99 lines
2 KiB
C
99 lines
2 KiB
C
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/*++
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Copyright (c) 1999 Microsoft Corporation
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Module Name:
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ldexp.c
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Abstract:
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multiply by a power of two
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Author:
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Revision History:
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29-sept-1999 ATM Shafiqul Khalid [askhalid] copied from rtl library.
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--*/
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#include <math.h>
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#include <float.h>
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#include <trans.h>
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#include <limits.h>
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/***
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*double ldexp(double x, int exp)
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*
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*Purpose:
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* Compute x * 2^exp
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*
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*Entry:
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*
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*Exit:
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*
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*Exceptions:
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* I U O P
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*
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*******************************************************************************/
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double ldexp(double x, int exp)
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{
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unsigned int savedcw;
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int oldexp;
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long newexp; /* for checking out of bounds exponents */
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double result, mant;
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/* save user fp control word */
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savedcw = _maskfp();
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/* check for infinity or NAN */
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if (IS_D_SPECIAL(x)){
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switch (_sptype(x)) {
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case T_PINF:
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case T_NINF:
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RETURN(savedcw,x);
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case T_QNAN:
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return _handle_qnan2(OP_LDEXP, x, (double)exp, savedcw);
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default: //T_SNAN
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return _except2(FP_I,OP_LDEXP,x,(double)exp,_s2qnan(x),savedcw);
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}
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}
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if (x == 0.0) {
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RETURN(savedcw,x);
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}
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mant = _decomp(x, &oldexp);
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if (ABS(exp) > INT_MAX)
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newexp = exp; // avoid possible integer overflow
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else
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newexp = oldexp + exp;
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/* out of bounds cases */
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if (newexp > MAXEXP + IEEE_ADJUST) {
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return _except2(FP_O|FP_P,OP_LDEXP,x,(double)exp,_copysign(D_INF,mant),savedcw);
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}
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if (newexp > MAXEXP) {
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result = _set_exp(mant, newexp-IEEE_ADJUST);
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return _except2(FP_O|FP_P,OP_LDEXP,x,(double)exp,result,savedcw);
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}
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if (newexp < MINEXP - IEEE_ADJUST) {
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return _except2(FP_U|FP_P,OP_LDEXP,x,(double)exp,mant*0.0,savedcw);
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}
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if (newexp < MINEXP) {
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result = _set_exp(mant, newexp+IEEE_ADJUST);
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return _except2(FP_U|FP_P,OP_LDEXP,x,(double)exp,result,savedcw);
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}
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result = _set_exp(mant, (int)newexp);
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RETURN(savedcw,result);
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}
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