1 /*- 2 * Copyright (c) 1992, 1993 3 * The Regents of the University of California. 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 8.1 (Berkeley) 06/04/93"; 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 #ifdef notdef /* this falls afoul of a GCC bug */ 40 if (f >= UQUAD_MAX) 41 return (UQUAD_MAX); 42 #else /* so we wire in 2^64-1 instead */ 43 if (f >= 18446744073709551615.0) 44 return (UQUAD_MAX); 45 #endif 46 x = f; 47 /* 48 * Get the upper part of the result. Note that the divide 49 * may round up; we want to avoid this if possible, so we 50 * subtract `1/2' first. 51 */ 52 toppart = (x - ONE_HALF) / ONE; 53 /* 54 * Now build a u_quad_t out of the top part. The difference 55 * between x and this is the bottom part (this may introduce 56 * a few fuzzy bits, but what the heck). With any luck this 57 * difference will be nonnegative: x should wind up in the 58 * range [0..ULONG_MAX]. For paranoia, we assume [LONG_MIN.. 59 * 2*ULONG_MAX] instead. 60 */ 61 t.ul[H] = (unsigned long)toppart; 62 t.ul[L] = 0; 63 x -= (double)t.uq; 64 if (x < 0) { 65 t.ul[H]--; 66 x += ULONG_MAX; 67 } 68 if (x > ULONG_MAX) { 69 t.ul[H]++; 70 x -= ULONG_MAX; 71 } 72 t.ul[L] = (u_long)x; 73 return (t.uq); 74 } 75