136 lines
2.7 KiB
C
136 lines
2.7 KiB
C
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/***
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*fmod.c - floating point remainder
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*
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* Copyright (c) 1991-2001, 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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* 1-13-92 GDP support IEEE exceptions
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* 3-04-92 GDP complete rewrite for improved accuracy
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* 3-16-92 GDP restore cw properly, do not raise Inexact exception
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* 06-23-92 GDP support NCEG special return values (signed 0's etc)
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* 02-06-95 JWM Mac merge
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* 10-07-97 RDL Added IA64.
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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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#if defined(_M_IA64)
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#pragma function(fmod)
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#endif
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/***
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*double fmod(double x, double y)
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*
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*Purpose:
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* Return f, s.t. x = i*y + f, where i is an integer, f has the same
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* sign as x, and |f| < |y|
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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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#define SCALE 53
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double fmod(double x, double y)
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{
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uintptr_t savedcw;
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int neg=0;
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int denorm=0;
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double d,tx,ty,fx,fy;
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int nx, ny, nexp;
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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(y) || IS_D_SPECIAL(x)){
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if (IS_D_SNAN(y) || IS_D_SNAN(x)){
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return _except2(FP_I,OP_FMOD,x,y,_d_snan2(x,y),savedcw);
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}
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if (IS_D_QNAN(y) || IS_D_QNAN(x)){
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return _handle_qnan2(OP_FMOD,x,y,savedcw);
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}
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if (IS_D_INF(x) || IS_D_MINF(x)) {
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return _except2(FP_I,OP_FMOD,x,y,QNAN_FMOD,savedcw);
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}
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RETURN(savedcw, x);
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}
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if (y == 0) {
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return _except2(FP_I,OP_FMOD,x,y,QNAN_FMOD,savedcw);
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}
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if (x == 0) {
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RETURN(savedcw, x); // NCEG spec
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}
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if (x < 0) {
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tx = -x;
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neg = 1;
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}
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else {
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tx = x;
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}
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ty = ABS(y);
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while (tx >= ty) {
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fx = _decomp(tx, &nx);
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fy = _decomp(ty, &ny);
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if (nx < MINEXP) {
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// tx is a denormalized number
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denorm = 1;
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nx += SCALE;
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ny += SCALE;
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tx = _set_exp(fx, nx);
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ty = _set_exp(fy, ny);
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}
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if (fx >= fy) {
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nexp = nx ;
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}
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else {
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nexp = nx - 1;
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}
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d = _set_exp(fy, nexp);
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tx -= d;
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}
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if (denorm) {
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//
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// raise only FP_U exception
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//
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return _except2(FP_U,
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OP_FMOD,
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x,
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y,
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_add_exp(tx, IEEE_ADJUST-SCALE),
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savedcw);
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}
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if (neg) {
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tx = -tx;
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}
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RETURN(savedcw,tx);
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}
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