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-rw-r--r--src/math/modf.c70
1 files changed, 70 insertions, 0 deletions
diff --git a/src/math/modf.c b/src/math/modf.c
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+/* origin: FreeBSD /usr/src/lib/msun/src/s_modf.c */
+/*
+ * ====================================================
+ * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+ *
+ * Developed at SunPro, a Sun Microsystems, Inc. business.
+ * Permission to use, copy, modify, and distribute this
+ * software is freely granted, provided that this notice
+ * is preserved.
+ * ====================================================
+ */
+/*
+ * modf(double x, double *iptr)
+ * return fraction part of x, and return x's integral part in *iptr.
+ * Method:
+ * Bit twiddling.
+ *
+ * Exception:
+ * No exception.
+ */
+
+#include "libm.h"
+
+static const double one = 1.0;
+
+double modf(double x, double *iptr)
+{
+ int32_t i0,i1,j0;
+ uint32_t i;
+
+ EXTRACT_WORDS(i0, i1, x);
+ j0 = ((i0>>20) & 0x7ff) - 0x3ff; /* exponent of x */
+ if (j0 < 20) { /* integer part in high x */
+ if (j0 < 0) { /* |x| < 1 */
+ INSERT_WORDS(*iptr, i0 & 0x80000000, 0); /* *iptr = +-0 */
+ return x;
+ }
+ i = 0x000fffff >> j0;
+ if (((i0&i)|i1) == 0) { /* x is integral */
+ uint32_t high;
+ *iptr = x;
+ GET_HIGH_WORD(high, x);
+ INSERT_WORDS(x, high & 0x80000000, 0); /* return +-0 */
+ return x;
+ }
+ INSERT_WORDS(*iptr, i0&~i, 0);
+ return x - *iptr;
+ } else if (j0 > 51) { /* no fraction part */
+ uint32_t high;
+ if (j0 == 0x400) { /* inf/NaN */
+ *iptr = x;
+ return 0.0 / x;
+ }
+ *iptr = x*one;
+ GET_HIGH_WORD(high, x);
+ INSERT_WORDS(x, high & 0x80000000, 0); /* return +-0 */
+ return x;
+ } else { /* fraction part in low x */
+ i = (uint32_t)0xffffffff >> (j0 - 20);
+ if ((i1&i) == 0) { /* x is integral */
+ uint32_t high;
+ *iptr = x;
+ GET_HIGH_WORD(high, x);
+ INSERT_WORDS(x, high & 0x80000000, 0); /* return +-0 */
+ return x;
+ }
+ INSERT_WORDS(*iptr, i0, i1&~i);
+ return x - *iptr;
+ }
+}