projects / unix-history / blame
| Commit | Line | Data |
|---|---|---|
| 9ef392c7 | 1 | /*- |
| f7e479c4 KB |
2 | * Copyright (c) 1992, 1993 |
| 3 | * The Regents of the University of California. All rights reserved. | |
| 9ef392c7 CT |
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) | |
| f7e479c4 | 13 | static char sccsid[] = "@(#)fixunssfdi.c 8.1 (Berkeley) %G%"; |
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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??? */ | |
| f4d23f5b | 39 | #ifdef notdef /* this falls afoul of a GCC bug */ |
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40 | if (f >= UQUAD_MAX) |
| 41 | return (UQUAD_MAX); | |
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42 | #else /* so we wire in 2^64-1 instead */ |
| 43 | if (f >= 18446744073709551615.0) | |
| 44 | return (UQUAD_MAX); | |
| 45 | #endif | |
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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 | } |