aboutsummaryrefslogtreecommitdiff
path: root/include/rapidjson/internal/strtod.h
diff options
context:
space:
mode:
Diffstat (limited to 'include/rapidjson/internal/strtod.h')
-rw-r--r--include/rapidjson/internal/strtod.h269
1 files changed, 0 insertions, 269 deletions
diff --git a/include/rapidjson/internal/strtod.h b/include/rapidjson/internal/strtod.h
deleted file mode 100644
index 289c413b..00000000
--- a/include/rapidjson/internal/strtod.h
+++ /dev/null
@@ -1,269 +0,0 @@
-// 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.
-
-#ifndef RAPIDJSON_STRTOD_
-#define RAPIDJSON_STRTOD_
-
-#include "ieee754.h"
-#include "biginteger.h"
-#include "diyfp.h"
-#include "pow10.h"
-
-RAPIDJSON_NAMESPACE_BEGIN
-namespace internal {
-
-inline double FastPath(double significand, int exp) {
- if (exp < -308)
- return 0.0;
- else if (exp >= 0)
- return significand * internal::Pow10(exp);
- else
- return significand / internal::Pow10(-exp);
-}
-
-inline double StrtodNormalPrecision(double d, int p) {
- if (p < -308) {
- // Prevent expSum < -308, making Pow10(p) = 0
- d = FastPath(d, -308);
- d = FastPath(d, p + 308);
- }
- else
- d = FastPath(d, p);
- return d;
-}
-
-template <typename T>
-inline T Min3(T a, T b, T c) {
- T m = a;
- if (m > b) m = b;
- if (m > c) m = c;
- return m;
-}
-
-inline int CheckWithinHalfULP(double b, const BigInteger& d, int dExp) {
- const Double db(b);
- const uint64_t bInt = db.IntegerSignificand();
- const int bExp = db.IntegerExponent();
- const int hExp = bExp - 1;
-
- int dS_Exp2 = 0, dS_Exp5 = 0, bS_Exp2 = 0, bS_Exp5 = 0, hS_Exp2 = 0, 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 = Min3(dS_Exp2, bS_Exp2, hS_Exp2);
- dS_Exp2 -= common_Exp2;
- bS_Exp2 -= common_Exp2;
- hS_Exp2 -= common_Exp2;
-
- BigInteger dS = d;
- dS.MultiplyPow5(static_cast<unsigned>(dS_Exp5)) <<= static_cast<unsigned>(dS_Exp2);
-
- BigInteger bS(bInt);
- bS.MultiplyPow5(static_cast<unsigned>(bS_Exp5)) <<= static_cast<unsigned>(bS_Exp2);
-
- BigInteger hS(1);
- hS.MultiplyPow5(static_cast<unsigned>(hS_Exp5)) <<= static_cast<unsigned>(hS_Exp2);
-
- BigInteger delta(0);
- dS.Difference(bS, &delta);
-
- return delta.Compare(hS);
-}
-
-inline bool StrtodFast(double d, int p, double* result) {
- // Use fast path for string-to-double conversion if possible
- // see http://www.exploringbinary.com/fast-path-decimal-to-floating-point-conversion/
- if (p > 22 && p < 22 + 16) {
- // Fast Path Cases In Disguise
- d *= internal::Pow10(p - 22);
- p = 22;
- }
-
- if (p >= -22 && p <= 22 && d <= 9007199254740991.0) { // 2^53 - 1
- *result = FastPath(d, p);
- return true;
- }
- else
- return false;
-}
-
-// Compute an approximation and see if it is within 1/2 ULP
-inline bool StrtodDiyFp(const char* decimals, size_t length, size_t decimalPosition, int exp, double* result) {
- uint64_t significand = 0;
- size_t i = 0; // 2^64 - 1 = 18446744073709551615, 1844674407370955161 = 0x1999999999999999
- for (; i < length; 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 < length && decimals[i] >= '5') // Rounding
- significand++;
-
- size_t remaining = length - i;
- const unsigned kUlpShift = 3;
- const unsigned kUlp = 1 << kUlpShift;
- int64_t error = (remaining == 0) ? 0 : kUlp / 2;
-
- DiyFp v(significand, 0);
- v = v.Normalize();
- error <<= -v.e;
-
- const int dExp = static_cast<int>(decimalPosition) - static_cast<int>(i) + exp;
-
- int actualExp;
- DiyFp cachedPower = GetCachedPower10(dExp, &actualExp);
- if (actualExp != dExp) {
- static const DiyFp kPow10[] = {
- DiyFp(RAPIDJSON_UINT64_C2(0xa0000000, 00000000), -60), // 10^1
- DiyFp(RAPIDJSON_UINT64_C2(0xc8000000, 00000000), -57), // 10^2
- DiyFp(RAPIDJSON_UINT64_C2(0xfa000000, 00000000), -54), // 10^3
- DiyFp(RAPIDJSON_UINT64_C2(0x9c400000, 00000000), -50), // 10^4
- DiyFp(RAPIDJSON_UINT64_C2(0xc3500000, 00000000), -47), // 10^5
- DiyFp(RAPIDJSON_UINT64_C2(0xf4240000, 00000000), -44), // 10^6
- DiyFp(RAPIDJSON_UINT64_C2(0x98968000, 00000000), -40) // 10^7
- };
- int adjustment = dExp - actualExp - 1;
- RAPIDJSON_ASSERT(adjustment >= 0 && adjustment < 7);
- v = v * kPow10[adjustment];
- if (length + static_cast<unsigned>(adjustment)> 19u) // 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 unsigned effectiveSignificandSize = Double::EffectiveSignificandSize(64 + v.e);
- unsigned precisionSize = 64 - effectiveSignificandSize;
- if (precisionSize + kUlpShift >= 64) {
- unsigned scaleExp = (precisionSize + kUlpShift) - 63;
- v.f >>= scaleExp;
- v.e += scaleExp;
- error = (error >> scaleExp) + 1 + static_cast<int>(kUlp);
- precisionSize -= scaleExp;
- }
-
- DiyFp rounded(v.f >> precisionSize, v.e + static_cast<int>(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);
-}
-
-inline double StrtodBigInteger(double approx, const char* decimals, size_t length, size_t decimalPosition, int exp) {
- const BigInteger dInt(decimals, length);
- const int dExp = static_cast<int>(decimalPosition) - static_cast<int>(length) + exp;
- Double a(approx);
- int cmp = CheckWithinHalfULP(a.Value(), dInt, dExp);
- if (cmp < 0)
- return a.Value(); // within half ULP
- else if (cmp == 0) {
- // Round towards even
- if (a.Significand() & 1)
- return a.NextPositiveDouble();
- else
- return a.Value();
- }
- else // adjustment
- return a.NextPositiveDouble();
-}
-
-inline double StrtodFullPrecision(double d, int p, const char* decimals, size_t length, size_t decimalPosition, int exp) {
- RAPIDJSON_ASSERT(d >= 0.0);
- RAPIDJSON_ASSERT(length >= 1);
-
- double result;
- if (StrtodFast(d, p, &result))
- return result;
-
- // Trim leading zeros
- while (*decimals == '0' && length > 1) {
- length--;
- decimals++;
- decimalPosition--;
- }
-
- // Trim trailing zeros
- while (decimals[length - 1] == '0' && length > 1) {
- length--;
- decimalPosition--;
- exp++;
- }
-
- // Trim right-most digits
- const int kMaxDecimalDigit = 780;
- if (static_cast<int>(length) > kMaxDecimalDigit) {
- int delta = (static_cast<int>(length) - kMaxDecimalDigit);
- exp += delta;
- decimalPosition -= static_cast<unsigned>(delta);
- length = kMaxDecimalDigit;
- }
-
- // If too small, underflow to zero
- if (int(length) + exp < -324)
- return 0.0;
-
- if (StrtodDiyFp(decimals, length, decimalPosition, exp, &result))
- return result;
-
- // Use approximation from StrtodDiyFp and make adjustment with BigInteger comparison
- return StrtodBigInteger(result, decimals, length, decimalPosition, exp);
-}
-
-} // namespace internal
-RAPIDJSON_NAMESPACE_END
-
-#endif // RAPIDJSON_STRTOD_
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-01 19:37:35 +0000