Maxim Integrated / Mbed OS MAXREFDES155#

DeepCover Embedded Security in IoT: Public-key Secured Data Paths

Dependencies:   MaximInterface

The MAXREFDES155# is an internet-of-things (IoT) embedded-security reference design, built to authenticate and control a sensing node using elliptic-curve-based public-key cryptography with control and notification from a web server.

The hardware includes an ARM® mbed™ shield and attached sensor endpoint. The shield contains a DS2476 DeepCover® ECDSA/SHA-2 coprocessor, Wifi communication, LCD push-button controls, and status LEDs. The sensor endpoint is attached to the shield using a 300mm cable and contains a DS28C36 DeepCover ECDSA/SHA-2 authenticator, IR-thermal sensor, and aiming laser for the IR sensor. The MAXREFDES155# is equipped with a standard Arduino® form-factor shield connector for immediate testing using an mbed board such as the MAX32600MBED#. The combination of these two devices represent an IoT device. Communication to the web server is accomplished with the shield Wifi circuitry. Communication from the shield to the attached sensor module is accomplished over I2C . The sensor module represents an IoT endpoint that generates small data with a requirement for message authenticity/integrity and secure on/off operational control.

The design is hierarchical with each mbed platform and shield communicating data from the sensor node to a web server that maintains a centralized log and dispatches notifications as necessary. The simplicity of this design enables rapid integration into any star-topology IoT network to provide security with the low overhead and cost provided by the ECDSA-P256 asymmetric-key and SHA-256 symmetric-key algorithms.

More information about the MAXREFDES155# is available on the Maxim Integrated website.

rapidjson/internal/strtod.h@0:33d4e66780c0, 2017-02-24 (annotated)

Committer:
IanBenzMaxim
Date:
Fri Feb 24 11:23:12 2017 -0600
Revision:
0:33d4e66780c0
Initial commit.

Who changed what in which revision?

UserRevisionLine numberNew contents of line
IanBenzMaxim 0:33d4e66780c0 1 // Tencent is pleased to support the open source community by making RapidJSON available.
IanBenzMaxim 0:33d4e66780c0 2 //
IanBenzMaxim 0:33d4e66780c0 3 // Copyright (C) 2015 THL A29 Limited, a Tencent company, and Milo Yip. All rights reserved.
IanBenzMaxim 0:33d4e66780c0 4 //
IanBenzMaxim 0:33d4e66780c0 5 // Licensed under the MIT License (the "License"); you may not use this file except
IanBenzMaxim 0:33d4e66780c0 6 // in compliance with the License. You may obtain a copy of the License at
IanBenzMaxim 0:33d4e66780c0 7 //
IanBenzMaxim 0:33d4e66780c0 8 // http://opensource.org/licenses/MIT
IanBenzMaxim 0:33d4e66780c0 9 //
IanBenzMaxim 0:33d4e66780c0 10 // Unless required by applicable law or agreed to in writing, software distributed
IanBenzMaxim 0:33d4e66780c0 11 // under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
IanBenzMaxim 0:33d4e66780c0 12 // CONDITIONS OF ANY KIND, either express or implied. See the License for the
IanBenzMaxim 0:33d4e66780c0 13 // specific language governing permissions and limitations under the License.
IanBenzMaxim 0:33d4e66780c0 14
IanBenzMaxim 0:33d4e66780c0 15 #ifndef RAPIDJSON_STRTOD_
IanBenzMaxim 0:33d4e66780c0 16 #define RAPIDJSON_STRTOD_
IanBenzMaxim 0:33d4e66780c0 17
IanBenzMaxim 0:33d4e66780c0 18 #include "ieee754.h"
IanBenzMaxim 0:33d4e66780c0 19 #include "biginteger.h"
IanBenzMaxim 0:33d4e66780c0 20 #include "diyfp.h"
IanBenzMaxim 0:33d4e66780c0 21 #include "pow10.h"
IanBenzMaxim 0:33d4e66780c0 22
IanBenzMaxim 0:33d4e66780c0 23 RAPIDJSON_NAMESPACE_BEGIN
IanBenzMaxim 0:33d4e66780c0 24 namespace internal {
IanBenzMaxim 0:33d4e66780c0 25
IanBenzMaxim 0:33d4e66780c0 26 inline double FastPath(double significand, int exp) {
IanBenzMaxim 0:33d4e66780c0 27 if (exp < -308)
IanBenzMaxim 0:33d4e66780c0 28 return 0.0;
IanBenzMaxim 0:33d4e66780c0 29 else if (exp >= 0)
IanBenzMaxim 0:33d4e66780c0 30 return significand * internal::Pow10(exp);
IanBenzMaxim 0:33d4e66780c0 31 else
IanBenzMaxim 0:33d4e66780c0 32 return significand / internal::Pow10(-exp);
IanBenzMaxim 0:33d4e66780c0 33 }
IanBenzMaxim 0:33d4e66780c0 34
IanBenzMaxim 0:33d4e66780c0 35 inline double StrtodNormalPrecision(double d, int p) {
IanBenzMaxim 0:33d4e66780c0 36 if (p < -308) {
IanBenzMaxim 0:33d4e66780c0 37 // Prevent expSum < -308, making Pow10(p) = 0
IanBenzMaxim 0:33d4e66780c0 38 d = FastPath(d, -308);
IanBenzMaxim 0:33d4e66780c0 39 d = FastPath(d, p + 308);
IanBenzMaxim 0:33d4e66780c0 40 }
IanBenzMaxim 0:33d4e66780c0 41 else
IanBenzMaxim 0:33d4e66780c0 42 d = FastPath(d, p);
IanBenzMaxim 0:33d4e66780c0 43 return d;
IanBenzMaxim 0:33d4e66780c0 44 }
IanBenzMaxim 0:33d4e66780c0 45
IanBenzMaxim 0:33d4e66780c0 46 template <typename T>
IanBenzMaxim 0:33d4e66780c0 47 inline T Min3(T a, T b, T c) {
IanBenzMaxim 0:33d4e66780c0 48 T m = a;
IanBenzMaxim 0:33d4e66780c0 49 if (m > b) m = b;
IanBenzMaxim 0:33d4e66780c0 50 if (m > c) m = c;
IanBenzMaxim 0:33d4e66780c0 51 return m;
IanBenzMaxim 0:33d4e66780c0 52 }
IanBenzMaxim 0:33d4e66780c0 53
IanBenzMaxim 0:33d4e66780c0 54 inline int CheckWithinHalfULP(double b, const BigInteger& d, int dExp) {
IanBenzMaxim 0:33d4e66780c0 55 const Double db(b);
IanBenzMaxim 0:33d4e66780c0 56 const uint64_t bInt = db.IntegerSignificand();
IanBenzMaxim 0:33d4e66780c0 57 const int bExp = db.IntegerExponent();
IanBenzMaxim 0:33d4e66780c0 58 const int hExp = bExp - 1;
IanBenzMaxim 0:33d4e66780c0 59
IanBenzMaxim 0:33d4e66780c0 60 int dS_Exp2 = 0, dS_Exp5 = 0, bS_Exp2 = 0, bS_Exp5 = 0, hS_Exp2 = 0, hS_Exp5 = 0;
IanBenzMaxim 0:33d4e66780c0 61
IanBenzMaxim 0:33d4e66780c0 62 // Adjust for decimal exponent
IanBenzMaxim 0:33d4e66780c0 63 if (dExp >= 0) {
IanBenzMaxim 0:33d4e66780c0 64 dS_Exp2 += dExp;
IanBenzMaxim 0:33d4e66780c0 65 dS_Exp5 += dExp;
IanBenzMaxim 0:33d4e66780c0 66 }
IanBenzMaxim 0:33d4e66780c0 67 else {
IanBenzMaxim 0:33d4e66780c0 68 bS_Exp2 -= dExp;
IanBenzMaxim 0:33d4e66780c0 69 bS_Exp5 -= dExp;
IanBenzMaxim 0:33d4e66780c0 70 hS_Exp2 -= dExp;
IanBenzMaxim 0:33d4e66780c0 71 hS_Exp5 -= dExp;
IanBenzMaxim 0:33d4e66780c0 72 }
IanBenzMaxim 0:33d4e66780c0 73
IanBenzMaxim 0:33d4e66780c0 74 // Adjust for binary exponent
IanBenzMaxim 0:33d4e66780c0 75 if (bExp >= 0)
IanBenzMaxim 0:33d4e66780c0 76 bS_Exp2 += bExp;
IanBenzMaxim 0:33d4e66780c0 77 else {
IanBenzMaxim 0:33d4e66780c0 78 dS_Exp2 -= bExp;
IanBenzMaxim 0:33d4e66780c0 79 hS_Exp2 -= bExp;
IanBenzMaxim 0:33d4e66780c0 80 }
IanBenzMaxim 0:33d4e66780c0 81
IanBenzMaxim 0:33d4e66780c0 82 // Adjust for half ulp exponent
IanBenzMaxim 0:33d4e66780c0 83 if (hExp >= 0)
IanBenzMaxim 0:33d4e66780c0 84 hS_Exp2 += hExp;
IanBenzMaxim 0:33d4e66780c0 85 else {
IanBenzMaxim 0:33d4e66780c0 86 dS_Exp2 -= hExp;
IanBenzMaxim 0:33d4e66780c0 87 bS_Exp2 -= hExp;
IanBenzMaxim 0:33d4e66780c0 88 }
IanBenzMaxim 0:33d4e66780c0 89
IanBenzMaxim 0:33d4e66780c0 90 // Remove common power of two factor from all three scaled values
IanBenzMaxim 0:33d4e66780c0 91 int common_Exp2 = Min3(dS_Exp2, bS_Exp2, hS_Exp2);
IanBenzMaxim 0:33d4e66780c0 92 dS_Exp2 -= common_Exp2;
IanBenzMaxim 0:33d4e66780c0 93 bS_Exp2 -= common_Exp2;
IanBenzMaxim 0:33d4e66780c0 94 hS_Exp2 -= common_Exp2;
IanBenzMaxim 0:33d4e66780c0 95
IanBenzMaxim 0:33d4e66780c0 96 BigInteger dS = d;
IanBenzMaxim 0:33d4e66780c0 97 dS.MultiplyPow5(static_cast<unsigned>(dS_Exp5)) <<= static_cast<unsigned>(dS_Exp2);
IanBenzMaxim 0:33d4e66780c0 98
IanBenzMaxim 0:33d4e66780c0 99 BigInteger bS(bInt);
IanBenzMaxim 0:33d4e66780c0 100 bS.MultiplyPow5(static_cast<unsigned>(bS_Exp5)) <<= static_cast<unsigned>(bS_Exp2);
IanBenzMaxim 0:33d4e66780c0 101
IanBenzMaxim 0:33d4e66780c0 102 BigInteger hS(1);
IanBenzMaxim 0:33d4e66780c0 103 hS.MultiplyPow5(static_cast<unsigned>(hS_Exp5)) <<= static_cast<unsigned>(hS_Exp2);
IanBenzMaxim 0:33d4e66780c0 104
IanBenzMaxim 0:33d4e66780c0 105 BigInteger delta(0);
IanBenzMaxim 0:33d4e66780c0 106 dS.Difference(bS, &delta);
IanBenzMaxim 0:33d4e66780c0 107
IanBenzMaxim 0:33d4e66780c0 108 return delta.Compare(hS);
IanBenzMaxim 0:33d4e66780c0 109 }
IanBenzMaxim 0:33d4e66780c0 110
IanBenzMaxim 0:33d4e66780c0 111 inline bool StrtodFast(double d, int p, double* result) {
IanBenzMaxim 0:33d4e66780c0 112 // Use fast path for string-to-double conversion if possible
IanBenzMaxim 0:33d4e66780c0 113 // see http://www.exploringbinary.com/fast-path-decimal-to-floating-point-conversion/
IanBenzMaxim 0:33d4e66780c0 114 if (p > 22 && p < 22 + 16) {
IanBenzMaxim 0:33d4e66780c0 115 // Fast Path Cases In Disguise
IanBenzMaxim 0:33d4e66780c0 116 d *= internal::Pow10(p - 22);
IanBenzMaxim 0:33d4e66780c0 117 p = 22;
IanBenzMaxim 0:33d4e66780c0 118 }
IanBenzMaxim 0:33d4e66780c0 119
IanBenzMaxim 0:33d4e66780c0 120 if (p >= -22 && p <= 22 && d <= 9007199254740991.0) { // 2^53 - 1
IanBenzMaxim 0:33d4e66780c0 121 *result = FastPath(d, p);
IanBenzMaxim 0:33d4e66780c0 122 return true;
IanBenzMaxim 0:33d4e66780c0 123 }
IanBenzMaxim 0:33d4e66780c0 124 else
IanBenzMaxim 0:33d4e66780c0 125 return false;
IanBenzMaxim 0:33d4e66780c0 126 }
IanBenzMaxim 0:33d4e66780c0 127
IanBenzMaxim 0:33d4e66780c0 128 // Compute an approximation and see if it is within 1/2 ULP
IanBenzMaxim 0:33d4e66780c0 129 inline bool StrtodDiyFp(const char* decimals, size_t length, size_t decimalPosition, int exp, double* result) {
IanBenzMaxim 0:33d4e66780c0 130 uint64_t significand = 0;
IanBenzMaxim 0:33d4e66780c0 131 size_t i = 0; // 2^64 - 1 = 18446744073709551615, 1844674407370955161 = 0x1999999999999999
IanBenzMaxim 0:33d4e66780c0 132 for (; i < length; i++) {
IanBenzMaxim 0:33d4e66780c0 133 if (significand > RAPIDJSON_UINT64_C2(0x19999999, 0x99999999) ||
IanBenzMaxim 0:33d4e66780c0 134 (significand == RAPIDJSON_UINT64_C2(0x19999999, 0x99999999) && decimals[i] > '5'))
IanBenzMaxim 0:33d4e66780c0 135 break;
IanBenzMaxim 0:33d4e66780c0 136 significand = significand * 10u + static_cast<unsigned>(decimals[i] - '0');
IanBenzMaxim 0:33d4e66780c0 137 }
IanBenzMaxim 0:33d4e66780c0 138
IanBenzMaxim 0:33d4e66780c0 139 if (i < length && decimals[i] >= '5') // Rounding
IanBenzMaxim 0:33d4e66780c0 140 significand++;
IanBenzMaxim 0:33d4e66780c0 141
IanBenzMaxim 0:33d4e66780c0 142 size_t remaining = length - i;
IanBenzMaxim 0:33d4e66780c0 143 const unsigned kUlpShift = 3;
IanBenzMaxim 0:33d4e66780c0 144 const unsigned kUlp = 1 << kUlpShift;
IanBenzMaxim 0:33d4e66780c0 145 int64_t error = (remaining == 0) ? 0 : kUlp / 2;
IanBenzMaxim 0:33d4e66780c0 146
IanBenzMaxim 0:33d4e66780c0 147 DiyFp v(significand, 0);
IanBenzMaxim 0:33d4e66780c0 148 v = v.Normalize();
IanBenzMaxim 0:33d4e66780c0 149 error <<= -v.e;
IanBenzMaxim 0:33d4e66780c0 150
IanBenzMaxim 0:33d4e66780c0 151 const int dExp = static_cast<int>(decimalPosition) - static_cast<int>(i) + exp;
IanBenzMaxim 0:33d4e66780c0 152
IanBenzMaxim 0:33d4e66780c0 153 int actualExp;
IanBenzMaxim 0:33d4e66780c0 154 DiyFp cachedPower = GetCachedPower10(dExp, &actualExp);
IanBenzMaxim 0:33d4e66780c0 155 if (actualExp != dExp) {
IanBenzMaxim 0:33d4e66780c0 156 static const DiyFp kPow10[] = {
IanBenzMaxim 0:33d4e66780c0 157 DiyFp(RAPIDJSON_UINT64_C2(0xa0000000, 00000000), -60), // 10^1
IanBenzMaxim 0:33d4e66780c0 158 DiyFp(RAPIDJSON_UINT64_C2(0xc8000000, 00000000), -57), // 10^2
IanBenzMaxim 0:33d4e66780c0 159 DiyFp(RAPIDJSON_UINT64_C2(0xfa000000, 00000000), -54), // 10^3
IanBenzMaxim 0:33d4e66780c0 160 DiyFp(RAPIDJSON_UINT64_C2(0x9c400000, 00000000), -50), // 10^4
IanBenzMaxim 0:33d4e66780c0 161 DiyFp(RAPIDJSON_UINT64_C2(0xc3500000, 00000000), -47), // 10^5
IanBenzMaxim 0:33d4e66780c0 162 DiyFp(RAPIDJSON_UINT64_C2(0xf4240000, 00000000), -44), // 10^6
IanBenzMaxim 0:33d4e66780c0 163 DiyFp(RAPIDJSON_UINT64_C2(0x98968000, 00000000), -40) // 10^7
IanBenzMaxim 0:33d4e66780c0 164 };
IanBenzMaxim 0:33d4e66780c0 165 int adjustment = dExp - actualExp - 1;
IanBenzMaxim 0:33d4e66780c0 166 RAPIDJSON_ASSERT(adjustment >= 0 && adjustment < 7);
IanBenzMaxim 0:33d4e66780c0 167 v = v * kPow10[adjustment];
IanBenzMaxim 0:33d4e66780c0 168 if (length + static_cast<unsigned>(adjustment)> 19u) // has more digits than decimal digits in 64-bit
IanBenzMaxim 0:33d4e66780c0 169 error += kUlp / 2;
IanBenzMaxim 0:33d4e66780c0 170 }
IanBenzMaxim 0:33d4e66780c0 171
IanBenzMaxim 0:33d4e66780c0 172 v = v * cachedPower;
IanBenzMaxim 0:33d4e66780c0 173
IanBenzMaxim 0:33d4e66780c0 174 error += kUlp + (error == 0 ? 0 : 1);
IanBenzMaxim 0:33d4e66780c0 175
IanBenzMaxim 0:33d4e66780c0 176 const int oldExp = v.e;
IanBenzMaxim 0:33d4e66780c0 177 v = v.Normalize();
IanBenzMaxim 0:33d4e66780c0 178 error <<= oldExp - v.e;
IanBenzMaxim 0:33d4e66780c0 179
IanBenzMaxim 0:33d4e66780c0 180 const unsigned effectiveSignificandSize = Double::EffectiveSignificandSize(64 + v.e);
IanBenzMaxim 0:33d4e66780c0 181 unsigned precisionSize = 64 - effectiveSignificandSize;
IanBenzMaxim 0:33d4e66780c0 182 if (precisionSize + kUlpShift >= 64) {
IanBenzMaxim 0:33d4e66780c0 183 unsigned scaleExp = (precisionSize + kUlpShift) - 63;
IanBenzMaxim 0:33d4e66780c0 184 v.f >>= scaleExp;
IanBenzMaxim 0:33d4e66780c0 185 v.e += scaleExp;
IanBenzMaxim 0:33d4e66780c0 186 error = (error >> scaleExp) + 1 + static_cast<int>(kUlp);
IanBenzMaxim 0:33d4e66780c0 187 precisionSize -= scaleExp;
IanBenzMaxim 0:33d4e66780c0 188 }
IanBenzMaxim 0:33d4e66780c0 189
IanBenzMaxim 0:33d4e66780c0 190 DiyFp rounded(v.f >> precisionSize, v.e + static_cast<int>(precisionSize));
IanBenzMaxim 0:33d4e66780c0 191 const uint64_t precisionBits = (v.f & ((uint64_t(1) << precisionSize) - 1)) * kUlp;
IanBenzMaxim 0:33d4e66780c0 192 const uint64_t halfWay = (uint64_t(1) << (precisionSize - 1)) * kUlp;
IanBenzMaxim 0:33d4e66780c0 193 if (precisionBits >= halfWay + static_cast<unsigned>(error)) {
IanBenzMaxim 0:33d4e66780c0 194 rounded.f++;
IanBenzMaxim 0:33d4e66780c0 195 if (rounded.f & (DiyFp::kDpHiddenBit << 1)) { // rounding overflows mantissa (issue #340)
IanBenzMaxim 0:33d4e66780c0 196 rounded.f >>= 1;
IanBenzMaxim 0:33d4e66780c0 197 rounded.e++;
IanBenzMaxim 0:33d4e66780c0 198 }
IanBenzMaxim 0:33d4e66780c0 199 }
IanBenzMaxim 0:33d4e66780c0 200
IanBenzMaxim 0:33d4e66780c0 201 *result = rounded.ToDouble();
IanBenzMaxim 0:33d4e66780c0 202
IanBenzMaxim 0:33d4e66780c0 203 return halfWay - static_cast<unsigned>(error) >= precisionBits || precisionBits >= halfWay + static_cast<unsigned>(error);
IanBenzMaxim 0:33d4e66780c0 204 }
IanBenzMaxim 0:33d4e66780c0 205
IanBenzMaxim 0:33d4e66780c0 206 inline double StrtodBigInteger(double approx, const char* decimals, size_t length, size_t decimalPosition, int exp) {
IanBenzMaxim 0:33d4e66780c0 207 const BigInteger dInt(decimals, length);
IanBenzMaxim 0:33d4e66780c0 208 const int dExp = static_cast<int>(decimalPosition) - static_cast<int>(length) + exp;
IanBenzMaxim 0:33d4e66780c0 209 Double a(approx);
IanBenzMaxim 0:33d4e66780c0 210 int cmp = CheckWithinHalfULP(a.Value(), dInt, dExp);
IanBenzMaxim 0:33d4e66780c0 211 if (cmp < 0)
IanBenzMaxim 0:33d4e66780c0 212 return a.Value(); // within half ULP
IanBenzMaxim 0:33d4e66780c0 213 else if (cmp == 0) {
IanBenzMaxim 0:33d4e66780c0 214 // Round towards even
IanBenzMaxim 0:33d4e66780c0 215 if (a.Significand() & 1)
IanBenzMaxim 0:33d4e66780c0 216 return a.NextPositiveDouble();
IanBenzMaxim 0:33d4e66780c0 217 else
IanBenzMaxim 0:33d4e66780c0 218 return a.Value();
IanBenzMaxim 0:33d4e66780c0 219 }
IanBenzMaxim 0:33d4e66780c0 220 else // adjustment
IanBenzMaxim 0:33d4e66780c0 221 return a.NextPositiveDouble();
IanBenzMaxim 0:33d4e66780c0 222 }
IanBenzMaxim 0:33d4e66780c0 223
IanBenzMaxim 0:33d4e66780c0 224 inline double StrtodFullPrecision(double d, int p, const char* decimals, size_t length, size_t decimalPosition, int exp) {
IanBenzMaxim 0:33d4e66780c0 225 RAPIDJSON_ASSERT(d >= 0.0);
IanBenzMaxim 0:33d4e66780c0 226 RAPIDJSON_ASSERT(length >= 1);
IanBenzMaxim 0:33d4e66780c0 227
IanBenzMaxim 0:33d4e66780c0 228 double result;
IanBenzMaxim 0:33d4e66780c0 229 if (StrtodFast(d, p, &result))
IanBenzMaxim 0:33d4e66780c0 230 return result;
IanBenzMaxim 0:33d4e66780c0 231
IanBenzMaxim 0:33d4e66780c0 232 // Trim leading zeros
IanBenzMaxim 0:33d4e66780c0 233 while (*decimals == '0' && length > 1) {
IanBenzMaxim 0:33d4e66780c0 234 length--;
IanBenzMaxim 0:33d4e66780c0 235 decimals++;
IanBenzMaxim 0:33d4e66780c0 236 decimalPosition--;
IanBenzMaxim 0:33d4e66780c0 237 }
IanBenzMaxim 0:33d4e66780c0 238
IanBenzMaxim 0:33d4e66780c0 239 // Trim trailing zeros
IanBenzMaxim 0:33d4e66780c0 240 while (decimals[length - 1] == '0' && length > 1) {
IanBenzMaxim 0:33d4e66780c0 241 length--;
IanBenzMaxim 0:33d4e66780c0 242 decimalPosition--;
IanBenzMaxim 0:33d4e66780c0 243 exp++;
IanBenzMaxim 0:33d4e66780c0 244 }
IanBenzMaxim 0:33d4e66780c0 245
IanBenzMaxim 0:33d4e66780c0 246 // Trim right-most digits
IanBenzMaxim 0:33d4e66780c0 247 const int kMaxDecimalDigit = 780;
IanBenzMaxim 0:33d4e66780c0 248 if (static_cast<int>(length) > kMaxDecimalDigit) {
IanBenzMaxim 0:33d4e66780c0 249 int delta = (static_cast<int>(length) - kMaxDecimalDigit);
IanBenzMaxim 0:33d4e66780c0 250 exp += delta;
IanBenzMaxim 0:33d4e66780c0 251 decimalPosition -= static_cast<unsigned>(delta);
IanBenzMaxim 0:33d4e66780c0 252 length = kMaxDecimalDigit;
IanBenzMaxim 0:33d4e66780c0 253 }
IanBenzMaxim 0:33d4e66780c0 254
IanBenzMaxim 0:33d4e66780c0 255 // If too small, underflow to zero
IanBenzMaxim 0:33d4e66780c0 256 if (int(length) + exp < -324)
IanBenzMaxim 0:33d4e66780c0 257 return 0.0;
IanBenzMaxim 0:33d4e66780c0 258
IanBenzMaxim 0:33d4e66780c0 259 if (StrtodDiyFp(decimals, length, decimalPosition, exp, &result))
IanBenzMaxim 0:33d4e66780c0 260 return result;
IanBenzMaxim 0:33d4e66780c0 261
IanBenzMaxim 0:33d4e66780c0 262 // Use approximation from StrtodDiyFp and make adjustment with BigInteger comparison
IanBenzMaxim 0:33d4e66780c0 263 return StrtodBigInteger(result, decimals, length, decimalPosition, exp);
IanBenzMaxim 0:33d4e66780c0 264 }
IanBenzMaxim 0:33d4e66780c0 265
IanBenzMaxim 0:33d4e66780c0 266 } // namespace internal
IanBenzMaxim 0:33d4e66780c0 267 RAPIDJSON_NAMESPACE_END
IanBenzMaxim 0:33d4e66780c0 268
IanBenzMaxim 0:33d4e66780c0 269 #endif // RAPIDJSON_STRTOD_