| // 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. |
| |
| // This is a C++ header-only implementation of Grisu2 algorithm from the publication: |
| // Loitsch, Florian. "Printing floating-point numbers quickly and accurately with |
| // integers." ACM Sigplan Notices 45.6 (2010): 233-243. |
| |
| #ifndef RAPIDJSON_DTOA_ |
| #define RAPIDJSON_DTOA_ |
| |
| #include "itoa.h" // GetDigitsLut() |
| #include "diyfp.h" |
| #include "ieee754.h" |
| |
| RAPIDJSON_NAMESPACE_BEGIN |
| namespace internal { |
| |
| #ifdef __GNUC__ |
| RAPIDJSON_DIAG_PUSH |
| RAPIDJSON_DIAG_OFF(effc++) |
| RAPIDJSON_DIAG_OFF(array-bounds) // some gcc versions generate wrong warnings https://gcc.gnu.org/bugzilla/show_bug.cgi?id=59124 |
| #endif |
| |
| inline void GrisuRound(char* buffer, int len, uint64_t delta, uint64_t rest, uint64_t ten_kappa, uint64_t wp_w) { |
| while (rest < wp_w && delta - rest >= ten_kappa && |
| (rest + ten_kappa < wp_w || /// closer |
| wp_w - rest > rest + ten_kappa - wp_w)) { |
| buffer[len - 1]--; |
| rest += ten_kappa; |
| } |
| } |
| |
| inline int CountDecimalDigit32(uint32_t n) { |
| // Simple pure C++ implementation was faster than __builtin_clz version in this situation. |
| if (n < 10) return 1; |
| if (n < 100) return 2; |
| if (n < 1000) return 3; |
| if (n < 10000) return 4; |
| if (n < 100000) return 5; |
| if (n < 1000000) return 6; |
| if (n < 10000000) return 7; |
| if (n < 100000000) return 8; |
| // Will not reach 10 digits in DigitGen() |
| //if (n < 1000000000) return 9; |
| //return 10; |
| return 9; |
| } |
| |
| inline void DigitGen(const DiyFp& W, const DiyFp& Mp, uint64_t delta, char* buffer, int* len, int* K) { |
| static const uint32_t kPow10[] = { 1, 10, 100, 1000, 10000, 100000, 1000000, 10000000, 100000000, 1000000000 }; |
| const DiyFp one(uint64_t(1) << -Mp.e, Mp.e); |
| const DiyFp wp_w = Mp - W; |
| uint32_t p1 = static_cast<uint32_t>(Mp.f >> -one.e); |
| uint64_t p2 = Mp.f & (one.f - 1); |
| int kappa = CountDecimalDigit32(p1); // kappa in [0, 9] |
| *len = 0; |
| |
| while (kappa > 0) { |
| uint32_t d = 0; |
| switch (kappa) { |
| case 9: d = p1 / 100000000; p1 %= 100000000; break; |
| case 8: d = p1 / 10000000; p1 %= 10000000; break; |
| case 7: d = p1 / 1000000; p1 %= 1000000; break; |
| case 6: d = p1 / 100000; p1 %= 100000; break; |
| case 5: d = p1 / 10000; p1 %= 10000; break; |
| case 4: d = p1 / 1000; p1 %= 1000; break; |
| case 3: d = p1 / 100; p1 %= 100; break; |
| case 2: d = p1 / 10; p1 %= 10; break; |
| case 1: d = p1; p1 = 0; break; |
| default:; |
| } |
| if (d || *len) |
| buffer[(*len)++] = static_cast<char>('0' + static_cast<char>(d)); |
| kappa--; |
| uint64_t tmp = (static_cast<uint64_t>(p1) << -one.e) + p2; |
| if (tmp <= delta) { |
| *K += kappa; |
| GrisuRound(buffer, *len, delta, tmp, static_cast<uint64_t>(kPow10[kappa]) << -one.e, wp_w.f); |
| return; |
| } |
| } |
| |
| // kappa = 0 |
| for (;;) { |
| p2 *= 10; |
| delta *= 10; |
| char d = static_cast<char>(p2 >> -one.e); |
| if (d || *len) |
| buffer[(*len)++] = static_cast<char>('0' + d); |
| p2 &= one.f - 1; |
| kappa--; |
| if (p2 < delta) { |
| *K += kappa; |
| int index = -kappa; |
| GrisuRound(buffer, *len, delta, p2, one.f, wp_w.f * (index < 9 ? kPow10[index] : 0)); |
| return; |
| } |
| } |
| } |
| |
| inline void Grisu2(double value, char* buffer, int* length, int* K) { |
| const DiyFp v(value); |
| DiyFp w_m, w_p; |
| v.NormalizedBoundaries(&w_m, &w_p); |
| |
| const DiyFp c_mk = GetCachedPower(w_p.e, K); |
| const DiyFp W = v.Normalize() * c_mk; |
| DiyFp Wp = w_p * c_mk; |
| DiyFp Wm = w_m * c_mk; |
| Wm.f++; |
| Wp.f--; |
| DigitGen(W, Wp, Wp.f - Wm.f, buffer, length, K); |
| } |
| |
| inline char* WriteExponent(int K, char* buffer) { |
| if (K < 0) { |
| *buffer++ = '-'; |
| K = -K; |
| } |
| |
| if (K >= 100) { |
| *buffer++ = static_cast<char>('0' + static_cast<char>(K / 100)); |
| K %= 100; |
| const char* d = GetDigitsLut() + K * 2; |
| *buffer++ = d[0]; |
| *buffer++ = d[1]; |
| } |
| else if (K >= 10) { |
| const char* d = GetDigitsLut() + K * 2; |
| *buffer++ = d[0]; |
| *buffer++ = d[1]; |
| } |
| else |
| *buffer++ = static_cast<char>('0' + static_cast<char>(K)); |
| |
| return buffer; |
| } |
| |
| inline char* Prettify(char* buffer, int length, int k, int maxDecimalPlaces) { |
| const int kk = length + k; // 10^(kk-1) <= v < 10^kk |
| |
| if (0 <= k && kk <= 21) { |
| // 1234e7 -> 12340000000 |
| for (int i = length; i < kk; i++) |
| buffer[i] = '0'; |
| buffer[kk] = '.'; |
| buffer[kk + 1] = '0'; |
| return &buffer[kk + 2]; |
| } |
| else if (0 < kk && kk <= 21) { |
| // 1234e-2 -> 12.34 |
| std::memmove(&buffer[kk + 1], &buffer[kk], static_cast<size_t>(length - kk)); |
| buffer[kk] = '.'; |
| if (0 > k + maxDecimalPlaces) { |
| // When maxDecimalPlaces = 2, 1.2345 -> 1.23, 1.102 -> 1.1 |
| // Remove extra trailing zeros (at least one) after truncation. |
| for (int i = kk + maxDecimalPlaces; i > kk + 1; i--) |
| if (buffer[i] != '0') |
| return &buffer[i + 1]; |
| return &buffer[kk + 2]; // Reserve one zero |
| } |
| else |
| return &buffer[length + 1]; |
| } |
| else if (-6 < kk && kk <= 0) { |
| // 1234e-6 -> 0.001234 |
| const int offset = 2 - kk; |
| std::memmove(&buffer[offset], &buffer[0], static_cast<size_t>(length)); |
| buffer[0] = '0'; |
| buffer[1] = '.'; |
| for (int i = 2; i < offset; i++) |
| buffer[i] = '0'; |
| if (length - kk > maxDecimalPlaces) { |
| // When maxDecimalPlaces = 2, 0.123 -> 0.12, 0.102 -> 0.1 |
| // Remove extra trailing zeros (at least one) after truncation. |
| for (int i = maxDecimalPlaces + 1; i > 2; i--) |
| if (buffer[i] != '0') |
| return &buffer[i + 1]; |
| return &buffer[3]; // Reserve one zero |
| } |
| else |
| return &buffer[length + offset]; |
| } |
| else if (kk < -maxDecimalPlaces) { |
| // Truncate to zero |
| buffer[0] = '0'; |
| buffer[1] = '.'; |
| buffer[2] = '0'; |
| return &buffer[3]; |
| } |
| else if (length == 1) { |
| // 1e30 |
| buffer[1] = 'e'; |
| return WriteExponent(kk - 1, &buffer[2]); |
| } |
| else { |
| // 1234e30 -> 1.234e33 |
| std::memmove(&buffer[2], &buffer[1], static_cast<size_t>(length - 1)); |
| buffer[1] = '.'; |
| buffer[length + 1] = 'e'; |
| return WriteExponent(kk - 1, &buffer[0 + length + 2]); |
| } |
| } |
| |
| inline char* dtoa(double value, char* buffer, int maxDecimalPlaces = 324) { |
| RAPIDJSON_ASSERT(maxDecimalPlaces >= 1); |
| Double d(value); |
| if (d.IsZero()) { |
| if (d.Sign()) |
| *buffer++ = '-'; // -0.0, Issue #289 |
| buffer[0] = '0'; |
| buffer[1] = '.'; |
| buffer[2] = '0'; |
| return &buffer[3]; |
| } |
| else { |
| if (value < 0) { |
| *buffer++ = '-'; |
| value = -value; |
| } |
| int length, K; |
| Grisu2(value, buffer, &length, &K); |
| return Prettify(buffer, length, K, maxDecimalPlaces); |
| } |
| } |
| |
| #ifdef __GNUC__ |
| RAPIDJSON_DIAG_POP |
| #endif |
| |
| } // namespace internal |
| RAPIDJSON_NAMESPACE_END |
| |
| #endif // RAPIDJSON_DTOA_ |
