uint128_t 添加 c++ 重载类型强制转换

实现函数：

  1 uint128::uint128(const std::string &sz)
  2    :hi(0),lo(0)
  3 {
  4    // do we have at least one character?
  5    if (!sz.empty()) {
  6       // make some reasonable assumptions
  7       int radix = 10;
  8       bool minus = false;
  9 
 10       std::string::const_iterator i = sz.begin();
 11 
 12       // check for minus sign,i suppose technically this should only apply
 13       // to base 10,but who says that -0x1 should be invalid?
 14       if (*i == ‘-‘) {
 15          ++i;
 16          minus = true;
 17       }
 18 
 19       // check if there is radix changing prefix (0 or 0x)
 20       if (i != sz.end()) {
 21          if (*i == ‘0‘) {
 22             radix = 8;
 23             ++i;
 24             if (i != sz.end()) {
 25                if (*i == ‘x‘) {
 26                   radix = 16;
 27                   ++i;
 28                }
 29             }
 30          }
 31 
 32          while (i != sz.end()) {
 33             unsigned int n = 0;
 34             const char ch = *i;
 35 
 36             if (ch >= ‘A‘ && ch <= ‘Z‘) {
 37                if (((ch - ‘A‘) + 10) < radix) {
 38                   n = (ch - ‘A‘) + 10;
 39                }
 40                else {
 41                   break;
 42                }
 43             }
 44             else if (ch >= ‘a‘ && ch <= ‘z‘) {
 45                if (((ch - ‘a‘) + 10) < radix) {
 46                   n = (ch - ‘a‘) + 10;
 47                }
 48                else {
 49                   break;
 50                }
 51             }
 52             else if (ch >= ‘0‘ && ch <= ‘9‘) {
 53                if ((ch - ‘0‘) < radix) {
 54                   n = (ch - ‘0‘);
 55                }
 56                else {
 57                   break;
 58                }
 59             }
 60             else {
 61                /* completely invalid character */
 62                break;
 63             }
 64 
 65             (*this) *= radix;
 66             (*this) += n;
 67 
 68             ++i;
 69          }
 70       }
 71 
 72       if (minus) {
 73          *this = -*this;
 74       }
 75    }
 76 }
 77 
 78 uint128& uint128::operator<<=(const uint128& rhs)
 79 {
 80    if (rhs >= 128)
 81    {
 82       hi = 0;
 83       lo = 0;
 84    }
 85    else
 86    {
 87       unsigned int n = rhs.to_integer();
 88       const unsigned int halfsize = 128 / 2;
 89 
 90       if (n >= halfsize){
 91          n -= halfsize;
 92          hi = lo;
 93          lo = 0;
 94       }
 95 
 96       if (n != 0) {
 97          // shift high half
 98          hi <<= n;
 99 
100          const uint64_t mask(~(uint64_t(-1) >> n));
101 
102          // and add them to high half
103          hi |= (lo & mask) >> (halfsize - n);
104 
105          // and finally shift also low half
106          lo <<= n;
107       }
108    }
109 
110    return *this;
111 }
112 
113 uint128 & uint128::operator>>=(const uint128& rhs)
114 {
115    if (rhs >= 128)
116    {
117       hi = 0;
118       lo = 0;
119    }
120    else
121    {
122       unsigned int n = rhs.to_integer();
123       const unsigned int halfsize = 128 / 2;
124 
125       if (n >= halfsize) {
126          n -= halfsize;
127          lo = hi;
128          hi = 0;
129       }
130 
131       if (n != 0) {
132          // shift low half
133          lo >>= n;
134 
135          // get lower N bits of high half
136          const uint64_t mask(~(uint64_t(-1) << n));
137 
138          // and add them to low qword
139          lo |= (hi & mask) << (halfsize - n);
140 
141          // and finally shift also high half
142          hi >>= n;
143       }
144    }
145    return *this;
146 }
147 
148 uint128& uint128::operator*=(const uint128 &b)
149 {
150    uint64_t a0 = (uint32_t)(this->lo);
151    uint64_t a1 = (uint32_t)(this->lo >> 0x20);
152    uint64_t a2 = (uint32_t)(this->hi);
153    uint64_t a3 = (uint32_t)(this->hi >> 0x20);
154 
155    uint64_t b0 = (uint32_t)(b.lo);
156    uint64_t b1 = (uint32_t)(b.lo >> 0x20);
157    uint64_t b2 = (uint32_t)(b.hi);
158    uint64_t b3 = (uint32_t)(b.hi >> 0x20);
159 
160 
161    this->hi = 0;
162    this->lo = a3*b0;
163    (*this) += a2*b1;
164    (*this) += a1*b2;
165    (*this) += a0*b3;
166    (*this) <<= 0x20;
167    (*this) += a2*b0;
168    (*this) += a1*b1;
169    (*this) += a0*b2;
170    (*this) <<= 0x20;
171    (*this) += a1*b0;
172    (*this) += a0*b1;
173    (*this) <<= 0x20;
174    (*this) += a0*b0;
175 
176    return *this;
177 }

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