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/*
* BigInt Base
* (C) 1999-2011,2012 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/bigint.h>
#include <botan/internal/mp_core.h>
#include <botan/get_byte.h>
#include <botan/parsing.h>
#include <botan/internal/rounding.h>
#include <botan/internal/bit_ops.h>
namespace Botan {
/*
* Construct a BigInt from a regular number
*/
BigInt::BigInt(u64bit n)
{
if(n == 0)
return;
const size_t limbs_needed = sizeof(u64bit) / sizeof(word);
m_reg.resize(4*limbs_needed);
for(size_t i = 0; i != limbs_needed; ++i)
m_reg[i] = ((n >> (i*MP_WORD_BITS)) & MP_WORD_MASK);
}
/*
* Construct a BigInt of the specified size
*/
BigInt::BigInt(Sign s, size_t size)
{
m_reg.resize(round_up<size_t>(size, 8));
m_signedness = s;
}
/*
* Copy constructor
*/
BigInt::BigInt(const BigInt& other)
{
m_reg = other.m_reg;
m_signedness = other.m_signedness;
}
/*
* Construct a BigInt from a string
*/
BigInt::BigInt(const std::string& str)
{
Base base = Decimal;
size_t markers = 0;
bool negative = false;
if(str.length() > 0 && str[0] == '-')
{
markers += 1;
negative = true;
}
if(str.length() > markers + 2 && str[markers ] == '0' &&
str[markers + 1] == 'x')
{
markers += 2;
base = Hexadecimal;
}
*this = decode(reinterpret_cast<const byte*>(str.data()) + markers,
str.length() - markers, base);
if(negative) set_sign(Negative);
else set_sign(Positive);
}
/*
* Construct a BigInt from an encoded BigInt
*/
BigInt::BigInt(const byte input[], size_t length, Base base)
{
*this = decode(input, length, base);
}
/*
* Construct a BigInt from an encoded BigInt
*/
BigInt::BigInt(RandomNumberGenerator& rng, size_t bits)
{
randomize(rng, bits);
}
/*
* Grow the internal storage
*/
void BigInt::grow_to(size_t n)
{
if(n > size())
m_reg.resize(round_up<size_t>(n, 8));
}
/*
* Comparison Function
*/
s32bit BigInt::cmp(const BigInt& other, bool check_signs) const
{
if(check_signs)
{
if(other.is_positive() && this->is_negative())
return -1;
if(other.is_negative() && this->is_positive())
return 1;
if(other.is_negative() && this->is_negative())
return (-bigint_cmp(this->data(), this->sig_words(),
other.data(), other.sig_words()));
}
return bigint_cmp(this->data(), this->sig_words(),
other.data(), other.sig_words());
}
/*
* Return bits {offset...offset+length}
*/
u32bit BigInt::get_substring(size_t offset, size_t length) const
{
if(length > 32)
throw Invalid_Argument("BigInt::get_substring: Substring size too big");
u64bit piece = 0;
for(size_t i = 0; i != 8; ++i)
{
const byte part = byte_at((offset / 8) + (7-i));
piece = (piece << 8) | part;
}
const u64bit mask = (static_cast<u64bit>(1) << length) - 1;
const size_t shift = (offset % 8);
return static_cast<u32bit>((piece >> shift) & mask);
}
/*
* Convert this number to a u32bit, if possible
*/
u32bit BigInt::to_u32bit() const
{
if(is_negative())
throw Encoding_Error("BigInt::to_u32bit: Number is negative");
if(bits() >= 32)
throw Encoding_Error("BigInt::to_u32bit: Number is too big to convert");
u32bit out = 0;
for(u32bit j = 0; j != 4; ++j)
out = (out << 8) | byte_at(3-j);
return out;
}
/*
* Set bit number n
*/
void BigInt::set_bit(size_t n)
{
const size_t which = n / MP_WORD_BITS;
const word mask = static_cast<word>(1) << (n % MP_WORD_BITS);
if(which >= size()) grow_to(which + 1);
m_reg[which] |= mask;
}
/*
* Clear bit number n
*/
void BigInt::clear_bit(size_t n)
{
const size_t which = n / MP_WORD_BITS;
const word mask = static_cast<word>(1) << (n % MP_WORD_BITS);
if(which < size())
m_reg[which] &= ~mask;
}
/*
* Clear all but the lowest n bits
*/
void BigInt::mask_bits(size_t n)
{
if(n == 0) { clear(); return; }
const size_t top_word = n / MP_WORD_BITS;
const word mask = (static_cast<word>(1) << (n % MP_WORD_BITS)) - 1;
if(top_word < size())
clear_mem(&m_reg[top_word+1], size() - (top_word + 1));
m_reg[top_word] &= mask;
}
/*
* Count how many bytes are being used
*/
size_t BigInt::bytes() const
{
return (bits() + 7) / 8;
}
/*
* Count how many bits are being used
*/
size_t BigInt::bits() const
{
const size_t words = sig_words();
if(words == 0)
return 0;
const size_t full_words = words - 1;
return (full_words * MP_WORD_BITS + high_bit(word_at(full_words)));
}
/*
* Calcluate the size in a certain base
*/
size_t BigInt::encoded_size(Base base) const
{
static const double LOG_2_BASE_10 = 0.30102999566;
if(base == Binary)
return bytes();
else if(base == Hexadecimal)
return 2*bytes();
else if(base == Decimal)
return static_cast<size_t>((bits() * LOG_2_BASE_10) + 1);
else
throw Invalid_Argument("Unknown base for BigInt encoding");
}
/*
* Set the sign
*/
void BigInt::set_sign(Sign s)
{
if(is_zero())
m_signedness = Positive;
else
m_signedness = s;
}
/*
* Reverse the value of the sign flag
*/
void BigInt::flip_sign()
{
set_sign(reverse_sign());
}
/*
* Return the opposite value of the current sign
*/
BigInt::Sign BigInt::reverse_sign() const
{
if(sign() == Positive)
return Negative;
return Positive;
}
/*
* Return the negation of this number
*/
BigInt BigInt::operator-() const
{
BigInt x = (*this);
x.flip_sign();
return x;
}
/*
* Return the absolute value of this number
*/
BigInt BigInt::abs() const
{
BigInt x = (*this);
x.set_sign(Positive);
return x;
}
/*
* Encode this number into bytes
*/
void BigInt::binary_encode(byte output[]) const
{
const size_t sig_bytes = bytes();
for(size_t i = 0; i != sig_bytes; ++i)
output[sig_bytes-i-1] = byte_at(i);
}
/*
* Set this number to the value in buf
*/
void BigInt::binary_decode(const byte buf[], size_t length)
{
const size_t WORD_BYTES = sizeof(word);
clear();
m_reg.resize(round_up<size_t>((length / WORD_BYTES) + 1, 8));
for(size_t i = 0; i != length / WORD_BYTES; ++i)
{
const size_t top = length - WORD_BYTES*i;
for(size_t j = WORD_BYTES; j > 0; --j)
m_reg[i] = (m_reg[i] << 8) | buf[top - j];
}
for(size_t i = 0; i != length % WORD_BYTES; ++i)
m_reg[length / WORD_BYTES] = (m_reg[length / WORD_BYTES] << 8) | buf[i];
}
}
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