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Implement hexadecimal float conversion in MathLib::toDoubleNumber ind… (#1506) 

* Implement hexadecimal float conversion in MathLib::toDoubleNumber independent of C99/C++17
* Refactor MathLib::isFloatHex and cure some false results
This commit is contained in:
amai2012 2018-12-06 22:16:16 +01:00 committed by GitHub
parent a90c56ad76
commit a68086c959
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2 changed files with 106 additions and 30 deletions
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116
lib/mathlib.cpp
View File

@ -548,6 +548,55 @@ MathLib::bigint MathLib::toLongNumber(const std::string & str)
return ret;
}
// in-place conversion of (sub)string to double. Requires no heap.
static double myStod(const std::string& str, std::string::const_iterator from, std::string::const_iterator to, int base)
{
double result = 0.;
bool positivesign = true;
std::string::const_iterator it;
if ('+' == *from) {
it = from + 1;
} else if ('-' == *from) {
it = from + 1;
positivesign = false;
} else
it = from;
const std::size_t decimalsep = str.find('.', it-str.begin());
int distance;
if (std::string::npos == decimalsep) {
distance = to - it;
} else if (decimalsep > (to - str.begin()))
return 0.; // error handling??
else
distance = int(decimalsep)-(from - str.begin());
auto digitval = [&](char c) {
if ((10 < base) && (c > '9'))
return 10 + std::tolower(c) - 'a';
else
return c - '0';
};
for (; it!=to; ++it) {
if ('.' == *it)
continue;
else
--distance;
result += digitval(*it)* std::pow(base, distance);
}
return (positivesign)?result:-result;
}
// Assuming a limited support of built-in hexadecimal floats (see C99, C++17) that is a fall-back implementation.
// Performance has been optimized WRT to heap activity, however the calculation part is not optimized.
static double FloatHexToDoubleNumber(const std::string& str)
{
const std::size_t p = str.find_first_of("pP",3);
const double factor1 = myStod(str, str.begin() + 2, str.begin()+p, 16);
const bool suffix = (str.back() == 'f') || (str.back() == 'F') || (str.back() == 'l') || (str.back() == 'L');
const double exponent = myStod(str, str.begin() + p + 1, (suffix)?str.end()-1:str.end(), 10);
const double factor2 = std::pow(2, exponent);
return factor1 * factor2;
}
double MathLib::toDoubleNumber(const std::string &str)
{
@ -563,6 +612,8 @@ double MathLib::toDoubleNumber(const std::string &str)
// TODO : handle locale
return std::strtod(str.c_str(), nullptr);
#endif
if (isFloatHex(str))
return FloatHexToDoubleNumber(str);
// otherwise, convert to double
std::istringstream istr(str);
istr.imbue(std::locale::classic());
@ -794,69 +845,76 @@ bool MathLib::isIntHex(const std::string& str)
bool MathLib::isFloatHex(const std::string& str)
{
enum Status {
START, PLUSMINUS, HEX_PREFIX, WHOLE_NUMBER_DIGIT, WHOLE_NUMBER_DIGITS, FRACTION, EXPONENT_DIGIT, EXPONENT_DIGITS
START, HEX_0, HEX_X, WHOLE_NUMBER_DIGIT, POINT, FRACTION, EXPONENT_P, EXPONENT_SIGN, EXPONENT_DIGITS, EXPONENT_SUFFIX
} state = START;
for (std::string::const_iterator it = str.begin(); it != str.end(); ++it) {
switch (state) {
case START:
if (*it == '+' || *it == '-')
state = PLUSMINUS;
else if (*it == '0')
state = HEX_PREFIX;
else
return false;
break;
case PLUSMINUS:
if (*it == '0')
state = HEX_PREFIX;
state = HEX_0;
else
return false;
break;
case HEX_PREFIX:
case HEX_0:
if (*it == 'x' || *it == 'X')
state = HEX_X;
else
return false;
break;
case HEX_X:
if (isxdigit(static_cast<unsigned char>(*it)))
state = WHOLE_NUMBER_DIGIT;
else if (*it == '.')
state = POINT;
else
return false;
break;
case WHOLE_NUMBER_DIGIT:
if (isxdigit(static_cast<unsigned char>(*it)))
state = WHOLE_NUMBER_DIGITS;
else
return false;
break;
case WHOLE_NUMBER_DIGITS:
if (isxdigit(static_cast<unsigned char>(*it)))
state = WHOLE_NUMBER_DIGITS;
; // state = WHOLE_NUMBER_DIGITS;
else if (*it=='.')
state = FRACTION;
else if (*it=='p' || *it=='P')
state = EXPONENT_DIGIT;
state = EXPONENT_P;
else
return false;
break;
case POINT:
case FRACTION:
if (isxdigit(static_cast<unsigned char>(*it)))
state = FRACTION;
else if (*it=='p' || *it=='P')
state = EXPONENT_DIGIT;
state=FRACTION;
else if (*it == 'p' || *it == 'P')
state = EXPONENT_P;
else
return false;
break;
case EXPONENT_DIGIT:
if (isxdigit(static_cast<unsigned char>(*it)))
case EXPONENT_P:
if (isdigit(static_cast<unsigned char>(*it)))
state = EXPONENT_DIGITS;
else if (*it=='+' || *it=='-')
else if (*it == '+' || *it == '-')
state = EXPONENT_SIGN;
else
return false;
break;
case EXPONENT_SIGN:
if (isdigit(static_cast<unsigned char>(*it)))
state = EXPONENT_DIGITS;
else
return false;
break;
case EXPONENT_DIGITS:
if (isxdigit(static_cast<unsigned char>(*it)))
state = EXPONENT_DIGITS;
if (isdigit(static_cast<unsigned char>(*it)))
; // state = EXPONENT_DIGITS;
else if (*it == 'f' || *it == 'F' || *it == 'l' || *it == 'L')
state = EXPONENT_SUFFIX;
else
return *it=='f'||*it=='F'||*it=='l'||*it=='L';
return false;
break;
case EXPONENT_SUFFIX:
return false;
}
}
return state==EXPONENT_DIGITS;
return (EXPONENT_DIGITS==state) || (EXPONENT_SUFFIX == state);
}
bool MathLib::isValidIntegerSuffix(const std::string& str)

20
test/testmathlib.cpp
View File

@ -371,6 +371,15 @@ private:
ASSERT_EQUALS_DOUBLE(0.0, MathLib::toDoubleNumber("+0.0"), 0.000001);
ASSERT_EQUALS_DOUBLE('0', MathLib::toDoubleNumber("'0'"), 0.000001);
ASSERT_EQUALS_DOUBLE(192, MathLib::toDoubleNumber("0x0.3p10"), 0.000001);
ASSERT_EQUALS_DOUBLE(5.42101e-20, MathLib::toDoubleNumber("0x1p-64"), 1e-20);
ASSERT_EQUALS_DOUBLE(3.14159, MathLib::toDoubleNumber("0x1.921fb5p+1"), 0.000001);
ASSERT_EQUALS_DOUBLE(2006, MathLib::toDoubleNumber("0x1.f58000p+10"), 0.000001);
ASSERT_EQUALS_DOUBLE(1e-010, MathLib::toDoubleNumber("0x1.b7cdfep-34"), 0.000001);
ASSERT_EQUALS_DOUBLE(.484375, MathLib::toDoubleNumber("0x1.fp-2"), 0.000001);
ASSERT_EQUALS_DOUBLE(9.0, MathLib::toDoubleNumber("0x1.2P3"), 0.000001);
ASSERT_EQUALS_DOUBLE(0.0625, MathLib::toDoubleNumber("0x.1P0"), 0.000001);
// verify: string --> double --> string conversion
ASSERT_EQUALS("1.0", MathLib::toString(MathLib::toDoubleNumber("1.0f")));
ASSERT_EQUALS("1.0", MathLib::toString(MathLib::toDoubleNumber("1.0")));
@ -598,7 +607,6 @@ private:
void isFloatHex() const {
// hex number syntax: [sign]0x[hexnumbers][suffix]
ASSERT_EQUALS(false, MathLib::isFloatHex(""));
ASSERT_EQUALS(true, MathLib::isFloatHex("0x1.999999999999ap-4"));
ASSERT_EQUALS(true, MathLib::isFloatHex("0x0.3p10"));
ASSERT_EQUALS(true, MathLib::isFloatHex("0x1.fp3"));
@ -606,7 +614,13 @@ private:
ASSERT_EQUALS(true, MathLib::isFloatHex("0xcc.ccccccccccdp-11"));
ASSERT_EQUALS(true, MathLib::isFloatHex("0x3.243F6A88p+03"));
ASSERT_EQUALS(true, MathLib::isFloatHex("0xA.Fp-10"));
ASSERT_EQUALS(true, MathLib::isFloatHex("0x1.2p-10f"));
ASSERT_EQUALS(true, MathLib::isFloatHex("0x1.2p+10F"));
ASSERT_EQUALS(true, MathLib::isFloatHex("0x1.2p+10l"));
ASSERT_EQUALS(true, MathLib::isFloatHex("0x1.2p+10L"));
ASSERT_EQUALS(true, MathLib::isFloatHex("0X.2p-0"));
ASSERT_EQUALS(false, MathLib::isFloatHex(""));
ASSERT_EQUALS(false, MathLib::isFloatHex("0"));
ASSERT_EQUALS(false, MathLib::isFloatHex("0x"));
ASSERT_EQUALS(false, MathLib::isFloatHex("0xa"));
@ -616,6 +630,10 @@ private:
ASSERT_EQUALS(false, MathLib::isFloatHex("0x."));
ASSERT_EQUALS(false, MathLib::isFloatHex("0XP"));
ASSERT_EQUALS(false, MathLib::isFloatHex("0xx"));
ASSERT_EQUALS(false, MathLib::isFloatHex("0x1P+-1"));
ASSERT_EQUALS(false, MathLib::isFloatHex("0x1p+10e"));
ASSERT_EQUALS(false, MathLib::isFloatHex("0x1p+1af"));
ASSERT_EQUALS(false, MathLib::isFloatHex("0x1p+10LL"));
}
void isIntHex() const {