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/*
* Copyright (c) 2023
* Canonical Ltd. (All rights reserved)
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of version 2 of the GNU General Public
* License published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, contact Canonical Ltd.
*/
#ifndef __AA_BIGNUM_H
#define __AA_BIGNUM_H
#include <iostream>
#include <vector>
#include <sstream>
#include <algorithm>
#include <string>
class bignum
{
public:
std::vector<uint8_t> data;
uint8_t base;
bool negative = false;
bignum () : base(0) {}
bignum (unsigned long val) {
if (val == 0)
data.push_back(val);
else {
while(val > 0) {
data.push_back(val % 10);
val /= 10;
}
}
base = 10;
}
bignum (const char *val) {
while (*val) {
data.push_back(*val - 48);
val++;
}
std::reverse(data.begin(), data.end());
base = 10;
}
bignum (const uint8_t val[16]) {
size_t i;
bool flag = true;
for (i = 0; i < 16; i++) {
if (flag && (val[i] & 0xF0) >> 4 != 0)
flag = false;
if (!flag)
data.push_back((val[i] & 0xF0) >> 4);
if (flag && (val[i] & 0x0F) != 0)
flag = false;
if (!flag)
data.push_back(val[i] & 0x0F);
}
std::reverse(data.begin(), data.end());
base = 16;
}
bignum operator+(const bignum &brhs) const {
bignum b1 = this->size() < brhs.size() ? *this : brhs;
bignum b2 = this->size() < brhs.size() ? brhs : *this;
bignum result;
result.base = this->base;
uint8_t carryover = 0;
uint8_t sum;
size_t i;
for (i = 0; i < b1.size(); i++) {
sum = b1[i] + b2[i] + carryover;
if (sum > base - 1)
carryover = 1;
else
carryover = 0;
result.data.push_back(sum % base);
}
for (; i < b2.size(); i++) {
sum = b2[i] + carryover;
if (sum > base - 1)
carryover = 1;
else
carryover = 0;
result.data.push_back(sum % base);
}
if (carryover != 0)
result.data.push_back(carryover);
return result;
}
bignum operator-(const bignum &brhs) const {
bignum b1 = this->size() < brhs.size() ? *this : brhs;
bignum b2 = this->size() < brhs.size() ? brhs : *this;
bignum result;
result.negative = *this < brhs;
result.base = this->base;
int8_t borrow = 0;
int8_t sub;
size_t i;
for (i = 0; i < b1.size(); i++) {
sub = b2[i] - b1[i] - borrow;
if (sub < 0) {
sub += base;
borrow = 1;
} else
borrow = 0;
result.data.push_back(sub);
}
for (; i < b2.size(); i++) {
sub = b2[i] - borrow;
if (sub < 0) {
sub += base;
borrow = 1;
} else
borrow = 0;
result.data.push_back(sub);
}
if (borrow) {
int8_t tmp = result.data[result.size() - 1] -= base;
tmp *= -1;
result.data[result.size() - 1] = tmp;
}
while (result.size() > 1 && result.data[result.size() - 1] == 0)
result.data.pop_back();
return result;
}
bool operator>=(const bignum &rhs) const {
return cmp_bignum(this->data, rhs.data) >= 0;
}
bool operator<=(const bignum &rhs) const {
return cmp_bignum(this->data, rhs.data) <= 0;
}
bool operator>(const bignum &rhs) const {
return cmp_bignum(this->data, rhs.data) > 0;
}
bool operator<(const bignum &rhs) const {
return cmp_bignum(this->data, rhs.data) < 0;
}
int operator[](int index) const {
return this->data[index];
}
friend std::ostream &operator<<(std::ostream &os, bignum &bn);
size_t size() const {
return data.size();
}
/*
returns:
- 0, if the lhs and rhs are equal;
- a negative value if lhs is less than rhs;
- a positive value if lhs is greater than rhs.
*/
int cmp_bignum(std::vector<uint8_t> lhs, std::vector<uint8_t> rhs) const
{
if (lhs.size() > rhs.size())
return 1;
else if (lhs.size() < rhs.size())
return -1;
else {
/* assumes the digits are stored in reverse order */
std::reverse(lhs.begin(), lhs.end());
std::reverse(rhs.begin(), rhs.end());
for (size_t i = 0; i < lhs.size(); i++) {
if (lhs[i] > rhs[i])
return 1;
if (lhs[i] < rhs[i])
return -1;
}
}
return 0;
}
static bignum lower_bound_regex(bignum val)
{
/* single digit numbers reduce to 0 */
if (val.size() == 1) {
val.data[0] = 0;
return val;
}
for (auto& j : val.data) {
uint8_t tmp = j;
j = 0;
if (tmp != val.base - 1) {
break;
}
if (&j == &val.data[val.size()-2]) {
val.data[val.size()-1] = 1;
break;
}
}
return val;
}
static bignum upper_bound_regex(bignum val)
{
for (auto& j : val.data) {
uint8_t tmp = j;
j = val.base - 1;
if (tmp != 0) {
break;
}
}
return val;
}
};
inline std::ostream &operator<<(std::ostream &os, bignum &bn)
{
std::stringstream ss;
bignum tmp = bn;
std::reverse(tmp.data.begin(), tmp.data.end());
for (auto i : tmp.data)
ss << std::hex << (int) i;
os << ss.str();
return os;
};
#endif /* __AA_BIGNUM_H */
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