SubBytesWithRuneCheck/SubStringWithByteLimit get sub string very fast for limit the size of bytes or string when it's very large.
s := `123456789壹贰叁肆伍陆柒捌玖éèǔ`
SubStringWithByteLimit(s, 9) // 123456789
SubStringWithByteLimit(s, 10) // 123456789
SubStringWithByteLimit(s, 12) // 123456789壹| BenchmarkSubBytesWithRuneCheck-8 | 143022060 | 8.38 ns/op | 0 B/op | 0 allocs/op |
| BenchmarkSubStringWithByteLimit-8 | 24984644 | 44.9 ns/op | 48 B/op | 1 allocs/op |