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[] = "@(#)fixunsdfdi.c 5.3 (Berkeley) 06/02/92"; 14 #endif /* LIBC_SCCS and not lint */ 15 16 #include "quad.h" 17 18 #ifndef UQUAD_MAX /* should be in <limits.h> maybe? */ 19 #define UQUAD_MAX ((u_quad)0 - 1) 20 #endif 21 22 #define ONE_FOURTH (1 << (LONG_BITS - 2)) 23 #define ONE_HALF (ONE_FOURTH * 2.0) 24 #define ONE (ONE_FOURTH * 4.0) 25 26 /* 27 * Convert double to (unsigned) quad. 28 * Not sure what to do with negative numbers---for now, anything out 29 * of range becomes UQUAD_MAX. 30 */ 31 u_quad 32 __fixunsdfdi(double x) 33 { 34 double toppart; 35 union uu t; 36 37 if (x < 0) 38 return (UQUAD_MAX); /* ??? should be 0? ERANGE??? */ 39 if (x >= UQUAD_MAX) 40 return (UQUAD_MAX); 41 /* 42 * Get the upper part of the result. Note that the divide 43 * may round up; we want to avoid this if possible, so we 44 * subtract `1/2' first. 45 */ 46 toppart = (x - ONE_HALF) / ONE; 47 /* 48 * Now build a u_quad out of the top part. The difference 49 * between x and this is the bottom part (this may introduce 50 * a few fuzzy bits, but what the heck). With any luck this 51 * difference will be nonnegative: x should wind up in the 52 * range [0..ULONG_MAX]. For paranoia, we assume [LONG_MIN.. 53 * 2*ULONG_MAX] instead. 54 */ 55 t.ul[H] = (unsigned long)toppart; 56 t.ul[L] = 0; 57 x -= (double)t.uq; 58 if (x < 0) { 59 t.ul[H]--; 60 x += ULONG_MAX; 61 } 62 if (x > ULONG_MAX) { 63 t.ul[H]++; 64 x -= ULONG_MAX; 65 } 66 t.ul[L] = (u_long)x; 67 return (t.uq); 68 } 69