module rand import time // uuid_v4 generates a random (v4) UUID // See https://en.wikipedia.org/wiki/Universally_unique_identifier#Version_4_(random) pub fn uuid_v4() string { buflen := 36 mut buf := unsafe { malloc_noscan(37) } mut i_buf := 0 mut x := u64(0) mut d := byte(0) for i_buf < buflen { mut c := 0 x = default_rng.u64() // do most of the bit manipulation at once: x &= 0x0F0F0F0F0F0F0F0F x += 0x3030303030303030 // write the ASCII codes to the buffer: for c < 8 && i_buf < buflen { d = byte(x) unsafe { buf[i_buf] = if d > 0x39 { d + 0x27 } else { d } } i_buf++ c++ x = x >> 8 } } // there are still some random bits in x: x = x >> 8 d = byte(x) unsafe { buf[19] = if d > 0x39 { d + 0x27 } else { d } buf[8] = `-` buf[13] = `-` buf[18] = `-` buf[23] = `-` buf[14] = `4` buf[buflen] = 0 return buf.vstring_with_len(buflen) } } const ( ulid_encoding = '0123456789ABCDEFGHJKMNPQRSTVWXYZ' ) // ulid generates an Unique Lexicographically sortable IDentifier. // See https://github.com/ulid/spec . // NB: ULIDs can leak timing information, if you make them public, because // you can infer the rate at which some resource is being created, like // users or business transactions. // (https://news.ycombinator.com/item?id=14526173) pub fn ulid() string { return ulid_at_millisecond(u64(time.utc().unix_time_milli())) } // ulid_at_millisecond does the same as `ulid` but takes a custom Unix millisecond timestamp via `unix_time_milli`. pub fn ulid_at_millisecond(unix_time_milli u64) string { buflen := 26 mut buf := unsafe { malloc_noscan(27) } mut t := unix_time_milli mut i := 9 for i >= 0 { unsafe { buf[i] = rand.ulid_encoding[t & 0x1F] } t = t >> 5 i-- } // first rand set mut x := default_rng.u64() i = 10 for i < 19 { unsafe { buf[i] = rand.ulid_encoding[x & 0x1F] } x = x >> 5 i++ } // second rand set x = default_rng.u64() for i < 26 { unsafe { buf[i] = rand.ulid_encoding[x & 0x1F] } x = x >> 5 i++ } unsafe { buf[26] = 0 return buf.vstring_with_len(buflen) } } // string_from_set returns a string of length `len` containing random characters sampled from the given `charset` pub fn string_from_set(charset string, len int) string { if len == 0 { return '' } mut buf := unsafe { malloc_noscan(len + 1) } for i in 0 .. len { unsafe { buf[i] = charset[intn(charset.len)] } } unsafe { buf[len] = 0 } return unsafe { buf.vstring_with_len(len) } } // string returns a string of length `len` containing random characters in range `[a-zA-Z]`. pub fn string(len int) string { return string_from_set(english_letters, len) } // hex returns a hexadecimal number of length `len` containing random characters in range `[a-f0-9]`. pub fn hex(len int) string { return string_from_set(hex_chars, len) } // ascii returns a random string of the printable ASCII characters with length `len`. pub fn ascii(len int) string { return string_from_set(ascii_chars, len) }