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Merge pull request #96 from Alexhuszagh/bigint

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Implement the big-integer arithmetic algorithm.
This commit is contained in:
Daniel Lemire 2021-09-13 21:23:14 -04:00 committed by GitHub
commit 3f0ba09a95
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8 changed files with 1142 additions and 191 deletions
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157
include/fast_float/ascii_number.h
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@ -91,15 +91,19 @@ CXX20_CONSTEXPR fastfloat_really_inline bool is_made_of_eight_digits_fast(const
return is_made_of_eight_digits_fast(read_u64(chars)); return is_made_of_eight_digits_fast(read_u64(chars));
} }
struct parsed_number_string { typedef span<const char> byte_span;
int64_t exponent;
uint64_t mantissa;
const char *lastmatch;
bool negative;
bool valid;
bool too_many_digits;
};
struct parsed_number_string {
int64_t exponent{0};
uint64_t mantissa{0};
const char *lastmatch{nullptr};
bool negative{false};
bool valid{false};
bool too_many_digits{false};
// contains the range of the significant digits
byte_span integer{}; // non-nullable
byte_span fraction{}; // nullable
};
// Assuming that you use no more than 19 digits, this will // Assuming that you use no more than 19 digits, this will
// parse an ASCII string. // parse an ASCII string.
@ -125,6 +129,10 @@ parsed_number_string parse_number_string(const char *p, const char *pend, parse_
uint64_t i = 0; // an unsigned int avoids signed overflows (which are bad) uint64_t i = 0; // an unsigned int avoids signed overflows (which are bad)
while ((std::distance(p, pend) >= 8) && is_made_of_eight_digits_fast(p)) {
i = i * 100000000 + parse_eight_digits_unrolled(p); // in rare cases, this will overflow, but that's ok
p += 8;
}
while ((p != pend) && is_integer(*p)) { while ((p != pend) && is_integer(*p)) {
// a multiplication by 10 is cheaper than an arbitrary integer // a multiplication by 10 is cheaper than an arbitrary integer
// multiplication // multiplication
@ -134,24 +142,24 @@ parsed_number_string parse_number_string(const char *p, const char *pend, parse_
} }
const char *const end_of_integer_part = p; const char *const end_of_integer_part = p;
int64_t digit_count = int64_t(end_of_integer_part - start_digits); int64_t digit_count = int64_t(end_of_integer_part - start_digits);
answer.integer = byte_span(start_digits, size_t(digit_count));
int64_t exponent = 0; int64_t exponent = 0;
if ((p != pend) && (*p == decimal_point)) { if ((p != pend) && (*p == decimal_point)) {
++p; ++p;
// Fast approach only tested under little endian systems const char* before = p;
if ((std::distance(p, pend) >= 8) && is_made_of_eight_digits_fast(p)) { // can occur at most twice without overflowing, but let it occur more, since
// for integers with many digits, digit parsing is the primary bottleneck.
while ((std::distance(p, pend) >= 8) && is_made_of_eight_digits_fast(p)) {
i = i * 100000000 + parse_eight_digits_unrolled(p); // in rare cases, this will overflow, but that's ok i = i * 100000000 + parse_eight_digits_unrolled(p); // in rare cases, this will overflow, but that's ok
p += 8; p += 8;
if ((std::distance(p, pend) >= 8) && is_made_of_eight_digits_fast(p)) {
i = i * 100000000 + parse_eight_digits_unrolled(p); // in rare cases, this will overflow, but that's ok
p += 8;
}
} }
while ((p != pend) && is_integer(*p)) { while ((p != pend) && is_integer(*p)) {
uint8_t digit = uint8_t(*p - '0'); uint8_t digit = uint8_t(*p - '0');
++p; ++p;
i = i * 10 + digit; // in rare cases, this will overflow, but that's ok i = i * 10 + digit; // in rare cases, this will overflow, but that's ok
} }
exponent = end_of_integer_part + 1 - p; exponent = before - p;
answer.fraction = byte_span(before, size_t(p - before));
digit_count -= exponent; digit_count -= exponent;
} }
// we must have encountered at least one integer! // we must have encountered at least one integer!
@ -179,7 +187,7 @@ parsed_number_string parse_number_string(const char *p, const char *pend, parse_
} else { } else {
while ((p != pend) && is_integer(*p)) { while ((p != pend) && is_integer(*p)) {
uint8_t digit = uint8_t(*p - '0'); uint8_t digit = uint8_t(*p - '0');
if (exp_number < 0x10000) { if (exp_number < 0x10000000) {
exp_number = 10 * exp_number + digit; exp_number = 10 * exp_number + digit;
} }
++p; ++p;
@ -212,23 +220,26 @@ parsed_number_string parse_number_string(const char *p, const char *pend, parse_
if (digit_count > 19) { if (digit_count > 19) {
answer.too_many_digits = true; answer.too_many_digits = true;
// Let us start again, this time, avoiding overflows. // Let us start again, this time, avoiding overflows.
// We don't need to check if is_integer, since we use the
// pre-tokenized spans from above.
i = 0; i = 0;
p = start_digits; p = answer.integer.ptr;
const char* int_end = p + answer.integer.len();
const uint64_t minimal_nineteen_digit_integer{1000000000000000000}; const uint64_t minimal_nineteen_digit_integer{1000000000000000000};
while((i < minimal_nineteen_digit_integer) && (p != pend) && is_integer(*p)) { while((i < minimal_nineteen_digit_integer) && (p != int_end)) {
i = i * 10 + uint64_t(*p - '0'); i = i * 10 + uint64_t(*p - '0');
++p; ++p;
} }
if (i >= minimal_nineteen_digit_integer) { // We have a big integers if (i >= minimal_nineteen_digit_integer) { // We have a big integers
exponent = end_of_integer_part - p + exp_number; exponent = end_of_integer_part - p + exp_number;
} else { // We have a value with a fractional component. } else { // We have a value with a fractional component.
p++; // skip the dot p = answer.fraction.ptr;
const char *first_after_period = p; const char* frac_end = p + answer.fraction.len();
while((i < minimal_nineteen_digit_integer) && (p != pend) && is_integer(*p)) { while((i < minimal_nineteen_digit_integer) && (p != frac_end)) {
i = i * 10 + uint64_t(*p - '0'); i = i * 10 + uint64_t(*p - '0');
++p; ++p;
} }
exponent = first_after_period - p + exp_number; exponent = answer.fraction.ptr - p + exp_number;
} }
// We have now corrected both exponent and i, to a truncated value // We have now corrected both exponent and i, to a truncated value
} }
@ -238,108 +249,6 @@ parsed_number_string parse_number_string(const char *p, const char *pend, parse_
return answer; return answer;
} }
// This should always succeed since it follows a call to parse_number_string
// This function could be optimized. In particular, we could stop after 19 digits
// and try to bail out. Furthermore, we should be able to recover the computed
// exponent from the pass in parse_number_string.
CXX20_CONSTEXPR fastfloat_really_inline decimal parse_decimal(const char *p, const char *pend, parse_options options) noexcept {
const char decimal_point = options.decimal_point;
decimal answer;
answer.num_digits = 0;
answer.decimal_point = 0;
answer.truncated = false;
answer.negative = (*p == '-');
if (*p == '-') { // C++17 20.19.3.(7.1) explicitly forbids '+' sign here
++p;
}
// skip leading zeroes
while ((p != pend) && (*p == '0')) {
++p;
}
while ((p != pend) && is_integer(*p)) {
if (answer.num_digits < max_digits) {
answer.digits[answer.num_digits] = uint8_t(*p - '0');
}
answer.num_digits++;
++p;
}
if ((p != pend) && (*p == decimal_point)) {
++p;
const char *first_after_period = p;
// if we have not yet encountered a zero, we have to skip it as well
if(answer.num_digits == 0) {
// skip zeros
while ((p != pend) && (*p == '0')) {
++p;
}
}
// We expect that this loop will often take the bulk of the running time
// because when a value has lots of digits, these digits often
while ((std::distance(p, pend) >= 8) && (answer.num_digits + 8 < max_digits)) {
uint64_t val = read_u64(p);
if(! is_made_of_eight_digits_fast(val)) { break; }
// We have eight digits, process them in one go!
val -= 0x3030303030303030;
write_u64(answer.digits + answer.num_digits, val);
answer.num_digits += 8;
p += 8;
}
while ((p != pend) && is_integer(*p)) {
if (answer.num_digits < max_digits) {
answer.digits[answer.num_digits] = uint8_t(*p - '0');
}
answer.num_digits++;
++p;
}
answer.decimal_point = int32_t(first_after_period - p);
}
// We want num_digits to be the number of significant digits, excluding
// leading *and* trailing zeros! Otherwise the truncated flag later is
// going to be misleading.
if(answer.num_digits > 0) {
// We potentially need the answer.num_digits > 0 guard because we
// prune leading zeros. So with answer.num_digits > 0, we know that
// we have at least one non-zero digit.
const char *preverse = p - 1;
int32_t trailing_zeros = 0;
while ((*preverse == '0') || (*preverse == decimal_point)) {
if(*preverse == '0') { trailing_zeros++; };
--preverse;
}
answer.decimal_point += int32_t(answer.num_digits);
answer.num_digits -= uint32_t(trailing_zeros);
}
if(answer.num_digits > max_digits) {
answer.truncated = true;
answer.num_digits = max_digits;
}
if ((p != pend) && (('e' == *p) || ('E' == *p))) {
++p;
bool neg_exp = false;
if ((p != pend) && ('-' == *p)) {
neg_exp = true;
++p;
} else if ((p != pend) && ('+' == *p)) { // '+' on exponent is allowed by C++17 20.19.3.(7.1)
++p;
}
int32_t exp_number = 0; // exponential part
while ((p != pend) && is_integer(*p)) {
uint8_t digit = uint8_t(*p - '0');
if (exp_number < 0x10000) {
exp_number = 10 * exp_number + digit;
}
++p;
}
answer.decimal_point += (neg_exp ? -exp_number : exp_number);
}
// In very rare cases, we may have fewer than 19 digits, we want to be able to reliably
// assume that all digits up to max_digit_without_overflow have been initialized.
for(uint32_t i = answer.num_digits; i < max_digit_without_overflow; i++) { answer.digits[i] = 0; }
return answer;
}
} // namespace fast_float } // namespace fast_float
#endif #endif

590
include/fast_float/bigint.h Normal file
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@ -0,0 +1,590 @@
#ifndef FASTFLOAT_BIGINT_H
#define FASTFLOAT_BIGINT_H
#include <algorithm>
#include <cstdint>
#include <climits>
#include <cstring>
#include "float_common.h"
namespace fast_float {
// the limb width: we want efficient multiplication of double the bits in
// limb, or for 64-bit limbs, at least 64-bit multiplication where we can
// extract the high and low parts efficiently. this is every 64-bit
// architecture except for sparc, which emulates 128-bit multiplication.
// we might have platforms where `CHAR_BIT` is not 8, so let's avoid
// doing `8 * sizeof(limb)`.
#if defined(FASTFLOAT_64BIT) && !defined(__sparc)
#define FASTFLOAT_64BIT_LIMB
typedef uint64_t limb;
constexpr size_t limb_bits = 64;
#else
#define FASTFLOAT_32BIT_LIMB
typedef uint32_t limb;
constexpr size_t limb_bits = 32;
#endif
typedef span<limb> limb_span;
// number of bits in a bigint. this needs to be at least the number
// of bits required to store the largest bigint, which is
// `log2(10**(digits + max_exp))`, or `log2(10**(767 + 342))`, or
// ~3600 bits, so we round to 4000.
constexpr size_t bigint_bits = 4000;
constexpr size_t bigint_limbs = bigint_bits / limb_bits;
// vector-like type that is allocated on the stack. the entire
// buffer is pre-allocated, and only the length changes.
template <uint16_t size>
struct stackvec {
limb data[size];
// we never need more than 150 limbs
uint16_t length{0};
stackvec() = default;
stackvec(const stackvec &) = delete;
stackvec &operator=(const stackvec &) = delete;
stackvec(stackvec &&) = delete;
stackvec &operator=(stackvec &&other) = delete;
// create stack vector from existing limb span.
stackvec(limb_span s) {
FASTFLOAT_ASSERT(try_extend(s));
}
limb& operator[](size_t index) noexcept {
FASTFLOAT_DEBUG_ASSERT(index < length);
return data[index];
}
const limb& operator[](size_t index) const noexcept {
FASTFLOAT_DEBUG_ASSERT(index < length);
return data[index];
}
// index from the end of the container
const limb& rindex(size_t index) const noexcept {
FASTFLOAT_DEBUG_ASSERT(index < length);
size_t rindex = length - index - 1;
return data[rindex];
}
// set the length, without bounds checking.
void set_len(size_t len) noexcept {
length = uint16_t(len);
}
constexpr size_t len() const noexcept {
return length;
}
constexpr bool is_empty() const noexcept {
return length == 0;
}
constexpr size_t capacity() const noexcept {
return size;
}
// append item to vector, without bounds checking
void push_unchecked(limb value) noexcept {
data[length] = value;
length++;
}
// append item to vector, returning if item was added
bool try_push(limb value) noexcept {
if (len() < capacity()) {
push_unchecked(value);
return true;
} else {
return false;
}
}
// add items to the vector, from a span, without bounds checking
void extend_unchecked(limb_span s) noexcept {
limb* ptr = data + length;
::memcpy((void*)ptr, (const void*)s.ptr, sizeof(limb) * s.len());
set_len(len() + s.len());
}
// try to add items to the vector, returning if items were added
bool try_extend(limb_span s) noexcept {
if (len() + s.len() <= capacity()) {
extend_unchecked(s);
return true;
} else {
return false;
}
}
// resize the vector, without bounds checking
// if the new size is longer than the vector, assign value to each
// appended item.
void resize_unchecked(size_t new_len, limb value) noexcept {
if (new_len > len()) {
size_t count = new_len - len();
limb* first = data + len();
limb* last = first + count;
::std::fill(first, last, value);
set_len(new_len);
} else {
set_len(new_len);
}
}
// try to resize the vector, returning if the vector was resized.
bool try_resize(size_t new_len, limb value) noexcept {
if (new_len > capacity()) {
return false;
} else {
resize_unchecked(new_len, value);
return true;
}
}
// check if any limbs are non-zero after the given index.
// this needs to be done in reverse order, since the index
// is relative to the most significant limbs.
bool nonzero(size_t index) const noexcept {
while (index < len()) {
if (rindex(index) != 0) {
return true;
}
index++;
}
return false;
}
// normalize the big integer, so most-significant zero limbs are removed.
void normalize() noexcept {
while (len() > 0 && rindex(0) == 0) {
length--;
}
}
};
fastfloat_really_inline
uint64_t empty_hi64(bool& truncated) noexcept {
truncated = false;
return 0;
}
fastfloat_really_inline
uint64_t uint64_hi64(uint64_t r0, bool& truncated) noexcept {
truncated = false;
int shl = leading_zeroes(r0);
return r0 << shl;
}
fastfloat_really_inline
uint64_t uint64_hi64(uint64_t r0, uint64_t r1, bool& truncated) noexcept {
int shl = leading_zeroes(r0);
if (shl == 0) {
truncated = r1 != 0;
return r0;
} else {
int shr = 64 - shl;
truncated = (r1 << shl) != 0;
return (r0 << shl) | (r1 >> shr);
}
}
fastfloat_really_inline
uint64_t uint32_hi64(uint32_t r0, bool& truncated) noexcept {
return uint64_hi64(r0, truncated);
}
fastfloat_really_inline
uint64_t uint32_hi64(uint32_t r0, uint32_t r1, bool& truncated) noexcept {
uint64_t x0 = r0;
uint64_t x1 = r1;
return uint64_hi64((x0 << 32) | x1, truncated);
}
fastfloat_really_inline
uint64_t uint32_hi64(uint32_t r0, uint32_t r1, uint32_t r2, bool& truncated) noexcept {
uint64_t x0 = r0;
uint64_t x1 = r1;
uint64_t x2 = r2;
return uint64_hi64(x0, (x1 << 32) | x2, truncated);
}
// add two small integers, checking for overflow.
// we want an efficient operation. for msvc, where
// we don't have built-in intrinsics, this is still
// pretty fast.
fastfloat_really_inline
limb scalar_add(limb x, limb y, bool& overflow) noexcept {
limb z;
// gcc and clang
#if defined(__has_builtin)
#if __has_builtin(__builtin_add_overflow)
overflow = __builtin_add_overflow(x, y, &z);
return z;
#endif
#endif
// generic, this still optimizes correctly on MSVC.
z = x + y;
overflow = z < x;
return z;
}
// multiply two small integers, getting both the high and low bits.
fastfloat_really_inline
limb scalar_mul(limb x, limb y, limb& carry) noexcept {
#ifdef FASTFLOAT_64BIT_LIMB
#if defined(__SIZEOF_INT128__)
// GCC and clang both define it as an extension.
__uint128_t z = __uint128_t(x) * __uint128_t(y) + __uint128_t(carry);
carry = limb(z >> limb_bits);
return limb(z);
#else
// fallback, no native 128-bit integer multiplication with carry.
// on msvc, this optimizes identically, somehow.
value128 z = full_multiplication(x, y);
bool overflow;
z.low = scalar_add(z.low, carry, overflow);
z.high += uint64_t(overflow); // cannot overflow
carry = z.high;
return z.low;
#endif
#else
uint64_t z = uint64_t(x) * uint64_t(y) + uint64_t(carry);
carry = limb(z >> limb_bits);
return limb(z);
#endif
}
// add scalar value to bigint starting from offset.
// used in grade school multiplication
template <uint16_t size>
inline bool small_add_from(stackvec<size>& vec, limb y, size_t start) noexcept {
size_t index = start;
limb carry = y;
bool overflow;
while (carry != 0 && index < vec.len()) {
vec[index] = scalar_add(vec[index], carry, overflow);
carry = limb(overflow);
index += 1;
}
if (carry != 0) {
FASTFLOAT_TRY(vec.try_push(carry));
}
return true;
}
// add scalar value to bigint.
template <uint16_t size>
fastfloat_really_inline bool small_add(stackvec<size>& vec, limb y) noexcept {
return small_add_from(vec, y, 0);
}
// multiply bigint by scalar value.
template <uint16_t size>
inline bool small_mul(stackvec<size>& vec, limb y) noexcept {
limb carry = 0;
for (size_t index = 0; index < vec.len(); index++) {
vec[index] = scalar_mul(vec[index], y, carry);
}
if (carry != 0) {
FASTFLOAT_TRY(vec.try_push(carry));
}
return true;
}
// add bigint to bigint starting from index.
// used in grade school multiplication
template <uint16_t size>
bool large_add_from(stackvec<size>& x, limb_span y, size_t start) noexcept {
// the effective x buffer is from `xstart..x.len()`, so exit early
// if we can't get that current range.
if (x.len() < start || y.len() > x.len() - start) {
FASTFLOAT_TRY(x.try_resize(y.len() + start, 0));
}
bool carry = false;
for (size_t index = 0; index < y.len(); index++) {
limb xi = x[index + start];
limb yi = y[index];
bool c1 = false;
bool c2 = false;
xi = scalar_add(xi, yi, c1);
if (carry) {
xi = scalar_add(xi, 1, c2);
}
x[index + start] = xi;
carry = c1 | c2;
}
// handle overflow
if (carry) {
FASTFLOAT_TRY(small_add_from(x, 1, y.len() + start));
}
return true;
}
// add bigint to bigint.
template <uint16_t size>
fastfloat_really_inline bool large_add_from(stackvec<size>& x, limb_span y) noexcept {
return large_add_from(x, y, 0);
}
// grade-school multiplication algorithm
template <uint16_t size>
bool long_mul(stackvec<size>& x, limb_span y) noexcept {
limb_span xs = limb_span(x.data, x.len());
stackvec<size> z(xs);
limb_span zs = limb_span(z.data, z.len());
if (y.len() != 0) {
limb y0 = y[0];
FASTFLOAT_TRY(small_mul(x, y0));
for (size_t index = 1; index < y.len(); index++) {
limb yi = y[index];
stackvec<size> zi;
if (yi != 0) {
// re-use the same buffer throughout
zi.set_len(0);
FASTFLOAT_TRY(zi.try_extend(zs));
FASTFLOAT_TRY(small_mul(zi, yi));
limb_span zis = limb_span(zi.data, zi.len());
FASTFLOAT_TRY(large_add_from(x, zis, index));
}
}
}
x.normalize();
return true;
}
// grade-school multiplication algorithm
template <uint16_t size>
bool large_mul(stackvec<size>& x, limb_span y) noexcept {
if (y.len() == 1) {
FASTFLOAT_TRY(small_mul(x, y[0]));
} else {
FASTFLOAT_TRY(long_mul(x, y));
}
return true;
}
// big integer type. implements a small subset of big integer
// arithmetic, using simple algorithms since asymptotically
// faster algorithms are slower for a small number of limbs.
// all operations assume the big-integer is normalized.
struct bigint {
// storage of the limbs, in little-endian order.
stackvec<bigint_limbs> vec;
bigint(): vec() {}
bigint(const bigint &) = delete;
bigint &operator=(const bigint &) = delete;
bigint(bigint &&) = delete;
bigint &operator=(bigint &&other) = delete;
bigint(uint64_t value): vec() {
#ifdef FASTFLOAT_64BIT_LIMB
vec.push_unchecked(value);
#else
vec.push_unchecked(uint32_t(value));
vec.push_unchecked(uint32_t(value >> 32));
#endif
vec.normalize();
}
// get the high 64 bits from the vector, and if bits were truncated.
// this is to get the significant digits for the float.
uint64_t hi64(bool& truncated) const noexcept {
#ifdef FASTFLOAT_64BIT_LIMB
if (vec.len() == 0) {
return empty_hi64(truncated);
} else if (vec.len() == 1) {
return uint64_hi64(vec.rindex(0), truncated);
} else {
uint64_t result = uint64_hi64(vec.rindex(0), vec.rindex(1), truncated);
truncated |= vec.nonzero(2);
return result;
}
#else
if (vec.len() == 0) {
return empty_hi64(truncated);
} else if (vec.len() == 1) {
return uint32_hi64(vec.rindex(0), truncated);
} else if (vec.len() == 2) {
return uint32_hi64(vec.rindex(0), vec.rindex(1), truncated);
} else {
uint64_t result = uint32_hi64(vec.rindex(0), vec.rindex(1), vec.rindex(2), truncated);
truncated |= vec.nonzero(3);
return result;
}
#endif
}
// compare two big integers, returning the large value.
// assumes both are normalized. if the return value is
// negative, other is larger, if the return value is
// positive, this is larger, otherwise they are equal.
// the limbs are stored in little-endian order, so we
// must compare the limbs in ever order.
int compare(const bigint& other) const noexcept {
if (vec.len() > other.vec.len()) {
return 1;
} else if (vec.len() < other.vec.len()) {
return -1;
} else {
for (size_t index = vec.len(); index > 0; index--) {
limb xi = vec[index - 1];
limb yi = other.vec[index - 1];
if (xi > yi) {
return 1;
} else if (xi < yi) {
return -1;
}
}
return 0;
}
}
// shift left each limb n bits, carrying over to the new limb
// returns true if we were able to shift all the digits.
bool shl_bits(size_t n) noexcept {
// Internally, for each item, we shift left by n, and add the previous
// right shifted limb-bits.
// For example, we transform (for u8) shifted left 2, to:
// b10100100 b01000010
// b10 b10010001 b00001000
FASTFLOAT_DEBUG_ASSERT(n != 0);
FASTFLOAT_DEBUG_ASSERT(n < sizeof(limb) * 8);
size_t shl = n;
size_t shr = limb_bits - shl;
limb prev = 0;
for (size_t index = 0; index < vec.len(); index++) {
limb xi = vec[index];
vec[index] = (xi << shl) | (prev >> shr);
prev = xi;
}
limb carry = prev >> shr;
if (carry != 0) {
return vec.try_push(carry);
}
return true;
}
// move the limbs left by `n` limbs.
bool shl_limbs(size_t n) noexcept {
FASTFLOAT_DEBUG_ASSERT(n != 0);
if (n + vec.len() > vec.capacity()) {
return false;
} else if (!vec.is_empty()) {
// move limbs
limb* dst = vec.data + n;
const limb* src = vec.data;
::memmove(dst, src, sizeof(limb) * vec.len());
// fill in empty limbs
limb* first = vec.data;
limb* last = first + n;
::std::fill(first, last, 0);
vec.set_len(n + vec.len());
return true;
} else {
return true;
}
}
// move the limbs left by `n` bits.
bool shl(size_t n) noexcept {
size_t rem = n % limb_bits;
size_t div = n / limb_bits;
if (rem != 0) {
FASTFLOAT_TRY(shl_bits(rem));
}
if (div != 0) {
FASTFLOAT_TRY(shl_limbs(div));
}
return true;
}
// get the number of leading zeros in the bigint.
int ctlz() const noexcept {
if (vec.is_empty()) {
return 0;
} else {
#ifdef FASTFLOAT_64BIT_LIMB
return leading_zeroes(vec.rindex(0));
#else
// no use defining a specialized leading_zeroes for a 32-bit type.
uint64_t r0 = vec.rindex(0);
return leading_zeroes(r0 << 32);
#endif
}
}
// get the number of bits in the bigint.
int bit_length() const noexcept {
int lz = ctlz();
return int(limb_bits * vec.len()) - lz;
}
bool mul(limb y) noexcept {
return small_mul(vec, y);
}
bool add(limb y) noexcept {
return small_add(vec, y);
}
// multiply as if by 2 raised to a power.
bool pow2(uint32_t exp) noexcept {
return shl(exp);
}
// multiply as if by 5 raised to a power.
bool pow5(uint32_t exp) noexcept {
// multiply by a power of 5
static constexpr uint32_t large_step = 135;
static constexpr uint64_t small_power_of_5[] = {
1UL, 5UL, 25UL, 125UL, 625UL, 3125UL, 15625UL, 78125UL, 390625UL,
1953125UL, 9765625UL, 48828125UL, 244140625UL, 1220703125UL,
6103515625UL, 30517578125UL, 152587890625UL, 762939453125UL,
3814697265625UL, 19073486328125UL, 95367431640625UL, 476837158203125UL,
2384185791015625UL, 11920928955078125UL, 59604644775390625UL,
298023223876953125UL, 1490116119384765625UL, 7450580596923828125UL,
};
#ifdef FASTFLOAT_64BIT_LIMB
constexpr static limb large_power_of_5[] = {
1414648277510068013UL, 9180637584431281687UL, 4539964771860779200UL,
10482974169319127550UL, 198276706040285095UL};
#else
constexpr static limb large_power_of_5[] = {
4279965485U, 329373468U, 4020270615U, 2137533757U, 4287402176U,
1057042919U, 1071430142U, 2440757623U, 381945767U, 46164893U};
#endif
size_t large_length = sizeof(large_power_of_5) / sizeof(limb);
limb_span large = limb_span(large_power_of_5, large_length);
while (exp >= large_step) {
FASTFLOAT_TRY(large_mul(vec, large));
exp -= large_step;
}
#ifdef FASTFLOAT_64BIT_LIMB
uint32_t small_step = 27;
limb max_native = 7450580596923828125UL;
#else
uint32_t small_step = 13;
limb max_native = 1220703125U;
#endif
while (exp >= small_step) {
FASTFLOAT_TRY(small_mul(vec, max_native));
exp -= small_step;
}
if (exp != 0) {
FASTFLOAT_TRY(small_mul(vec, limb(small_power_of_5[exp])));
}
return true;
}
// multiply as if by 10 raised to a power.
bool pow10(uint32_t exp) noexcept {
FASTFLOAT_TRY(pow5(exp));
return pow2(exp);
}
};
} // namespace fast_float
#endif

31
include/fast_float/decimal_to_binary.h
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@ -55,11 +55,34 @@ namespace detail {
* where * where
* p = log(5**-q)/log(2) = -q * log(5)/log(2) * p = log(5**-q)/log(2) = -q * log(5)/log(2)
*/ */
constexpr fastfloat_really_inline int power(int q) noexcept { constexpr fastfloat_really_inline int32_t power(int32_t q) noexcept {
return (((152170 + 65536) * q) >> 16) + 63; return (((152170 + 65536) * q) >> 16) + 63;
} }
} // namespace detail } // namespace detail
// create an adjusted mantissa, biased by the invalid power2
// for significant digits already multiplied by 10 ** q.
template <typename binary>
fastfloat_really_inline
adjusted_mantissa compute_error_scaled(int64_t q, uint64_t w, int lz) noexcept {
int hilz = int(w >> 63) ^ 1;
adjusted_mantissa answer;
answer.mantissa = w << hilz;
int bias = binary::mantissa_explicit_bits() - binary::minimum_exponent();
answer.power2 = int32_t(detail::power(int32_t(q)) + bias - hilz - lz - 62 + invalid_am_bias);
return answer;
}
// w * 10 ** q, without rounding the representation up.
// the power2 in the exponent will be adjusted by invalid_am_bias.
template <typename binary>
fastfloat_really_inline
adjusted_mantissa compute_error(int64_t q, uint64_t w) noexcept {
int lz = leading_zeroes(w);
w <<= lz;
value128 product = compute_product_approximation<binary::mantissa_explicit_bits() + 3>(q, w);
return compute_error_scaled<binary>(q, product.high, lz);
}
// w * 10 ** q // w * 10 ** q
// The returned value should be a valid ieee64 number that simply need to be packed. // The returned value should be a valid ieee64 number that simply need to be packed.
@ -101,8 +124,7 @@ adjusted_mantissa compute_float(int64_t q, uint64_t w) noexcept {
const bool inside_safe_exponent = (q >= -27) && (q <= 55); // always good because 5**q <2**128 when q>=0, const bool inside_safe_exponent = (q >= -27) && (q <= 55); // always good because 5**q <2**128 when q>=0,
// and otherwise, for q<0, we have 5**-q<2**64 and the 128-bit reciprocal allows for exact computation. // and otherwise, for q<0, we have 5**-q<2**64 and the 128-bit reciprocal allows for exact computation.
if(!inside_safe_exponent) { if(!inside_safe_exponent) {
answer.power2 = -1; // This (a negative value) indicates an error condition. return compute_error_scaled<binary>(q, product.high, lz);
return answer;
} }
} }
// The "compute_product_approximation" function can be slightly slower than a branchless approach: // The "compute_product_approximation" function can be slightly slower than a branchless approach:
@ -113,7 +135,7 @@ adjusted_mantissa compute_float(int64_t q, uint64_t w) noexcept {
answer.mantissa = product.high >> (upperbit + 64 - binary::mantissa_explicit_bits() - 3); answer.mantissa = product.high >> (upperbit + 64 - binary::mantissa_explicit_bits() - 3);
answer.power2 = int(detail::power(int(q)) + upperbit - lz - binary::minimum_exponent()); answer.power2 = int32_t(detail::power(int32_t(q)) + upperbit - lz - binary::minimum_exponent());
if (answer.power2 <= 0) { // we have a subnormal? if (answer.power2 <= 0) { // we have a subnormal?
// Here have that answer.power2 <= 0 so -answer.power2 >= 0 // Here have that answer.power2 <= 0 so -answer.power2 >= 0
if(-answer.power2 + 1 >= 64) { // if we have more than 64 bits below the minimum exponent, you have a zero for sure. if(-answer.power2 + 1 >= 64) { // if we have more than 64 bits below the minimum exponent, you have a zero for sure.
@ -167,7 +189,6 @@ adjusted_mantissa compute_float(int64_t q, uint64_t w) noexcept {
return answer; return answer;
} }
} // namespace fast_float } // namespace fast_float
#endif #endif

423
include/fast_float/digit_comparison.h Normal file
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@ -0,0 +1,423 @@
#ifndef FASTFLOAT_DIGIT_COMPARISON_H
#define FASTFLOAT_DIGIT_COMPARISON_H
#include <algorithm>
#include <cstdint>
#include <cstring>
#include <iterator>
#include "float_common.h"
#include "bigint.h"
#include "ascii_number.h"
namespace fast_float {
// 1e0 to 1e19
constexpr static uint64_t powers_of_ten_uint64[] = {
1UL, 10UL, 100UL, 1000UL, 10000UL, 100000UL, 1000000UL, 10000000UL, 100000000UL,
1000000000UL, 10000000000UL, 100000000000UL, 1000000000000UL, 10000000000000UL,
100000000000000UL, 1000000000000000UL, 10000000000000000UL, 100000000000000000UL,
1000000000000000000UL, 10000000000000000000UL};
// calculate the exponent, in scientific notation, of the number.
// this algorithm is not even close to optimized, but it has no practical
// effect on performance: in order to have a faster algorithm, we'd need
// to slow down performance for faster algorithms, and this is still fast.
fastfloat_really_inline int32_t scientific_exponent(parsed_number_string& num) noexcept {
uint64_t mantissa = num.mantissa;
int32_t exponent = int32_t(num.exponent);
while (mantissa >= 10000) {
mantissa /= 10000;
exponent += 4;
}
while (mantissa >= 100) {
mantissa /= 100;
exponent += 2;
}
while (mantissa >= 10) {
mantissa /= 10;
exponent += 1;
}
return exponent;
}
// this converts a native floating-point number to an extended-precision float.
template <typename T>
fastfloat_really_inline adjusted_mantissa to_extended(T value) noexcept {
adjusted_mantissa am;
int32_t bias = binary_format<T>::mantissa_explicit_bits() - binary_format<T>::minimum_exponent();
if (std::is_same<T, float>::value) {
constexpr uint32_t exponent_mask = 0x7F800000;
constexpr uint32_t mantissa_mask = 0x007FFFFF;
constexpr uint64_t hidden_bit_mask = 0x00800000;
uint32_t bits;
::memcpy(&bits, &value, sizeof(T));
if ((bits & exponent_mask) == 0) {
// denormal
am.power2 = 1 - bias;
am.mantissa = bits & mantissa_mask;
} else {
// normal
am.power2 = int32_t((bits & exponent_mask) >> binary_format<T>::mantissa_explicit_bits());
am.power2 -= bias;
am.mantissa = (bits & mantissa_mask) | hidden_bit_mask;
}
} else {
constexpr uint64_t exponent_mask = 0x7FF0000000000000;
constexpr uint64_t mantissa_mask = 0x000FFFFFFFFFFFFF;
constexpr uint64_t hidden_bit_mask = 0x0010000000000000;
uint64_t bits;
::memcpy(&bits, &value, sizeof(T));
if ((bits & exponent_mask) == 0) {
// denormal
am.power2 = 1 - bias;
am.mantissa = bits & mantissa_mask;
} else {
// normal
am.power2 = int32_t((bits & exponent_mask) >> binary_format<T>::mantissa_explicit_bits());
am.power2 -= bias;
am.mantissa = (bits & mantissa_mask) | hidden_bit_mask;
}
}
return am;
}
// get the extended precision value of the halfway point between b and b+u.
// we are given a native float that represents b, so we need to adjust it
// halfway between b and b+u.
template <typename T>
fastfloat_really_inline adjusted_mantissa to_extended_halfway(T value) noexcept {
adjusted_mantissa am = to_extended(value);
am.mantissa <<= 1;
am.mantissa += 1;
am.power2 -= 1;
return am;
}
// round an extended-precision float to the nearest machine float.
template <typename T, typename callback>
fastfloat_really_inline void round(adjusted_mantissa& am, callback cb) noexcept {
int32_t mantissa_shift = 64 - binary_format<T>::mantissa_explicit_bits() - 1;
if (-am.power2 >= mantissa_shift) {
// have a denormal float
int32_t shift = -am.power2 + 1;
cb(am, std::min(shift, 64));
// check for round-up: if rounding-nearest carried us to the hidden bit.
am.power2 = (am.mantissa < (uint64_t(1) << binary_format<T>::mantissa_explicit_bits())) ? 0 : 1;
return;
}
// have a normal float, use the default shift.
cb(am, mantissa_shift);
// check for carry
if (am.mantissa >= (uint64_t(2) << binary_format<T>::mantissa_explicit_bits())) {
am.mantissa = (uint64_t(1) << binary_format<T>::mantissa_explicit_bits());
am.power2++;
}
// check for infinite: we could have carried to an infinite power
am.mantissa &= ~(uint64_t(1) << binary_format<T>::mantissa_explicit_bits());
if (am.power2 >= binary_format<T>::infinite_power()) {
am.power2 = binary_format<T>::infinite_power();
am.mantissa = 0;
}
}
template <typename callback>
fastfloat_really_inline
void round_nearest_tie_even(adjusted_mantissa& am, int32_t shift, callback cb) noexcept {
uint64_t mask;
uint64_t halfway;
if (shift == 64) {
mask = UINT64_MAX;
} else {
mask = (uint64_t(1) << shift) - 1;
}
if (shift == 0) {
halfway = 0;
} else {
halfway = uint64_t(1) << (shift - 1);
}
uint64_t truncated_bits = am.mantissa & mask;
uint64_t is_above = truncated_bits > halfway;
uint64_t is_halfway = truncated_bits == halfway;
// shift digits into position
if (shift == 64) {
am.mantissa = 0;
} else {
am.mantissa >>= shift;
}
am.power2 += shift;
bool is_odd = (am.mantissa & 1) == 1;
am.mantissa += uint64_t(cb(is_odd, is_halfway, is_above));
}
fastfloat_really_inline void round_down(adjusted_mantissa& am, int32_t shift) noexcept {
if (shift == 64) {
am.mantissa = 0;
} else {
am.mantissa >>= shift;
}
am.power2 += shift;
}
fastfloat_really_inline void skip_zeros(const char*& first, const char* last) noexcept {
uint64_t val;
while (std::distance(first, last) >= 8) {
::memcpy(&val, first, sizeof(uint64_t));
if (val != 0x3030303030303030) {
break;
}
first += 8;
}
while (first != last) {
if (*first != '0') {
break;
}
first++;
}
}
// determine if any non-zero digits were truncated.
// all characters must be valid digits.
fastfloat_really_inline bool is_truncated(const char* first, const char* last) noexcept {
// do 8-bit optimizations, can just compare to 8 literal 0s.
uint64_t val;
while (std::distance(first, last) >= 8) {
::memcpy(&val, first, sizeof(uint64_t));
if (val != 0x3030303030303030) {
return true;
}
first += 8;
}
while (first != last) {
if (*first != '0') {
return true;
}
first++;
}
return false;
}
fastfloat_really_inline bool is_truncated(byte_span s) noexcept {
return is_truncated(s.ptr, s.ptr + s.len());
}
fastfloat_really_inline
void parse_eight_digits(const char*& p, limb& value, size_t& counter, size_t& count) noexcept {
value = value * 100000000 + parse_eight_digits_unrolled(p);
p += 8;
counter += 8;
count += 8;
}
fastfloat_really_inline
void parse_one_digit(const char*& p, limb& value, size_t& counter, size_t& count) noexcept {
value = value * 10 + limb(*p - '0');
p++;
counter++;
count++;
}
fastfloat_really_inline
void add_native(bigint& big, limb power, limb value) noexcept {
big.mul(power);
big.add(value);
}
fastfloat_really_inline void round_up_bigint(bigint& big, size_t& count) noexcept {
// need to round-up the digits, but need to avoid rounding
// ....9999 to ...10000, which could cause a false halfway point.
add_native(big, 10, 1);
count++;
}
// parse the significant digits into a big integer
inline void parse_mantissa(bigint& result, parsed_number_string& num, size_t max_digits, size_t& digits) noexcept {
// try to minimize the number of big integer and scalar multiplication.
// therefore, try to parse 8 digits at a time, and multiply by the largest
// scalar value (9 or 19 digits) for each step.
size_t counter = 0;
digits = 0;
limb value = 0;
#ifdef FASTFLOAT_64BIT_LIMB
size_t step = 19;
#else
size_t step = 9;
#endif
// process all integer digits.
const char* p = num.integer.ptr;
const char* pend = p + num.integer.len();
skip_zeros(p, pend);
// process all digits, in increments of step per loop
while (p != pend) {
while ((std::distance(p, pend) >= 8) && (step - counter >= 8) && (max_digits - digits >= 8)) {
parse_eight_digits(p, value, counter, digits);
}
while (counter < step && p != pend && digits < max_digits) {
parse_one_digit(p, value, counter, digits);
}
if (digits == max_digits) {
// add the temporary value, then check if we've truncated any digits
add_native(result, limb(powers_of_ten_uint64[counter]), value);
bool truncated = is_truncated(p, pend);
if (num.fraction.ptr != nullptr) {
truncated |= is_truncated(num.fraction);
}
if (truncated) {
round_up_bigint(result, digits);
}
return;
} else {
add_native(result, limb(powers_of_ten_uint64[counter]), value);
counter = 0;
value = 0;
}
}
// add our fraction digits, if they're available.
if (num.fraction.ptr != nullptr) {
p = num.fraction.ptr;
pend = p + num.fraction.len();
if (digits == 0) {
skip_zeros(p, pend);
}
// process all digits, in increments of step per loop
while (p != pend) {
while ((std::distance(p, pend) >= 8) && (step - counter >= 8) && (max_digits - digits >= 8)) {
parse_eight_digits(p, value, counter, digits);
}
while (counter < step && p != pend && digits < max_digits) {
parse_one_digit(p, value, counter, digits);
}
if (digits == max_digits) {
// add the temporary value, then check if we've truncated any digits
add_native(result, limb(powers_of_ten_uint64[counter]), value);
bool truncated = is_truncated(p, pend);
if (truncated) {
round_up_bigint(result, digits);
}
return;
} else {
add_native(result, limb(powers_of_ten_uint64[counter]), value);
counter = 0;
value = 0;
}
}
}
if (counter != 0) {
add_native(result, limb(powers_of_ten_uint64[counter]), value);
}
}
template <typename T>
inline adjusted_mantissa positive_digit_comp(bigint& bigmant, int32_t exponent) noexcept {
FASTFLOAT_ASSERT(bigmant.pow10(uint32_t(exponent)));
adjusted_mantissa answer;
bool truncated;
answer.mantissa = bigmant.hi64(truncated);
int bias = binary_format<T>::mantissa_explicit_bits() - binary_format<T>::minimum_exponent();
answer.power2 = bigmant.bit_length() - 64 + bias;
round<T>(answer, [truncated](adjusted_mantissa& a, int32_t shift) {
round_nearest_tie_even(a, shift, [truncated](bool is_odd, bool is_halfway, bool is_above) -> bool {
return is_above || (is_halfway && truncated) || (is_odd && is_halfway);
});
});
return answer;
}
// the scaling here is quite simple: we have, for the real digits `m * 10^e`,
// and for the theoretical digits `n * 2^f`. Since `e` is always negative,
// to scale them identically, we do `n * 2^f * 5^-f`, so we now have `m * 2^e`.
// we then need to scale by `2^(f- e)`, and then the two significant digits
// are of the same magnitude.
template <typename T>
inline adjusted_mantissa negative_digit_comp(bigint& bigmant, adjusted_mantissa am, int32_t exponent) noexcept {
bigint& real_digits = bigmant;
int32_t real_exp = exponent;
// get the value of `b`, rounded down, and get a bigint representation of b+h
adjusted_mantissa am_b = am;
// gcc7 buf: use a lambda to remove the noexcept qualifier bug with -Wnoexcept-type.
round<T>(am_b, [](adjusted_mantissa&a, int32_t shift) { round_down(a, shift); });
T b;
to_float(false, am_b, b);
adjusted_mantissa theor = to_extended_halfway(b);
bigint theor_digits(theor.mantissa);
int32_t theor_exp = theor.power2;
// scale real digits and theor digits to be same power.
int32_t pow2_exp = theor_exp - real_exp;
uint32_t pow5_exp = uint32_t(-real_exp);
if (pow5_exp != 0) {
FASTFLOAT_ASSERT(theor_digits.pow5(pow5_exp));
}
if (pow2_exp > 0) {
FASTFLOAT_ASSERT(theor_digits.pow2(uint32_t(pow2_exp)));
} else if (pow2_exp < 0) {
FASTFLOAT_ASSERT(real_digits.pow2(uint32_t(-pow2_exp)));
}
// compare digits, and use it to director rounding
int ord = real_digits.compare(theor_digits);
adjusted_mantissa answer = am;
round<T>(answer, [ord](adjusted_mantissa& a, int32_t shift) {
round_nearest_tie_even(a, shift, [ord](bool is_odd, bool _, bool __) -> bool {
(void)_; // not needed, since we've done our comparison
(void)__; // not needed, since we've done our comparison
if (ord > 0) {
return true;
} else if (ord < 0) {
return false;
} else {
return is_odd;
}
});
});
return answer;
}
// parse the significant digits as a big integer to unambiguously round the
// the significant digits. here, we are trying to determine how to round
// an extended float representation close to `b+h`, halfway between `b`
// (the float rounded-down) and `b+u`, the next positive float. this
// algorithm is always correct, and uses one of two approaches. when
// the exponent is positive relative to the significant digits (such as
// 1234), we create a big-integer representation, get the high 64-bits,
// determine if any lower bits are truncated, and use that to direct
// rounding. in case of a negative exponent relative to the significant
// digits (such as 1.2345), we create a theoretical representation of
// `b` as a big-integer type, scaled to the same binary exponent as
// the actual digits. we then compare the big integer representations
// of both, and use that to direct rounding.
template <typename T>
inline adjusted_mantissa digit_comp(parsed_number_string& num, adjusted_mantissa am) noexcept {
// remove the invalid exponent bias
am.power2 -= invalid_am_bias;
int32_t sci_exp = scientific_exponent(num);
size_t max_digits = binary_format<T>::max_digits();
size_t digits = 0;
bigint bigmant;
parse_mantissa(bigmant, num, max_digits, digits);
// can't underflow, since digits is at most max_digits.
int32_t exponent = sci_exp + 1 - int32_t(digits);
if (exponent >= 0) {
return positive_digit_comp<T>(bigmant, exponent);
} else {
return negative_digit_comp<T>(bigmant, am, exponent);
}
}
} // namespace fast_float
#endif

93
include/fast_float/float_common.h
View File

@ -4,6 +4,7 @@
#include <cfloat> #include <cfloat>
#include <cstdint> #include <cstdint>
#include <cassert> #include <cassert>
#include <cstring>
#if (defined(__x86_64) || defined(__x86_64__) || defined(_M_X64) \ #if (defined(__x86_64) || defined(__x86_64__) || defined(_M_X64) \
|| defined(__amd64) || defined(__aarch64__) || defined(_M_ARM64) \ || defined(__amd64) || defined(__aarch64__) || defined(_M_ARM64) \
@ -87,6 +88,18 @@
#endif #endif
#endif #endif
#ifndef FASTFLOAT_ASSERT
#define FASTFLOAT_ASSERT(x) { if (!(x)) abort(); }
#endif
#ifndef FASTFLOAT_DEBUG_ASSERT
#include <cassert>
#define FASTFLOAT_DEBUG_ASSERT(x) assert(x)
#endif
// rust style `try!()` macro, or `?` operator
#define FASTFLOAT_TRY(x) { if (!(x)) return false; }
namespace fast_float { namespace fast_float {
// Compares two ASCII strings in a case insensitive manner. // Compares two ASCII strings in a case insensitive manner.
@ -103,11 +116,23 @@ CXX20_CONSTEXPR inline bool fastfloat_strncasecmp(const char *input1, const char
#error "FLT_EVAL_METHOD should be defined, please include cfloat." #error "FLT_EVAL_METHOD should be defined, please include cfloat."
#endif #endif
namespace { // a pointer and a length to a contiguous block of memory
constexpr uint32_t max_digits = 768; template <typename T>
constexpr uint32_t max_digit_without_overflow = 19; struct span {
constexpr int32_t decimal_point_range = 2047; const T* ptr;
} // namespace size_t length;
span(const T* _ptr, size_t _length) : ptr(_ptr), length(_length) {}
span() : ptr(nullptr), length(0) {}
constexpr size_t len() noexcept {
return length;
}
const T& operator[](size_t index) const noexcept {
FASTFLOAT_DEBUG_ASSERT(index < length);
return ptr[index];
}
};
struct value128 { struct value128 {
uint64_t low; uint64_t low;
@ -186,10 +211,9 @@ fastfloat_really_inline value128 full_multiplication(uint64_t a,
return answer; return answer;
} }
struct adjusted_mantissa { struct adjusted_mantissa {
uint64_t mantissa{0}; uint64_t mantissa{0};
int power2{0}; // a negative value indicates an invalid result int32_t power2{0}; // a negative value indicates an invalid result
adjusted_mantissa() = default; adjusted_mantissa() = default;
bool operator==(const adjusted_mantissa &o) const { bool operator==(const adjusted_mantissa &o) const {
return mantissa == o.mantissa && power2 == o.power2; return mantissa == o.mantissa && power2 == o.power2;
@ -199,21 +223,8 @@ struct adjusted_mantissa {
} }
}; };
struct decimal { // Bias so we can get the real exponent with an invalid adjusted_mantissa.
uint32_t num_digits{0}; constexpr static int32_t invalid_am_bias = -0x8000;
int32_t decimal_point{0};
bool negative{false};
bool truncated{false};
uint8_t digits[max_digits];
decimal() = default;
// Copies are not allowed since this is a fat object.
decimal(const decimal &) = delete;
// Copies are not allowed since this is a fat object.
decimal &operator=(const decimal &) = delete;
// Moves are allowed:
decimal(decimal &&) = default;
decimal &operator=(decimal &&other) = default;
};
constexpr static double powers_of_ten_double[] = { constexpr static double powers_of_ten_double[] = {
1e0, 1e1, 1e2, 1e3, 1e4, 1e5, 1e6, 1e7, 1e8, 1e9, 1e10, 1e11, 1e0, 1e1, 1e2, 1e3, 1e4, 1e5, 1e6, 1e7, 1e8, 1e9, 1e10, 1e11,
@ -234,6 +245,7 @@ template <typename T> struct binary_format {
static inline constexpr int largest_power_of_ten(); static inline constexpr int largest_power_of_ten();
static inline constexpr int smallest_power_of_ten(); static inline constexpr int smallest_power_of_ten();
static inline constexpr T exact_power_of_ten(int64_t power); static inline constexpr T exact_power_of_ten(int64_t power);
static inline constexpr size_t max_digits();
}; };
template <> inline constexpr int binary_format<double>::mantissa_explicit_bits() { template <> inline constexpr int binary_format<double>::mantissa_explicit_bits() {
@ -334,17 +346,32 @@ inline constexpr int binary_format<float>::smallest_power_of_ten() {
return -65; return -65;
} }
} // namespace fast_float template <> inline constexpr size_t binary_format<double>::max_digits() {
return 769;
// for convenience: }
template<class OStream> template <> inline constexpr size_t binary_format<float>::max_digits() {
inline OStream& operator<<(OStream &out, const fast_float::decimal &d) { return 114;
out << "0.";
for (size_t i = 0; i < d.num_digits; i++) {
out << int32_t(d.digits[i]);
}
out << " * 10 ** " << d.decimal_point;
return out;
} }
template<typename T>
CXX20_CONSTEXPR
fastfloat_really_inline void to_float(bool negative, adjusted_mantissa am, T &value) {
uint64_t word = am.mantissa;
word |= uint64_t(am.power2) << binary_format<T>::mantissa_explicit_bits();
word = negative
? word | (uint64_t(1) << binary_format<T>::sign_index()) : word;
#if FASTFLOAT_IS_BIG_ENDIAN == 1
if (std::is_same<T, float>::value) {
::memcpy(&value, (char *)&word + 4, sizeof(T)); // extract value at offset 4-7 if float on big-endian
} else {
::memcpy(&value, &word, sizeof(T));
}
#else
// For little-endian systems:
::memcpy(&value, &word, sizeof(T));
#endif
}
} // namespace fast_float
#endif #endif

30
include/fast_float/parse_number.h
View File

@ -3,7 +3,7 @@
#include "ascii_number.h" #include "ascii_number.h"
#include "decimal_to_binary.h" #include "decimal_to_binary.h"
#include "simple_decimal_conversion.h" #include "digit_comparison.h"
#include <cmath> #include <cmath>
#include <cstring> #include <cstring>
@ -60,28 +60,8 @@ CXX20_CONSTEXPR from_chars_result parse_infnan(const char *first, const char *la
return answer; return answer;
} }
template<typename T>
CXX20_CONSTEXPR fastfloat_really_inline void to_float(bool negative, adjusted_mantissa am, T &value) {
uint64_t word = am.mantissa;
word |= uint64_t(am.power2) << binary_format<T>::mantissa_explicit_bits();
word = negative
? word | (uint64_t(1) << binary_format<T>::sign_index()) : word;
#if FASTFLOAT_IS_BIG_ENDIAN == 1
if (std::is_same<T, float>::value) {
::memcpy(&value, (char *)&word + 4, sizeof(T)); // extract value at offset 4-7 if float on big-endian
} else {
::memcpy(&value, &word, sizeof(T));
}
#else
// For little-endian systems:
::memcpy(&value, &word, sizeof(T));
#endif
}
} // namespace detail } // namespace detail
template<typename T> template<typename T>
CXX20_CONSTEXPR from_chars_result from_chars(const char *first, const char *last, CXX20_CONSTEXPR from_chars_result from_chars(const char *first, const char *last,
T &value, chars_format fmt /*= chars_format::general*/) noexcept { T &value, chars_format fmt /*= chars_format::general*/) noexcept {
@ -116,15 +96,15 @@ CXX20_CONSTEXPR from_chars_result from_chars_advanced(const char *first, const c
return answer; return answer;
} }
adjusted_mantissa am = compute_float<binary_format<T>>(pns.exponent, pns.mantissa); adjusted_mantissa am = compute_float<binary_format<T>>(pns.exponent, pns.mantissa);
if(pns.too_many_digits) { if(pns.too_many_digits && am.power2 >= 0) {
if(am != compute_float<binary_format<T>>(pns.exponent, pns.mantissa + 1)) { if(am != compute_float<binary_format<T>>(pns.exponent, pns.mantissa + 1)) {
am.power2 = -1; // value is invalid. am = compute_error<binary_format<T>>(pns.exponent, pns.mantissa);
} }
} }
// If we called compute_float<binary_format<T>>(pns.exponent, pns.mantissa) and we have an invalid power (am.power2 < 0), // If we called compute_float<binary_format<T>>(pns.exponent, pns.mantissa) and we have an invalid power (am.power2 < 0),
// then we need to go the long way around again. This is very uncommon. // then we need to go the long way around again. This is very uncommon.
if(am.power2 < 0) { am = parse_long_mantissa<binary_format<T>>(first, last, options); } if(am.power2 < 0) { am = digit_comp<T>(pns, am); }
detail::to_float(pns.negative, am, value); to_float(pns.negative, am, value);
return answer; return answer;
} }

8
script/amalgamate.py
View File

@ -22,8 +22,8 @@ for filename in ['LICENSE-MIT', 'LICENSE-APACHE']:
# code # code
for filename in [ 'fast_float.h', 'float_common.h', 'ascii_number.h', for filename in [ 'fast_float.h', 'float_common.h', 'ascii_number.h',
'fast_table.h', 'decimal_to_binary.h', 'ascii_number.h', 'fast_table.h', 'decimal_to_binary.h', 'bigint.h',
'simple_decimal_conversion.h', 'parse_number.h']: 'ascii_number.h', 'digit_comparison.h', 'parse_number.h']:
with open('include/fast_float/' + filename) as f: with open('include/fast_float/' + filename) as f:
text = '' text = ''
for line in f: for line in f:
@ -45,8 +45,8 @@ text = '\n\n'.join([
processed_files['LICENSE-' + args.license], processed_files['LICENSE-' + args.license],
processed_files['fast_float.h'], processed_files['float_common.h'], processed_files['fast_float.h'], processed_files['float_common.h'],
processed_files['ascii_number.h'], processed_files['fast_table.h'], processed_files['ascii_number.h'], processed_files['fast_table.h'],
processed_files['decimal_to_binary.h'], processed_files['ascii_number.h'], processed_files['decimal_to_binary.h'], processed_files['bigint.h'],
processed_files['simple_decimal_conversion.h'], processed_files['ascii_number.h'], processed_files['digit_comparison.h'],
processed_files['parse_number.h']]) processed_files['parse_number.h']])
if args.output: if args.output:

1
tests/basictest.cpp
View File

@ -532,6 +532,7 @@ TEST_CASE("64bit.general") {
verify("0.000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000044501477170144022721148195934182639518696390927032912960468522194496444440421538910330590478162701758282983178260792422137401728773891892910553144148156412434867599762821265346585071045737627442980259622449029037796981144446145705102663115100318287949527959668236039986479250965780342141637013812613333119898765515451440315261253813266652951306000184917766328660755595837392240989947807556594098101021612198814605258742579179000071675999344145086087205681577915435923018910334964869420614052182892431445797605163650903606514140377217442262561590244668525767372446430075513332450079650686719491377688478005309963967709758965844137894433796621993967316936280457084866613206797017728916080020698679408551343728867675409720757232455434770912461317493580281734466552734375", 0.000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000044501477170144022721148195934182639518696390927032912960468522194496444440421538910330590478162701758282983178260792422137401728773891892910553144148156412434867599762821265346585071045737627442980259622449029037796981144446145705102663115100318287949527959668236039986479250965780342141637013812613333119898765515451440315261253813266652951306000184917766328660755595837392240989947807556594098101021612198814605258742579179000071675999344145086087205681577915435923018910334964869420614052182892431445797605163650903606514140377217442262561590244668525767372446430075513332450079650686719491377688478005309963967709758965844137894433796621993967316936280457084866613206797017728916080020698679408551343728867675409720757232455434770912461317493580281734466552734375); verify("0.000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000044501477170144022721148195934182639518696390927032912960468522194496444440421538910330590478162701758282983178260792422137401728773891892910553144148156412434867599762821265346585071045737627442980259622449029037796981144446145705102663115100318287949527959668236039986479250965780342141637013812613333119898765515451440315261253813266652951306000184917766328660755595837392240989947807556594098101021612198814605258742579179000071675999344145086087205681577915435923018910334964869420614052182892431445797605163650903606514140377217442262561590244668525767372446430075513332450079650686719491377688478005309963967709758965844137894433796621993967316936280457084866613206797017728916080020698679408551343728867675409720757232455434770912461317493580281734466552734375", 0.000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000044501477170144022721148195934182639518696390927032912960468522194496444440421538910330590478162701758282983178260792422137401728773891892910553144148156412434867599762821265346585071045737627442980259622449029037796981144446145705102663115100318287949527959668236039986479250965780342141637013812613333119898765515451440315261253813266652951306000184917766328660755595837392240989947807556594098101021612198814605258742579179000071675999344145086087205681577915435923018910334964869420614052182892431445797605163650903606514140377217442262561590244668525767372446430075513332450079650686719491377688478005309963967709758965844137894433796621993967316936280457084866613206797017728916080020698679408551343728867675409720757232455434770912461317493580281734466552734375);
verify("0.000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000022250738585072008890245868760858598876504231122409594654935248025624400092282356951787758888037591552642309780950434312085877387158357291821993020294379224223559819827501242041788969571311791082261043971979604000454897391938079198936081525613113376149842043271751033627391549782731594143828136275113838604094249464942286316695429105080201815926642134996606517803095075913058719846423906068637102005108723282784678843631944515866135041223479014792369585208321597621066375401613736583044193603714778355306682834535634005074073040135602968046375918583163124224521599262546494300836851861719422417646455137135420132217031370496583210154654068035397417906022589503023501937519773030945763173210852507299305089761582519159720757232455434770912461317493580281734466552734375", 0.000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000022250738585072008890245868760858598876504231122409594654935248025624400092282356951787758888037591552642309780950434312085877387158357291821993020294379224223559819827501242041788969571311791082261043971979604000454897391938079198936081525613113376149842043271751033627391549782731594143828136275113838604094249464942286316695429105080201815926642134996606517803095075913058719846423906068637102005108723282784678843631944515866135041223479014792369585208321597621066375401613736583044193603714778355306682834535634005074073040135602968046375918583163124224521599262546494300836851861719422417646455137135420132217031370496583210154654068035397417906022589503023501937519773030945763173210852507299305089761582519159720757232455434770912461317493580281734466552734375); verify("0.000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000022250738585072008890245868760858598876504231122409594654935248025624400092282356951787758888037591552642309780950434312085877387158357291821993020294379224223559819827501242041788969571311791082261043971979604000454897391938079198936081525613113376149842043271751033627391549782731594143828136275113838604094249464942286316695429105080201815926642134996606517803095075913058719846423906068637102005108723282784678843631944515866135041223479014792369585208321597621066375401613736583044193603714778355306682834535634005074073040135602968046375918583163124224521599262546494300836851861719422417646455137135420132217031370496583210154654068035397417906022589503023501937519773030945763173210852507299305089761582519159720757232455434770912461317493580281734466552734375", 0.000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000022250738585072008890245868760858598876504231122409594654935248025624400092282356951787758888037591552642309780950434312085877387158357291821993020294379224223559819827501242041788969571311791082261043971979604000454897391938079198936081525613113376149842043271751033627391549782731594143828136275113838604094249464942286316695429105080201815926642134996606517803095075913058719846423906068637102005108723282784678843631944515866135041223479014792369585208321597621066375401613736583044193603714778355306682834535634005074073040135602968046375918583163124224521599262546494300836851861719422417646455137135420132217031370496583210154654068035397417906022589503023501937519773030945763173210852507299305089761582519159720757232455434770912461317493580281734466552734375);
verify("1438456663141390273526118207642235581183227845246331231162636653790368152091394196930365828634687637948157940776599182791387527135353034738357134110310609455693900824193549772792016543182680519740580354365467985440183598701312257624545562331397018329928613196125590274187720073914818062530830316533158098624984118889298281371812288789537310599037529113415438738954894752124724983067241108764488346454376699018673078404751121414804937224240805993123816932326223683090770561597570457793932985826162604255884529134126396282202126526253389383421806727954588525596114379801269094096329805054803089299736996870951258573010877404407451953846698609198213926882692078557033228265259305481198526059813164469187586693257335779522020407645498684263339921905227556616698129967412891282231685504660671277927198290009824680186319750978665734576683784255802269708917361719466043175201158849097881370477111850171579869056016061666173029059588433776015644439705050377554277696143928278093453792803846252715966016733222646442382892123940052441346822429721593884378212558701004356924243030059517489346646577724622498919752597382095222500311124181823512251071356181769376577651390028297796156208815375089159128394945710515861334486267101797497111125909272505194792870889617179758703442608016143343262159998149700606597792535574457560429226974273443630323818747730771316763398572110874959981923732463076884528677392654150010269822239401993427482376513231389212353583573566376915572650916866553612366187378959554983566712767093372906030188976220169058025354973622211666504549316958271880975697143546564469806791358707318873075708383345004090151974068325838177531266954177406661392229801349994695941509935655355652985723782153570084089560139142231.738475042362596875449154552392299548947138162081694168675340677843807613129780449323363759027012972466987370921816813162658754726545121090545507240267000456594786540949605260722461937870630634874991729398208026467698131898691830012167897399682179601734569071423681e-733", std::numeric_limits<double>::infinity()); verify("1438456663141390273526118207642235581183227845246331231162636653790368152091394196930365828634687637948157940776599182791387527135353034738357134110310609455693900824193549772792016543182680519740580354365467985440183598701312257624545562331397018329928613196125590274187720073914818062530830316533158098624984118889298281371812288789537310599037529113415438738954894752124724983067241108764488346454376699018673078404751121414804937224240805993123816932326223683090770561597570457793932985826162604255884529134126396282202126526253389383421806727954588525596114379801269094096329805054803089299736996870951258573010877404407451953846698609198213926882692078557033228265259305481198526059813164469187586693257335779522020407645498684263339921905227556616698129967412891282231685504660671277927198290009824680186319750978665734576683784255802269708917361719466043175201158849097881370477111850171579869056016061666173029059588433776015644439705050377554277696143928278093453792803846252715966016733222646442382892123940052441346822429721593884378212558701004356924243030059517489346646577724622498919752597382095222500311124181823512251071356181769376577651390028297796156208815375089159128394945710515861334486267101797497111125909272505194792870889617179758703442608016143343262159998149700606597792535574457560429226974273443630323818747730771316763398572110874959981923732463076884528677392654150010269822239401993427482376513231389212353583573566376915572650916866553612366187378959554983566712767093372906030188976220169058025354973622211666504549316958271880975697143546564469806791358707318873075708383345004090151974068325838177531266954177406661392229801349994695941509935655355652985723782153570084089560139142231.738475042362596875449154552392299548947138162081694168675340677843807613129780449323363759027012972466987370921816813162658754726545121090545507240267000456594786540949605260722461937870630634874991729398208026467698131898691830012167897399682179601734569071423681e-733", std::numeric_limits<double>::infinity());
verify("-2240084132271013504.131248280843119943687942846658579428", -0x1.f1660a65b00bfp+60);
} }
TEST_CASE("64bit.decimal_point") { TEST_CASE("64bit.decimal_point") {