Minor tweak.

This commit is contained in:
Daniel Lemire 2020-10-27 20:10:42 -04:00
parent eb1103393e
commit c53bfc4176
3 changed files with 34 additions and 88 deletions

View File

@ -16,31 +16,36 @@ fastfloat_really_inline bool is_integer(char c) noexcept { return (c >= '0' &&
// credit: https://johnnylee-sde.github.io/Fast-numeric-string-to-int/ // credit: https://johnnylee-sde.github.io/Fast-numeric-string-to-int/
fastfloat_really_inline uint32_t parse_eight_digits_unrolled(const char *chars) noexcept { fastfloat_really_inline uint32_t parse_eight_digits_unrolled(const char *chars) noexcept {
uint64_t val; uint64_t val;
memcpy(&val, chars, sizeof(uint64_t)); ::memcpy(&val, chars, sizeof(uint64_t));
val = (val & 0x0F0F0F0F0F0F0F0F) * 2561 >> 8; val = (val & 0x0F0F0F0F0F0F0F0F) * 2561 >> 8;
val = (val & 0x00FF00FF00FF00FF) * 6553601 >> 16; val = (val & 0x00FF00FF00FF00FF) * 6553601 >> 16;
return uint32_t((val & 0x0000FFFF0000FFFF) * 42949672960001 >> 32); return uint32_t((val & 0x0000FFFF0000FFFF) * 42949672960001 >> 32);
} }
fastfloat_really_inline bool is_made_of_eight_digits_fast(const char *chars) noexcept { fastfloat_really_inline bool is_made_of_eight_digits_fast(uint64_t val) noexcept {
uint64_t val;
memcpy(&val, chars, 8);
return (((val & 0xF0F0F0F0F0F0F0F0) | return (((val & 0xF0F0F0F0F0F0F0F0) |
(((val + 0x0606060606060606) & 0xF0F0F0F0F0F0F0F0) >> 4)) == (((val + 0x0606060606060606) & 0xF0F0F0F0F0F0F0F0) >> 4)) ==
0x3333333333333333); 0x3333333333333333);
} }
fastfloat_really_inline bool is_made_of_eight_digits_fast(const char *chars) noexcept {
uint64_t val;
::memcpy(&val, chars, 8);
return is_made_of_eight_digits_fast(val);
}
fastfloat_really_inline uint32_t parse_four_digits_unrolled(const char *chars) noexcept { fastfloat_really_inline uint32_t parse_four_digits_unrolled(const char *chars) noexcept {
uint32_t val; uint32_t val;
memcpy(&val, chars, sizeof(uint32_t)); ::memcpy(&val, chars, sizeof(uint32_t));
val = (val & 0x0F0F0F0F) * 2561 >> 8; val = (val & 0x0F0F0F0F) * 2561 >> 8;
return (val & 0x00FF00FF) * 6553601 >> 16; return (val & 0x00FF00FF) * 6553601 >> 16;
} }
fastfloat_really_inline bool is_made_of_four_digits_fast(const char *chars) noexcept { fastfloat_really_inline bool is_made_of_four_digits_fast(const char *chars) noexcept {
uint32_t val; uint32_t val;
memcpy(&val, chars, 4); ::memcpy(&val, chars, 4);
return (((val & 0xF0F0F0F0) | return (((val & 0xF0F0F0F0) |
(((val + 0x06060606) & 0xF0F0F0F0) >> 4)) == (((val + 0x06060606) & 0xF0F0F0F0) >> 4)) ==
0x33333333); 0x33333333);
@ -162,95 +167,20 @@ parsed_number_string parse_number_string(const char *p, const char *pend, chars_
return answer; return answer;
} }
// This should always succeed since it follows a call to parse_number_string.
// It assumes that there are more than 19 mantissa digits to parse.
parsed_number_string parse_truncated_decimal(const char *&p, const char *pend) noexcept {
parsed_number_string answer;
answer.valid = true;
answer.negative = (*p == '-');
if ((*p == '-') || (*p == '+')) {
++p;
}
size_t number_of_digits{0};
uint64_t i = 0;
while ((p != pend) && is_integer(*p)) {
// a multiplication by 10 is cheaper than an arbitrary integer
// multiplication
if(number_of_digits < 19) {
uint8_t digit = uint8_t(*p - '0');
i = 10 * i + digit;
number_of_digits ++;
}
++p;
}
int64_t exponent = 0;
if ((p != pend) && (*p == '.')) {
++p;
const char *first_after_period = p;
while ((p != pend) && is_integer(*p)) {
if(number_of_digits < 19) {
uint8_t digit = uint8_t(*p - '0');
i = i * 10 + digit;
number_of_digits ++;
} else if (exponent == 0) {
exponent = first_after_period - p;
}
++p;
}
}
if ((p != pend) && (('e' == *p) || ('E' == *p))) {
int64_t exp_number = 0; // exponential part
++p;
bool neg_exp = false;
if ((p != pend) && ('-' == *p)) {
neg_exp = true;
++p;
} else if ((p != pend) && ('+' == *p)) {
++p;
}
if ((p == pend) || !is_integer(*p)) {
return answer;
}
while ((p != pend) && is_integer(*p)) {
uint8_t digit = uint8_t(*p - '0');
if (exp_number < 0x10000) {
exp_number = 10 * exp_number + digit;
}
++p;
}
exponent += (neg_exp ? -exp_number : exp_number);
}
answer.lastmatch = p;
answer.valid = true;
answer.too_many_digits = true; // assumed
answer.exponent = exponent;
answer.mantissa = i;
return answer;
}
// This should always succeed since it follows a call to parse_number_string. // This should always succeed since it follows a call to parse_number_string.
decimal parse_decimal(const char *&p, const char *pend) noexcept { decimal parse_decimal(const char *p, const char *pend) noexcept {
decimal answer; decimal answer;
answer.num_digits = 0; answer.num_digits = 0;
answer.decimal_point = 0; answer.decimal_point = 0;
answer.negative = false; answer.negative = false;
answer.truncated = false; answer.truncated = false;
// skip leading whitespace // any whitespace has been skipped.
while (fast_float::is_space(*p)) {
p++;
}
answer.negative = (*p == '-'); answer.negative = (*p == '-');
if ((*p == '-') || (*p == '+')) { if ((*p == '-') || (*p == '+')) {
++p; ++p;
} }
// skip leading zeroes
while ((p != pend) && (*p == '0')) { while ((p != pend) && (*p == '0')) {
++p; ++p;
} }
@ -273,8 +203,17 @@ decimal parse_decimal(const char *&p, const char *pend) noexcept {
++p; ++p;
} }
} }
while ((p + 8 <= pend) && (answer.num_digits + 8 < max_digits)) {
uint64_t val;
::memcpy(&val, p, sizeof(uint64_t));
if(! is_made_of_eight_digits_fast(val)) break;
val -= 0x3030303030303030;
::memcpy(answer.digits + answer.num_digits, &val, sizeof(uint64_t));
answer.num_digits += 8;
p += 8;
}
while ((p != pend) && is_integer(*p)) { while ((p != pend) && is_integer(*p)) {
if (answer.num_digits + 1 < max_digits) { if (answer.num_digits < max_digits) {
answer.digits[answer.num_digits] = uint8_t(*p - '0'); answer.digits[answer.num_digits] = uint8_t(*p - '0');
} else { } else {
answer.truncated = true; answer.truncated = true;

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@ -139,7 +139,14 @@ struct decimal {
bool negative; bool negative;
bool truncated; bool truncated;
uint8_t digits[max_digits]; 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;
// Generates a mantissa by truncating to 19 digits; this function assumes // Generates a mantissa by truncating to 19 digits; this function assumes
// that num_digits >= 19 (the caller is responsible for the check). // that num_digits >= 19 (the caller is responsible for the check).
// This function should be reasonably fast. // This function should be reasonably fast.

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@ -107,7 +107,7 @@ from_chars_result from_chars(const char *first, const char *last,
word |= uint64_t(am.power2) << binary_format<T>::mantissa_explicit_bits(); word |= uint64_t(am.power2) << binary_format<T>::mantissa_explicit_bits();
word = pns.negative word = pns.negative
? word | (uint64_t(1) << binary_format<T>::sign_index()) : word; ? word | (uint64_t(1) << binary_format<T>::sign_index()) : word;
memcpy(&value, &word, sizeof(T)); ::memcpy(&value, &word, sizeof(T));
return answer; return answer;
} }