OpenTTD Source  20241111-master-gce64d5f5d9
math_func.cpp
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1 /*
2  * This file is part of OpenTTD.
3  * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
4  * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
5  * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
6  */
7 
10 #include "../stdafx.h"
11 
12 #include "../3rdparty/catch2/catch.hpp"
13 
14 #include "../core/math_func.hpp"
15 
16 TEST_CASE("DivideApproxTest - Negative")
17 {
18  CHECK(-2 == DivideApprox(-5, 2));
19  CHECK(2 == DivideApprox(-5, -2));
20  CHECK(-1 == DivideApprox(-66, 80));
21 }
22 
23 TEST_CASE("DivideApproxTest, Divide")
24 {
25  CHECK(2 == DivideApprox(5, 2));
26  CHECK(3 == DivideApprox(80, 30));
27  CHECK(3 == DivideApprox(8, 3));
28  CHECK(0 == DivideApprox(3, 8));
29 }
30 
31 TEST_CASE("IntSqrtTest - Zero")
32 {
33  CHECK(0 == IntSqrt(0));
34 }
35 
36 TEST_CASE("IntSqrtTest - FindSqRt")
37 {
38  CHECK(5 == IntSqrt(25));
39  CHECK(10 == IntSqrt(100));
40  CHECK(9 == IntSqrt(88));
41  CHECK(1696 == IntSqrt(2876278));
42 }
43 
44 
45 TEST_CASE("ClampTo")
46 {
47  CHECK(0 == ClampTo<uint8_t>(std::numeric_limits<int64_t>::lowest()));
48  CHECK(0 == ClampTo<uint8_t>(-1));
49  CHECK(0 == ClampTo<uint8_t>(0));
50  CHECK(1 == ClampTo<uint8_t>(1));
51 
52  CHECK(255 == ClampTo<uint8_t>(std::numeric_limits<uint64_t>::max()));
53  CHECK(255 == ClampTo<uint8_t>(256));
54  CHECK(255 == ClampTo<uint8_t>(255));
55  CHECK(254 == ClampTo<uint8_t>(254));
56 
57  CHECK(-128 == ClampTo<int8_t>(std::numeric_limits<int64_t>::lowest()));
58  CHECK(-128 == ClampTo<int8_t>(-129));
59  CHECK(-128 == ClampTo<int8_t>(-128));
60  CHECK(-127 == ClampTo<int8_t>(-127));
61 
62  CHECK(127 == ClampTo<int8_t>(std::numeric_limits<uint64_t>::max()));
63  CHECK(127 == ClampTo<int8_t>(128));
64  CHECK(127 == ClampTo<int8_t>(127));
65  CHECK(126 == ClampTo<int8_t>(126));
66 
67  CHECK(126 == ClampTo<int64_t>(static_cast<uint8_t>(126)));
68  CHECK(126 == ClampTo<uint64_t>(static_cast<int8_t>(126)));
69  CHECK(0 == ClampTo<uint64_t>(static_cast<int8_t>(-126)));
70  CHECK(0 == ClampTo<uint8_t>(static_cast<int8_t>(-126)));
71 
72  /* The realm around 64 bits types is tricky as there is not one type/method that works for all. */
73 
74  /* lowest/max uint64_t does not get clamped when clamping to uint64_t. */
75  CHECK(std::numeric_limits<uint64_t>::lowest() == ClampTo<uint64_t>(std::numeric_limits<uint64_t>::lowest()));
76  CHECK(std::numeric_limits<uint64_t>::max() == ClampTo<uint64_t>(std::numeric_limits<uint64_t>::max()));
77 
78  /* negative int64_t get clamped to 0. */
79  CHECK(0 == ClampTo<uint64_t>(std::numeric_limits<int64_t>::lowest()));
80  CHECK(0 == ClampTo<uint64_t>(int64_t(-1)));
81  /* positive int64_t remain the same. */
82  CHECK(1 == ClampTo<uint64_t>(int64_t(1)));
83  CHECK(static_cast<uint64_t>(std::numeric_limits<int64_t>::max()) == ClampTo<uint64_t>(std::numeric_limits<int64_t>::max()));
84 
85  /* max uint64_t gets clamped to max int64_t. */
86  CHECK(std::numeric_limits<int64_t>::max() == ClampTo<int64_t>(std::numeric_limits<uint64_t>::max()));
87 }
88 
89 
90 TEST_CASE("SoftClamp")
91 {
92  /* Special behaviour of soft clamp returning the average of min/max when min is higher than max. */
93  CHECK(1250 == SoftClamp(0, 1500, 1000));
94  int million = 1000 * 1000;
95  CHECK(1250 * million == SoftClamp(0, 1500 * million, 1000 * million));
96  CHECK(0 == SoftClamp(0, 1500 * million, -1500 * million));
97 }
int DivideApprox(int a, int b)
Deterministic approximate division.
Definition: math_func.cpp:22
uint32_t IntSqrt(uint32_t num)
Compute the integer square root.
Definition: math_func.cpp:42
constexpr T SoftClamp(const T a, const T min, const T max)
Clamp a value between an interval.
Definition: math_func.hpp:102