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// re2rust $INPUT -o $OUTPUT -c
/*!conditions:re2c*/
const ERROR: u64 = std::u32::MAX as u64 + 1; // overflow
// Add digit with the given base, checking for overflow.
fn add(num: &mut u64, str: &[u8], cur: usize, offs: u8, base: u64) {
let digit = unsafe { str.get_unchecked(cur - 1) } - offs;
*num = std::cmp::min(*num * base + digit as u64, ERROR);
}
fn parse_u32(str: &[u8]) -> Option<u32> {
let (mut cur, mut mar) = (0, 0);
let mut cond = YYC_INIT;
let mut num = 0u64; // Store number in u64 to simplify overflow checks.
'lex: loop {/*!re2c
re2c:define:YYCTYPE = u8;
re2c:define:YYPEEK = "*str.get_unchecked(cur)";
re2c:define:YYSKIP = "cur += 1;";
re2c:define:YYBACKUP = "mar = cur;";
re2c:define:YYRESTORE = "cur = mar;";
re2c:define:YYSHIFT = "cur = (cur as isize + @@) as usize;";
re2c:define:YYGETCONDITION = "cond";
re2c:define:YYSETCONDITION = "cond = @@;";
re2c:yyfill:enable = 0;
<INIT> '0b' / [01] :=> BIN
<INIT> "0" :=> OCT
<INIT> "" / [1-9] :=> DEC
<INIT> '0x' / [0-9a-fA-F] :=> HEX
<INIT> * { return None; }
<BIN> [01] { add(&mut num, str, cur, 48, 2); continue 'lex; }
<OCT> [0-7] { add(&mut num, str, cur, 48, 8); continue 'lex; }
<DEC> [0-9] { add(&mut num, str, cur, 48, 10); continue 'lex; }
<HEX> [0-9] { add(&mut num, str, cur, 48, 16); continue 'lex; }
<HEX> [a-f] { add(&mut num, str, cur, 87, 16); continue 'lex; }
<HEX> [A-F] { add(&mut num, str, cur, 55, 16); continue 'lex; }
<BIN, OCT, DEC, HEX> * {
return if num < ERROR { Some(num as u32) } else { None };
}
*/}
}
fn main() {
assert_eq!(parse_u32(b"\0"), None);
assert_eq!(parse_u32(b"1234567890\0"), Some(1234567890));
assert_eq!(parse_u32(b"0b1101\0"), Some(13));
assert_eq!(parse_u32(b"0x7Fe\0"), Some(2046));
assert_eq!(parse_u32(b"0644\0"), Some(420));
assert_eq!(parse_u32(b"9999999999\0"), None);
}