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#include "bid_internal.h"

BID_EXTERN_C double fabs(double);
BID_EXTERN_C double log(double);
BID_EXTERN_C double log1p(double);

static BID_UINT32 BID32_MINUS_HALF = 0xb2000005ul;
static BID_UINT32 BID32_1 = 0x32800001ul;
#define BID32_NAN 0x7c000000ul

BID_TYPE0_FUNCTION_ARGTYPE1(BID_UINT32, bid32_log1p, BID_UINT32, x)

// Declare local variables

  BID_UINT32 res, y;
  int sm;
  double xd, yd;

// Check for NaN and just return the same NaN, quieted and canonized

  if ((x & NAN_MASK32) == NAN_MASK32)
   {
     #ifdef BID_SET_STATUS_FLAGS
     if ((x & SNAN_MASK32) == SNAN_MASK32)
        __set_status_flags (pfpsf, BID_INVALID_EXCEPTION);
     #endif
     res = x & 0xfc0ffffful;
     if ((res & 0x000ffffful) > 999999ul) res &= ~0x000ffffful;
     BID_RETURN(res);
   }

// If x < -1/2 we have condition issues with the naive computation.
// Instead, do y = 1 + x exactly in decimal and call usual log function.

  BIDECIMAL_CALL2_NORND(bid32_quiet_less,sm,x,BID32_MINUS_HALF);
  if (sm)
   { BIDECIMAL_CALL2(bid32_add,y,x,BID32_1);
     if ((y & SIGNMASK32) == SIGNMASK32)
      {                                               
        #ifdef BID_SET_STATUS_FLAGS                                              
        __set_status_flags (pfpsf, BID_INVALID_EXCEPTION);                     
        #endif                                                              
        BID_RETURN(BID32_NAN);                                           
      }                                                           
     BIDECIMAL_CALL1(bid32_to_binary64,xd,y);
     yd = log(xd);
     BIDECIMAL_CALL1(binary64_to_bid32,res,yd);
     BID_RETURN(res);
   }

// Otherwise just do the operation "naively".
// Inherit all other special cases (infinity, negative,...) from binary.

  else
   { BIDECIMAL_CALL1(bid32_to_binary64,xd,x);
     yd = log1p(xd);
     BIDECIMAL_CALL1(binary64_to_bid32,res,yd);
     BID_RETURN (res);
   }
}
