double-conversion-strtod.cpp [plain text]
#include "unicode/utypes.h"
#if !UCONFIG_NO_FORMATTING
#include <stdarg.h>
#include <limits.h>
#include "double-conversion-strtod.h"
#include "double-conversion-bignum.h"
#include "double-conversion-cached-powers.h"
#include "double-conversion-ieee.h"
U_NAMESPACE_BEGIN
namespace double_conversion {
static const int kMaxExactDoubleIntegerDecimalDigits = 15;
static const int kMaxUint64DecimalDigits = 19;
static const int kMaxDecimalPower = 309;
static const int kMinDecimalPower = -324;
static const uint64_t kMaxUint64 = UINT64_2PART_C(0xFFFFFFFF, FFFFFFFF);
static const double exact_powers_of_ten[] = {
1.0, 10.0,
100.0,
1000.0,
10000.0,
100000.0,
1000000.0,
10000000.0,
100000000.0,
1000000000.0,
10000000000.0, 100000000000.0,
1000000000000.0,
10000000000000.0,
100000000000000.0,
1000000000000000.0,
10000000000000000.0,
100000000000000000.0,
1000000000000000000.0,
10000000000000000000.0,
100000000000000000000.0, 1000000000000000000000.0,
10000000000000000000000.0
};
static const int kExactPowersOfTenSize = ARRAY_SIZE(exact_powers_of_ten);
static const int kMaxSignificantDecimalDigits = 780;
static Vector<const char> TrimLeadingZeros(Vector<const char> buffer) {
for (int i = 0; i < buffer.length(); i++) {
if (buffer[i] != '0') {
return buffer.SubVector(i, buffer.length());
}
}
return Vector<const char>(buffer.start(), 0);
}
static Vector<const char> TrimTrailingZeros(Vector<const char> buffer) {
for (int i = buffer.length() - 1; i >= 0; --i) {
if (buffer[i] != '0') {
return buffer.SubVector(0, i + 1);
}
}
return Vector<const char>(buffer.start(), 0);
}
static void CutToMaxSignificantDigits(Vector<const char> buffer,
int exponent,
char* significant_buffer,
int* significant_exponent) {
for (int i = 0; i < kMaxSignificantDecimalDigits - 1; ++i) {
significant_buffer[i] = buffer[i];
}
ASSERT(buffer[buffer.length() - 1] != '0');
significant_buffer[kMaxSignificantDecimalDigits - 1] = '1';
*significant_exponent =
exponent + (buffer.length() - kMaxSignificantDecimalDigits);
}
static void TrimAndCut(Vector<const char> buffer, int exponent,
char* buffer_copy_space, int space_size,
Vector<const char>* trimmed, int* updated_exponent) {
Vector<const char> left_trimmed = TrimLeadingZeros(buffer);
Vector<const char> right_trimmed = TrimTrailingZeros(left_trimmed);
exponent += left_trimmed.length() - right_trimmed.length();
if (right_trimmed.length() > kMaxSignificantDecimalDigits) {
(void) space_size; ASSERT(space_size >= kMaxSignificantDecimalDigits);
CutToMaxSignificantDigits(right_trimmed, exponent,
buffer_copy_space, updated_exponent);
*trimmed = Vector<const char>(buffer_copy_space,
kMaxSignificantDecimalDigits);
} else {
*trimmed = right_trimmed;
*updated_exponent = exponent;
}
}
static uint64_t ReadUint64(Vector<const char> buffer,
int* number_of_read_digits) {
uint64_t result = 0;
int i = 0;
while (i < buffer.length() && result <= (kMaxUint64 / 10 - 1)) {
int digit = buffer[i++] - '0';
ASSERT(0 <= digit && digit <= 9);
result = 10 * result + digit;
}
*number_of_read_digits = i;
return result;
}
static void ReadDiyFp(Vector<const char> buffer,
DiyFp* result,
int* remaining_decimals) {
int read_digits;
uint64_t significand = ReadUint64(buffer, &read_digits);
if (buffer.length() == read_digits) {
*result = DiyFp(significand, 0);
*remaining_decimals = 0;
} else {
if (buffer[read_digits] >= '5') {
significand++;
}
int exponent = 0;
*result = DiyFp(significand, exponent);
*remaining_decimals = buffer.length() - read_digits;
}
}
static bool DoubleStrtod(Vector<const char> trimmed,
int exponent,
double* result) {
#if !defined(DOUBLE_CONVERSION_CORRECT_DOUBLE_OPERATIONS)
return false;
#endif
if (trimmed.length() <= kMaxExactDoubleIntegerDecimalDigits) {
int read_digits;
if (exponent < 0 && -exponent < kExactPowersOfTenSize) {
*result = static_cast<double>(ReadUint64(trimmed, &read_digits));
ASSERT(read_digits == trimmed.length());
*result /= exact_powers_of_ten[-exponent];
return true;
}
if (0 <= exponent && exponent < kExactPowersOfTenSize) {
*result = static_cast<double>(ReadUint64(trimmed, &read_digits));
ASSERT(read_digits == trimmed.length());
*result *= exact_powers_of_ten[exponent];
return true;
}
int remaining_digits =
kMaxExactDoubleIntegerDecimalDigits - trimmed.length();
if ((0 <= exponent) &&
(exponent - remaining_digits < kExactPowersOfTenSize)) {
*result = static_cast<double>(ReadUint64(trimmed, &read_digits));
ASSERT(read_digits == trimmed.length());
*result *= exact_powers_of_ten[remaining_digits];
*result *= exact_powers_of_ten[exponent - remaining_digits];
return true;
}
}
return false;
}
static DiyFp AdjustmentPowerOfTen(int exponent) {
ASSERT(0 < exponent);
ASSERT(exponent < PowersOfTenCache::kDecimalExponentDistance);
ASSERT(PowersOfTenCache::kDecimalExponentDistance == 8);
switch (exponent) {
case 1: return DiyFp(UINT64_2PART_C(0xa0000000, 00000000), -60);
case 2: return DiyFp(UINT64_2PART_C(0xc8000000, 00000000), -57);
case 3: return DiyFp(UINT64_2PART_C(0xfa000000, 00000000), -54);
case 4: return DiyFp(UINT64_2PART_C(0x9c400000, 00000000), -50);
case 5: return DiyFp(UINT64_2PART_C(0xc3500000, 00000000), -47);
case 6: return DiyFp(UINT64_2PART_C(0xf4240000, 00000000), -44);
case 7: return DiyFp(UINT64_2PART_C(0x98968000, 00000000), -40);
default:
UNREACHABLE();
}
}
static bool DiyFpStrtod(Vector<const char> buffer,
int exponent,
double* result) {
DiyFp input;
int remaining_decimals;
ReadDiyFp(buffer, &input, &remaining_decimals);
const int kDenominatorLog = 3;
const int kDenominator = 1 << kDenominatorLog;
exponent += remaining_decimals;
uint64_t error = (remaining_decimals == 0 ? 0 : kDenominator / 2);
int old_e = input.e();
input.Normalize();
error <<= old_e - input.e();
ASSERT(exponent <= PowersOfTenCache::kMaxDecimalExponent);
if (exponent < PowersOfTenCache::kMinDecimalExponent) {
*result = 0.0;
return true;
}
DiyFp cached_power;
int cached_decimal_exponent;
PowersOfTenCache::GetCachedPowerForDecimalExponent(exponent,
&cached_power,
&cached_decimal_exponent);
if (cached_decimal_exponent != exponent) {
int adjustment_exponent = exponent - cached_decimal_exponent;
DiyFp adjustment_power = AdjustmentPowerOfTen(adjustment_exponent);
input.Multiply(adjustment_power);
if (kMaxUint64DecimalDigits - buffer.length() >= adjustment_exponent) {
ASSERT(DiyFp::kSignificandSize == 64);
} else {
error += kDenominator / 2;
}
}
input.Multiply(cached_power);
int error_b = kDenominator / 2;
int error_ab = (error == 0 ? 0 : 1); int fixed_error = kDenominator / 2;
error += error_b + error_ab + fixed_error;
old_e = input.e();
input.Normalize();
error <<= old_e - input.e();
int order_of_magnitude = DiyFp::kSignificandSize + input.e();
int effective_significand_size =
Double::SignificandSizeForOrderOfMagnitude(order_of_magnitude);
int precision_digits_count =
DiyFp::kSignificandSize - effective_significand_size;
if (precision_digits_count + kDenominatorLog >= DiyFp::kSignificandSize) {
int shift_amount = (precision_digits_count + kDenominatorLog) -
DiyFp::kSignificandSize + 1;
input.set_f(input.f() >> shift_amount);
input.set_e(input.e() + shift_amount);
error = (error >> shift_amount) + 1 + kDenominator;
precision_digits_count -= shift_amount;
}
ASSERT(DiyFp::kSignificandSize == 64);
ASSERT(precision_digits_count < 64);
uint64_t one64 = 1;
uint64_t precision_bits_mask = (one64 << precision_digits_count) - 1;
uint64_t precision_bits = input.f() & precision_bits_mask;
uint64_t half_way = one64 << (precision_digits_count - 1);
precision_bits *= kDenominator;
half_way *= kDenominator;
DiyFp rounded_input(input.f() >> precision_digits_count,
input.e() + precision_digits_count);
if (precision_bits >= half_way + error) {
rounded_input.set_f(rounded_input.f() + 1);
}
*result = Double(rounded_input).value();
if (half_way - error < precision_bits && precision_bits < half_way + error) {
return false;
} else {
return true;
}
}
static int CompareBufferWithDiyFp(Vector<const char> buffer,
int exponent,
DiyFp diy_fp) {
ASSERT(buffer.length() + exponent <= kMaxDecimalPower + 1);
ASSERT(buffer.length() + exponent > kMinDecimalPower);
ASSERT(buffer.length() <= kMaxSignificantDecimalDigits);
ASSERT(((kMaxDecimalPower + 1) * 333 / 100) < Bignum::kMaxSignificantBits);
Bignum buffer_bignum;
Bignum diy_fp_bignum;
buffer_bignum.AssignDecimalString(buffer);
diy_fp_bignum.AssignUInt64(diy_fp.f());
if (exponent >= 0) {
buffer_bignum.MultiplyByPowerOfTen(exponent);
} else {
diy_fp_bignum.MultiplyByPowerOfTen(-exponent);
}
if (diy_fp.e() > 0) {
diy_fp_bignum.ShiftLeft(diy_fp.e());
} else {
buffer_bignum.ShiftLeft(-diy_fp.e());
}
return Bignum::Compare(buffer_bignum, diy_fp_bignum);
}
static bool ComputeGuess(Vector<const char> trimmed, int exponent,
double* guess) {
if (trimmed.length() == 0) {
*guess = 0.0;
return true;
}
if (exponent + trimmed.length() - 1 >= kMaxDecimalPower) {
*guess = Double::Infinity();
return true;
}
if (exponent + trimmed.length() <= kMinDecimalPower) {
*guess = 0.0;
return true;
}
if (DoubleStrtod(trimmed, exponent, guess) ||
DiyFpStrtod(trimmed, exponent, guess)) {
return true;
}
if (*guess == Double::Infinity()) {
return true;
}
return false;
}
double Strtod(Vector<const char> buffer, int exponent) {
char copy_buffer[kMaxSignificantDecimalDigits];
Vector<const char> trimmed;
int updated_exponent;
TrimAndCut(buffer, exponent, copy_buffer, kMaxSignificantDecimalDigits,
&trimmed, &updated_exponent);
exponent = updated_exponent;
double guess;
bool is_correct = ComputeGuess(trimmed, exponent, &guess);
if (is_correct) return guess;
DiyFp upper_boundary = Double(guess).UpperBoundary();
int comparison = CompareBufferWithDiyFp(trimmed, exponent, upper_boundary);
if (comparison < 0) {
return guess;
} else if (comparison > 0) {
return Double(guess).NextDouble();
} else if ((Double(guess).Significand() & 1) == 0) {
return guess;
} else {
return Double(guess).NextDouble();
}
}
float Strtof(Vector<const char> buffer, int exponent) {
char copy_buffer[kMaxSignificantDecimalDigits];
Vector<const char> trimmed;
int updated_exponent;
TrimAndCut(buffer, exponent, copy_buffer, kMaxSignificantDecimalDigits,
&trimmed, &updated_exponent);
exponent = updated_exponent;
double double_guess;
bool is_correct = ComputeGuess(trimmed, exponent, &double_guess);
float float_guess = static_cast<float>(double_guess);
if (float_guess == double_guess) {
return float_guess;
}
double double_next = Double(double_guess).NextDouble();
double double_previous = Double(double_guess).PreviousDouble();
float f1 = static_cast<float>(double_previous);
float f2 = float_guess;
float f3 = static_cast<float>(double_next);
float f4;
if (is_correct) {
f4 = f3;
} else {
double double_next2 = Double(double_next).NextDouble();
f4 = static_cast<float>(double_next2);
}
(void) f2; ASSERT(f1 <= f2 && f2 <= f3 && f3 <= f4);
if (f1 == f4) {
return float_guess;
}
ASSERT((f1 != f2 && f2 == f3 && f3 == f4) ||
(f1 == f2 && f2 != f3 && f3 == f4) ||
(f1 == f2 && f2 == f3 && f3 != f4));
float guess = f1;
float next = f4;
DiyFp upper_boundary;
if (guess == 0.0f) {
float min_float = 1e-45f;
upper_boundary = Double(static_cast<double>(min_float) / 2).AsDiyFp();
} else {
upper_boundary = Single(guess).UpperBoundary();
}
int comparison = CompareBufferWithDiyFp(trimmed, exponent, upper_boundary);
if (comparison < 0) {
return guess;
} else if (comparison > 0) {
return next;
} else if ((Single(guess).Significand() & 1) == 0) {
return guess;
} else {
return next;
}
}
}
U_NAMESPACE_END
#endif // ICU PATCH: close #if !UCONFIG_NO_FORMATTING