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/*
* rfc4251_gmp.C -- implements mpint/gmp conversions for rfc4251::string
*
* these functions need linking against libgmp
*
* Copyright (C) 2013 Timo Weingärtner <timo@tiwe.de>
*
* This file is part of ssh-agent-filter.
*
* ssh-agent-filter is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* ssh-agent-filter 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 ssh-agent-filter. If not, see <http://www.gnu.org/licenses/>.
*/
#include "rfc4251.H"
namespace rfc4251 {
string::string (mpz_srcptr x) {
if (mpz_sgn(x) == 0)
return;
auto const import_positive = [] (mpz_srcptr x, std::vector<char> & value) {
size_t bits{mpz_sizeinbase(x, 2)};
size_t bytes{(bits + 7) / 8};
size_t extrabyte{(bits % 8) == 0}; // need extra byte if MSB is 1 to keep it non-negative
if (bytes + extrabyte > std::numeric_limits<uint32_t>::max())
throw std::length_error{"32-bit limit for rfc4251::string exceeded"};
value.resize(bytes + extrabyte);
value[0] = 0;
mpz_export(value.data() + extrabyte, nullptr, 1, 1, 1, 0, x);
};
if (mpz_sgn(x) == 1)
import_positive(x, value);
else {
// handle two's complement: add 1, invert all bits
mpz_class tmp{x};
tmp += 1;
import_positive(tmp.get_mpz_t(), value);
for (auto & i : value)
i ^= 0xff;
}
}
string::operator mpz_class () const {
mpz_class ret;
mpz_import(ret.get_mpz_t(), value.size(), 1, 1, 1, 0, value.data());
if (mpz_sizeinbase(ret.get_mpz_t(), 2) == value.size() * 8) { // negative
mpz_com(ret.get_mpz_t(), ret.get_mpz_t());
ret += 1;
mpz_neg(ret.get_mpz_t(), ret.get_mpz_t());
}
return ret;
}
}
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