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dtoa_milo.h
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dtoa_milo.h
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/*
* Copyright (C) 2014 Milo Yip
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
// Modified by Alvin at 2020.5.8.
#pragma once
#include <assert.h>
#include <math.h>
#include <string.h>
#include <stdint.h>
#include <stdio.h>
#ifdef _MSC_VER
#include <intrin.h>
#endif
namespace milo {
#if (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 6)) && defined(__x86_64__)
namespace gcc_ints
{
__extension__ typedef __int128 int128;
__extension__ typedef unsigned __int128 uint128;
}
#endif
#define UINT64_C2(h, l) ((static_cast<uint64_t>(h) << 32) | static_cast<uint64_t>(l))
struct DiyFp {
DiyFp() {}
DiyFp(uint64_t f, int e) : f(f), e(e) {}
DiyFp(double d) {
union {
double d;
uint64_t u64;
} u = { d };
int biased_e = (u.u64 & kDpExponentMask) >> kDpSignificandSize;
uint64_t significand = (u.u64 & kDpSignificandMask);
if (biased_e != 0) {
f = significand + kDpHiddenBit;
e = biased_e - kDpExponentBias;
}
else {
f = significand;
e = kDpMinExponent + 1;
}
}
DiyFp operator-(const DiyFp& rhs) const {
assert(e == rhs.e);
assert(f >= rhs.f);
return DiyFp(f - rhs.f, e);
}
DiyFp operator*(const DiyFp& rhs) const {
#if defined(_MSC_VER) && defined(_M_AMD64)
uint64_t h;
uint64_t l = _umul128(f, rhs.f, &h);
if (l & (uint64_t(1) << 63)) h++; // rounding
return DiyFp(h, e + rhs.e + 64);
#elif (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 6)) && defined(__x86_64__)
gcc_ints::uint128 p = static_cast<gcc_ints::uint128>(f) * static_cast<gcc_ints::uint128>(rhs.f);
uint64_t h = p >> 64;
uint64_t l = static_cast<uint64_t>(p);
if (l & (uint64_t(1) << 63)) h++; // rounding
return DiyFp(h, e + rhs.e + 64);
#else
const uint64_t M32 = 0xFFFFFFFF;
const uint64_t a = f >> 32;
const uint64_t b = f & M32;
const uint64_t c = rhs.f >> 32;
const uint64_t d = rhs.f & M32;
const uint64_t ac = a * c;
const uint64_t bc = b * c;
const uint64_t ad = a * d;
const uint64_t bd = b * d;
uint64_t tmp = (bd >> 32) + (ad & M32) + (bc & M32);
tmp += 1U << 31; /// mult_round
return DiyFp(ac + (ad >> 32) + (bc >> 32) + (tmp >> 32), e + rhs.e + 64);
#endif
}
DiyFp Normalize() const {
#if defined(_MSC_VER) && defined(_M_AMD64)
unsigned long index;
_BitScanReverse64(&index, f);
return DiyFp(f << (63 - index), e - (63 - index));
#elif defined(__GNUC__)
int s = __builtin_clzll(f);
return DiyFp(f << s, e - s);
#else
DiyFp res = *this;
while (!(res.f & kDpHiddenBit)) {
res.f <<= 1;
res.e--;
}
res.f <<= (kDiySignificandSize - kDpSignificandSize - 1);
res.e = res.e - (kDiySignificandSize - kDpSignificandSize - 1);
return res;
#endif
}
DiyFp NormalizeBoundary() const {
#if defined(_MSC_VER) && defined(_M_AMD64)
unsigned long index;
_BitScanReverse64(&index, f);
return DiyFp (f << (63 - index), e - (63 - index));
#else
DiyFp res = *this;
while (!(res.f & (kDpHiddenBit << 1))) {
res.f <<= 1;
res.e--;
}
res.f <<= (kDiySignificandSize - kDpSignificandSize - 2);
res.e = res.e - (kDiySignificandSize - kDpSignificandSize - 2);
return res;
#endif
}
void NormalizedBoundaries(DiyFp* minus, DiyFp* plus) const {
DiyFp pl = DiyFp((f << 1) + 1, e - 1).NormalizeBoundary();
DiyFp mi = (f == kDpHiddenBit) ? DiyFp((f << 2) - 1, e - 2) : DiyFp((f << 1) - 1, e - 1);
mi.f <<= mi.e - pl.e;
mi.e = pl.e;
*plus = pl;
*minus = mi;
}
static const int kDiySignificandSize = 64;
static const int kDpSignificandSize = 52;
static const int kDpExponentBias = 0x3FF + kDpSignificandSize;
static const int kDpMinExponent = -kDpExponentBias;
static const uint64_t kDpExponentMask = UINT64_C2(0x7FF00000, 0x00000000);
static const uint64_t kDpSignificandMask = UINT64_C2(0x000FFFFF, 0xFFFFFFFF);
static const uint64_t kDpHiddenBit = UINT64_C2(0x00100000, 0x00000000);
uint64_t f;
int e;
};
inline DiyFp GetCachedPower(int e, int* K) {
// 10^-348, 10^-340, ..., 10^340
static const uint64_t kCachedPowers_F[] = {
UINT64_C2(0xfa8fd5a0, 0x081c0288), UINT64_C2(0xbaaee17f, 0xa23ebf76),
UINT64_C2(0x8b16fb20, 0x3055ac76), UINT64_C2(0xcf42894a, 0x5dce35ea),
UINT64_C2(0x9a6bb0aa, 0x55653b2d), UINT64_C2(0xe61acf03, 0x3d1a45df),
UINT64_C2(0xab70fe17, 0xc79ac6ca), UINT64_C2(0xff77b1fc, 0xbebcdc4f),
UINT64_C2(0xbe5691ef, 0x416bd60c), UINT64_C2(0x8dd01fad, 0x907ffc3c),
UINT64_C2(0xd3515c28, 0x31559a83), UINT64_C2(0x9d71ac8f, 0xada6c9b5),
UINT64_C2(0xea9c2277, 0x23ee8bcb), UINT64_C2(0xaecc4991, 0x4078536d),
UINT64_C2(0x823c1279, 0x5db6ce57), UINT64_C2(0xc2109436, 0x4dfb5637),
UINT64_C2(0x9096ea6f, 0x3848984f), UINT64_C2(0xd77485cb, 0x25823ac7),
UINT64_C2(0xa086cfcd, 0x97bf97f4), UINT64_C2(0xef340a98, 0x172aace5),
UINT64_C2(0xb23867fb, 0x2a35b28e), UINT64_C2(0x84c8d4df, 0xd2c63f3b),
UINT64_C2(0xc5dd4427, 0x1ad3cdba), UINT64_C2(0x936b9fce, 0xbb25c996),
UINT64_C2(0xdbac6c24, 0x7d62a584), UINT64_C2(0xa3ab6658, 0x0d5fdaf6),
UINT64_C2(0xf3e2f893, 0xdec3f126), UINT64_C2(0xb5b5ada8, 0xaaff80b8),
UINT64_C2(0x87625f05, 0x6c7c4a8b), UINT64_C2(0xc9bcff60, 0x34c13053),
UINT64_C2(0x964e858c, 0x91ba2655), UINT64_C2(0xdff97724, 0x70297ebd),
UINT64_C2(0xa6dfbd9f, 0xb8e5b88f), UINT64_C2(0xf8a95fcf, 0x88747d94),
UINT64_C2(0xb9447093, 0x8fa89bcf), UINT64_C2(0x8a08f0f8, 0xbf0f156b),
UINT64_C2(0xcdb02555, 0x653131b6), UINT64_C2(0x993fe2c6, 0xd07b7fac),
UINT64_C2(0xe45c10c4, 0x2a2b3b06), UINT64_C2(0xaa242499, 0x697392d3),
UINT64_C2(0xfd87b5f2, 0x8300ca0e), UINT64_C2(0xbce50864, 0x92111aeb),
UINT64_C2(0x8cbccc09, 0x6f5088cc), UINT64_C2(0xd1b71758, 0xe219652c),
UINT64_C2(0x9c400000, 0x00000000), UINT64_C2(0xe8d4a510, 0x00000000),
UINT64_C2(0xad78ebc5, 0xac620000), UINT64_C2(0x813f3978, 0xf8940984),
UINT64_C2(0xc097ce7b, 0xc90715b3), UINT64_C2(0x8f7e32ce, 0x7bea5c70),
UINT64_C2(0xd5d238a4, 0xabe98068), UINT64_C2(0x9f4f2726, 0x179a2245),
UINT64_C2(0xed63a231, 0xd4c4fb27), UINT64_C2(0xb0de6538, 0x8cc8ada8),
UINT64_C2(0x83c7088e, 0x1aab65db), UINT64_C2(0xc45d1df9, 0x42711d9a),
UINT64_C2(0x924d692c, 0xa61be758), UINT64_C2(0xda01ee64, 0x1a708dea),
UINT64_C2(0xa26da399, 0x9aef774a), UINT64_C2(0xf209787b, 0xb47d6b85),
UINT64_C2(0xb454e4a1, 0x79dd1877), UINT64_C2(0x865b8692, 0x5b9bc5c2),
UINT64_C2(0xc83553c5, 0xc8965d3d), UINT64_C2(0x952ab45c, 0xfa97a0b3),
UINT64_C2(0xde469fbd, 0x99a05fe3), UINT64_C2(0xa59bc234, 0xdb398c25),
UINT64_C2(0xf6c69a72, 0xa3989f5c), UINT64_C2(0xb7dcbf53, 0x54e9bece),
UINT64_C2(0x88fcf317, 0xf22241e2), UINT64_C2(0xcc20ce9b, 0xd35c78a5),
UINT64_C2(0x98165af3, 0x7b2153df), UINT64_C2(0xe2a0b5dc, 0x971f303a),
UINT64_C2(0xa8d9d153, 0x5ce3b396), UINT64_C2(0xfb9b7cd9, 0xa4a7443c),
UINT64_C2(0xbb764c4c, 0xa7a44410), UINT64_C2(0x8bab8eef, 0xb6409c1a),
UINT64_C2(0xd01fef10, 0xa657842c), UINT64_C2(0x9b10a4e5, 0xe9913129),
UINT64_C2(0xe7109bfb, 0xa19c0c9d), UINT64_C2(0xac2820d9, 0x623bf429),
UINT64_C2(0x80444b5e, 0x7aa7cf85), UINT64_C2(0xbf21e440, 0x03acdd2d),
UINT64_C2(0x8e679c2f, 0x5e44ff8f), UINT64_C2(0xd433179d, 0x9c8cb841),
UINT64_C2(0x9e19db92, 0xb4e31ba9), UINT64_C2(0xeb96bf6e, 0xbadf77d9),
UINT64_C2(0xaf87023b, 0x9bf0ee6b)
};
static const int16_t kCachedPowers_E[] = {
-1220, -1193, -1166, -1140, -1113, -1087, -1060, -1034, -1007, -980,
-954, -927, -901, -874, -847, -821, -794, -768, -741, -715,
-688, -661, -635, -608, -582, -555, -529, -502, -475, -449,
-422, -396, -369, -343, -316, -289, -263, -236, -210, -183,
-157, -130, -103, -77, -50, -24, 3, 30, 56, 83,
109, 136, 162, 189, 216, 242, 269, 295, 322, 348,
375, 402, 428, 455, 481, 508, 534, 561, 588, 614,
641, 667, 694, 720, 747, 774, 800, 827, 853, 880,
907, 933, 960, 986, 1013, 1039, 1066
};
//int k = static_cast<int>(ceil((-61 - e) * 0.30102999566398114)) + 374;
double dk = (-61 - e) * 0.30102999566398114 + 347; // dk must be positive, so can do ceiling in positive
int k = static_cast<int>(dk);
if (dk - k > 0.0) k++;
unsigned index = static_cast<unsigned>((k >> 3) + 1);
*K = -(-348 + static_cast<int>(index << 3)); // decimal exponent no need lookup table
assert(index < sizeof(kCachedPowers_F) / sizeof(kCachedPowers_F[0]));
return DiyFp(kCachedPowers_F[index], kCachedPowers_E[index]);
}
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 unsigned 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;
if (n < 1000000000) return 9;
return 10;
}
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 = static_cast<int>(CountDecimalDigit32(p1));
*len = 0;
while (kappa > 0) {
uint32_t d;
switch (kappa) {
case 10: d = p1 / 1000000000; p1 %= 1000000000; break;
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 defined(_MSC_VER)
__assume(0);
#elif __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 5)
__builtin_unreachable();
#else
d = 0;
#endif
}
if (d || *len) buffer[(*len)++] = '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)++] = '0' + d;
p2 &= one.f - 1;
kappa--;
if (p2 < delta) {
*K += kappa;
const int index = -kappa;
GrisuRound(buffer, *len, delta, p2, one.f, wp_w.f * (index < 10 ? 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 const char* GetDigitsLut() {
static const char cDigitsLut[200] = {
'0', '0', '0', '1', '0', '2', '0', '3', '0', '4', '0', '5', '0', '6', '0', '7', '0', '8', '0', '9',
'1', '0', '1', '1', '1', '2', '1', '3', '1', '4', '1', '5', '1', '6', '1', '7', '1', '8', '1', '9',
'2', '0', '2', '1', '2', '2', '2', '3', '2', '4', '2', '5', '2', '6', '2', '7', '2', '8', '2', '9',
'3', '0', '3', '1', '3', '2', '3', '3', '3', '4', '3', '5', '3', '6', '3', '7', '3', '8', '3', '9',
'4', '0', '4', '1', '4', '2', '4', '3', '4', '4', '4', '5', '4', '6', '4', '7', '4', '8', '4', '9',
'5', '0', '5', '1', '5', '2', '5', '3', '5', '4', '5', '5', '5', '6', '5', '7', '5', '8', '5', '9',
'6', '0', '6', '1', '6', '2', '6', '3', '6', '4', '6', '5', '6', '6', '6', '7', '6', '8', '6', '9',
'7', '0', '7', '1', '7', '2', '7', '3', '7', '4', '7', '5', '7', '6', '7', '7', '7', '8', '7', '9',
'8', '0', '8', '1', '8', '2', '8', '3', '8', '4', '8', '5', '8', '6', '8', '7', '8', '8', '8', '9',
'9', '0', '9', '1', '9', '2', '9', '3', '9', '4', '9', '5', '9', '6', '9', '7', '9', '8', '9', '9'
};
return cDigitsLut;
}
inline char* WriteExponent(int K, char* buffer) {
if (K < 0) {
*buffer++ = '-';
K = -K;
}
if (K >= 100) {
*buffer++ = '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++ = '0' + static_cast<char>(K);
*buffer = '\0';
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
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 (kk == 0 || (-3 < kk && kk < 0 && -maxDecimalPlaces <= k)) {
// 1234e-6 -> 0.001234
const int offset = 2 - kk;
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 (length == 1) {
// 1e30
buffer[1] = 'e';
return WriteExponent(kk - 1, &buffer[2]);
}
else {
// 1234e30 -> 1.234e33
// 12345e-8 -> 1.23e-4 (mdp = 2)
size_t x = maxDecimalPlaces < length - 1 ? maxDecimalPlaces + 1 : length;
memmove(&buffer[2], &buffer[1], x - 1);
buffer[1] = '.';
while (x > 2 && buffer[x] == '0') --x;
buffer[x + 1] = 'e';
return WriteExponent(kk - 1, &buffer[x + 2]);
}
}
inline int dtoa(double value, char* buffer, int maxDecimalPlaces=324) {
// Not handling NaN and inf
//assert(!isnan(value));
//assert(!isinf(value));
assert(maxDecimalPlaces > 0);
if (value == 0) {
buffer[0] = '0';
buffer[1] = '.';
buffer[2] = '0';
buffer[3] = '\0';
return 3;
}
else {
char* p = buffer;
if (value < 0) {
*buffer++ = '-';
value = -value;
}
int length, K;
Grisu2(value, buffer, &length, &K);
return static_cast<int>(Prettify(buffer, length, K, maxDecimalPlaces) - p);
}
}
#undef UINT64_C2
} // milo