1 // Copyright (c) 2017 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4
5 #include <math.h>
6
7 #include "base/stl_util.h"
8 #include "testing/gtest/include/gtest/gtest.h"
9 #include "ui/gfx/half_float.h"
10
11 namespace gfx {
12
13 class HalfFloatTest : public testing::Test {
14 public:
15 union FloatUIntUnion {
16 // this must come first for the initializations below to work
17 uint32_t fUInt;
18 float fFloat;
19 };
20
21 // Convert an IEEE 754 half-float to a float value
22 // that we can do math on.
FromHalfFloat(HalfFloat half_float)23 float FromHalfFloat(HalfFloat half_float) {
24 int sign = (half_float & 0x8000) ? -1 : 1;
25 int exponent = (half_float >> 10) & 0x1F;
26 int fraction = half_float & 0x3FF;
27 if (exponent == 0) {
28 return powf(2.0f, -24.0f) * fraction;
29 } else if (exponent == 0x1F) {
30 return sign * 1000000000000.0f;
31 } else {
32 return pow(2.0f, exponent - 25) * (0x400 + fraction);
33 }
34 }
35
ConvertTruth(float f)36 HalfFloat ConvertTruth(float f) {
37 if (f < 0.0)
38 return 0x8000 | ConvertTruth(-f);
39 int max = 0x8000;
40 int min = 0;
41 while (max - min > 1) {
42 int mid = (min + max) >> 1;
43 if (FromHalfFloat(mid) > f) {
44 max = mid;
45 } else {
46 min = mid;
47 }
48 }
49 float low = FromHalfFloat(min);
50 float high = FromHalfFloat(min + 1);
51 if (f - low <= high - f) {
52 return min;
53 } else {
54 return min + 1;
55 }
56 }
57
Convert(float f)58 HalfFloat Convert(float f) {
59 HalfFloat ret;
60 FloatToHalfFloat(&f, &ret, 1);
61 return ret;
62 }
63 };
64
TEST_F(HalfFloatTest,NoCrashTest)65 TEST_F(HalfFloatTest, NoCrashTest) {
66 Convert(nanf(""));
67 Convert(1.0E30f);
68 Convert(-1.0E30f);
69 Convert(1.0E-30f);
70 Convert(-1.0E-30f);
71 }
72
TEST_F(HalfFloatTest,SimpleTest)73 TEST_F(HalfFloatTest, SimpleTest) {
74 static float test[] = {
75 0.0f, 1.0f, 10.0f, 1000.0f, 65503.0f,
76 1.0E-3f, 1.0E-6f, 1.0E-20f, 1.0E-44f,
77 };
78 for (size_t i = 0; i < base::size(test); i++) {
79 EXPECT_EQ(ConvertTruth(test[i]), Convert(test[i])) << " float = "
80 << test[i];
81 if (test[i] != 0.0) {
82 EXPECT_EQ(ConvertTruth(-test[i]), Convert(-test[i])) << " float = "
83 << -test[i];
84 }
85 }
86 }
87
88 } // namespace
89