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71 lines
1.7 KiB
71 lines
1.7 KiB
/***
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*floor.c - floor
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*
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* Copyright (c) 1991-1991, Microsoft Corporation. All rights reserved.
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*
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*Purpose:
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*
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*Revision History:
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* 8-24-91 GDP written
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* 1-09-92 GDP support IEEE exceptions
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*
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*******************************************************************************/
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#include <math.h>
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#include <trans.h>
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extern double _frnd(double);
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/***
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*double floor(double x) - floor
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*
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*Purpose:
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* Return a double representing the largest integer that is
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* less than or equal to x
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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, P
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*******************************************************************************/
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static unsigned int newcw = (ICW & ~IMCW_RC) | (IRC_DOWN & IMCW_RC);
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double floor(double x)
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{
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unsigned int savedcw;
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double result;
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/* save user fp control word */
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savedcw = _ctrlfp(newcw,IMCW); /* round down */
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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 _except1(FP_I, OP_FLOOR, x, QNAN_FLOOR, savedcw);
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case T_QNAN:
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return _handle_qnan1(OP_FLOOR, x, savedcw);
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default: //T_SNAN
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return _except1(FP_I, OP_FLOOR, x, _s2qnan(x), savedcw);
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}
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}
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result = _frnd(x); /* round according to the current rounding mode */
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// In general, the Precision Exception should be raised if
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// _frnd reports a precision loss. In order to detect this with
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// masked exceptions, the status word needs to be cleared.
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// However, we want to avoid this, since the 387 instruction
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// set does not provide an fast way to restore the status word
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if (result == x) {
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RETURN(savedcw,result);
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}
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else {
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RETURN_INEXACT1(OP_FLOOR, x, result, savedcw);
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}
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}
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