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Check "fast path cases in disguise" in strtod

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This commit is contained in:
miloyip 2014-09-03 14:45:37 +08:00
parent 818f6f1f2e
commit b0436911a8
2 changed files with 13 additions and 2 deletions
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14
include/rapidjson/reader.h
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@ -877,11 +877,21 @@ private:
if (useDouble) {
int p = exp + expFrac;
double d;
uint64_t significand = use64bit ? i64 : i;
double significand = use64bit ? i64 : i;
// Use fast path for string-to-double conversion if possible
// see http://www.exploringbinary.com/fast-path-decimal-to-floating-point-conversion/
if (!useStrtod && p >= -22 && p <= 22 && significand <= RAPIDJSON_UINT64_C2(0x001FFFFF, 0xFFFFFFFF)) {
if (!useStrtod && p > 22) {
if (p < 22 + 16) {
// Fast Path Cases In Disguise
significand *= internal::Pow10(p - 22);
p = 22;
}
else
useStrtod = true;
}
if (!useStrtod && p >= -22 && significand <= 9007199254740991.0) { // 2^53 - 1
if (p >= 0)
d = significand * internal::Pow10(p);
else

1
test/unittest/readertest.cpp
View File

@ -165,6 +165,7 @@ TEST(Reader, ParseNumberHandler) {
TEST_DOUBLE("18446744073709551616", 18446744073709551616.0); // 2^64 (max of uint64_t + 1, force to use double)
TEST_DOUBLE("-9223372036854775809", -9223372036854775809.0); // -2^63 - 1(min of int64_t + 1, force to use double)
TEST_DOUBLE("0.9868011474609375", 0.9868011474609375); // https://github.com/miloyip/rapidjson/issues/120
TEST_DOUBLE("123e34", 123e34); // Fast Path Cases In Disguise
{
char n1e308[310]; // '1' followed by 308 '0'