133 lines
4.2 KiB
C++
133 lines
4.2 KiB
C++
// Tencent is pleased to support the open source community by making RapidJSON available.
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//
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// Copyright (C) 2015 THL A29 Limited, a Tencent company, and Milo Yip. All rights reserved.
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//
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// Licensed under the MIT License (the "License"); you may not use this file except
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// in compliance with the License. You may obtain a copy of the License at
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//
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// http://opensource.org/licenses/MIT
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//
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// Unless required by applicable law or agreed to in writing, software distributed
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// under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
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// CONDITIONS OF ANY KIND, either express or implied. See the License for the
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// specific language governing permissions and limitations under the License.
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#include "unittest.h"
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#include "rapidjson/internal/strtod.h"
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#ifdef __clang__
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RAPIDJSON_DIAG_PUSH
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RAPIDJSON_DIAG_OFF(unreachable-code)
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#endif
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#define BIGINTEGER_LITERAL(s) BigInteger(s, sizeof(s) - 1)
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using namespace rapidjson::internal;
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TEST(Strtod, CheckApproximationCase) {
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static const int kSignificandSize = 52;
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static const int kExponentBias = 0x3FF;
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static const uint64_t kExponentMask = RAPIDJSON_UINT64_C2(0x7FF00000, 0x00000000);
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static const uint64_t kSignificandMask = RAPIDJSON_UINT64_C2(0x000FFFFF, 0xFFFFFFFF);
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static const uint64_t kHiddenBit = RAPIDJSON_UINT64_C2(0x00100000, 0x00000000);
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// http://www.exploringbinary.com/using-integers-to-check-a-floating-point-approximation/
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// Let b = 0x1.465a72e467d88p-149
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// = 5741268244528520 x 2^-201
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union {
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double d;
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uint64_t u;
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}u;
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u.u = 0x465a72e467d88 | ((static_cast<uint64_t>(-149 + kExponentBias)) << kSignificandSize);
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const double b = u.d;
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const uint64_t bInt = (u.u & kSignificandMask) | kHiddenBit;
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const int bExp = static_cast<int>(((u.u & kExponentMask) >> kSignificandSize) - kExponentBias - kSignificandSize);
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EXPECT_DOUBLE_EQ(1.7864e-45, b);
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EXPECT_EQ(RAPIDJSON_UINT64_C2(0x001465a7, 0x2e467d88), bInt);
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EXPECT_EQ(-201, bExp);
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// Let d = 17864 x 10-49
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const char dInt[] = "17864";
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const int dExp = -49;
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// Let h = 2^(bExp-1)
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const int hExp = bExp - 1;
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EXPECT_EQ(-202, hExp);
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int dS_Exp2 = 0;
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int dS_Exp5 = 0;
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int bS_Exp2 = 0;
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int bS_Exp5 = 0;
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int hS_Exp2 = 0;
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int hS_Exp5 = 0;
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// Adjust for decimal exponent
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if (dExp >= 0) {
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dS_Exp2 += dExp;
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dS_Exp5 += dExp;
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}
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else {
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bS_Exp2 -= dExp;
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bS_Exp5 -= dExp;
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hS_Exp2 -= dExp;
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hS_Exp5 -= dExp;
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}
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// Adjust for binary exponent
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if (bExp >= 0)
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bS_Exp2 += bExp;
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else {
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dS_Exp2 -= bExp;
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hS_Exp2 -= bExp;
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}
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// Adjust for half ulp exponent
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if (hExp >= 0)
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hS_Exp2 += hExp;
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else {
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dS_Exp2 -= hExp;
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bS_Exp2 -= hExp;
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}
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// Remove common power of two factor from all three scaled values
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int common_Exp2 = std::min(dS_Exp2, std::min(bS_Exp2, hS_Exp2));
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dS_Exp2 -= common_Exp2;
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bS_Exp2 -= common_Exp2;
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hS_Exp2 -= common_Exp2;
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EXPECT_EQ(153, dS_Exp2);
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EXPECT_EQ(0, dS_Exp5);
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EXPECT_EQ(1, bS_Exp2);
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EXPECT_EQ(49, bS_Exp5);
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EXPECT_EQ(0, hS_Exp2);
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EXPECT_EQ(49, hS_Exp5);
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BigInteger dS = BIGINTEGER_LITERAL(dInt);
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dS.MultiplyPow5(static_cast<unsigned>(dS_Exp5)) <<= static_cast<size_t>(dS_Exp2);
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BigInteger bS(bInt);
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bS.MultiplyPow5(static_cast<unsigned>(bS_Exp5)) <<= static_cast<size_t>(bS_Exp2);
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BigInteger hS(1);
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hS.MultiplyPow5(static_cast<unsigned>(hS_Exp5)) <<= static_cast<size_t>(hS_Exp2);
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EXPECT_TRUE(BIGINTEGER_LITERAL("203970822259994138521801764465966248930731085529088") == dS);
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EXPECT_TRUE(BIGINTEGER_LITERAL("203970822259994122305215569213032722473144531250000") == bS);
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EXPECT_TRUE(BIGINTEGER_LITERAL("17763568394002504646778106689453125") == hS);
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EXPECT_EQ(1, dS.Compare(bS));
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BigInteger delta(0);
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EXPECT_FALSE(dS.Difference(bS, &delta));
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EXPECT_TRUE(BIGINTEGER_LITERAL("16216586195252933526457586554279088") == delta);
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EXPECT_TRUE(bS.Difference(dS, &delta));
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EXPECT_TRUE(BIGINTEGER_LITERAL("16216586195252933526457586554279088") == delta);
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EXPECT_EQ(-1, delta.Compare(hS));
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}
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#ifdef __clang__
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RAPIDJSON_DIAG_POP
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#endif
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