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simdjson-simdjson/include/simdjson/numberparsing.h
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Daniel Lemire 66ffc1b2d6 Adding a remark.
2019-08-01 11:33:51 -04:00

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#ifndef SIMDJSON_NUMBERPARSING_H
#define SIMDJSON_NUMBERPARSING_H
#include "simdjson/common_defs.h"
#include "simdjson/jsoncharutils.h"
#include "simdjson/parsedjson.h"
#include "simdjson/portability.h"
#ifdef JSON_TEST_NUMBERS // for unit testing
void found_invalid_number(const uint8_t *buf);
void found_integer(int64_t result, const uint8_t *buf);
void found_float(double result, const uint8_t *buf);
#endif
namespace simdjson {
// Allowable floating-point values range from
// std::numeric_limits<double>::lowest() to std::numeric_limits<double>::max(),
// so from -1.7976e308 all the way to 1.7975e308 in binary64. The lowest
// non-zero normal values is std::numeric_limits<double>::min() or
// about 2.225074e-308.
static const double power_of_ten[] = {
1e-308, 1e-307, 1e-306, 1e-305, 1e-304, 1e-303, 1e-302, 1e-301, 1e-300,
1e-299, 1e-298, 1e-297, 1e-296, 1e-295, 1e-294, 1e-293, 1e-292, 1e-291,
1e-290, 1e-289, 1e-288, 1e-287, 1e-286, 1e-285, 1e-284, 1e-283, 1e-282,
1e-281, 1e-280, 1e-279, 1e-278, 1e-277, 1e-276, 1e-275, 1e-274, 1e-273,
1e-272, 1e-271, 1e-270, 1e-269, 1e-268, 1e-267, 1e-266, 1e-265, 1e-264,
1e-263, 1e-262, 1e-261, 1e-260, 1e-259, 1e-258, 1e-257, 1e-256, 1e-255,
1e-254, 1e-253, 1e-252, 1e-251, 1e-250, 1e-249, 1e-248, 1e-247, 1e-246,
1e-245, 1e-244, 1e-243, 1e-242, 1e-241, 1e-240, 1e-239, 1e-238, 1e-237,
1e-236, 1e-235, 1e-234, 1e-233, 1e-232, 1e-231, 1e-230, 1e-229, 1e-228,
1e-227, 1e-226, 1e-225, 1e-224, 1e-223, 1e-222, 1e-221, 1e-220, 1e-219,
1e-218, 1e-217, 1e-216, 1e-215, 1e-214, 1e-213, 1e-212, 1e-211, 1e-210,
1e-209, 1e-208, 1e-207, 1e-206, 1e-205, 1e-204, 1e-203, 1e-202, 1e-201,
1e-200, 1e-199, 1e-198, 1e-197, 1e-196, 1e-195, 1e-194, 1e-193, 1e-192,
1e-191, 1e-190, 1e-189, 1e-188, 1e-187, 1e-186, 1e-185, 1e-184, 1e-183,
1e-182, 1e-181, 1e-180, 1e-179, 1e-178, 1e-177, 1e-176, 1e-175, 1e-174,
1e-173, 1e-172, 1e-171, 1e-170, 1e-169, 1e-168, 1e-167, 1e-166, 1e-165,
1e-164, 1e-163, 1e-162, 1e-161, 1e-160, 1e-159, 1e-158, 1e-157, 1e-156,
1e-155, 1e-154, 1e-153, 1e-152, 1e-151, 1e-150, 1e-149, 1e-148, 1e-147,
1e-146, 1e-145, 1e-144, 1e-143, 1e-142, 1e-141, 1e-140, 1e-139, 1e-138,
1e-137, 1e-136, 1e-135, 1e-134, 1e-133, 1e-132, 1e-131, 1e-130, 1e-129,
1e-128, 1e-127, 1e-126, 1e-125, 1e-124, 1e-123, 1e-122, 1e-121, 1e-120,
1e-119, 1e-118, 1e-117, 1e-116, 1e-115, 1e-114, 1e-113, 1e-112, 1e-111,
1e-110, 1e-109, 1e-108, 1e-107, 1e-106, 1e-105, 1e-104, 1e-103, 1e-102,
1e-101, 1e-100, 1e-99, 1e-98, 1e-97, 1e-96, 1e-95, 1e-94, 1e-93,
1e-92, 1e-91, 1e-90, 1e-89, 1e-88, 1e-87, 1e-86, 1e-85, 1e-84,
1e-83, 1e-82, 1e-81, 1e-80, 1e-79, 1e-78, 1e-77, 1e-76, 1e-75,
1e-74, 1e-73, 1e-72, 1e-71, 1e-70, 1e-69, 1e-68, 1e-67, 1e-66,
1e-65, 1e-64, 1e-63, 1e-62, 1e-61, 1e-60, 1e-59, 1e-58, 1e-57,
1e-56, 1e-55, 1e-54, 1e-53, 1e-52, 1e-51, 1e-50, 1e-49, 1e-48,
1e-47, 1e-46, 1e-45, 1e-44, 1e-43, 1e-42, 1e-41, 1e-40, 1e-39,
1e-38, 1e-37, 1e-36, 1e-35, 1e-34, 1e-33, 1e-32, 1e-31, 1e-30,
1e-29, 1e-28, 1e-27, 1e-26, 1e-25, 1e-24, 1e-23, 1e-22, 1e-21,
1e-20, 1e-19, 1e-18, 1e-17, 1e-16, 1e-15, 1e-14, 1e-13, 1e-12,
1e-11, 1e-10, 1e-9, 1e-8, 1e-7, 1e-6, 1e-5, 1e-4, 1e-3,
1e-2, 1e-1, 1e0, 1e1, 1e2, 1e3, 1e4, 1e5, 1e6,
1e7, 1e8, 1e9, 1e10, 1e11, 1e12, 1e13, 1e14, 1e15,
1e16, 1e17, 1e18, 1e19, 1e20, 1e21, 1e22, 1e23, 1e24,
1e25, 1e26, 1e27, 1e28, 1e29, 1e30, 1e31, 1e32, 1e33,
1e34, 1e35, 1e36, 1e37, 1e38, 1e39, 1e40, 1e41, 1e42,
1e43, 1e44, 1e45, 1e46, 1e47, 1e48, 1e49, 1e50, 1e51,
1e52, 1e53, 1e54, 1e55, 1e56, 1e57, 1e58, 1e59, 1e60,
1e61, 1e62, 1e63, 1e64, 1e65, 1e66, 1e67, 1e68, 1e69,
1e70, 1e71, 1e72, 1e73, 1e74, 1e75, 1e76, 1e77, 1e78,
1e79, 1e80, 1e81, 1e82, 1e83, 1e84, 1e85, 1e86, 1e87,
1e88, 1e89, 1e90, 1e91, 1e92, 1e93, 1e94, 1e95, 1e96,
1e97, 1e98, 1e99, 1e100, 1e101, 1e102, 1e103, 1e104, 1e105,
1e106, 1e107, 1e108, 1e109, 1e110, 1e111, 1e112, 1e113, 1e114,
1e115, 1e116, 1e117, 1e118, 1e119, 1e120, 1e121, 1e122, 1e123,
1e124, 1e125, 1e126, 1e127, 1e128, 1e129, 1e130, 1e131, 1e132,
1e133, 1e134, 1e135, 1e136, 1e137, 1e138, 1e139, 1e140, 1e141,
1e142, 1e143, 1e144, 1e145, 1e146, 1e147, 1e148, 1e149, 1e150,
1e151, 1e152, 1e153, 1e154, 1e155, 1e156, 1e157, 1e158, 1e159,
1e160, 1e161, 1e162, 1e163, 1e164, 1e165, 1e166, 1e167, 1e168,
1e169, 1e170, 1e171, 1e172, 1e173, 1e174, 1e175, 1e176, 1e177,
1e178, 1e179, 1e180, 1e181, 1e182, 1e183, 1e184, 1e185, 1e186,
1e187, 1e188, 1e189, 1e190, 1e191, 1e192, 1e193, 1e194, 1e195,
1e196, 1e197, 1e198, 1e199, 1e200, 1e201, 1e202, 1e203, 1e204,
1e205, 1e206, 1e207, 1e208, 1e209, 1e210, 1e211, 1e212, 1e213,
1e214, 1e215, 1e216, 1e217, 1e218, 1e219, 1e220, 1e221, 1e222,
1e223, 1e224, 1e225, 1e226, 1e227, 1e228, 1e229, 1e230, 1e231,
1e232, 1e233, 1e234, 1e235, 1e236, 1e237, 1e238, 1e239, 1e240,
1e241, 1e242, 1e243, 1e244, 1e245, 1e246, 1e247, 1e248, 1e249,
1e250, 1e251, 1e252, 1e253, 1e254, 1e255, 1e256, 1e257, 1e258,
1e259, 1e260, 1e261, 1e262, 1e263, 1e264, 1e265, 1e266, 1e267,
1e268, 1e269, 1e270, 1e271, 1e272, 1e273, 1e274, 1e275, 1e276,
1e277, 1e278, 1e279, 1e280, 1e281, 1e282, 1e283, 1e284, 1e285,
1e286, 1e287, 1e288, 1e289, 1e290, 1e291, 1e292, 1e293, 1e294,
1e295, 1e296, 1e297, 1e298, 1e299, 1e300, 1e301, 1e302, 1e303,
1e304, 1e305, 1e306, 1e307, 1e308};
static inline bool is_integer(char c) {
return (c >= '0' && c <= '9');
// this gets compiled to (uint8_t)(c - '0') <= 9 on all decent compilers
}
// We need to check that the character following a zero is valid. This is
// probably frequent and it is hard than it looks. We are building all of this
// just to differentiate between 0x1 (invalid), 0,1 (valid) 0e1 (valid)...
const bool structural_or_whitespace_or_exponent_or_decimal_negated[256] = {
1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 0, 1,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 0, 1, 1,
1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 0, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1};
really_inline bool
is_not_structural_or_whitespace_or_exponent_or_decimal(unsigned char c) {
return structural_or_whitespace_or_exponent_or_decimal_negated[c];
}
} // namespace simdjson
#ifndef SIMDJSON_DISABLE_SWAR_NUMBER_PARSING
#define SWAR_NUMBER_PARSING
#endif
#ifdef SWAR_NUMBER_PARSING
namespace simdjson {
// check quickly whether the next 8 chars are made of digits
// at a glance, it looks better than Mula's
// http://0x80.pl/articles/swar-digits-validate.html
static inline bool is_made_of_eight_digits_fast(const char *chars) {
uint64_t val;
// this can read up to 7 bytes beyond the buffer size, but we require
// SIMDJSON_PADDING of padding
static_assert(7 <= SIMDJSON_PADDING);
memcpy(&val, chars, 8);
// a branchy method might be faster:
// return (( val & 0xF0F0F0F0F0F0F0F0 ) == 0x3030303030303030)
// && (( (val + 0x0606060606060606) & 0xF0F0F0F0F0F0F0F0 ) ==
// 0x3030303030303030);
return (((val & 0xF0F0F0F0F0F0F0F0) |
(((val + 0x0606060606060606) & 0xF0F0F0F0F0F0F0F0) >> 4)) ==
0x3333333333333333);
}
} // namespace simdjson
#ifdef IS_X86_64
TARGET_WESTMERE
namespace simdjson {
static inline uint32_t parse_eight_digits_unrolled(const char *chars) {
// this actually computes *16* values so we are being wasteful.
const __m128i ascii0 = _mm_set1_epi8('0');
const __m128i mul_1_10 =
_mm_setr_epi8(10, 1, 10, 1, 10, 1, 10, 1, 10, 1, 10, 1, 10, 1, 10, 1);
const __m128i mul_1_100 = _mm_setr_epi16(100, 1, 100, 1, 100, 1, 100, 1);
const __m128i mul_1_10000 =
_mm_setr_epi16(10000, 1, 10000, 1, 10000, 1, 10000, 1);
const __m128i input = _mm_sub_epi8(
_mm_loadu_si128(reinterpret_cast<const __m128i *>(chars)), ascii0);
const __m128i t1 = _mm_maddubs_epi16(input, mul_1_10);
const __m128i t2 = _mm_madd_epi16(t1, mul_1_100);
const __m128i t3 = _mm_packus_epi32(t2, t2);
const __m128i t4 = _mm_madd_epi16(t3, mul_1_10000);
return _mm_cvtsi128_si32(
t4); // only captures the sum of the first 8 digits, drop the rest
}
} // namespace simdjson
UNTARGET_REGION
#endif
namespace simdjson {
#ifdef IS_ARM64
// we don't have SSE, so let us use a scalar function
// credit: https://johnnylee-sde.github.io/Fast-numeric-string-to-int/
static inline uint32_t parse_eight_digits_unrolled(const char *chars) {
uint64_t val;
memcpy(&val, chars, sizeof(uint64_t));
val = (val & 0x0F0F0F0F0F0F0F0F) * 2561 >> 8;
val = (val & 0x00FF00FF00FF00FF) * 6553601 >> 16;
return (val & 0x0000FFFF0000FFFF) * 42949672960001 >> 32;
}
#endif
#endif
//
// This function computes base * 10 ^ (- negative_exponent ).
// It is only even going to be used when negative_exponent is tiny.
static double subnormal_power10(double base, int negative_exponent) {
// this is probably not going to be fast
return base * 1e-308 * pow(10, negative_exponent + 308);
}
// called by parse_number when we know that the output is a float,
// but where there might be some integer overflow. The trick here is to
// parse using floats from the start.
// Do not call this function directly as it skips some of the checks from
// parse_number
//
// This function will almost never be called!!!
//
// Note: a redesign could avoid this function entirely.
//
static never_inline bool parse_float(const uint8_t *const buf, ParsedJson &pj,
const uint32_t offset, bool found_minus) {
const char *p = reinterpret_cast<const char *>(buf + offset);
bool negative = false;
if (found_minus) {
++p;
negative = true;
}
long double i;
if (*p == '0') { // 0 cannot be followed by an integer
++p;
i = 0;
} else {
unsigned char digit = *p - '0';
i = digit;
p++;
while (is_integer(*p)) {
digit = *p - '0';
i = 10 * i + digit;
++p;
}
}
if ('.' == *p) {
++p;
int fractional_weight = 308;
if (is_integer(*p)) {
unsigned char digit = *p - '0';
++p;
fractional_weight--;
i = i + digit * (fractional_weight >= 0 ? power_of_ten[fractional_weight]
: 0);
} else {
#ifdef JSON_TEST_NUMBERS // for unit testing
found_invalid_number(buf + offset);
#endif
return false;
}
while (is_integer(*p)) {
unsigned char digit = *p - '0';
++p;
fractional_weight--;
i = i + digit * (fractional_weight >= 0 ? power_of_ten[fractional_weight]
: 0);
}
}
if (('e' == *p) || ('E' == *p)) {
++p;
bool neg_exp = false;
if ('-' == *p) {
neg_exp = true;
++p;
} else if ('+' == *p) {
++p;
}
if (!is_integer(*p)) {
#ifdef JSON_TEST_NUMBERS // for unit testing
found_invalid_number(buf + offset);
#endif
return false;
}
unsigned char digit = *p - '0';
int64_t exp_number = digit; // exponential part
p++;
if (is_integer(*p)) {
digit = *p - '0';
exp_number = 10 * exp_number + digit;
++p;
}
if (is_integer(*p)) {
digit = *p - '0';
exp_number = 10 * exp_number + digit;
++p;
}
if (is_integer(*p)) {
digit = *p - '0';
exp_number = 10 * exp_number + digit;
++p;
}
while (is_integer(*p)) {
if (exp_number > 0x100000000) { // we need to check for overflows
// we refuse to parse this
#ifdef JSON_TEST_NUMBERS // for unit testing
found_invalid_number(buf + offset);
#endif
return false;
}
digit = *p - '0';
exp_number = 10 * exp_number + digit;
++p;
}
if (unlikely(exp_number > 308)) {
// this path is unlikely
if (neg_exp) {
// We either have zero or a subnormal.
// We expect this to be uncommon so we go through a slow path.
i = subnormal_power10(i, -exp_number);
} else {
// We know for sure that we have a number that is too large,
// we refuse to parse this
#ifdef JSON_TEST_NUMBERS // for unit testing
found_invalid_number(buf + offset);
#endif
return false;
}
} else {
int exponent = (neg_exp ? -exp_number : exp_number);
// we have that exp_number is [0,308] so that
// exponent is [-308,308] so that
// 308 + exponent is in [0, 2 * 308]
i *= power_of_ten[308 + exponent];
}
}
if (is_not_structural_or_whitespace(*p)) {
return false;
}
double d = negative ? -i : i;
pj.write_tape_double(d);
#ifdef JSON_TEST_NUMBERS // for unit testing
found_float(d, buf + offset);
#endif
return is_structural_or_whitespace(*p);
}
// called by parse_number when we know that the output is an integer,
// but where there might be some integer overflow.
// we want to catch overflows!
// Do not call this function directly as it skips some of the checks from
// parse_number
//
// This function will almost never be called!!!
//
static never_inline bool parse_large_integer(const uint8_t *const buf,
ParsedJson &pj,
const uint32_t offset,
bool found_minus) {
const char *p = reinterpret_cast<const char *>(buf + offset);
bool negative = false;
if (found_minus) {
++p;
negative = true;
}
uint64_t i;
if (*p == '0') { // 0 cannot be followed by an integer
++p;
i = 0;
} else {
unsigned char digit = *p - '0';
i = digit;
p++;
// the is_made_of_eight_digits_fast routine is unlikely to help here because
// we rarely see large integer parts like 123456789
while (is_integer(*p)) {
digit = *p - '0';
if (mul_overflow(i, 10, &i)) {
#ifdef JSON_TEST_NUMBERS // for unit testing
found_invalid_number(buf + offset);
#endif
return false; // overflow
}
if (add_overflow(i, digit, &i)) {
#ifdef JSON_TEST_NUMBERS // for unit testing
found_invalid_number(buf + offset);
#endif
return false; // overflow
}
++p;
}
}
if (negative) {
if (i > 0x8000000000000000) {
// overflows!
#ifdef JSON_TEST_NUMBERS // for unit testing
found_invalid_number(buf + offset);
#endif
return false; // overflow
}
} else {
if (i >= 0x8000000000000000) {
// overflows!
#ifdef JSON_TEST_NUMBERS // for unit testing
found_invalid_number(buf + offset);
#endif
return false; // overflow
}
}
int64_t signed_answer =
negative ? -static_cast<int64_t>(i) : static_cast<int64_t>(i);
pj.write_tape_s64(signed_answer);
#ifdef JSON_TEST_NUMBERS // for unit testing
found_integer(signed_answer, buf + offset);
#endif
return is_structural_or_whitespace(*p);
}
// parse the number at buf + offset
// define JSON_TEST_NUMBERS for unit testing
//
// It is assumed that the number is followed by a structural ({,},],[) character
// or a white space character. If that is not the case (e.g., when the JSON
// document is made of a single number), then it is necessary to copy the
// content and append a space before calling this function.
//
// Our objective is accurate parsing (ULP of 0 or 1) at high speed.
static really_inline bool parse_number(const uint8_t *const buf, ParsedJson &pj,
const uint32_t offset,
bool found_minus) {
#ifdef SIMDJSON_SKIPNUMBERPARSING // for performance analysis, it is sometimes
// useful to skip parsing
pj.write_tape_s64(0); // always write zero
return true; // always succeeds
#else
const char *p = reinterpret_cast<const char *>(buf + offset);
bool negative = false;
if (found_minus) {
++p;
negative = true;
if (!is_integer(*p)) { // a negative sign must be followed by an integer
#ifdef JSON_TEST_NUMBERS // for unit testing
found_invalid_number(buf + offset);
#endif
return false;
}
}
const char *const start_digits = p;
uint64_t i; // an unsigned int avoids signed overflows (which are bad)
if (*p == '0') { // 0 cannot be followed by an integer
++p;
if (is_not_structural_or_whitespace_or_exponent_or_decimal(*p)) {
#ifdef JSON_TEST_NUMBERS // for unit testing
found_invalid_number(buf + offset);
#endif
return false;
}
i = 0;
} else {
if (!(is_integer(*p))) { // must start with an integer
#ifdef JSON_TEST_NUMBERS // for unit testing
found_invalid_number(buf + offset);
#endif
return false;
}
unsigned char digit = *p - '0';
i = digit;
p++;
// the is_made_of_eight_digits_fast routine is unlikely to help here because
// we rarely see large integer parts like 123456789
while (is_integer(*p)) {
digit = *p - '0';
// a multiplication by 10 is cheaper than an arbitrary integer
// multiplication
i = 10 * i + digit; // might overflow, we will handle the overflow later
++p;
}
}
int64_t exponent = 0;
bool is_float = false;
if ('.' == *p) {
is_float = true; // At this point we know that we have a float
// we continue with the fiction that we have an integer. If the
// floating point number is representable as x * 10^z for some integer
// z that fits in 53 bits, then we will be able to convert back the
// the integer into a float in a lossless manner.
++p;
const char *const first_after_period = p;
if (is_integer(*p)) {
unsigned char digit = *p - '0';
++p;
i = i * 10 + digit; // might overflow + multiplication by 10 is likely
// cheaper than arbitrary mult.
// we will handle the overflow later
} else {
#ifdef JSON_TEST_NUMBERS // for unit testing
found_invalid_number(buf + offset);
#endif
return false;
}
#ifdef SWAR_NUMBER_PARSING
// this helps if we have lots of decimals!
// this turns out to be frequent enough.
if (is_made_of_eight_digits_fast(p)) {
i = i * 100000000 + parse_eight_digits_unrolled(p);
p += 8;
}
#endif
while (is_integer(*p)) {
unsigned char digit = *p - '0';
++p;
i = i * 10 + digit; // in rare cases, this will overflow, but that's ok
// because we have parse_highprecision_float later.
}
exponent = first_after_period - p;
}
int digit_count =
p - start_digits - 1; // used later to guard against overflows
int64_t exp_number = 0; // exponential part
if (('e' == *p) || ('E' == *p)) {
is_float = true;
++p;
bool neg_exp = false;
if ('-' == *p) {
neg_exp = true;
++p;
} else if ('+' == *p) {
++p;
}
if (!is_integer(*p)) {
#ifdef JSON_TEST_NUMBERS // for unit testing
found_invalid_number(buf + offset);
#endif
return false;
}
unsigned char digit = *p - '0';
exp_number = digit;
p++;
if (is_integer(*p)) {
digit = *p - '0';
exp_number = 10 * exp_number + digit;
++p;
}
if (is_integer(*p)) {
digit = *p - '0';
exp_number = 10 * exp_number + digit;
++p;
}
while (is_integer(*p)) {
if (exp_number > 0x100000000) { // we need to check for overflows
// we refuse to parse this
#ifdef JSON_TEST_NUMBERS // for unit testing
found_invalid_number(buf + offset);
#endif
return false;
}
digit = *p - '0';
exp_number = 10 * exp_number + digit;
++p;
}
exponent += (neg_exp ? -exp_number : exp_number);
}
if (is_float) {
uint64_t power_index = 308 + exponent;
if (unlikely((digit_count >= 19))) { // this is uncommon
// It is possible that the integer had an overflow.
// We have to handle the case where we have 0.0000somenumber.
const char *start = start_digits;
while ((*start == '0') || (*start == '.')) {
start++;
}
// we over-decrement by one when there is a '.'
digit_count -= (start - start_digits);
if (digit_count >= 19) {
// Ok, chances are good that we had an overflow!
// this is almost never going to get called!!!
// we start anew, going slowly!!!
return parse_float(buf, pj, offset, found_minus);
}
}
if (unlikely((power_index > 2 * 308))) { // this is uncommon!!!
// this is almost never going to get called!!!
// we start anew, going slowly!!!
return parse_float(buf, pj, offset, found_minus);
}
double factor = power_of_ten[power_index];
factor = negative ? -factor : factor;
double d = i * factor;
pj.write_tape_double(d);
#ifdef JSON_TEST_NUMBERS // for unit testing
found_float(d, buf + offset);
#endif
} else {
if (unlikely(digit_count >= 18)) { // this is uncommon!!!
// there is a good chance that we had an overflow, so we need
// need to recover: we parse the whole thing again.
return parse_large_integer(buf, pj, offset, found_minus);
}
i = negative ? 0 - i : i;
pj.write_tape_s64(i);
#ifdef JSON_TEST_NUMBERS // for unit testing
found_integer(i, buf + offset);
#endif
}
return is_structural_or_whitespace(*p);
#endif // SIMDJSON_SKIPNUMBERPARSING
}
} // simdjson
#endif
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