 m_buffer_out |= j;
165
166 // and update counters
167 missing_bits -= i;
168 m_remaining_bits -= i;
169 }while(0 < missing_bits);
170 m_buffer_out_full = true;
171}
172
173} // namespace iterators
174} // namespace archive
175} // namespace boost
176
177#endif // BOOST_ARCHIVE_ITERATORS_TRANSFORM_WIDTH_HPP
178

source code of boost/libs/serialization/include/boost/archive/iterators/transform_width.hpp