| 1 | /*
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| 2 | * Copyright (c) 2014 Martin Decky
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| 3 | * All rights reserved.
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| 4 | *
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| 5 | * Redistribution and use in source and binary forms, with or without
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| 6 | * modification, are permitted provided that the following conditions
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| 7 | * are met:
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| 8 | *
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| 9 | * - Redistributions of source code must retain the above copyright
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| 10 | * notice, this list of conditions and the following disclaimer.
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| 11 | * - Redistributions in binary form must reproduce the above copyright
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| 12 | * notice, this list of conditions and the following disclaimer in the
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| 13 | * documentation and/or other materials provided with the distribution.
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| 14 | * - The name of the author may not be used to endorse or promote products
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| 15 | * derived from this software without specific prior written permission.
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| 16 | *
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| 17 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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| 18 | * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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| 19 | * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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| 20 | * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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| 21 | * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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| 22 | * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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| 23 | * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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| 24 | * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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| 25 | * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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| 26 | * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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| 27 | */
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| 28 |
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| 29 | /** @addtogroup libmath
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| 30 | * @{
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| 31 | */
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| 32 | /** @file
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| 33 | */
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| 34 |
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| 35 | #include <mathtypes.h>
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| 36 | #include <trunc.h>
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| 37 |
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| 38 | /** Truncate fractional part (round towards zero)
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| 39 | *
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| 40 | * Truncate the fractional part of IEEE 754 double
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| 41 | * precision floating point number by zeroing fraction
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| 42 | * bits, effectively rounding the number towards zero
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| 43 | * to the nearest whole number.
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| 44 | *
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| 45 | * If the argument is infinity or NaN, an exception
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| 46 | * should be indicated. This is not implemented yet.
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| 47 | *
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| 48 | * @param val Floating point number.
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| 49 | *
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| 50 | * @return Number rounded towards zero.
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| 51 | *
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| 52 | */
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| 53 | float64 trunc_float64(float64 val)
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| 54 | {
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| 55 | int32_t exp = val.parts.exp - FLOAT64_BIAS;
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| 56 |
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| 57 | if (exp < 0) {
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| 58 | /* -1 < val < 1 => result is +0 or -0 */
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| 59 | val.parts.exp = 0;
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| 60 | val.parts.fraction = 0;
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| 61 | } else if (exp >= FLOAT64_FRACTION_SIZE) {
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| 62 | if (exp == 1024) {
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| 63 | /* val is +inf, -inf or NaN => trigger an exception */
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| 64 | // FIXME TODO
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| 65 | }
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| 66 |
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| 67 | /* All bits in val are relevant for the result */
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| 68 | } else {
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| 69 | /* Truncate irrelevant fraction bits */
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| 70 | val.parts.fraction &= ~(UINT64_C(0x000fffffffffffff) >> exp);
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| 71 | }
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| 72 |
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| 73 | return val;
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| 74 | }
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| 75 |
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| 76 | /** @}
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| 77 | */
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