1 // Tencent is pleased to support the open source community by making RapidJSON available.
3 // Copyright (C) 2015 THL A29 Limited, a Tencent company, and Milo Yip. All rights reserved.
5 // Licensed under the MIT License (the "License"); you may not use this file except
6 // in compliance with the License. You may obtain a copy of the License at
8 // http://opensource.org/licenses/MIT
10 // Unless required by applicable law or agreed to in writing, software distributed
11 // under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
12 // CONDITIONS OF ANY KIND, either express or implied. See the License for the
13 // specific language governing permissions and limitations under the License.
15 // This is a C++ header-only implementation of Grisu2 algorithm from the publication:
16 // Loitsch, Florian. "Printing floating-point numbers quickly and accurately with
17 // integers." ACM Sigplan Notices 45.6 (2010): 233-243.
19 #ifndef RAPIDJSON_DIYFP_H_
20 #define RAPIDJSON_DIYFP_H_
22 #include "../rapidjson.h"
25 #if defined(_MSC_VER) && defined(_M_AMD64) && !defined(__INTEL_COMPILER)
27 #pragma intrinsic(_BitScanReverse64)
28 #pragma intrinsic(_umul128)
31 RAPIDJSON_NAMESPACE_BEGIN
36 RAPIDJSON_DIAG_OFF(effc++)
41 RAPIDJSON_DIAG_OFF(padded)
47 DiyFp(uint64_t fp, int exp) : f(fp), e(exp) {}
49 explicit DiyFp(double d) {
55 int biased_e = static_cast<int>((u.u64 & kDpExponentMask) >> kDpSignificandSize);
56 uint64_t significand = (u.u64 & kDpSignificandMask);
58 f = significand + kDpHiddenBit;
59 e = biased_e - kDpExponentBias;
63 e = kDpMinExponent + 1;
67 DiyFp operator-(const DiyFp& rhs) const {
68 return DiyFp(f - rhs.f, e);
71 DiyFp operator*(const DiyFp& rhs) const {
72 #if defined(_MSC_VER) && defined(_M_AMD64)
74 uint64_t l = _umul128(f, rhs.f, &h);
75 if (l & (uint64_t(1) << 63)) // rounding
77 return DiyFp(h, e + rhs.e + 64);
78 #elif (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 6)) && defined(__x86_64__)
79 __extension__ typedef unsigned __int128 uint128;
80 uint128 p = static_cast<uint128>(f) * static_cast<uint128>(rhs.f);
81 uint64_t h = static_cast<uint64_t>(p >> 64);
82 uint64_t l = static_cast<uint64_t>(p);
83 if (l & (uint64_t(1) << 63)) // rounding
85 return DiyFp(h, e + rhs.e + 64);
87 const uint64_t M32 = 0xFFFFFFFF;
88 const uint64_t a = f >> 32;
89 const uint64_t b = f & M32;
90 const uint64_t c = rhs.f >> 32;
91 const uint64_t d = rhs.f & M32;
92 const uint64_t ac = a * c;
93 const uint64_t bc = b * c;
94 const uint64_t ad = a * d;
95 const uint64_t bd = b * d;
96 uint64_t tmp = (bd >> 32) + (ad & M32) + (bc & M32);
97 tmp += 1U << 31; /// mult_round
98 return DiyFp(ac + (ad >> 32) + (bc >> 32) + (tmp >> 32), e + rhs.e + 64);
102 DiyFp Normalize() const {
103 RAPIDJSON_ASSERT(f != 0); // https://stackoverflow.com/a/26809183/291737
104 #if defined(_MSC_VER) && defined(_M_AMD64)
106 _BitScanReverse64(&index, f);
107 return DiyFp(f << (63 - index), e - (63 - index));
108 #elif defined(__GNUC__) && __GNUC__ >= 4
109 int s = __builtin_clzll(f);
110 return DiyFp(f << s, e - s);
113 while (!(res.f & (static_cast<uint64_t>(1) << 63))) {
121 DiyFp NormalizeBoundary() const {
123 while (!(res.f & (kDpHiddenBit << 1))) {
127 res.f <<= (kDiySignificandSize - kDpSignificandSize - 2);
128 res.e = res.e - (kDiySignificandSize - kDpSignificandSize - 2);
132 void NormalizedBoundaries(DiyFp* minus, DiyFp* plus) const {
133 DiyFp pl = DiyFp((f << 1) + 1, e - 1).NormalizeBoundary();
134 DiyFp mi = (f == kDpHiddenBit) ? DiyFp((f << 2) - 1, e - 2) : DiyFp((f << 1) - 1, e - 1);
135 mi.f <<= mi.e - pl.e;
141 double ToDouble() const {
146 RAPIDJSON_ASSERT(f <= kDpHiddenBit + kDpSignificandMask);
147 if (e < kDpDenormalExponent) {
151 if (e >= kDpMaxExponent) {
153 return std::numeric_limits<double>::infinity();
155 const uint64_t be = (e == kDpDenormalExponent && (f & kDpHiddenBit) == 0) ? 0 :
156 static_cast<uint64_t>(e + kDpExponentBias);
157 u.u64 = (f & kDpSignificandMask) | (be << kDpSignificandSize);
161 static const int kDiySignificandSize = 64;
162 static const int kDpSignificandSize = 52;
163 static const int kDpExponentBias = 0x3FF + kDpSignificandSize;
164 static const int kDpMaxExponent = 0x7FF - kDpExponentBias;
165 static const int kDpMinExponent = -kDpExponentBias;
166 static const int kDpDenormalExponent = -kDpExponentBias + 1;
167 static const uint64_t kDpExponentMask = RAPIDJSON_UINT64_C2(0x7FF00000, 0x00000000);
168 static const uint64_t kDpSignificandMask = RAPIDJSON_UINT64_C2(0x000FFFFF, 0xFFFFFFFF);
169 static const uint64_t kDpHiddenBit = RAPIDJSON_UINT64_C2(0x00100000, 0x00000000);
175 inline DiyFp GetCachedPowerByIndex(size_t index) {
176 // 10^-348, 10^-340, ..., 10^340
177 static const uint64_t kCachedPowers_F[] = {
178 RAPIDJSON_UINT64_C2(0xfa8fd5a0, 0x081c0288), RAPIDJSON_UINT64_C2(0xbaaee17f, 0xa23ebf76),
179 RAPIDJSON_UINT64_C2(0x8b16fb20, 0x3055ac76), RAPIDJSON_UINT64_C2(0xcf42894a, 0x5dce35ea),
180 RAPIDJSON_UINT64_C2(0x9a6bb0aa, 0x55653b2d), RAPIDJSON_UINT64_C2(0xe61acf03, 0x3d1a45df),
181 RAPIDJSON_UINT64_C2(0xab70fe17, 0xc79ac6ca), RAPIDJSON_UINT64_C2(0xff77b1fc, 0xbebcdc4f),
182 RAPIDJSON_UINT64_C2(0xbe5691ef, 0x416bd60c), RAPIDJSON_UINT64_C2(0x8dd01fad, 0x907ffc3c),
183 RAPIDJSON_UINT64_C2(0xd3515c28, 0x31559a83), RAPIDJSON_UINT64_C2(0x9d71ac8f, 0xada6c9b5),
184 RAPIDJSON_UINT64_C2(0xea9c2277, 0x23ee8bcb), RAPIDJSON_UINT64_C2(0xaecc4991, 0x4078536d),
185 RAPIDJSON_UINT64_C2(0x823c1279, 0x5db6ce57), RAPIDJSON_UINT64_C2(0xc2109436, 0x4dfb5637),
186 RAPIDJSON_UINT64_C2(0x9096ea6f, 0x3848984f), RAPIDJSON_UINT64_C2(0xd77485cb, 0x25823ac7),
187 RAPIDJSON_UINT64_C2(0xa086cfcd, 0x97bf97f4), RAPIDJSON_UINT64_C2(0xef340a98, 0x172aace5),
188 RAPIDJSON_UINT64_C2(0xb23867fb, 0x2a35b28e), RAPIDJSON_UINT64_C2(0x84c8d4df, 0xd2c63f3b),
189 RAPIDJSON_UINT64_C2(0xc5dd4427, 0x1ad3cdba), RAPIDJSON_UINT64_C2(0x936b9fce, 0xbb25c996),
190 RAPIDJSON_UINT64_C2(0xdbac6c24, 0x7d62a584), RAPIDJSON_UINT64_C2(0xa3ab6658, 0x0d5fdaf6),
191 RAPIDJSON_UINT64_C2(0xf3e2f893, 0xdec3f126), RAPIDJSON_UINT64_C2(0xb5b5ada8, 0xaaff80b8),
192 RAPIDJSON_UINT64_C2(0x87625f05, 0x6c7c4a8b), RAPIDJSON_UINT64_C2(0xc9bcff60, 0x34c13053),
193 RAPIDJSON_UINT64_C2(0x964e858c, 0x91ba2655), RAPIDJSON_UINT64_C2(0xdff97724, 0x70297ebd),
194 RAPIDJSON_UINT64_C2(0xa6dfbd9f, 0xb8e5b88f), RAPIDJSON_UINT64_C2(0xf8a95fcf, 0x88747d94),
195 RAPIDJSON_UINT64_C2(0xb9447093, 0x8fa89bcf), RAPIDJSON_UINT64_C2(0x8a08f0f8, 0xbf0f156b),
196 RAPIDJSON_UINT64_C2(0xcdb02555, 0x653131b6), RAPIDJSON_UINT64_C2(0x993fe2c6, 0xd07b7fac),
197 RAPIDJSON_UINT64_C2(0xe45c10c4, 0x2a2b3b06), RAPIDJSON_UINT64_C2(0xaa242499, 0x697392d3),
198 RAPIDJSON_UINT64_C2(0xfd87b5f2, 0x8300ca0e), RAPIDJSON_UINT64_C2(0xbce50864, 0x92111aeb),
199 RAPIDJSON_UINT64_C2(0x8cbccc09, 0x6f5088cc), RAPIDJSON_UINT64_C2(0xd1b71758, 0xe219652c),
200 RAPIDJSON_UINT64_C2(0x9c400000, 0x00000000), RAPIDJSON_UINT64_C2(0xe8d4a510, 0x00000000),
201 RAPIDJSON_UINT64_C2(0xad78ebc5, 0xac620000), RAPIDJSON_UINT64_C2(0x813f3978, 0xf8940984),
202 RAPIDJSON_UINT64_C2(0xc097ce7b, 0xc90715b3), RAPIDJSON_UINT64_C2(0x8f7e32ce, 0x7bea5c70),
203 RAPIDJSON_UINT64_C2(0xd5d238a4, 0xabe98068), RAPIDJSON_UINT64_C2(0x9f4f2726, 0x179a2245),
204 RAPIDJSON_UINT64_C2(0xed63a231, 0xd4c4fb27), RAPIDJSON_UINT64_C2(0xb0de6538, 0x8cc8ada8),
205 RAPIDJSON_UINT64_C2(0x83c7088e, 0x1aab65db), RAPIDJSON_UINT64_C2(0xc45d1df9, 0x42711d9a),
206 RAPIDJSON_UINT64_C2(0x924d692c, 0xa61be758), RAPIDJSON_UINT64_C2(0xda01ee64, 0x1a708dea),
207 RAPIDJSON_UINT64_C2(0xa26da399, 0x9aef774a), RAPIDJSON_UINT64_C2(0xf209787b, 0xb47d6b85),
208 RAPIDJSON_UINT64_C2(0xb454e4a1, 0x79dd1877), RAPIDJSON_UINT64_C2(0x865b8692, 0x5b9bc5c2),
209 RAPIDJSON_UINT64_C2(0xc83553c5, 0xc8965d3d), RAPIDJSON_UINT64_C2(0x952ab45c, 0xfa97a0b3),
210 RAPIDJSON_UINT64_C2(0xde469fbd, 0x99a05fe3), RAPIDJSON_UINT64_C2(0xa59bc234, 0xdb398c25),
211 RAPIDJSON_UINT64_C2(0xf6c69a72, 0xa3989f5c), RAPIDJSON_UINT64_C2(0xb7dcbf53, 0x54e9bece),
212 RAPIDJSON_UINT64_C2(0x88fcf317, 0xf22241e2), RAPIDJSON_UINT64_C2(0xcc20ce9b, 0xd35c78a5),
213 RAPIDJSON_UINT64_C2(0x98165af3, 0x7b2153df), RAPIDJSON_UINT64_C2(0xe2a0b5dc, 0x971f303a),
214 RAPIDJSON_UINT64_C2(0xa8d9d153, 0x5ce3b396), RAPIDJSON_UINT64_C2(0xfb9b7cd9, 0xa4a7443c),
215 RAPIDJSON_UINT64_C2(0xbb764c4c, 0xa7a44410), RAPIDJSON_UINT64_C2(0x8bab8eef, 0xb6409c1a),
216 RAPIDJSON_UINT64_C2(0xd01fef10, 0xa657842c), RAPIDJSON_UINT64_C2(0x9b10a4e5, 0xe9913129),
217 RAPIDJSON_UINT64_C2(0xe7109bfb, 0xa19c0c9d), RAPIDJSON_UINT64_C2(0xac2820d9, 0x623bf429),
218 RAPIDJSON_UINT64_C2(0x80444b5e, 0x7aa7cf85), RAPIDJSON_UINT64_C2(0xbf21e440, 0x03acdd2d),
219 RAPIDJSON_UINT64_C2(0x8e679c2f, 0x5e44ff8f), RAPIDJSON_UINT64_C2(0xd433179d, 0x9c8cb841),
220 RAPIDJSON_UINT64_C2(0x9e19db92, 0xb4e31ba9), RAPIDJSON_UINT64_C2(0xeb96bf6e, 0xbadf77d9),
221 RAPIDJSON_UINT64_C2(0xaf87023b, 0x9bf0ee6b)
223 static const int16_t kCachedPowers_E[] = {
224 -1220, -1193, -1166, -1140, -1113, -1087, -1060, -1034, -1007, -980,
225 -954, -927, -901, -874, -847, -821, -794, -768, -741, -715,
226 -688, -661, -635, -608, -582, -555, -529, -502, -475, -449,
227 -422, -396, -369, -343, -316, -289, -263, -236, -210, -183,
228 -157, -130, -103, -77, -50, -24, 3, 30, 56, 83,
229 109, 136, 162, 189, 216, 242, 269, 295, 322, 348,
230 375, 402, 428, 455, 481, 508, 534, 561, 588, 614,
231 641, 667, 694, 720, 747, 774, 800, 827, 853, 880,
232 907, 933, 960, 986, 1013, 1039, 1066
234 RAPIDJSON_ASSERT(index < 87);
235 return DiyFp(kCachedPowers_F[index], kCachedPowers_E[index]);
238 inline DiyFp GetCachedPower(int e, int* K) {
240 //int k = static_cast<int>(ceil((-61 - e) * 0.30102999566398114)) + 374;
241 double dk = (-61 - e) * 0.30102999566398114 + 347; // dk must be positive, so can do ceiling in positive
242 int k = static_cast<int>(dk);
246 unsigned index = static_cast<unsigned>((k >> 3) + 1);
247 *K = -(-348 + static_cast<int>(index << 3)); // decimal exponent no need lookup table
249 return GetCachedPowerByIndex(index);
252 inline DiyFp GetCachedPower10(int exp, int *outExp) {
253 RAPIDJSON_ASSERT(exp >= -348);
254 unsigned index = static_cast<unsigned>(exp + 348) / 8u;
255 *outExp = -348 + static_cast<int>(index) * 8;
256 return GetCachedPowerByIndex(index);
265 RAPIDJSON_DIAG_OFF(padded)
268 } // namespace internal
269 RAPIDJSON_NAMESPACE_END
271 #endif // RAPIDJSON_DIYFP_H_