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/*
* BigInt Encoding/Decoding
* (C) 1999-2010,2012,2019 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/bigint.h>
#include <botan/internal/divide.h>
#include <botan/hex.h>
namespace Botan {
std::string BigInt::to_dec_string() const
{
BigInt copy = *this;
copy.set_sign(Positive);
uint8_t remainder;
secure_vector<uint8_t> digits;
// (over-)estimate of the number of digits, log2(10) ~= 3.32
digits.reserve(3.4 * this->bits());
while(copy > 0)
{
ct_divide_u8(copy, 100, copy, remainder);
const uint8_t ld = remainder % 10;
const uint8_t td = (remainder - ld) / 10;
digits.push_back(ld);
if(copy > 0 || td > 0)
digits.push_back(td);
}
std::string s;
if(is_negative())
s += "-";
for(auto i = digits.rbegin(); i != digits.rend(); ++i)
{
s.push_back(*i + '0');
}
if(s.empty())
s += "0";
return s;
}
std::string BigInt::to_hex_string() const
{
std::vector<uint8_t> bits = BigInt::encode(*this);
if(bits.empty())
bits.push_back(0);
std::string hrep;
if(is_negative())
hrep += "-";
hrep += "0x";
hrep += hex_encode(bits);
return hrep;
}
/*
* Encode a BigInt, with leading 0s if needed
*/
secure_vector<uint8_t> BigInt::encode_1363(const BigInt& n, size_t bytes)
{
if(n.bytes() > bytes)
throw Encoding_Error("encode_1363: n is too large to encode properly");
secure_vector<uint8_t> output(bytes);
n.binary_encode(output.data(), output.size());
return output;
}
//static
void BigInt::encode_1363(uint8_t output[], size_t bytes, const BigInt& n)
{
if(n.bytes() > bytes)
throw Encoding_Error("encode_1363: n is too large to encode properly");
n.binary_encode(output, bytes);
}
/*
* Encode two BigInt, with leading 0s if needed, and concatenate
*/
secure_vector<uint8_t> BigInt::encode_fixed_length_int_pair(const BigInt& n1, const BigInt& n2, size_t bytes)
{
if(n1.bytes() > bytes || n2.bytes() > bytes)
throw Encoding_Error("encode_fixed_length_int_pair: values too large to encode properly");
secure_vector<uint8_t> output(2 * bytes);
n1.binary_encode(output.data() , bytes);
n2.binary_encode(output.data() + bytes, bytes);
return output;
}
/*
* Decode a BigInt
*/
BigInt BigInt::decode(const uint8_t buf[], size_t length, Base base)
{
BigInt r;
if(base == Binary)
{
r.binary_decode(buf, length);
}
else if(base == Hexadecimal)
{
secure_vector<uint8_t> binary;
if(length % 2)
{
// Handle lack of leading 0
const char buf0_with_leading_0[2] =
{ '0', static_cast<char>(buf[0]) };
binary = hex_decode_locked(buf0_with_leading_0, 2);
binary += hex_decode_locked(cast_uint8_ptr_to_char(&buf[1]),
length - 1,
false);
}
else
binary = hex_decode_locked(cast_uint8_ptr_to_char(buf),
length, false);
r.binary_decode(binary.data(), binary.size());
}
else if(base == Decimal)
{
for(size_t i = 0; i != length; ++i)
{
const char c = buf[i];
if(c < '0' || c > '9')
throw Invalid_Argument("BigInt::decode: invalid decimal char");
const uint8_t x = c - '0';
BOTAN_ASSERT_NOMSG(x < 10);
r *= 10;
r += x;
}
}
else
throw Invalid_Argument("Unknown BigInt decoding method");
return r;
}
}
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