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#define BID_128RES
#include "bid_internal.h"


BID128_FUNCTION_ARG128_CUSTOMARGTYPE2_PLAIN(bid128_frexp, x, int*, exp)
/* 
  If x is not a floating-point number, the results are unspecified (this
  implementation returns x and *exp = 0). Otherwise, the frexp function 
  returns the value res, such that res has a magnitude in the interval 
  [1/10, 1) or zero, and x = res*2^*exp. If x is zero, both parts of the 
  result are zero
  frexp does not raise any exceptions
 */

  BID_UINT128 res;
  BID_UINT128 sig_x; 
  unsigned int exp_x;
  BID_UI64DOUBLE tmp;
  int x_nr_bits, q;

  if ((x.w[1] & MASK_SPECIAL) == MASK_SPECIAL) {
    // if NaN or infinity
    *exp = 0;
    res = x;
    // the binary frexp quitetizes SNaNs, so do the same
    if ((x.w[1] & MASK_SNAN) == MASK_SNAN) { // x is SNAN 
    //   // set invalid flag
    //   *pfpsf |= BID_INVALID_EXCEPTION;
      // return quiet (x)
      res.w[1] = x.w[1] & 0xfdffffffffffffffull;
    }
    BID_RETURN (res); 
  } else {
    // x is 0, non-canonical, normal, or subnormal
    // check for non-canonical values with 114 bit-significands; can be zero too
    if ((x.w[1] & 0x6000000000000000ull) == 0x6000000000000000ull) {
      *exp = 0;
      exp_x = (x.w[1] & MASK_EXP2) >> 47; // biased
      res.w[1] = (x.w[1] & 0x8000000000000000ull) | ((BID_UINT64)exp_x << 49); 
          // zero of same sign
      res.w[0] = 0x0000000000000000ull;
      BID_RETURN (res);
    }
    // unpack x
    exp_x = (x.w[1] & MASK_EXP) >> 49; // biased
    sig_x.w[1] = x.w[1] & MASK_COEFF;   
    sig_x.w[0] = x.w[0]; 
    // check for non-canonical values or zero
    if ((sig_x.w[1] > 0x0001ed09bead87c0ull)
        || (sig_x.w[1] == 0x0001ed09bead87c0ull
            && (sig_x.w[0] > 0x378d8e63ffffffffull)) ||
          ((sig_x.w[1] == 0x0ull) && (sig_x.w[0] == 0x0ull))) {
      *exp = 0;
      res.w[1] = (x.w[1] & 0x8000000000000000ull) | ((BID_UINT64)exp_x << 49); 
          // zero of same sign
      res.w[0] = 0x0000000000000000ull;
      BID_RETURN (res);
    } else {
      ; // continue, x is neither zero nor non-canonical 
    }
    // x is normal or subnormal, with exp_x=biased exponent & sig_x=coefficient
    // determine the number of decimal digits in sig_x, which fits in 113 bits
    // q = nr. of decimal digits in sig_x (1 <= q <= 34) 
    //  determine first the nr. of bits in sig_x
    if (sig_x.w[1] == 0) {
      if (sig_x.w[0] >= 0x0020000000000000ull) { // z >= 2^53
        // split the 64-bit value in two 32-bit halves to avoid rounding errors
        if (sig_x.w[0] >= 0x0000000100000000ull) { // z >= 2^32
          tmp.d = (double) (sig_x.w[0] >> 32); // exact conversion
          x_nr_bits =
            32 + ((((unsigned int) (tmp.ui64 >> 52)) & 0x7ff) - 0x3ff);
        } else { // z < 2^32
          tmp.d = (double) sig_x.w[0]; // exact conversion
          x_nr_bits =
            ((((unsigned int) (tmp.ui64 >> 52)) & 0x7ff) - 0x3ff);
        }
      } else { // if z < 2^53
        tmp.d = (double) sig_x.w[0]; // exact conversion
        x_nr_bits = ((((unsigned int) (tmp.ui64 >> 52)) & 0x7ff) - 0x3ff);
      }
    } else { // sig_x.w[1] != 0 => nr. bits = 65 + nr_bits (sig_x.w[1])
      tmp.d = (double) sig_x.w[1]; // exact conversion
      x_nr_bits = 64 + ((((unsigned int) (tmp.ui64 >> 52)) & 0x7ff) - 0x3ff);
    }
    q = bid_nr_digits[x_nr_bits].digits;
    if (q == 0) {
      q = bid_nr_digits[x_nr_bits].digits1;
      if (sig_x.w[1] > bid_nr_digits[x_nr_bits].threshold_hi ||
          (sig_x.w[1] == bid_nr_digits[x_nr_bits].threshold_hi &&
           sig_x.w[0] >= bid_nr_digits[x_nr_bits].threshold_lo))
        q++;
    }
    // Do not add trailing zeros if q < 34; leave sig_x with q digits
    *exp = exp_x - 6176 + q;
    // assemble the result; sig_x < 2^113 so it fits in 113 bits
    res.w[1] = (x.w[1] & 0x8001ffffffffffffull) | ((-q + 6176ull) << 49); 
    res.w[0] = x.w[0]; 
      // replace exponent
    BID_RETURN (res);
  }
}
