///
/// If \p C is not a valid hex digit, -1U is returned.
inline unsigned hexDigitValue(char C) {
- if (C >= '0' && C <= '9') return C-'0';
- if (C >= 'a' && C <= 'f') return C-'a'+10U;
- if (C >= 'A' && C <= 'F') return C-'A'+10U;
- return -1U;
+ struct HexTable {
+ unsigned LUT[255] = {};
+ constexpr HexTable() {
+ // Default initialize everything to invalid.
+ for (int i = 0; i < 255; ++i)
+ LUT[i] = -1U;
+ // Initialize `0`-`9`.
+ for (int i = 0; i < 10; ++i)
+ LUT['0' + i] = i;
+ // Initialize `A`-`F` and `a`-`f`.
+ for (int i = 0; i < 6; ++i)
+ LUT['A' + i] = LUT['a' + i] = 10 + i;
+ }
+ };
+ constexpr HexTable Table;
+ return Table.LUT[static_cast<unsigned char>(C)];
}
/// Checks if character \p C is one of the 10 decimal digits.