1 files changed, 132 insertions, 0 deletions
diff --git a/src/rapidjson/test/unittest/strtodtest.cpp b/src/rapidjson/test/unittest/strtodtest.cpp
new file mode 100644
index 000000000..cde836c7e
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+++ b/src/rapidjson/test/unittest/strtodtest.cpp
@@ -0,0 +1,132 @@
+// Tencent is pleased to support the open source community by making RapidJSON available.
+// 
+// Copyright (C) 2015 THL A29 Limited, a Tencent company, and Milo Yip. All rights reserved.
+//
+// Licensed under the MIT License (the "License"); you may not use this file except
+// in compliance with the License. You may obtain a copy of the License at
+//
+// http://opensource.org/licenses/MIT
+//
+// 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 "unittest.h"
+
+#include "rapidjson/internal/strtod.h"
+
+#ifdef __clang__
+RAPIDJSON_DIAG_PUSH
+RAPIDJSON_DIAG_OFF(unreachable-code)
+#endif
+
+#define BIGINTEGER_LITERAL(s) BigInteger(s, sizeof(s) - 1)
+
+using namespace rapidjson::internal;
+
+TEST(Strtod, CheckApproximationCase) {
+    static const int kSignificandSize = 52;
+    static const int kExponentBias = 0x3FF;
+    static const uint64_t kExponentMask = RAPIDJSON_UINT64_C2(0x7FF00000, 0x00000000);
+    static const uint64_t kSignificandMask = RAPIDJSON_UINT64_C2(0x000FFFFF, 0xFFFFFFFF);
+    static const uint64_t kHiddenBit = RAPIDJSON_UINT64_C2(0x00100000, 0x00000000);
+
+    // http://www.exploringbinary.com/using-integers-to-check-a-floating-point-approximation/
+    // Let b = 0x1.465a72e467d88p-149
+    //       = 5741268244528520 x 2^-201
+    union {
+        double d;
+        uint64_t u;
+    }u;
+    u.u = 0x465a72e467d88 | ((static_cast<uint64_t>(-149 + kExponentBias)) << kSignificandSize);
+    const double b = u.d;
+    const uint64_t bInt = (u.u & kSignificandMask) | kHiddenBit;
+    const int bExp = static_cast<int>(((u.u & kExponentMask) >> kSignificandSize) - kExponentBias - kSignificandSize);
+    EXPECT_DOUBLE_EQ(1.7864e-45, b);
+    EXPECT_EQ(RAPIDJSON_UINT64_C2(0x001465a7, 0x2e467d88), bInt);
+    EXPECT_EQ(-201, bExp);
+
+    // Let d = 17864 x 10-49
+    const char dInt[] = "17864";
+    const int dExp = -49;
+
+    // Let h = 2^(bExp-1)
+    const int hExp = bExp - 1;
+    EXPECT_EQ(-202, hExp);
+
+    int dS_Exp2 = 0;
+    int dS_Exp5 = 0;
+    int bS_Exp2 = 0;
+    int bS_Exp5 = 0;
+    int hS_Exp2 = 0;
+    int hS_Exp5 = 0;
+
+    // Adjust for decimal exponent
+    if (dExp >= 0) {
+        dS_Exp2 += dExp;
+        dS_Exp5 += dExp;
+    }
+    else {
+        bS_Exp2 -= dExp;
+        bS_Exp5 -= dExp;
+        hS_Exp2 -= dExp;
+        hS_Exp5 -= dExp;
+    }
+
+    // Adjust for binary exponent
+    if (bExp >= 0)
+        bS_Exp2 += bExp;
+    else {
+        dS_Exp2 -= bExp;
+        hS_Exp2 -= bExp;
+    }
+
+    // Adjust for half ulp exponent
+    if (hExp >= 0)
+        hS_Exp2 += hExp;
+    else {
+        dS_Exp2 -= hExp;
+        bS_Exp2 -= hExp;
+    }
+
+    // Remove common power of two factor from all three scaled values
+    int common_Exp2 = std::min(dS_Exp2, std::min(bS_Exp2, hS_Exp2));
+    dS_Exp2 -= common_Exp2;
+    bS_Exp2 -= common_Exp2;
+    hS_Exp2 -= common_Exp2;
+
+    EXPECT_EQ(153, dS_Exp2);
+    EXPECT_EQ(0, dS_Exp5);
+    EXPECT_EQ(1, bS_Exp2);
+    EXPECT_EQ(49, bS_Exp5);
+    EXPECT_EQ(0, hS_Exp2);
+    EXPECT_EQ(49, hS_Exp5);
+
+    BigInteger dS = BIGINTEGER_LITERAL(dInt);
+    dS.MultiplyPow5(static_cast<unsigned>(dS_Exp5)) <<= static_cast<size_t>(dS_Exp2);
+
+    BigInteger bS(bInt);
+    bS.MultiplyPow5(static_cast<unsigned>(bS_Exp5)) <<= static_cast<size_t>(bS_Exp2);
+
+    BigInteger hS(1);
+    hS.MultiplyPow5(static_cast<unsigned>(hS_Exp5)) <<= static_cast<size_t>(hS_Exp2);
+
+    EXPECT_TRUE(BIGINTEGER_LITERAL("203970822259994138521801764465966248930731085529088") == dS);
+    EXPECT_TRUE(BIGINTEGER_LITERAL("203970822259994122305215569213032722473144531250000") == bS);
+    EXPECT_TRUE(BIGINTEGER_LITERAL("17763568394002504646778106689453125") == hS);
+
+    EXPECT_EQ(1, dS.Compare(bS));
+    
+    BigInteger delta(0);
+    EXPECT_FALSE(dS.Difference(bS, &delta));
+    EXPECT_TRUE(BIGINTEGER_LITERAL("16216586195252933526457586554279088") == delta);
+    EXPECT_TRUE(bS.Difference(dS, &delta));
+    EXPECT_TRUE(BIGINTEGER_LITERAL("16216586195252933526457586554279088") == delta);
+
+    EXPECT_EQ(-1, delta.Compare(hS));
+}
+
+#ifdef __clang__
+RAPIDJSON_DIAG_POP
+#endif