inline bool StrtodDiyFp()

in src/main/cpp/sdk/common/rapidjson/internal/strtod.h [131:206]
64 lines of code
15 McCabe index (conditional complexity)

inline bool StrtodDiyFp(const char* decimals, int dLen, int dExp, double* result) {
    uint64_t significand = 0;
    int i = 0;   // 2^64 - 1 = 18446744073709551615, 1844674407370955161 = 0x1999999999999999    
    for (; i < dLen; i++) {
        if (significand  >  RAPIDJSON_UINT64_C2(0x19999999, 0x99999999) ||
            (significand == RAPIDJSON_UINT64_C2(0x19999999, 0x99999999) && decimals[i] > '5'))
            break;
        significand = significand * 10u + static_cast<unsigned>(decimals[i] - '0');
    }
    
    if (i < dLen && decimals[i] >= '5') // Rounding
        significand++;

    int remaining = dLen - i;
    const int kUlpShift = 3;
    const int kUlp = 1 << kUlpShift;
    int64_t error = (remaining == 0) ? 0 : kUlp / 2;

    DiyFp v(significand, 0);
    v = v.Normalize();
    error <<= -v.e;

    dExp += remaining;

    int actualExp;
    DiyFp cachedPower = GetCachedPower10(dExp, &actualExp);
    if (actualExp != dExp) {
        static const DiyFp kPow10[] = {
            DiyFp(RAPIDJSON_UINT64_C2(0xa0000000, 0x00000000), -60),  // 10^1
            DiyFp(RAPIDJSON_UINT64_C2(0xc8000000, 0x00000000), -57),  // 10^2
            DiyFp(RAPIDJSON_UINT64_C2(0xfa000000, 0x00000000), -54),  // 10^3
            DiyFp(RAPIDJSON_UINT64_C2(0x9c400000, 0x00000000), -50),  // 10^4
            DiyFp(RAPIDJSON_UINT64_C2(0xc3500000, 0x00000000), -47),  // 10^5
            DiyFp(RAPIDJSON_UINT64_C2(0xf4240000, 0x00000000), -44),  // 10^6
            DiyFp(RAPIDJSON_UINT64_C2(0x98968000, 0x00000000), -40)   // 10^7
        };
        int adjustment = dExp - actualExp;
        RAPIDJSON_ASSERT(adjustment >= 1 && adjustment < 8);
        v = v * kPow10[adjustment - 1];
        if (dLen + adjustment > 19) // has more digits than decimal digits in 64-bit
            error += kUlp / 2;
    }

    v = v * cachedPower;

    error += kUlp + (error == 0 ? 0 : 1);

    const int oldExp = v.e;
    v = v.Normalize();
    error <<= oldExp - v.e;

    const int effectiveSignificandSize = Double::EffectiveSignificandSize(64 + v.e);
    int precisionSize = 64 - effectiveSignificandSize;
    if (precisionSize + kUlpShift >= 64) {
        int scaleExp = (precisionSize + kUlpShift) - 63;
        v.f >>= scaleExp;
        v.e += scaleExp; 
        error = (error >> scaleExp) + 1 + kUlp;
        precisionSize -= scaleExp;
    }

    DiyFp rounded(v.f >> precisionSize, v.e + precisionSize);
    const uint64_t precisionBits = (v.f & ((uint64_t(1) << precisionSize) - 1)) * kUlp;
    const uint64_t halfWay = (uint64_t(1) << (precisionSize - 1)) * kUlp;
    if (precisionBits >= halfWay + static_cast<unsigned>(error)) {
        rounded.f++;
        if (rounded.f & (DiyFp::kDpHiddenBit << 1)) { // rounding overflows mantissa (issue #340)
            rounded.f >>= 1;
            rounded.e++;
        }
    }

    *result = rounded.ToDouble();

    return halfWay - static_cast<unsigned>(error) >= precisionBits || precisionBits >= halfWay + static_cast<unsigned>(error);
}