/*************************************************
* BigInt Base Source File                        *
* (C) 1999-2005 The Botan Project                *
*************************************************/

#include <botan/bigint.h>
#include <botan/numthry.h>
#include <botan/mp_core.h>
#include <botan/bit_ops.h>
#include <botan/parsing.h>
#include <botan/rng.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(2*limbs_needed + 2);
   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(size);
   signedness = s;
   }

/*************************************************
* Construct a BigInt from a "raw" BigInt         *
*************************************************/
BigInt::BigInt(const BigInt& b)
   {
   if(b.sig_words())
      {
      reg.set(b.data(), b.sig_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);
   }

/*************************************************
* Construct a Random BigInt                      *
*************************************************/
BigInt::BigInt(NumberType type, u32bit bits)
   {
   set_sign(Positive);
   if(type == Random && bits)
      randomize(bits);
   else if(type == Power2)
      set_bit(bits);
   }

/*************************************************
* Swap this BigInt with another                  *
*************************************************/
void BigInt::swap(BigInt& other)
   {
   std::swap(reg, other.reg);
   std::swap(signedness, other.signedness);
   }

/*************************************************
* 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());
   }

/*************************************************
* Add n to this number                           *
*************************************************/
void BigInt::add(word n)
   {
   if(!n) return;
   word temp = reg[0];
   reg[0] += n;
   if(reg[0] > temp)
      return;
   for(u32bit j = 1; j != size(); j++)
      if(++reg[j]) return;
   grow_to(2*size());
   reg[size() / 2] = 1;
   }

/*************************************************
* Subtract n from this number                    *
*************************************************/
void BigInt::sub(word n)
   {
   if(!n) return;
   word temp = reg[0];
   reg[0] -= n;
   if(reg[0] < temp)
      return;
   for(u32bit j = 1; j != size(); j++)
      if(reg[j]--) return;
   reg.create(2);
   flip_sign();
   reg[0] = n - temp;
   }

/*************************************************
* Prefix Increment Operator                      *
*************************************************/
BigInt& BigInt::operator++()
   {
   if(is_negative()) sub(1);
   else              add(1);
   return (*this);
   }

/*************************************************
* Prefix Decrement Operator                      *
*************************************************/
BigInt& BigInt::operator--()
   {
   if(is_negative()) add(1);
   else              sub(1);
   return (*this);
   }

/*************************************************
* Return word n of this number                   *
*************************************************/
word BigInt::word_at(u32bit n) const
   {
   if(n >= size()) return 0;
   else            return reg[n];
   }

/*************************************************
* 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 nibble n of this number                 *
*************************************************/
u32bit BigInt::get_nibble(u32bit n, u32bit nibble_size) const
   {
   if(nibble_size > 32)
      throw Invalid_Argument("BigInt::get_nibble: Nibble size too large");

   u32bit nibble = 0;
   for(s32bit j = (s32bit)nibble_size-1; j >= 0; j--)
      {
      nibble <<= 1;
      if(get_bit(n * nibble_size + j))
         nibble |= 1;
      }
   return nibble;
   }

/*************************************************
* 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;
   }

/*************************************************
* Randomize this number                          *
*************************************************/
void BigInt::randomize(u32bit bitsize, RNG_Quality level)
   {
   set_sign(Positive);

   if(bitsize == 0)
      clear();
   else
      {
      SecureVector<byte> array((bitsize + 7) / 8);
      Global_RNG::randomize(array, array.size(), level);
      if(bitsize % 8)
         array[0] &= 0xFF >> (8 - (bitsize % 8));
      array[0] |= 0x80 >> ((bitsize % 8) ? (8 - bitsize % 8) : 0);
      binary_decode(array, array.size());
      }
   }

/*************************************************
* 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(length / WORD_BYTES + 1);

   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];
   }

/*************************************************
* Generate a random integer                      *
*************************************************/
BigInt random_integer(u32bit bits, RNG_Quality level)
   {
   BigInt x;
   x.randomize(bits, level);
   return x;
   }

/*************************************************
* Generate a random integer within given range   *
*************************************************/
BigInt random_integer(const BigInt& min, const BigInt& max, RNG_Quality level)
   {
   BigInt range = max - min;

   if(range <= 0)
      throw Invalid_Argument("random_integer: invalid min/max values");

   return (min + (random_integer(range.bits() + 2, level) % range));
   }

/*************************************************
* Generate a random safe prime                   *
*************************************************/
BigInt random_safe_prime(u32bit bits, RNG_Quality level)
   {
   if(bits <= 64)
      throw Invalid_Argument("random_safe_prime: Can't make a prime of " +
                             to_string(bits) + " bits");

   BigInt p;
   do
      p = (random_prime(bits - 1, level) << 1) + 1;
   while(!is_prime(p));
   return p;
   }

}