1 /*- 2 * Copyright (c) 1992 The Regents of the University of California. 3 * All rights reserved. 4 * 5 * This software was developed by the Computer Systems Engineering group 6 * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and 7 * contributed to Berkeley. 8 * 9 * %sccs.include.redist.c% 10 */ 11 12 #if defined(LIBC_SCCS) && !defined(lint) 13 static char sccsid[] = "@(#)fixunssfdi.c 5.1 (Berkeley) 07/07/92"; 14 #endif /* LIBC_SCCS and not lint */ 15 16 #include "quad.h" 17 18 #define ONE_FOURTH (1 << (LONG_BITS - 2)) 19 #define ONE_HALF (ONE_FOURTH * 2.0) 20 #define ONE (ONE_FOURTH * 4.0) 21 22 /* 23 * Convert float to (unsigned) quad. We do most of our work in double, 24 * out of sheer paranoia. 25 * 26 * Not sure what to do with negative numbers---for now, anything out 27 * of range becomes UQUAD_MAX. 28 * 29 * N.B.: must use new ANSI syntax (sorry). 30 */ 31 u_quad_t 32 __fixunssfdi(float f) 33 { 34 double x, toppart; 35 union uu t; 36 37 if (f < 0) 38 return (UQUAD_MAX); /* ??? should be 0? ERANGE??? */ 39 if (f >= UQUAD_MAX) 40 return (UQUAD_MAX); 41 x = f; 42 /* 43 * Get the upper part of the result. Note that the divide 44 * may round up; we want to avoid this if possible, so we 45 * subtract `1/2' first. 46 */ 47 toppart = (x - ONE_HALF) / ONE; 48 /* 49 * Now build a u_quad_t out of the top part. The difference 50 * between x and this is the bottom part (this may introduce 51 * a few fuzzy bits, but what the heck). With any luck this 52 * difference will be nonnegative: x should wind up in the 53 * range [0..ULONG_MAX]. For paranoia, we assume [LONG_MIN.. 54 * 2*ULONG_MAX] instead. 55 */ 56 t.ul[H] = (unsigned long)toppart; 57 t.ul[L] = 0; 58 x -= (double)t.uq; 59 if (x < 0) { 60 t.ul[H]--; 61 x += ULONG_MAX; 62 } 63 if (x > ULONG_MAX) { 64 t.ul[H]++; 65 x -= ULONG_MAX; 66 } 67 t.ul[L] = (u_long)x; 68 return (t.uq); 69 } 70