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//go:generate re2go $INPUT -o $OUTPUT -i
package main
import "errors"
const u32Limit uint64 = 1<<32
var (
eSyntax = errors.New("syntax error")
eOverflow = errors.New("overflow error")
)
func parse_u32(str string) (uint32, error) {
var cur, mar int
result := uint64(0)
add := func(base uint64, offset byte) {
result = result * base + uint64(str[cur-1] - offset)
if result >= u32Limit {
result = u32Limit
}
}
/*!re2c
re2c:yyfill:enable = 0;
re2c:define:YYCTYPE = byte;
re2c:define:YYPEEK = "str[cur]";
re2c:define:YYSKIP = "cur += 1";
re2c:define:YYSHIFT = "cur += @@{shift}";
re2c:define:YYBACKUP = "mar = cur";
re2c:define:YYRESTORE = "cur = mar";
end = "\x00";
'0b' / [01] { goto bin }
"0" { goto oct }
"" / [1-9] { goto dec }
'0x' / [0-9a-fA-F] { goto hex }
* { goto err }
*/
bin:
/*!re2c
end { goto end }
[01] { add(2, '0'); goto bin }
* { goto err }
*/
oct:
/*!re2c
end { goto end }
[0-7] { add(8, '0'); goto oct }
* { goto err }
*/
dec:
/*!re2c
end { goto end }
[0-9] { add(10, '0'); goto dec }
* { goto err }
*/
hex:
/*!re2c
end { goto end }
[0-9] { add(16, '0'); goto hex }
[a-f] { add(16, 'a'-10); goto hex }
[A-F] { add(16, 'A'-10); goto hex }
* { goto err }
*/
end:
if result < u32Limit {
return uint32(result), nil
} else {
return 0, eOverflow
}
err:
return 0, eSyntax
}
func main() {
test := func(num uint32, str string, err error) {
if n, e := parse_u32(str); !(n == num && e == err) {
panic("error")
}
}
test(1234567890, "1234567890\000", nil)
test(13, "0b1101\000", nil)
test(0x7fe, "0x007Fe\000", nil)
test(0644, "0644\000", nil)
test(0, "9999999999\000", eOverflow)
test(0, "123??\000", eSyntax)
}