src/arith_uint256.cpp

   1 // Copyright (c) 2009-2010 Satoshi Nakamoto
   2 // Copyright (c) 2009-2016 The Bitcoin Core developers
   3 // Distributed under the MIT software license, see the accompanying
   4 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
   5
   6 #include "arith_uint256.h"
   7
   8 #include "uint256.h"
   9 #include "utilstrencodings.h"
  10 #include "crypto/common.h"
  11
  12 #include <stdio.h>
  13 #include <string.h>
  14
  15 template <unsigned int BITS>
  16 base_uint<BITS>::base_uint(const std::string& str)
  17 {
  18     SetHex(str);
  19 }
  20
  21 template <unsigned int BITS>
  22 base_uint<BITS>& base_uint<BITS>::operator<<=(unsigned int shift)
  23 {
  24     base_uint<BITS> a(*this);
  25     for (int i = 0; i < WIDTH; i++)
  26         pn[i] = 0;
  27     int k = shift / 32;
  28     shift = shift % 32;
  29     for (int i = 0; i < WIDTH; i++) {
  30         if (i + k + 1 < WIDTH && shift != 0)
  31             pn[i + k + 1] |= (a.pn[i] >> (32 - shift));
  32         if (i + k < WIDTH)
  33             pn[i + k] |= (a.pn[i] << shift);
  34     }
  35     return *this;
  36 }
  37
  38 template <unsigned int BITS>
  39 base_uint<BITS>& base_uint<BITS>::operator>>=(unsigned int shift)
  40 {
  41     base_uint<BITS> a(*this);
  42     for (int i = 0; i < WIDTH; i++)
  43         pn[i] = 0;
  44     int k = shift / 32;
  45     shift = shift % 32;
  46     for (int i = 0; i < WIDTH; i++) {
  47         if (i - k - 1 >= 0 && shift != 0)
  48             pn[i - k - 1] |= (a.pn[i] << (32 - shift));
  49         if (i - k >= 0)
  50             pn[i - k] |= (a.pn[i] >> shift);
  51     }
  52     return *this;
  53 }
  54
  55 template <unsigned int BITS>
  56 base_uint<BITS>& base_uint<BITS>::operator*=(uint32_t b32)
  57 {
  58     uint64_t carry = 0;
  59     for (int i = 0; i < WIDTH; i++) {
  60         uint64_t n = carry + (uint64_t)b32 * pn[i];
  61         pn[i] = n & 0xffffffff;
  62         carry = n >> 32;
  63     }
  64     return *this;
  65 }
  66
  67 template <unsigned int BITS>
  68 base_uint<BITS>& base_uint<BITS>::operator*=(const base_uint& b)
  69 {
  70     base_uint<BITS> a = *this;
  71     *this = 0;
  72     for (int j = 0; j < WIDTH; j++) {
  73         uint64_t carry = 0;
  74         for (int i = 0; i + j < WIDTH; i++) {
  75             uint64_t n = carry + pn[i + j] + (uint64_t)a.pn[j] * b.pn[i];
  76             pn[i + j] = n & 0xffffffff;
  77             carry = n >> 32;
  78         }
  79     }
  80     return *this;
  81 }
  82
  83 template <unsigned int BITS>
  84 base_uint<BITS>& base_uint<BITS>::operator/=(const base_uint& b)
  85 {
  86     base_uint<BITS> div = b;     // make a copy, so we can shift.
  87     base_uint<BITS> num = *this; // make a copy, so we can subtract.
  88     *this = 0;                   // the quotient.
  89     int num_bits = num.bits();
  90     int div_bits = div.bits();
  91     if (div_bits == 0)
  92         throw uint_error("Division by zero");
  93     if (div_bits > num_bits) // the result is certainly 0.
  94         return *this;
  95     int shift = num_bits - div_bits;
  96     div <<= shift; // shift so that div and num align.
  97     while (shift >= 0) {
  98         if (num >= div) {
  99             num -= div;
 100             pn[shift / 32] |= (1 << (shift & 31)); // set a bit of the result.
 101         }
 102         div >>= 1; // shift back.
 103         shift--;
 104     }
 105     // num now contains the remainder of the division.
 106     return *this;
 107 }
 108
 109 template <unsigned int BITS>
 110 int base_uint<BITS>::CompareTo(const base_uint<BITS>& b) const
 111 {
 112     for (int i = WIDTH - 1; i >= 0; i--) {
 113         if (pn[i] < b.pn[i])
 114             return -1;
 115         if (pn[i] > b.pn[i])
 116             return 1;
 117     }
 118     return 0;
 119 }
 120
 121 template <unsigned int BITS>
 122 bool base_uint<BITS>::EqualTo(uint64_t b) const
 123 {
 124     for (int i = WIDTH - 1; i >= 2; i--) {
 125         if (pn[i])
 126             return false;
 127     }
 128     if (pn[1] != (b >> 32))
 129         return false;
 130     if (pn[0] != (b & 0xfffffffful))
 131         return false;
 132     return true;
 133 }
 134
 135 template <unsigned int BITS>
 136 double base_uint<BITS>::getdouble() const
 137 {
 138     double ret = 0.0;
 139     double fact = 1.0;
 140     for (int i = 0; i < WIDTH; i++) {
 141         ret += fact * pn[i];
 142         fact *= 4294967296.0;
 143     }
 144     return ret;
 145 }
 146
 147 template <unsigned int BITS>
 148 std::string base_uint<BITS>::GetHex() const
 149 {
 150     return ArithToUint256(*this).GetHex();
 151 }
 152
 153 template <unsigned int BITS>
 154 void base_uint<BITS>::SetHex(const char* psz)
 155 {
 156     *this = UintToArith256(uint256S(psz));
 157 }
 158
 159 template <unsigned int BITS>
 160 void base_uint<BITS>::SetHex(const std::string& str)
 161 {
 162     SetHex(str.c_str());
 163 }
 164
 165 template <unsigned int BITS>
 166 std::string base_uint<BITS>::ToString() const
 167 {
 168     return (GetHex());
 169 }
 170
 171 template <unsigned int BITS>
 172 unsigned int base_uint<BITS>::bits() const
 173 {
 174     for (int pos = WIDTH - 1; pos >= 0; pos--) {
 175         if (pn[pos]) {
 176             for (int nbits = 31; nbits > 0; nbits--) {
 177                 if (pn[pos] & 1 << nbits)
 178                     return 32 * pos + nbits + 1;
 179             }
 180             return 32 * pos + 1;
 181         }
 182     }
 183     return 0;
 184 }
 185
 186 // Explicit instantiations for base_uint<256>
 187 template base_uint<256>::base_uint(const std::string&);
 188 template base_uint<256>& base_uint<256>::operator<<=(unsigned int);
 189 template base_uint<256>& base_uint<256>::operator>>=(unsigned int);
 190 template base_uint<256>& base_uint<256>::operator*=(uint32_t b32);
 191 template base_uint<256>& base_uint<256>::operator*=(const base_uint<256>& b);
 192 template base_uint<256>& base_uint<256>::operator/=(const base_uint<256>& b);
 193 template int base_uint<256>::CompareTo(const base_uint<256>&) const;
 194 template bool base_uint<256>::EqualTo(uint64_t) const;
 195 template double base_uint<256>::getdouble() const;
 196 template std::string base_uint<256>::GetHex() const;
 197 template std::string base_uint<256>::ToString() const;
 198 template void base_uint<256>::SetHex(const char*);
 199 template void base_uint<256>::SetHex(const std::string&);
 200 template unsigned int base_uint<256>::bits() const;
 201
 202 // This implementation directly uses shifts instead of going
 203 // through an intermediate MPI representation.
 204 arith_uint256& arith_uint256::SetCompact(uint32_t nCompact, bool* pfNegative, bool* pfOverflow)
 205 {
 206     int nSize = nCompact >> 24;
 207     uint32_t nWord = nCompact & 0x007fffff;
 208     if (nSize <= 3) {
 209         nWord >>= 8 * (3 - nSize);
 210         *this = nWord;
 211     } else {
 212         *this = nWord;
 213         *this <<= 8 * (nSize - 3);
 214     }
 215     if (pfNegative)
 216         *pfNegative = nWord != 0 && (nCompact & 0x00800000) != 0;
 217     if (pfOverflow)
 218         *pfOverflow = nWord != 0 && ((nSize > 34) ||
 219                                      (nWord > 0xff && nSize > 33) ||
 220                                      (nWord > 0xffff && nSize > 32));
 221     return *this;
 222 }
 223
 224 uint32_t arith_uint256::GetCompact(bool fNegative) const
 225 {
 226     int nSize = (bits() + 7) / 8;
 227     uint32_t nCompact = 0;
 228     if (nSize <= 3) {
 229         nCompact = GetLow64() << 8 * (3 - nSize);
 230     } else {
 231         arith_uint256 bn = *this >> 8 * (nSize - 3);
 232         nCompact = bn.GetLow64();
 233     }
 234     // The 0x00800000 bit denotes the sign.
 235     // Thus, if it is already set, divide the mantissa by 256 and increase the exponent.
 236     if (nCompact & 0x00800000) {
 237         nCompact >>= 8;
 238         nSize++;
 239     }
 240     assert((nCompact & ~0x007fffff) == 0);
 241     assert(nSize < 256);
 242     nCompact |= nSize << 24;
 243     nCompact |= (fNegative && (nCompact & 0x007fffff) ? 0x00800000 : 0);
 244     return nCompact;
 245 }
 246
 247 uint256 ArithToUint256(const arith_uint256 &a)
 248 {
 249     uint256 b;
 250     for(int x=0; x<a.WIDTH; ++x)
 251         WriteLE32(b.begin() + x*4, a.pn[x]);
 252     return b;
 253 }
 254 arith_uint256 UintToArith256(const uint256 &a)
 255 {
 256     arith_uint256 b;
 257     for(int x=0; x<b.WIDTH; ++x)
 258         b.pn[x] = ReadLE32(a.begin() + x*4);
 259     return b;
 260 }