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Trimming leading/trailing zeros and correct underflow case

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This commit is contained in:
Milo Yip 2014-09-16 10:52:40 +08:00
parent 50fc3fedb2
commit a425ad5552
1 changed files with 26 additions and 1 deletions
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27
include/rapidjson/internal/strtod.h
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@ -449,6 +449,7 @@ inline int CheckWithinHalfULP(double b, const BigInteger& d, int dExp, bool* adj
inline double FullPrecision(double d, int p, const char* decimals, size_t length, size_t decimalPosition, int exp) { inline double FullPrecision(double d, int p, const char* decimals, size_t length, size_t decimalPosition, int exp) {
RAPIDJSON_ASSERT(d >= 0.0); RAPIDJSON_ASSERT(d >= 0.0);
RAPIDJSON_ASSERT(length >= 1);
// Use fast path for string-to-double conversion if possible // Use fast path for string-to-double conversion if possible
// see http://www.exploringbinary.com/fast-path-decimal-to-floating-point-conversion/ // see http://www.exploringbinary.com/fast-path-decimal-to-floating-point-conversion/
@ -463,7 +464,31 @@ inline double FullPrecision(double d, int p, const char* decimals, size_t length
if (p >= -22 && p <= 22 && d <= 9007199254740991.0) // 2^53 - 1 if (p >= -22 && p <= 22 && d <= 9007199254740991.0) // 2^53 - 1
return StrtodFastPath(d, p); return StrtodFastPath(d, p);
if (p + int(length) < -324) // Use slow-path with BigInteger comparison
// Trim leading zeros
while (decimals[0] == '0' && length > 1) {
decimals++;
length--;
decimalPosition--;
}
// Trim trailing zeros
while (decimals[length - 1] == '0' && length > 1) {
length--;
exp++;
decimalPosition--;
}
// Trim right-most digits
const int kMaxDecimalDigit = 780;
if (length > kMaxDecimalDigit) {
exp += (int(length) - kMaxDecimalDigit);
length = kMaxDecimalDigit;
}
// If too small, underflow to zero
if (int(length) + exp < -324)
return 0.0; return 0.0;
const BigInteger dInt(decimals, length); const BigInteger dInt(decimals, length);