120 lines
4.7 KiB
C++
120 lines
4.7 KiB
C++
// Copyright 2018 The Abseil Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// https://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#include "absl/strings/internal/pow10_helper.h"
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#include <cmath>
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#include "gtest/gtest.h"
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#include "absl/strings/str_format.h"
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namespace absl {
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namespace strings_internal {
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namespace {
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struct TestCase {
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int power; // Testing Pow10(power)
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uint64_t significand; // Raw bits of the expected value
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int radix; // significand is adjusted by 2^radix
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};
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TEST(Pow10HelperTest, Works) {
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// The logic in pow10_helper.cc is so simple that theoretically we don't even
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// need a test. However, we're paranoid and believe that there may be
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// compilers that don't round floating-point literals correctly, even though
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// it is specified by the standard. We check various edge cases, just to be
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// sure.
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constexpr TestCase kTestCases[] = {
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// Subnormals
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{-323, 0x2, -1074},
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{-322, 0x14, -1074},
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{-321, 0xca, -1074},
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{-320, 0x7e8, -1074},
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{-319, 0x4f10, -1074},
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{-318, 0x316a2, -1074},
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{-317, 0x1ee257, -1074},
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{-316, 0x134d761, -1074},
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{-315, 0xc1069cd, -1074},
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{-314, 0x78a42205, -1074},
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{-313, 0x4b6695433, -1074},
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{-312, 0x2f201d49fb, -1074},
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{-311, 0x1d74124e3d1, -1074},
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{-310, 0x12688b70e62b, -1074},
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{-309, 0xb8157268fdaf, -1074},
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{-308, 0x730d67819e8d2, -1074},
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// Values that are very close to rounding the other way.
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// Comment shows difference of significand from the true value.
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{-307, 0x11fa182c40c60d, -1072}, // -.4588
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{-290, 0x18f2b061aea072, -1016}, // .4854
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{-276, 0x11BA03F5B21000, -969}, // .4709
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{-259, 0x1899C2F6732210, -913}, // .4830
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{-252, 0x1D53844EE47DD1, -890}, // -.4743
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{-227, 0x1E5297287C2F45, -807}, // -.4708
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{-198, 0x1322E220A5B17E, -710}, // -.4714
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{-195, 0x12B010D3E1CF56, -700}, // .4928
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{-192, 0x123FF06EEA847A, -690}, // .4968
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{-163, 0x1708D0F84D3DE7, -594}, // -.4977
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{-145, 0x13FAAC3E3FA1F3, -534}, // -.4785
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{-111, 0x133D4032C2C7F5, -421}, // .4774
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{-106, 0x1D5B561574765B, -405}, // -.4869
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{-104, 0x16EF5B40C2FC77, -398}, // -.4741
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{-88, 0x197683DF2F268D, -345}, // -.4738
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{-86, 0x13E497065CD61F, -338}, // .4736
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{-76, 0x17288E1271F513, -305}, // -.4761
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{-63, 0x1A53FC9631D10D, -262}, // .4929
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{-30, 0x14484BFEEBC2A0, -152}, // .4758
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{-21, 0x12E3B40A0E9B4F, -122}, // -.4916
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{-5, 0x14F8B588E368F1, -69}, // .4829
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{23, 0x152D02C7E14AF6, 24}, // -.5000 (exactly, round-to-even)
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{29, 0x1431E0FAE6D721, 44}, // -.4870
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{34, 0x1ED09BEAD87C03, 60}, // -.4721
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{70, 0x172EBAD6DDC73D, 180}, // .4733
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{105, 0x1BE7ABD3781ECA, 296}, // -.4850
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{126, 0x17A2ECC414A03F, 366}, // -.4999
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{130, 0x1CDA62055B2D9E, 379}, // .4855
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{165, 0x115D847AD00087, 496}, // -.4913
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{172, 0x14B378469B6732, 519}, // .4818
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{187, 0x1262DFEEBBB0F9, 569}, // -.4805
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{210, 0x18557F31326BBB, 645}, // -.4992
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{212, 0x1302CB5E6F642A, 652}, // -.4838
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{215, 0x1290BA9A38C7D1, 662}, // -.4881
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{236, 0x1F736F9B3494E9, 731}, // .4707
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{244, 0x176EC98994F489, 758}, // .4924
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{250, 0x1658E3AB795204, 778}, // -.4963
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{252, 0x117571DDF6C814, 785}, // .4873
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{254, 0x1B4781EAD1989E, 791}, // -.4887
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{260, 0x1A03FDE214CAF1, 811}, // .4784
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{284, 0x1585041B2C477F, 891}, // .4798
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{304, 0x1D2A1BE4048F90, 957}, // -.4987
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// Out-of-range values
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{-324, 0x0, 0},
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{-325, 0x0, 0},
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{-326, 0x0, 0},
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{309, 1, 2000},
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{310, 1, 2000},
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{311, 1, 2000},
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};
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for (const TestCase& test_case : kTestCases) {
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EXPECT_EQ(Pow10(test_case.power),
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std::ldexp(test_case.significand, test_case.radix))
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<< absl::StrFormat("Failure for Pow10(%d): %a vs %a", test_case.power,
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Pow10(test_case.power),
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std::ldexp(test_case.significand, test_case.radix));
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}
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}
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} // namespace
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} // namespace strings_internal
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} // namespace absl
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