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/*************************************************
* BigInt Base Source File *
* (C) 1999-2006 The Botan Project *
*************************************************/
#include <botan/bigint.h>
#include <botan/mp_core.h>
#include <botan/bit_ops.h>
#include <botan/parsing.h>
#include <botan/util.h>
#include <assert.h>
namespace Botan {
/*************************************************
* Construct a BigInt from a regular number *
*************************************************/
BigInt::BigInt(u64bit n)
{
set_sign(Positive);
if(n == 0)
return;
const u32bit limbs_needed = sizeof(u64bit) / sizeof(word);
reg.create(4*limbs_needed);
for(u32bit j = 0; j != limbs_needed; ++j)
reg[j] = (word)((n >> (j*MP_WORD_BITS)) & MP_WORD_MASK);
}
/*************************************************
* Construct a BigInt of the specified size *
*************************************************/
BigInt::BigInt(Sign s, u32bit size)
{
reg.create(round_up(size, 8));
signedness = s;
}
/*************************************************
* Construct a BigInt from a "raw" BigInt *
*************************************************/
BigInt::BigInt(const BigInt& b)
{
const u32bit b_words = b.sig_words();
if(b_words)
{
reg.create(round_up(b_words, 8));
reg.copy(b.data(), b_words);
set_sign(b.sign());
}
else
{
reg.create(2);
set_sign(Positive);
}
}
/*************************************************
* Construct a BigInt from a string *
*************************************************/
BigInt::BigInt(const std::string& str)
{
Base base = Decimal;
u32bit 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; }
else if(str.length() > markers + 1 && str[markers] == '0')
{ markers += 1; base = Octal; }
*this = decode((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[], u32bit length, Base base)
{
set_sign(Positive);
*this = decode(input, length, base);
}
/*************************************************
* Swap this BigInt with another *
*************************************************/
void BigInt::swap(BigInt& other)
{
std::swap(reg, other.reg);
std::swap(signedness, other.signedness);
}
/*************************************************
* Grow the internal storage *
*************************************************/
void BigInt::grow_reg(u32bit n) const
{
reg.grow_to(round_up(size() + n, 8));
}
/*************************************************
* Grow the internal storage *
*************************************************/
void BigInt::grow_to(u32bit n) const
{
if(n > size())
reg.grow_to(round_up(n, 8));
}
/*************************************************
* Comparison Function *
*************************************************/
s32bit BigInt::cmp(const BigInt& n, bool check_signs) const
{
if(check_signs)
{
if(n.is_positive() && this->is_negative()) return -1;
if(n.is_negative() && this->is_positive()) return 1;
if(n.is_negative() && this->is_negative())
return (-bigint_cmp(data(), sig_words(), n.data(), n.sig_words()));
}
return bigint_cmp(data(), sig_words(), n.data(), n.sig_words());
}
/*************************************************
* 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;
}
/*************************************************
* Return byte n of this number *
*************************************************/
byte BigInt::byte_at(u32bit n) const
{
const u32bit WORD_BYTES = sizeof(word);
u32bit word_num = n / WORD_BYTES, byte_num = n % WORD_BYTES;
if(word_num >= size())
return 0;
else
return get_byte(WORD_BYTES - byte_num - 1, reg[word_num]);
}
/*************************************************
* Return bit n of this number *
*************************************************/
bool BigInt::get_bit(u32bit n) const
{
return ((word_at(n / MP_WORD_BITS) >> (n % MP_WORD_BITS)) & 1);
}
/*************************************************
* Return bits {offset...offset+length} *
*************************************************/
u32bit BigInt::get_substring(u32bit offset, u32bit length) const
{
if(length > 32)
throw Invalid_Argument("BigInt::get_substring: Substring size too big");
u64bit piece = 0;
for(u32bit j = 0; j != 8; ++j)
piece = (piece << 8) | byte_at((offset / 8) + (7-j));
u64bit mask = (1 << length) - 1;
u32bit shift = (offset % 8);
return ((piece >> shift) & mask);
}
/*************************************************
* Set bit number n *
*************************************************/
void BigInt::set_bit(u32bit n)
{
const u32bit which = n / MP_WORD_BITS;
const word mask = (word)1 << (n % MP_WORD_BITS);
if(which >= size()) grow_to(which + 1);
reg[which] |= mask;
}
/*************************************************
* Clear bit number n *
*************************************************/
void BigInt::clear_bit(u32bit n)
{
const u32bit which = n / MP_WORD_BITS;
const word mask = (word)1 << (n % MP_WORD_BITS);
if(which < size())
reg[which] &= ~mask;
}
/*************************************************
* Clear all but the lowest n bits *
*************************************************/
void BigInt::mask_bits(u32bit n)
{
if(n == 0) { clear(); return; }
if(n >= bits()) return;
const u32bit top_word = n / MP_WORD_BITS;
const word mask = ((word)1 << (n % MP_WORD_BITS)) - 1;
if(top_word < size())
for(u32bit j = top_word + 1; j != size(); ++j)
reg[j] = 0;
reg[top_word] &= mask;
}
/*************************************************
* Count the significant words *
*************************************************/
u32bit BigInt::sig_words() const
{
const word* x = data();
u32bit top_set = size();
while(top_set >= 4)
{
word sum = x[top_set-1] | x[top_set-2] | x[top_set-3] | x[top_set-4];
if(sum) break;
else top_set -= 4;
}
while(top_set && (x[top_set-1] == 0))
top_set--;
return top_set;
}
/*************************************************
* Count how many bytes are being used *
*************************************************/
u32bit BigInt::bytes() const
{
return (bits() + 7) / 8;
}
/*************************************************
* Count how many bits are being used *
*************************************************/
u32bit BigInt::bits() const
{
if(sig_words() == 0)
return 0;
u32bit full_words = sig_words() - 1, top_bits = MP_WORD_BITS;
word top_word = word_at(full_words), mask = MP_WORD_TOP_BIT;
while(top_bits && ((top_word & mask) == 0))
{ mask >>= 1; top_bits--; }
return (full_words * MP_WORD_BITS + top_bits);
}
/*************************************************
* Calcluate the size in a certain base *
*************************************************/
u32bit 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 == Octal)
return ((bits() + 2) / 3);
else if(base == Decimal)
return (u32bit)((bits() * LOG_2_BASE_10) + 1);
else
throw Invalid_Argument("Unknown base for BigInt encoding");
}
/*************************************************
* Return true if this number is zero *
*************************************************/
bool BigInt::is_zero() const
{
for(u32bit j = 0; j != size(); ++j)
if(reg[j]) return false;
return true;
}
/*************************************************
* Set the sign *
*************************************************/
void BigInt::set_sign(Sign s)
{
if(is_zero())
signedness = Positive;
else
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 u32bit sig_bytes = bytes();
for(u32bit j = 0; j != sig_bytes; ++j)
output[sig_bytes-j-1] = byte_at(j);
}
/*************************************************
* Set this number to the value in buf *
*************************************************/
void BigInt::binary_decode(const byte buf[], u32bit length)
{
const u32bit WORD_BYTES = sizeof(word);
reg.create(round_up((length / WORD_BYTES) + 1, 8));
for(u32bit j = 0; j != length / WORD_BYTES; ++j)
{
u32bit top = length - WORD_BYTES*j;
for(u32bit k = WORD_BYTES; k > 0; --k)
reg[j] = (reg[j] << 8) | buf[top - k];
}
for(u32bit j = 0; j != length % WORD_BYTES; ++j)
reg[length / WORD_BYTES] = (reg[length / WORD_BYTES] << 8) | buf[j];
}
}
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