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Minor refactoring before optimization trial

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This commit is contained in:
Milo Yip 2014-09-16 19:38:18 +08:00
parent 5171775d4c
commit 475b242087
2 changed files with 32 additions and 22 deletions
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50
include/rapidjson/internal/strtod.h
View File

@ -29,7 +29,7 @@
namespace rapidjson {
namespace internal {
inline double StrtodFastPath(double significand, int exp) {
inline double FastPath(double significand, int exp) {
if (exp < -308)
return 0.0;
else if (exp >= 0)
@ -38,14 +38,14 @@ inline double StrtodFastPath(double significand, int exp) {
return significand / internal::Pow10(-exp);
}
inline double NormalPrecision(double d, int p) {
inline double StrtodNormalPrecision(double d, int p) {
if (p < -308) {
// Prevent expSum < -308, making Pow10(p) = 0
d = StrtodFastPath(d, -308);
d = StrtodFastPath(d, p + 308);
d = FastPath(d, -308);
d = FastPath(d, p + 308);
}
else
d = StrtodFastPath(d, p);
d = FastPath(d, p);
return d;
}
@ -124,25 +124,24 @@ inline int CheckWithinHalfULP(double b, const BigInteger& d, int dExp, bool* adj
return cmp;
}
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(length >= 1);
inline bool StrtodFast(double d, int p, double* result) {
// Use fast path for string-to-double conversion if possible
// see http://www.exploringbinary.com/fast-path-decimal-to-floating-point-conversion/
if (p > 22) {
if (p < 22 + 16) {
// Fast Path Cases In Disguise
d *= internal::Pow10(p - 22);
p = 22;
}
if (p > 22 && p < 22 + 16) {
// Fast Path Cases In Disguise
d *= internal::Pow10(p - 22);
p = 22;
}
if (p >= -22 && p <= 22 && d <= 9007199254740991.0) // 2^53 - 1
return StrtodFastPath(d, p);
// Use slow-path with BigInteger comparison
if (p >= -22 && p <= 22 && d <= 9007199254740991.0) { // 2^53 - 1
*result = FastPath(d, p);
return true;
}
else
return false;
}
inline double StrtodBigInteger(double d, int p, const char* decimals, size_t length, size_t decimalPosition, int exp) {
// Trim leading zeros
while (*decimals == '0' && length > 1) {
length--;
@ -170,7 +169,7 @@ inline double FullPrecision(double d, int p, const char* decimals, size_t length
const BigInteger dInt(decimals, length);
const int dExp = (int)decimalPosition - (int)length + exp;
Double approx = NormalPrecision(d, p);
Double approx = StrtodNormalPrecision(d, p);
for (int i = 0; i < 10; i++) {
bool adjustToNegative;
int cmp = CheckWithinHalfULP(approx.Value(), dInt, dExp, &adjustToNegative);
@ -191,6 +190,17 @@ inline double FullPrecision(double d, int p, const char* decimals, size_t length
return approx.Value();
}
inline double StrtodFullPrecision(double d, int p, const char* decimals, size_t length, size_t decimalPosition, int exp) {
RAPIDJSON_ASSERT(d >= 0.0);
RAPIDJSON_ASSERT(length >= 1);
double result;
if (StrtodFast(d, p, &result))
return result;
return StrtodBigInteger(d, p, decimals, length, decimalPosition, exp);
}
} // namespace internal
} // namespace rapidjson

4
include/rapidjson/reader.h
View File

@ -941,9 +941,9 @@ private:
if (useDouble) {
int p = exp + expFrac;
if (parseFlags & kParseFullPrecisionFlag)
d = internal::FullPrecision(d, p, decimal, length, decimalPosition, exp);
d = internal::StrtodFullPrecision(d, p, decimal, length, decimalPosition, exp);
else
d = internal::NormalPrecision(d, p);
d = internal::StrtodNormalPrecision(d, p);
cont = handler.Double(minus ? -d : d);
}