Bitcoin

src/arith_uint256.cpp

// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2022 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
#include <arith_uint256.h>
#include <uint256.h>
#include <crypto/common.h>
#include <cassert>
template <unsigned int BITS>
base_uint<BITS>& base_uint<BITS>::operator<<=(unsigned int shift)
{
base_uint<BITS> a(*this);
for (int i = 0; i < WIDTH; i++)
pn[i] = 0;
int k = shift / 32;
shift = shift % 32;
for (int i = 0; i < WIDTH; i++) {
if (i + k + 1 < WIDTH && shift != 0)
pn[i + k + 1] |= (a.pn[i] >> (32 - shift));
if (i + k < WIDTH)
pn[i + k] |= (a.pn[i] << shift);
}
return *this;
}
template <unsigned int BITS>
base_uint<BITS>& base_uint<BITS>::operator>>=(unsigned int shift)
{
base_uint<BITS> a(*this);
for (int i = 0; i < WIDTH; i++)
pn[i] = 0;
int k = shift / 32;
shift = shift % 32;
for (int i = 0; i < WIDTH; i++) {
if (i - k - 1 >= 0 && shift != 0)
pn[i - k - 1] |= (a.pn[i] << (32 - shift));
if (i - k >= 0)
pn[i - k] |= (a.pn[i] >> shift);
}
return *this;
}
template <unsigned int BITS>
base_uint<BITS>& base_uint<BITS>::operator*=(uint32_t b32)
{
uint64_t carry = 0;
for (int i = 0; i < WIDTH; i++) {
uint64_t n = carry + (uint64_t)b32 * pn[i];
pn[i] = n & 0xffffffff;
carry = n >> 32;
}
return *this;
}
template <unsigned int BITS>
base_uint<BITS>& base_uint<BITS>::operator*=(const base_uint& b)
{
base_uint<BITS> a;
for (int j = 0; j < WIDTH; j++) {
uint64_t carry = 0;
for (int i = 0; i + j < WIDTH; i++) {
uint64_t n = carry + a.pn[i + j] + (uint64_t)pn[j] * b.pn[i];
a.pn[i + j] = n & 0xffffffff;
carry = n >> 32;
}
}
*this = a;
return *this;
}
template <unsigned int BITS>
base_uint<BITS>& base_uint<BITS>::operator/=(const base_uint& b)
{
base_uint<BITS> div = b; // make a copy, so we can shift.
base_uint<BITS> num = *this; // make a copy, so we can subtract.
*this = 0; // the quotient.
int num_bits = num.bits();
int div_bits = div.bits();
if (div_bits == 0)
throw uint_error("Division by zero");
if (div_bits > num_bits) // the result is certainly 0.
return *this;
int shift = num_bits - div_bits;
div <<= shift; // shift so that div and num align.
while (shift >= 0) {
if (num >= div) {
num -= div;
pn[shift / 32] |= (1U << (shift & 31)); // set a bit of the result.
}
div >>= 1; // shift back.
shift--;
}
// num now contains the remainder of the division.
return *this;
}
template <unsigned int BITS>
int base_uint<BITS>::CompareTo(const base_uint<BITS>& b) const
{
for (int i = WIDTH - 1; i >= 0; i--) {
if (pn[i] < b.pn[i])
return -1;
if (pn[i] > b.pn[i])
return 1;
}
return 0;
}
template <unsigned int BITS>
bool base_uint<BITS>::EqualTo(uint64_t b) const
{
for (int i = WIDTH - 1; i >= 2; i--) {
if (pn[i])
return false;
}
if (pn[1] != (b >> 32))
return false;
if (pn[0] != (b & 0xfffffffful))
return false;
return true;
}
template <unsigned int BITS>
double base_uint<BITS>::getdouble() const
{
double ret = 0.0;
double fact = 1.0;
for (int i = 0; i < WIDTH; i++) {
ret += fact * pn[i];
fact *= 4294967296.0;
}
return ret;
}
template <unsigned int BITS>
std::string base_uint<BITS>::GetHex() const
{
base_blob<BITS> b;
for (int x = 0; x < this->WIDTH; ++x) {
WriteLE32(b.begin() + x*4, this->pn[x]);
}
return b.GetHex();
}
template <unsigned int BITS>
std::string base_uint<BITS>::ToString() const
{
return GetHex();
}
template <unsigned int BITS>
unsigned int base_uint<BITS>::bits() const
{
for (int pos = WIDTH - 1; pos >= 0; pos--) {
if (pn[pos]) {
for (int nbits = 31; nbits > 0; nbits--) {
if (pn[pos] & 1U << nbits)
return 32 * pos + nbits + 1;
}
return 32 * pos + 1;
}
}
return 0;
}
// Explicit instantiations for base_uint<256>
template class base_uint<256>;
// This implementation directly uses shifts instead of going
// through an intermediate MPI representation.
arith_uint256& arith_uint256::SetCompact(uint32_t nCompact, bool* pfNegative, bool* pfOverflow)
{
int nSize = nCompact >> 24;
uint32_t nWord = nCompact & 0x007fffff;
if (nSize <= 3) {
nWord >>= 8 * (3 - nSize);
*this = nWord;
} else {
*this = nWord;
*this <<= 8 * (nSize - 3);
}
if (pfNegative)
*pfNegative = nWord != 0 && (nCompact & 0x00800000) != 0;
if (pfOverflow)
*pfOverflow = nWord != 0 && ((nSize > 34) ||
(nWord > 0xff && nSize > 33) ||
(nWord > 0xffff && nSize > 32));
return *this;
}
uint32_t arith_uint256::GetCompact(bool fNegative) const
{
int nSize = (bits() + 7) / 8;
uint32_t nCompact = 0;
if (nSize <= 3) {
nCompact = GetLow64() << 8 * (3 - nSize);
} else {
arith_uint256 bn = *this >> 8 * (nSize - 3);
nCompact = bn.GetLow64();
}
// The 0x00800000 bit denotes the sign.
// Thus, if it is already set, divide the mantissa by 256 and increase the exponent.
if (nCompact & 0x00800000) {
nCompact >>= 8;
nSize++;
}
assert((nCompact & ~0x007fffffU) == 0);
assert(nSize < 256);
nCompact |= nSize << 24;
nCompact |= (fNegative && (nCompact & 0x007fffff) ? 0x00800000 : 0);
return nCompact;
}
uint256 ArithToUint256(const arith_uint256 &a)
{
uint256 b;
for(int x=0; x<a.WIDTH; ++x)
WriteLE32(b.begin() + x*4, a.pn[x]);
return b;
}
arith_uint256 UintToArith256(const uint256 &a)
{
arith_uint256 b;
for(int x=0; x<b.WIDTH; ++x)
b.pn[x] = ReadLE32(a.begin() + x*4);
return b;
}
// Explicit instantiations for base_uint<6144> (used in test/fuzz/muhash.cpp).
template base_uint<6144>& base_uint<6144>::operator*=(const base_uint<6144>& b);
template base_uint<6144>& base_uint<6144>::operator/=(const base_uint<6144>& b);