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1// Copyright (C) 2004 Arkadiy Vertleyb
2// Use, modification and distribution is subject to the Boost Software
3// License, Version 1.0. (http://www.boost.org/LICENSE_1_0.txt)
4
5#ifndef BOOST_TYPEOF_INT_ENCODING_HPP_INCLUDED
6#define BOOST_TYPEOF_INT_ENCODING_HPP_INCLUDED
7
8#include <boost/mpl/if.hpp>
9#include <boost/mpl/size_t.hpp>
10#include <boost/config.hpp>
11
12namespace boost { namespace type_of {
13
14 template<class T> struct get_unsigned
15 {
16 typedef T type;
17 };
18 template<> struct get_unsigned<signed char>
19 {
20 typedef unsigned char type;
21 };
22 template<> struct get_unsigned<char>
23 {
24 typedef unsigned char type;
25 };
26 template<> struct get_unsigned<short>
27 {
28 typedef unsigned short type;
29 };
30 template<> struct get_unsigned<int>
31 {
32 typedef unsigned int type;
33 };
34 template<> struct get_unsigned<long>
35 {
36 typedef unsigned long type;
37 };
38
39 //////////////////////////
40
41 template<std::size_t n, bool Overflow>
42 struct pack
43 {
44 BOOST_STATIC_CONSTANT(std::size_t , value=((n + 1) * 2 + (Overflow ? 1 : 0)));
45 };
46
47 template<std::size_t m>
48 struct unpack
49 {
50 BOOST_STATIC_CONSTANT(std::size_t, value = (m / 2) - 1);
51 BOOST_STATIC_CONSTANT(std::size_t, overflow = (m % 2 == 1));
52 };
53
54 ////////////////////////////////
55
56 template<class V, std::size_t n, bool overflow = (n >= 0x3fffffff)>
57 struct encode_size_t : push_back<
58 V,
59 boost::mpl::size_t<pack<n, false>::value>
60 >
61 {};
62
63 template<class V, std::size_t n>
64 struct encode_size_t<V, n, true> : push_back<typename push_back<
65 V,
66 boost::mpl::size_t<pack<n % 0x3ffffffe, true>::value> >::type,
67 boost::mpl::size_t<n / 0x3ffffffe>
68 >
69 {};
70
71 template<class V, class T, T n>
72 struct encode_integral : encode_size_t< V, (typename get_unsigned<T>::type)n,(((typename get_unsigned<T>::type)n)>=0x3fffffff) >
73 {};
74
75 template<class V, bool b>
76 struct encode_integral<V, bool, b> : encode_size_t< V, b?1:0, false>
77 {};
78 ///////////////////////////
79
80 template<std::size_t n, class Iter, bool overflow>
81 struct decode_size_t;
82
83 template<std::size_t n, class Iter>
84 struct decode_size_t<n, Iter, false>
85 {
86 BOOST_STATIC_CONSTANT(std::size_t,value = n);
87 typedef Iter iter;
88 };
89
90 template<std::size_t n, class Iter>
91 struct decode_size_t<n, Iter, true>
92 {
93 BOOST_STATIC_CONSTANT(std::size_t,m = Iter::type::value);
94
95 BOOST_STATIC_CONSTANT(std::size_t,value = (std::size_t)m * 0x3ffffffe + n);
96 typedef typename Iter::next iter;
97 };
98
99 template<class T, class Iter>
100 struct decode_integral
101 {
102 typedef decode_integral<T,Iter> self_t;
103 BOOST_STATIC_CONSTANT(std::size_t,m = Iter::type::value);
104
105 BOOST_STATIC_CONSTANT(std::size_t,n = unpack<m>::value);
106
107 BOOST_STATIC_CONSTANT(std::size_t,overflow = unpack<m>::overflow);
108
109 typedef typename Iter::next nextpos;
110
111 static const T value = (T)(std::size_t)decode_size_t<n, nextpos, overflow>::value;
112
113 typedef typename decode_size_t<self_t::n, nextpos, self_t::overflow>::iter iter;
114 };
115
116}}//namespace
117
118#endif//BOOST_TYPEOF_INT_ENCODING_HPP_INCLUDED