FX_Number::FX_Number(ByteStringView strc)
: m_bInteger(true), m_bSigned(false), m_UnsignedValue(0) {
if (strc.IsEmpty())
return;
if (strc.Contains('.')) {
m_bInteger = false;
m_bSigned = true;
m_FloatValue = StringToFloat(strc);
return;
}
// Note, numbers in PDF are typically of the form 123, -123, etc. But,
// for things like the Permissions on the encryption hash the number is
// actually an unsigned value. We use a uint32_t so we can deal with the
// unsigned and then check for overflow if the user actually signed the value.
// The Permissions flag is listed in Table 3.20 PDF 1.7 spec.
pdfium::base::CheckedNumeric<uint32_t> unsigned_val = 0;
bool bNegative = false;
size_t cc = 0;
if (strc[0] == '+') {
cc++;
m_bSigned = true;
} else if (strc[0] == '-') {
bNegative = true;
m_bSigned = true;
cc++;
}
while (cc < strc.GetLength() && std::isdigit(strc[cc])) {
unsigned_val = unsigned_val * 10 + FXSYS_DecimalCharToInt(strc.CharAt(cc));
if (!unsigned_val.IsValid())
break;
cc++;
}
uint32_t uValue = unsigned_val.ValueOrDefault(0);
if (!m_bSigned) {
m_UnsignedValue = uValue;
return;
}
// We have a sign, so if the value was greater then the signed integer
// limits, then we've overflowed and must reset to the default value.
constexpr uint32_t uLimit =
static_cast<uint32_t>(std::numeric_limits<int>::max());
if (uValue > (bNegative ? uLimit + 1 : uLimit))
uValue = 0;
// Switch back to the int space so we can flip to a negative if we need.
int32_t value = static_cast<int32_t>(uValue);
if (bNegative) {
// |value| is usually positive, except in the corner case of "-2147483648",
// where |uValue| is 2147483648. When it gets casted to an int, |value|
// becomes -2147483648. For this case, avoid undefined behavior, because
// an int32_t cannot represent 2147483648.
static constexpr int kMinInt = std::numeric_limits<int>::min();
m_SignedValue = LIKELY(value != kMinInt) ? -value : kMinInt;
} else {
m_SignedValue = value;
}
}
