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