// Copyright 2013-2014 The Rust Project Developers.

// Copyright 2018 The Uuid Project Developers.

//

// See the COPYRIGHT file at the top-level directory of this distribution.

//

// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or

// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license

// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your

// option. This file may not be copied, modified, or distributed

// except according to those terms.

//! Generate and parse universally unique identifiers (UUIDs).

//!

//! Here's an example of a UUID:

//!

//! ```text

//! 67e55044-10b1-426f-9247-bb680e5fe0c8

//! ```

//!

//! A UUID is a unique 128-bit value, stored as 16 octets, and regularly

//! formatted as a hex string in five groups. UUIDs are used to assign unique

//! identifiers to entities without requiring a central allocating authority.

//!

//! They are particularly useful in distributed systems, though can be used in

//! disparate areas, such as databases and network protocols.  Typically a UUID

//! is displayed in a readable string form as a sequence of hexadecimal digits,

//! separated into groups by hyphens.

//!

//! The uniqueness property is not strictly guaranteed, however for all

//! practical purposes, it can be assumed that an unintentional collision would

//! be extremely unlikely.

//!

//! UUIDs have a number of standardized encodings that are specified in [RFC 9562](https://www.ietf.org/rfc/rfc9562.html).

//!

//! # Getting started

//!

//! Add the following to your `Cargo.toml`:

//!

//! ```toml

//! [dependencies.uuid]

//! version = "1.29.0"

//! # Lets you generate random UUIDs

//! features = [

//!     "v4",

//! ]

//! ```

//!

//! When you want a UUID, you can generate one:

//!

//! ```

//! # fn main() {

//! # #[cfg(feature = "v4")]

//! # {

//! use uuid::Uuid;

//!

//! let id = Uuid::new_v4();

//! # }

//! # }

//! ```

//!

//! If you have a UUID value, you can use its string literal form inline:

//!

//! ```

//! use uuid::{uuid, Uuid};

//!

//! const ID: Uuid = uuid!("67e55044-10b1-426f-9247-bb680e5fe0c8");

//! ```

//!

//! # Working with different UUID versions

//!

//! This library supports all standardized methods for generating UUIDs through individual Cargo features.

//!

//! By default, this crate depends on nothing but the Rust standard library and can parse and format

//! UUIDs, but cannot generate them. Depending on the kind of UUID you'd like to work with, there

//! are Cargo features that enable generating them:

//!

//! * `v1` - Version 1 UUIDs using a timestamp and monotonic counter.

//! * `v3` - Version 3 UUIDs based on the MD5 hash of some data.

//! * `v4` - Version 4 UUIDs with random data.

//! * `v5` - Version 5 UUIDs based on the SHA1 hash of some data.

//! * `v6` - Version 6 UUIDs using a timestamp and monotonic counter.

//! * `v7` - Version 7 UUIDs using a Unix timestamp.

//! * `v8` - Version 8 UUIDs using user-defined data.

//!

//! This library also includes a [`Builder`] type that can be used to help construct UUIDs of any

//! version without any additional dependencies or features. It's a lower-level API than [`Uuid`]

//! that can be used when you need control over implicit requirements on things like a source

//! of randomness.

//!

//! ## Which UUID version should I use?

//!

//! If you just want to generate unique identifiers then consider version 4 (`v4`) UUIDs. If you want

//! to use UUIDs as database keys or need to sort them then consider version 7 (`v7`) UUIDs.

//! Other versions should generally be avoided unless there's an existing need for them.

//!

//! Some UUID versions supersede others. Prefer version 6 over version 1 and version 5 over version 3.

//!

//! # Other features

//!

//! Other crate features can also be useful beyond the version support:

//!

//! * `serde` - adds the ability to serialize and deserialize a UUID using

//!   `serde`.

//! * `borsh` - adds the ability to serialize and deserialize a UUID using

//!   `borsh`.

//! * `arbitrary` - adds an `Arbitrary` trait implementation to `Uuid` for

//!   fuzzing.

//! * `fast-rng` - uses a faster algorithm for generating random UUIDs when available.

//!   This feature requires more dependencies to compile, but is just as suitable for

//!   UUIDs as the default algorithm.

//! * `rng-rand` - forces `rand` as the backend for randomness.

//! * `rng-getrandom` - forces `getrandom` as the backend for randomness.

//! * `bytemuck` - adds a `Pod` trait implementation to `Uuid` for byte manipulation

//!

//! # Unstable features

//!

//! Some features are unstable. They may be incomplete or depend on other

//! unstable libraries. These include:

//!

//! * `zerocopy` - adds support for zero-copy deserialization using the

//!   `zerocopy` library.

//!

//! Unstable features may break between minor releases.

//!

//! To allow unstable features, you'll need to enable the Cargo feature as

//! normal, but also pass an additional flag through your environment to opt-in

//! to unstable `uuid` features:

//!

//! ```text

//! RUSTFLAGS="--cfg uuid_unstable"

//! ```

//!

//! # Building for other targets

//!

//! ## WebAssembly

//!

//! For WebAssembly, enable the `js` feature:

//!

//! ```toml

//! [dependencies.uuid]

//! version = "1.29.0"

//! features = [

//!     "v4",

//!     "v7",

//!     "js",

//! ]

//! ```

//!

//! ## Embedded

//!

//! For embedded targets without the standard library, you'll need to

//! disable default features when building `uuid`:

//!

//! ```toml

//! [dependencies.uuid]

//! version = "1.29.0"

//! default-features = false

//! ```

//!

//! Some additional features are supported in no-std environments:

//!

//! * `v1`, `v3`, `v5`, `v6`, and `v8`.

//! * `serde`.

//!

//! If you need to use `v4` or `v7` in a no-std environment, you'll need to

//! produce random bytes yourself and then pass them to [`Builder::from_random_bytes`]

//! without enabling the `v4` or `v7` features.

//!

//! If you're using `getrandom`, you can specify the `rng-getrandom` or `rng-rand`

//! features of `uuid` and configure `getrandom`'s provider per its docs. `uuid`

//! may upgrade its version of `getrandom` in minor releases.

//!

//! # Examples

//!

//! Parse a UUID given in the simple format and print it as a URN:

//!

//! ```

//! # use uuid::Uuid;

//! # fn main() -> Result<(), uuid::Error> {

//! let my_uuid = Uuid::parse_str("a1a2a3a4b1b2c1c2d1d2d3d4d5d6d7d8")?;

//!

//! println!("{}", my_uuid.urn());

//! # Ok(())

//! # }

//! ```

//!

//! Generate a random UUID and print it out in hexadecimal form:

//!

//! ```

//! // Note that this requires the `v4` feature to be enabled.

//! # use uuid::Uuid;

//! # fn main() {

//! # #[cfg(feature = "v4")] {

//! let my_uuid = Uuid::new_v4();

//!

//! println!("{}", my_uuid);

//! # }

//! # }

//! ```

//!

//! # References

//!

//! * [Wikipedia: Universally Unique Identifier](http://en.wikipedia.org/wiki/Universally_unique_identifier)

//! * [RFC 9562: Universally Unique IDentifiers (UUID)](https://www.ietf.org/rfc/rfc9562.html).

//!

//! [`wasm-bindgen`]: https://crates.io/crates/wasm-bindgen

#![cfg_attr(docsrs, feature(doc_cfg))]

#![no_std]

#![deny(missing_debug_implementations, missing_docs)]

#![allow(clippy::mixed_attributes_style)]

#![doc(

    html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",

    html_favicon_url = "https://www.rust-lang.org/favicon.ico",

    html_root_url = "https://docs.rs/uuid/1.29.0"

)]

#[cfg(any(feature = "std", test))]

#[macro_use]

extern crate std;

#[cfg(all(not(feature = "std"), not(test)))]

#[macro_use]

extern crate core as std;

#[macro_use]

mod macros;

mod builder;

mod error;

mod non_nil;

mod parser;

pub mod fmt;

pub mod timestamp;

use core::hash::{Hash, Hasher};

pub use timestamp::{context::NoContext, ClockSequence, Timestamp};

#[cfg(any(feature = "v1", feature = "v6"))]

#[allow(deprecated)]

pub use timestamp::context::Context;

#[cfg(any(feature = "v1", feature = "v6"))]

pub use timestamp::context::ContextV1;

#[cfg(feature = "v7")]

pub use timestamp::context::ContextV7;

#[cfg(feature = "v1")]

#[doc(hidden)]

// Soft-deprecated (Rust doesn't support deprecating re-exports)

// Use `Context` from the crate root instead

pub mod v1;

#[cfg(feature = "v3")]

mod v3;

#[cfg(feature = "v4")]

mod v4;

#[cfg(feature = "v5")]

mod v5;

#[cfg(feature = "v6")]

mod v6;

#[cfg(feature = "v7")]

mod v7;

#[cfg(feature = "v8")]

mod v8;

#[cfg(feature = "md5")]

mod md5;

#[cfg(feature = "rng")]

mod rng;

#[cfg(feature = "sha1")]

mod sha1;

mod external;

#[doc(hidden)]

pub mod __macro_support {

    pub use crate::std::result::Result::{Err, Ok};

}

pub use crate::{builder::Builder, error::Error, non_nil::NonNilUuid};

/// A 128-bit (16 byte) buffer containing the UUID.

///

/// # ABI

///

/// The `Bytes` type is always guaranteed to be have the same ABI as [`Uuid`].

pub type Bytes = [u8; 16];

/// The version of the UUID, denoting the generating algorithm.

///

/// # References

///

/// * [Version Field in RFC 9562](https://www.ietf.org/rfc/rfc9562.html#section-4.2)

#[derive(Clone, Copy, Debug, PartialEq)]

#[non_exhaustive]

#[repr(u8)]

pub enum Version {

    /// The "nil" (all zeros) UUID.

    Nil = 0u8,

    /// Version 1: Timestamp and node ID.

    Mac = 1,

    /// Version 2: DCE Security.

    Dce = 2,

    /// Version 3: MD5 hash.

    Md5 = 3,

    /// Version 4: Random.

    Random = 4,

    /// Version 5: SHA-1 hash.

    Sha1 = 5,

    /// Version 6: Sortable Timestamp and node ID.

    SortMac = 6,

    /// Version 7: Timestamp and random.

    SortRand = 7,

    /// Version 8: Custom.

    Custom = 8,

    /// The "max" (all ones) UUID.

    Max = 0x0f,

}

/// The reserved variants of UUIDs.

///

/// Unlike the version field, which is a strict set of values, the variant

/// behaves more like a mask. Multiple bit patterns in a UUID's variant field may correspond

/// to the same variant value.

///

/// # References

///

/// * [Variant Field in RFC 9562](https://www.ietf.org/rfc/rfc9562.html#section-4.1)

#[derive(Clone, Copy, Debug, PartialEq)]

#[non_exhaustive]

#[repr(u8)]

pub enum Variant {

    /// Reserved by the NCS for backward compatibility.

    ///

    /// The Nil UUID will return this variant.

    NCS = 0u8,

    /// The variant specified in RFC9562.

    ///

    /// The majority of UUIDs use this variant.

    RFC4122,

    /// Reserved by Microsoft for backward compatibility.

    Microsoft,

    /// Reserved for future expansion.

    ///

    /// The Max UUID will return this variant.

    Future,

}

/// A Universally Unique Identifier (UUID).

///

/// # Examples

///

/// Parse a UUID given in the simple format and print it as a urn:

///

/// ```

/// # use uuid::Uuid;

/// # fn main() -> Result<(), uuid::Error> {

/// let my_uuid = Uuid::parse_str("a1a2a3a4b1b2c1c2d1d2d3d4d5d6d7d8")?;

///

/// println!("{}", my_uuid.urn());

/// # Ok(())

/// # }

/// ```

///

/// Create a new random (V4) UUID and print it out in hexadecimal form:

///

/// ```

/// // Note that this requires the `v4` feature enabled in the uuid crate.

/// # use uuid::Uuid;

/// # fn main() {

/// # #[cfg(feature = "v4")] {

/// let my_uuid = Uuid::new_v4();

///

/// println!("{}", my_uuid);

/// # }

/// # }

/// ```

///

/// # Formatting

///

/// A UUID can be formatted in one of a few ways:

///

/// * [`simple`](#method.simple): `a1a2a3a4b1b2c1c2d1d2d3d4d5d6d7d8`.

/// * [`hyphenated`](#method.hyphenated):

///   `a1a2a3a4-b1b2-c1c2-d1d2-d3d4d5d6d7d8`.

/// * [`urn`](#method.urn): `urn:uuid:A1A2A3A4-B1B2-C1C2-D1D2-D3D4D5D6D7D8`.

/// * [`braced`](#method.braced): `{a1a2a3a4-b1b2-c1c2-d1d2-d3d4d5d6d7d8}`.

///

/// The default representation when formatting a UUID with `Display` is

/// hyphenated:

///

/// ```

/// # use uuid::Uuid;

/// # fn main() -> Result<(), uuid::Error> {

/// let my_uuid = Uuid::parse_str("a1a2a3a4b1b2c1c2d1d2d3d4d5d6d7d8")?;

///

/// assert_eq!(

///     "a1a2a3a4-b1b2-c1c2-d1d2-d3d4d5d6d7d8",

///     my_uuid.to_string(),

/// );

/// # Ok(())

/// # }

/// ```

///

/// Other formats can be specified using adapter methods on the UUID:

///

/// ```

/// # use uuid::Uuid;

/// # fn main() -> Result<(), uuid::Error> {

/// let my_uuid = Uuid::parse_str("a1a2a3a4b1b2c1c2d1d2d3d4d5d6d7d8")?;

///

/// assert_eq!(

///     "urn:uuid:a1a2a3a4-b1b2-c1c2-d1d2-d3d4d5d6d7d8",

///     my_uuid.urn().to_string(),

/// );

/// # Ok(())

/// # }

/// ```

///

/// # Endianness

///

/// The specification for UUIDs encodes the integer fields that make up the

/// value in big-endian order. This crate assumes integer inputs are already in

/// the correct order by default, regardless of the endianness of the

/// environment. Most methods that accept integers have a `_le` variant (such as

/// `from_fields_le`) that assumes any integer values will need to have their

/// bytes flipped, regardless of the endianness of the environment.

///

/// Most users won't need to worry about endianness unless they need to operate

/// on individual fields (such as when converting between Microsoft GUIDs). The

/// important things to remember are:

///

/// - The endianness is in terms of the fields of the UUID, not the environment.

/// - The endianness is assumed to be big-endian when there's no `_le` suffix

///   somewhere.

/// - Byte-flipping in `_le` methods applies to each integer.

/// - Endianness roundtrips, so if you create a UUID with `from_fields_le`

///   you'll get the same values back out with `to_fields_le`.

///

/// # ABI

///

/// The `Uuid` type is always guaranteed to be have the same ABI as [`Bytes`].

#[derive(Clone, Copy, Eq, Ord, PartialEq, PartialOrd)]

#[repr(transparent)]

// NOTE: Also check `NonNilUuid` when ading new derives here

#[cfg_attr(

    feature = "borsh",

    derive(borsh_derive::BorshDeserialize, borsh_derive::BorshSerialize)

)]

#[cfg_attr(

    feature = "bytemuck",

    derive(bytemuck::Zeroable, bytemuck::Pod, bytemuck::TransparentWrapper)

)]

#[cfg_attr(

    all(uuid_unstable, feature = "zerocopy"),

    derive(

        zerocopy::IntoBytes,

        zerocopy::FromBytes,

        zerocopy::KnownLayout,

        zerocopy::Immutable,

        zerocopy::Unaligned

    )

)]

pub struct Uuid(Bytes);

impl Uuid {

    /// UUID namespace for Domain Name System (DNS).

    pub const NAMESPACE_DNS: Self = Uuid([

        0x6b, 0xa7, 0xb8, 0x10, 0x9d, 0xad, 0x11, 0xd1, 0x80, 0xb4, 0x00, 0xc0, 0x4f, 0xd4, 0x30,

        0xc8,

    ]);

    /// UUID namespace for ISO Object Identifiers (OIDs).

    pub const NAMESPACE_OID: Self = Uuid([

        0x6b, 0xa7, 0xb8, 0x12, 0x9d, 0xad, 0x11, 0xd1, 0x80, 0xb4, 0x00, 0xc0, 0x4f, 0xd4, 0x30,

        0xc8,

    ]);

    /// UUID namespace for Uniform Resource Locators (URLs).

    pub const NAMESPACE_URL: Self = Uuid([

        0x6b, 0xa7, 0xb8, 0x11, 0x9d, 0xad, 0x11, 0xd1, 0x80, 0xb4, 0x00, 0xc0, 0x4f, 0xd4, 0x30,

        0xc8,

    ]);

    /// UUID namespace for X.500 Distinguished Names (DNs).

    pub const NAMESPACE_X500: Self = Uuid([

        0x6b, 0xa7, 0xb8, 0x14, 0x9d, 0xad, 0x11, 0xd1, 0x80, 0xb4, 0x00, 0xc0, 0x4f, 0xd4, 0x30,

        0xc8,

    ]);

    /// Returns the variant of the UUID structure.

    ///

    /// This determines the interpretation of the structure of the UUID.

    /// This method simply reads the value of the variant byte. It doesn't

    /// validate the rest of the UUID as conforming to that variant.

    ///

    /// # Examples

    ///

    /// Basic usage:

    ///

    /// ```

    /// # use uuid::{Uuid, Variant};

    /// # fn main() -> Result<(), uuid::Error> {

    /// let my_uuid = Uuid::parse_str("02f09a3f-1624-3b1d-8409-44eff7708208")?;

    ///

    /// assert_eq!(Variant::RFC4122, my_uuid.get_variant());

    /// # Ok(())

    /// # }

    /// ```

    ///

    /// # References

    ///

    /// * [Variant Field in RFC 9562](https://www.ietf.org/rfc/rfc9562.html#section-4.1)

    pub const fn get_variant(&self) -> Variant {

        match self.as_bytes()[8] {

            x if x & 0x80 == 0x00 => Variant::NCS,

            x if x & 0xc0 == 0x80 => Variant::RFC4122,

            x if x & 0xe0 == 0xc0 => Variant::Microsoft,

            x if x & 0xe0 == 0xe0 => Variant::Future,

            // The above match arms are actually exhaustive

            // We just return `Future` here because we can't

            // use `unreachable!()` in a `const fn`

            _ => Variant::Future,

        }

    }

    /// Returns the version number of the UUID.

    ///

    /// This represents the algorithm used to generate the value.

    /// This method is the future-proof alternative to [`Uuid::get_version`].

    ///

    /// # Examples

    ///

    /// Basic usage:

    ///

    /// ```

    /// # use uuid::Uuid;

    /// # fn main() -> Result<(), uuid::Error> {

    /// let my_uuid = Uuid::parse_str("02f09a3f-1624-3b1d-8409-44eff7708208")?;

    ///

    /// assert_eq!(3, my_uuid.get_version_num());

    /// # Ok(())

    /// # }

    /// ```

    ///

    /// # References

    ///

    /// * [Version Field in RFC 9562](https://www.ietf.org/rfc/rfc9562.html#section-4.2)

    pub const fn get_version_num(&self) -> usize {

        (self.as_bytes()[6] >> 4) as usize

    }

    /// Returns the version of the UUID.

    ///

    /// This represents the algorithm used to generate the value.

    /// If the version field doesn't contain a recognized version then `None`

    /// is returned. If you're trying to read the version for a future extension

    /// you can also use [`Uuid::get_version_num`] to unconditionally return a

    /// number. Future extensions may start to return `Some` once they're

    /// standardized and supported.

    ///

    /// # Examples

    ///

    /// Basic usage:

    ///

    /// ```

    /// # use uuid::{Uuid, Version};

    /// # fn main() -> Result<(), uuid::Error> {

    /// let my_uuid = Uuid::parse_str("02f09a3f-1624-3b1d-8409-44eff7708208")?;

    ///

    /// assert_eq!(Some(Version::Md5), my_uuid.get_version());

    /// # Ok(())

    /// # }

    /// ```

    ///

    /// # References

    ///

    /// * [Version Field in RFC 9562](https://www.ietf.org/rfc/rfc9562.html#section-4.2)

    pub const fn get_version(&self) -> Option<Version> {

        match self.get_version_num() {

            0 if self.is_nil() => Some(Version::Nil),

            1 => Some(Version::Mac),

            2 => Some(Version::Dce),

            3 => Some(Version::Md5),

            4 => Some(Version::Random),

            5 => Some(Version::Sha1),

            6 => Some(Version::SortMac),

            7 => Some(Version::SortRand),

            8 => Some(Version::Custom),

            0xf if self.is_max() => Some(Version::Max),

            _ => None,

        }

    }

    /// Returns the four field values of the UUID.

    ///

    /// These values can be passed to the [`Uuid::from_fields`] method to get

    /// the original `Uuid` back.

    ///

    /// * The first field value represents the first group of (eight) hex

    ///   digits, taken as a big-endian `u32` value.  For V1 UUIDs, this field

    ///   represents the low 32 bits of the timestamp.

    /// * The second field value represents the second group of (four) hex

    ///   digits, taken as a big-endian `u16` value.  For V1 UUIDs, this field

    ///   represents the middle 16 bits of the timestamp.

    /// * The third field value represents the third group of (four) hex digits,

    ///   taken as a big-endian `u16` value.  The 4 most significant bits give

    ///   the UUID version, and for V1 UUIDs, the last 12 bits represent the

    ///   high 12 bits of the timestamp.

    /// * The last field value represents the last two groups of four and twelve

    ///   hex digits, taken in order.  The first 1-3 bits of this indicate the

    ///   UUID variant, and for V1 UUIDs, the next 13-15 bits indicate the clock

    ///   sequence and the last 48 bits indicate the node ID.

    ///

    /// # Examples

    ///

    /// ```

    /// # use uuid::Uuid;

    /// # fn main() -> Result<(), uuid::Error> {

    /// let uuid = Uuid::nil();

    ///

    /// assert_eq!(uuid.as_fields(), (0, 0, 0, &[0u8; 8]));

    ///

    /// let uuid = Uuid::parse_str("a1a2a3a4-b1b2-c1c2-d1d2-d3d4d5d6d7d8")?;

    ///

    /// assert_eq!(

    ///     uuid.as_fields(),

    ///     (

    ///         0xa1a2a3a4,

    ///         0xb1b2,

    ///         0xc1c2,

    ///         &[0xd1, 0xd2, 0xd3, 0xd4, 0xd5, 0xd6, 0xd7, 0xd8],

    ///     )

    /// );

    /// # Ok(())

    /// # }

    /// ```

    pub fn as_fields(&self) -> (u32, u16, u16, &[u8; 8]) {

        let bytes = self.as_bytes();

        let d1 = (bytes[0] as u32) << 24

            | (bytes[1] as u32) << 16

            | (bytes[2] as u32) << 8

            | (bytes[3] as u32);

        let d2 = (bytes[4] as u16) << 8 | (bytes[5] as u16);

        let d3 = (bytes[6] as u16) << 8 | (bytes[7] as u16);

        let d4: &[u8; 8] = bytes[8..16].try_into().unwrap();

        (d1, d2, d3, d4)

    }

    /// Returns the four field values of the UUID in little-endian order.

    ///

    /// The bytes in the returned integer fields will be converted from

    /// big-endian order. This is based on the endianness of the UUID,

    /// rather than the target environment so bytes will be flipped on both

    /// big and little endian machines.

    ///

    /// # Examples

    ///

    /// ```

    /// use uuid::Uuid;

    ///

    /// # fn main() -> Result<(), uuid::Error> {

    /// let uuid = Uuid::parse_str("a1a2a3a4-b1b2-c1c2-d1d2-d3d4d5d6d7d8")?;

    ///

    /// assert_eq!(

    ///     uuid.to_fields_le(),

    ///     (

    ///         0xa4a3a2a1,

    ///         0xb2b1,

    ///         0xc2c1,

    ///         &[0xd1, 0xd2, 0xd3, 0xd4, 0xd5, 0xd6, 0xd7, 0xd8],

    ///     )

    /// );

    /// # Ok(())

    /// # }

    /// ```

    pub fn to_fields_le(&self) -> (u32, u16, u16, &[u8; 8]) {

        let d1 = (self.as_bytes()[0] as u32)

            | (self.as_bytes()[1] as u32) << 8

            | (self.as_bytes()[2] as u32) << 16

            | (self.as_bytes()[3] as u32) << 24;

        let d2 = (self.as_bytes()[4] as u16) | (self.as_bytes()[5] as u16) << 8;

        let d3 = (self.as_bytes()[6] as u16) | (self.as_bytes()[7] as u16) << 8;

        let d4: &[u8; 8] = self.as_bytes()[8..16].try_into().unwrap();

        (d1, d2, d3, d4)

    }

    /// Returns a 128bit value containing the value.

    ///

    /// The bytes in the UUID will be packed directly into a `u128`.

    ///

    /// # Examples

    ///

    /// ```

    /// # use uuid::Uuid;

    /// # fn main() -> Result<(), uuid::Error> {

    /// let uuid = Uuid::parse_str("a1a2a3a4-b1b2-c1c2-d1d2-d3d4d5d6d7d8")?;

    ///

    /// assert_eq!(

    ///     uuid.as_u128(),

    ///     0xa1a2a3a4b1b2c1c2d1d2d3d4d5d6d7d8,

    /// );

    /// # Ok(())

    /// # }

    /// ```

    pub const fn as_u128(&self) -> u128 {

        u128::from_be_bytes(*self.as_bytes())

    }

    /// Returns a 128bit little-endian value containing the value.

    ///

    /// The bytes in the `u128` will be flipped to convert into big-endian

    /// order. This is based on the endianness of the UUID, rather than the

    /// target environment so bytes will be flipped on both big and little

    /// endian machines.

    ///

    /// Note that this will produce a different result than

    /// [`Uuid::to_fields_le`], because the entire UUID is reversed, rather

    /// than reversing the individual fields in-place.

    ///

    /// # Examples

    ///

    /// ```

    /// # use uuid::Uuid;

    /// # fn main() -> Result<(), uuid::Error> {

    /// let uuid = Uuid::parse_str("a1a2a3a4-b1b2-c1c2-d1d2-d3d4d5d6d7d8")?;

    ///

    /// assert_eq!(

    ///     uuid.to_u128_le(),

    ///     0xd8d7d6d5d4d3d2d1c2c1b2b1a4a3a2a1,

    /// );

    /// # Ok(())

    /// # }

    /// ```

    pub const fn to_u128_le(&self) -> u128 {

        u128::from_le_bytes(*self.as_bytes())

    }

    /// Returns two 64bit values containing the value.

    ///

    /// The bytes in the UUID will be split into two `u64`.

    /// The first u64 represents the 64 most significant bits,

    /// the second one represents the 64 least significant.

    ///

    /// # Examples

    ///

    /// ```

    /// # use uuid::Uuid;

    /// # fn main() -> Result<(), uuid::Error> {

    /// let uuid = Uuid::parse_str("a1a2a3a4-b1b2-c1c2-d1d2-d3d4d5d6d7d8")?;

    /// assert_eq!(

    ///     uuid.as_u64_pair(),

    ///     (0xa1a2a3a4b1b2c1c2, 0xd1d2d3d4d5d6d7d8),

    /// );

    /// # Ok(())

    /// # }

    /// ```

    pub const fn as_u64_pair(&self) -> (u64, u64) {

        let value = self.as_u128();

        ((value >> 64) as u64, value as u64)

    }

    /// Returns a slice of 16 octets containing the value.

    ///

    /// This method borrows the underlying byte value of the UUID.

    ///

    /// # Examples

    ///

    /// ```

    /// # use uuid::Uuid;

    /// let bytes1 = [

    ///     0xa1, 0xa2, 0xa3, 0xa4,

    ///     0xb1, 0xb2,

    ///     0xc1, 0xc2,

    ///     0xd1, 0xd2, 0xd3, 0xd4, 0xd5, 0xd6, 0xd7, 0xd8,

    /// ];

    /// let uuid1 = Uuid::from_bytes_ref(&bytes1);

    ///

    /// let bytes2 = uuid1.as_bytes();

    /// let uuid2 = Uuid::from_bytes_ref(bytes2);

    ///

    /// assert_eq!(uuid1, uuid2);

    ///

    /// assert!(std::ptr::eq(

    ///     uuid2 as *const Uuid as *const u8,

    ///     &bytes1 as *const [u8; 16] as *const u8,

    /// ));

    /// ```

    #[inline]

    pub const fn as_bytes(&self) -> &Bytes {

        &self.0

    }

    /// Consumes self and returns the underlying byte value of the UUID.

    ///

    /// # Examples

    ///

    /// ```

    /// # use uuid::Uuid;

    /// let bytes = [

    ///     0xa1, 0xa2, 0xa3, 0xa4,

    ///     0xb1, 0xb2,

    ///     0xc1, 0xc2,

    ///     0xd1, 0xd2, 0xd3, 0xd4, 0xd5, 0xd6, 0xd7, 0xd8,

    /// ];

    /// let uuid = Uuid::from_bytes(bytes);

    /// assert_eq!(bytes, uuid.into_bytes());

    /// ```

    #[inline]

    pub const fn into_bytes(self) -> Bytes {

        self.0

    }

    /// Returns the bytes of the UUID in little-endian order.

    ///

    /// The bytes for each field will be flipped to convert into little-endian order.

    /// This is based on the endianness of the UUID, rather than the target environment

    /// so bytes will be flipped on both big and little endian machines.

    ///

    /// Note that ordering is applied to each _field_, rather than to the bytes as a whole.

    /// This ordering is compatible with Microsoft's mixed endian GUID format.

    ///

    /// # Examples

    ///

    /// ```

    /// use uuid::Uuid;

    ///

    /// # fn main() -> Result<(), uuid::Error> {

    /// let uuid = Uuid::parse_str("a1a2a3a4-b1b2-c1c2-d1d2-d3d4d5d6d7d8")?;

    ///

    /// assert_eq!(

    ///     uuid.to_bytes_le(),

    ///     ([

    ///         0xa4, 0xa3, 0xa2, 0xa1, 0xb2, 0xb1, 0xc2, 0xc1, 0xd1, 0xd2,

    ///         0xd3, 0xd4, 0xd5, 0xd6, 0xd7, 0xd8

    ///     ])

    /// );

    /// # Ok(())

    /// # }

    /// ```

    pub const fn to_bytes_le(&self) -> Bytes {

        [

            self.0[3], self.0[2], self.0[1], self.0[0], self.0[5], self.0[4], self.0[7], self.0[6],

            self.0[8], self.0[9], self.0[10], self.0[11], self.0[12], self.0[13], self.0[14],

            self.0[15],

        ]

    }

    /// Tests if the UUID is nil (all zeros).

    pub const fn is_nil(&self) -> bool {

        self.as_u128() == u128::MIN

    }

    /// Tests if the UUID is max (all ones).

    pub const fn is_max(&self) -> bool {

        self.as_u128() == u128::MAX

    }

    /// A buffer that can be used for `encode_...` calls, that is

    /// guaranteed to be long enough for any of the format adapters.

    ///

    /// # Examples

    ///

    /// ```

    /// # use uuid::Uuid;

    /// let uuid = Uuid::nil();

    ///

    /// assert_eq!(

    ///     uuid.simple().encode_lower(&mut Uuid::encode_buffer()),

    ///     "00000000000000000000000000000000"

    /// );

    ///

    /// assert_eq!(

    ///     uuid.hyphenated()

    ///         .encode_lower(&mut Uuid::encode_buffer()),

    ///     "00000000-0000-0000-0000-000000000000"

    /// );

    ///

    /// assert_eq!(

    ///     uuid.urn().encode_lower(&mut Uuid::encode_buffer()),

    ///     "urn:uuid:00000000-0000-0000-0000-000000000000"

    /// );

    /// ```

    pub const fn encode_buffer() -> [u8; fmt::Urn::LENGTH] {

        [0; fmt::Urn::LENGTH]

    }

    /// If the UUID is the correct version (v1, v6, or v7) this will return

    /// the timestamp in a version-agnostic [`Timestamp`]. For other versions

    /// this will return `None`.

    ///

    /// # Roundtripping

    ///

    /// This method is unlikely to roundtrip a timestamp in a UUID due to the way

    /// UUIDs encode timestamps. The timestamp returned from this method will be truncated to

    /// 100ns precision for version 1 and 6 UUIDs, and to millisecond precision for version 7 UUIDs.

    pub const fn get_timestamp(&self) -> Option<Timestamp> {

        match self.get_version() {

            Some(Version::Mac) => {

                let (ticks, counter) = timestamp::decode_gregorian_timestamp(self);

                Some(Timestamp::from_gregorian_time(ticks, counter))

            }

            Some(Version::SortMac) => {

                let (ticks, counter) = timestamp::decode_sorted_gregorian_timestamp(self);

                Some(Timestamp::from_gregorian_time(ticks, counter))

            }

            Some(Version::SortRand) => {

                let millis = timestamp::decode_unix_timestamp_millis(self);

                let seconds = millis / 1000;

                let nanos = ((millis % 1000) * 1_000_000) as u32;

                Some(Timestamp::from_unix_time(seconds, nanos, 0, 0))

            }

            _ => None,

        }

    }

    /// If the UUID is the correct version (v1, or v6) this will return the

    /// node value as a 6-byte array. For other versions this will return `None`.

    pub const fn get_node_id(&self) -> Option<[u8; 6]> {

        match self.get_version() {

            Some(Version::Mac) | Some(Version::SortMac) => {

                let mut node_id = [0; 6];

                node_id[0] = self.0[10];

                node_id[1] = self.0[11];

                node_id[2] = self.0[12];

                node_id[3] = self.0[13];

                node_id[4] = self.0[14];

                node_id[5] = self.0[15];

                Some(node_id)

            }

            _ => None,

        }

    }

}

impl Hash for Uuid {

    fn hash<H: Hasher>(&self, state: &mut H) {

        state.write(&self.0);

    }

}

impl Default for Uuid {

    #[inline]

    fn default() -> Self {

        Uuid::nil()

    }

}

impl AsRef<Uuid> for Uuid {

    #[inline]

    fn as_ref(&self) -> &Uuid {

        self

    }

}

impl AsRef<[u8]> for Uuid {

    #[inline]

    fn as_ref(&self) -> &[u8] {

        &self.0

    }

}

#[cfg(feature = "std")]

impl From<Uuid> for std::vec::Vec<u8> {

    fn from(value: Uuid) -> Self {

        value.0.to_vec()

    }

}

#[cfg(feature = "std")]

impl TryFrom<std::vec::Vec<u8>> for Uuid {

    type Error = Error;

    fn try_from(value: std::vec::Vec<u8>) -> Result<Self, Self::Error> {

        Uuid::from_slice(&value)

    }

}

#[cfg(feature = "serde")]

pub mod serde {

    //! Adapters for alternative `serde` formats.

    //!

    //! This module contains adapters you can use with [`#[serde(with)]`](https://serde.rs/field-attrs.html#with)

    //! to change the way a [`Uuid`](../struct.Uuid.html) is serialized

    //! and deserialized.

    pub use crate::external::serde_support::{braced, bytes, compact, hyphenated, simple, urn};

}

#[cfg(test)]

mod tests {

    use super::*;

    use crate::std::string::{String, ToString};

    #[cfg(all(target_arch = "wasm32", any(target_os = "unknown", target_os = "none")))]

    use wasm_bindgen_test::*;

    macro_rules! check {

        ($buf:ident, $format:expr, $target:expr, $len:expr, $cond:expr) => {

            $buf.clear();

            write!($buf, $format, $target).unwrap();

            assert!($buf.len() == $len);

            assert!($buf.chars().all($cond), "{}", $buf);

            assert_eq!(Uuid::parse_str(&$buf).unwrap(), $target);

        };

    }

    pub fn some_uuid_nil() -> Uuid {

        Uuid::parse_str("00000000-0000-0000-0000-000000000000").unwrap()

    }

    pub fn some_uuid_v1() -> Uuid {

        Uuid::parse_str("20616934-4ba2-11e7-8000-010203040506").unwrap()

    }

    pub fn some_uuid_v3() -> Uuid {

        Uuid::parse_str("bcee7a9c-52f1-30c6-a3cc-8c72ba634990").unwrap()

    }

    pub fn some_uuid_v4() -> Uuid {

        Uuid::parse_str("67e55044-10b1-426f-9247-bb680e5fe0c8").unwrap()

    }

    pub fn some_uuid_v4_2() -> Uuid {

        Uuid::parse_str("c0dd0820-b35a-4c56-bc7d-0f0b04241adb").unwrap()

    }

    pub fn some_uuid_v5() -> Uuid {

        Uuid::parse_str("b11f79a5-1e6d-57ce-a4b5-ba8531ea03d0").unwrap()

    }

    pub fn some_uuid_v6() -> Uuid {

        Uuid::parse_str("1e74ba22-0616-6934-8000-010203040506").unwrap()

    }

    pub fn some_uuid_v7() -> Uuid {

        Uuid::parse_str("015c837b-9e84-7db5-b059-c75a84585688").unwrap()

    }

    pub fn some_uuid_v8() -> Uuid {

        Uuid::parse_str("0f0e0d0c-0b0a-8908-8706-050403020100").unwrap()

    }

    pub fn some_uuid_max() -> Uuid {

        Uuid::parse_str("ffffffff-ffff-ffff-ffff-ffffffffffff").unwrap()

    }

    pub fn some_uuid_iter() -> impl Iterator<Item = Uuid> {

        [

            some_uuid_nil(),

            some_uuid_v1(),

            some_uuid_v3(),

            some_uuid_v4(),

            some_uuid_v5(),

            some_uuid_v6(),

            some_uuid_v7(),

            some_uuid_v8(),

            some_uuid_max(),

        ]

        .into_iter()

    }

    pub fn some_uuid_v_iter() -> impl Iterator<Item = Uuid> {

        [

            some_uuid_v1(),

            some_uuid_v3(),

            some_uuid_v4(),

            some_uuid_v5(),

            some_uuid_v6(),

            some_uuid_v7(),

            some_uuid_v8(),

        ]