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use std::{
convert::TryInto,
error,
fmt,
result,
str::FromStr,
sync::atomic::{AtomicUsize, Ordering},
time::SystemTime,
};
use chrono::Utc;
use hex::{self, FromHexError};
use rand::{thread_rng, Rng};
use lazy_static::lazy_static;
const TIMESTAMP_SIZE: usize = 4;
const PROCESS_ID_SIZE: usize = 5;
const COUNTER_SIZE: usize = 3;
const TIMESTAMP_OFFSET: usize = 0;
const PROCESS_ID_OFFSET: usize = TIMESTAMP_OFFSET + TIMESTAMP_SIZE;
const COUNTER_OFFSET: usize = PROCESS_ID_OFFSET + PROCESS_ID_SIZE;
const MAX_U24: usize = 0xFF_FFFF;
lazy_static! {
static ref OID_COUNTER: AtomicUsize = AtomicUsize::new(thread_rng().gen_range(0, MAX_U24 + 1));
}
#[derive(Debug)]
#[non_exhaustive]
pub enum Error {
ArgumentError { message: String },
FromHexError(FromHexError),
}
impl From<FromHexError> for Error {
fn from(err: FromHexError) -> Error {
Error::FromHexError(err)
}
}
pub type Result<T> = result::Result<T, Error>;
impl fmt::Display for Error {
fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
match *self {
Error::ArgumentError { ref message } => message.fmt(fmt),
Error::FromHexError(ref inner) => inner.fmt(fmt),
}
}
}
impl error::Error for Error {
fn cause(&self) -> Option<&dyn error::Error> {
match *self {
Error::ArgumentError { .. } => None,
Error::FromHexError(ref inner) => Some(inner),
}
}
}
#[derive(Clone, PartialEq, PartialOrd, Eq, Ord, Hash)]
pub struct ObjectId {
id: [u8; 12],
}
impl Default for ObjectId {
fn default() -> Self {
Self::new()
}
}
impl FromStr for ObjectId {
type Err = Error;
fn from_str(s: &str) -> std::result::Result<Self, Self::Err> {
Self::with_string(s)
}
}
impl ObjectId {
pub fn new() -> ObjectId {
let timestamp = ObjectId::gen_timestamp();
let process_id = ObjectId::gen_process_id();
let counter = ObjectId::gen_count();
let mut buf: [u8; 12] = [0; 12];
buf[TIMESTAMP_OFFSET..(TIMESTAMP_SIZE + TIMESTAMP_OFFSET)]
.clone_from_slice(×tamp[..TIMESTAMP_SIZE]);
buf[PROCESS_ID_OFFSET..(PROCESS_ID_SIZE + PROCESS_ID_OFFSET)]
.clone_from_slice(&process_id[..PROCESS_ID_SIZE]);
buf[COUNTER_OFFSET..(COUNTER_SIZE + COUNTER_OFFSET)]
.clone_from_slice(&counter[..COUNTER_SIZE]);
ObjectId::with_bytes(buf)
}
pub fn with_bytes(bytes: [u8; 12]) -> ObjectId {
ObjectId { id: bytes }
}
pub fn with_string(s: &str) -> Result<ObjectId> {
let bytes: Vec<u8> = hex::decode(s.as_bytes())?;
if bytes.len() != 12 {
Err(Error::ArgumentError {
message: "Provided string must be a 12-byte hexadecimal string.".to_owned(),
})
} else {
let mut byte_array: [u8; 12] = [0; 12];
byte_array[..].copy_from_slice(&bytes[..]);
Ok(ObjectId::with_bytes(byte_array))
}
}
pub fn timestamp(&self) -> chrono::DateTime<Utc> {
let mut buf = [0; 4];
buf.copy_from_slice(&self.id[0..4]);
let seconds_since_epoch = u32::from_be_bytes(buf);
let naive_datetime = chrono::NaiveDateTime::from_timestamp(seconds_since_epoch as i64, 0);
let timestamp: chrono::DateTime<Utc> = chrono::DateTime::from_utc(naive_datetime, Utc);
timestamp
}
pub fn bytes(&self) -> [u8; 12] {
self.id
}
pub fn to_hex(&self) -> String {
hex::encode(self.id)
}
fn gen_timestamp() -> [u8; 4] {
let timestamp: u32 = SystemTime::now()
.duration_since(SystemTime::UNIX_EPOCH)
.expect("system clock is before 1970")
.as_secs()
.try_into()
.unwrap();
timestamp.to_be_bytes()
}
fn gen_process_id() -> [u8; 5] {
lazy_static! {
static ref BUF: [u8; 5] = thread_rng().gen();
}
*BUF
}
fn gen_count() -> [u8; 3] {
let u_counter = OID_COUNTER.fetch_add(1, Ordering::SeqCst);
let u = u_counter % (MAX_U24 + 1);
let u_int = u as u64;
let buf = u_int.to_be_bytes();
let buf_u24: [u8; 3] = [buf[5], buf[6], buf[7]];
buf_u24
}
}
impl fmt::Display for ObjectId {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
f.write_str(&self.to_hex())
}
}
impl fmt::Debug for ObjectId {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
f.write_str(&format!("ObjectId({})", self.to_hex()))
}
}
#[cfg(test)]
use crate::tests::LOCK;
#[test]
fn count_generated_is_big_endian() {
let _guard = LOCK.run_exclusively();
let start = 1_122_866;
OID_COUNTER.store(start, Ordering::SeqCst);
let count_bytes = ObjectId::gen_count();
let mut buf: [u8; 4] = [0; 4];
buf[1..=COUNTER_SIZE].clone_from_slice(&count_bytes[..COUNTER_SIZE]);
let count = u32::from_be_bytes(buf);
assert_eq!(start as u32, count);
let oid = ObjectId::new();
assert_eq!(0x11u8, oid.bytes()[COUNTER_OFFSET]);
assert_eq!(0x22u8, oid.bytes()[COUNTER_OFFSET + 1]);
assert_eq!(0x33u8, oid.bytes()[COUNTER_OFFSET + 2]);
}
#[test]
fn test_counter_overflow_u24_max() {
let _guard = LOCK.run_exclusively();
let start = MAX_U24;
OID_COUNTER.store(start, Ordering::SeqCst);
let oid = ObjectId::new();
assert_eq!(0xFFu8, oid.bytes()[COUNTER_OFFSET]);
assert_eq!(0xFFu8, oid.bytes()[COUNTER_OFFSET + 1]);
assert_eq!(0xFFu8, oid.bytes()[COUNTER_OFFSET + 2]);
let oid_new = ObjectId::new();
assert_eq!(0x00u8, oid_new.bytes()[COUNTER_OFFSET]);
assert_eq!(0x00u8, oid_new.bytes()[COUNTER_OFFSET + 1]);
assert_eq!(0x00u8, oid_new.bytes()[COUNTER_OFFSET + 2]);
}
#[test]
fn test_counter_overflow_usize_max() {
let _guard = LOCK.run_exclusively();
let start = usize::max_value();
OID_COUNTER.store(start, Ordering::SeqCst);
let oid = ObjectId::new();
assert_eq!(0xFFu8, oid.bytes()[COUNTER_OFFSET]);
assert_eq!(0xFFu8, oid.bytes()[COUNTER_OFFSET + 1]);
assert_eq!(0xFFu8, oid.bytes()[COUNTER_OFFSET + 2]);
let oid_new = ObjectId::new();
assert_eq!(0x00u8, oid_new.bytes()[COUNTER_OFFSET]);
assert_eq!(0x00u8, oid_new.bytes()[COUNTER_OFFSET + 1]);
assert_eq!(0x00u8, oid_new.bytes()[COUNTER_OFFSET + 2]);
}
#[cfg(test)]
mod test {
use chrono::{offset::TimeZone, Utc};
#[test]
fn test_display() {
let id = super::ObjectId::with_string("53e37d08776f724e42000000").unwrap();
assert_eq!(format!("{}", id), "53e37d08776f724e42000000")
}
#[test]
fn test_debug() {
let id = super::ObjectId::with_string("53e37d08776f724e42000000").unwrap();
assert_eq!(format!("{:?}", id), "ObjectId(53e37d08776f724e42000000)")
}
#[test]
fn test_timestamp() {
let id = super::ObjectId::with_string("000000000000000000000000").unwrap();
assert_eq!(Utc.ymd(1970, 1, 1).and_hms(0, 0, 0), id.timestamp());
let id = super::ObjectId::with_string("7FFFFFFF0000000000000000").unwrap();
assert_eq!(Utc.ymd(2038, 1, 19).and_hms(3, 14, 7), id.timestamp());
let id = super::ObjectId::with_string("800000000000000000000000").unwrap();
assert_eq!(Utc.ymd(2038, 1, 19).and_hms(3, 14, 8), id.timestamp());
let id = super::ObjectId::with_string("FFFFFFFF0000000000000000").unwrap();
assert_eq!(Utc.ymd(2106, 2, 7).and_hms(6, 28, 15), id.timestamp());
}
}