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use bytes::Bytes;
use serde::{Deserialize, Serialize};
use std::fmt;
use std::ops::Deref;
use std::str::{from_utf8, Utf8Error};
/// A `Subject` is an immutable string type that guarantees valid UTF-8 contents.
#[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
pub struct Subject {
bytes: Bytes,
}
impl Subject {
/// Creates a new `Subject` from a static string.
///
/// # Examples
///
/// ```
/// use async_nats::Subject;
///
/// let subject = Subject::from_static("Static string");
/// assert_eq!(subject.as_str(), "Static string");
/// ```
pub const fn from_static(input: &'static str) -> Self {
Subject {
bytes: Bytes::from_static(input.as_bytes()),
}
}
/// Creates a new `Subject` from a UTF-8 encoded byte vector.
///
/// Returns an error if the input is not valid UTF-8.
///
/// # Examples
///
/// ```
/// use async_nats::Subject;
///
/// let utf8_input = vec![72, 101, 108, 108, 111]; // "Hello" in UTF-8
/// let subject = Subject::from_utf8(utf8_input).unwrap();
/// assert_eq!(subject.as_ref(), "Hello");
/// ```
pub fn from_utf8<T>(input: T) -> Result<Self, Utf8Error>
where
T: Into<Bytes>,
{
let bytes = input.into();
from_utf8(bytes.as_ref())?;
Ok(Subject { bytes })
}
/// Extracts a string slice containing the entire `Subject`.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// use async_nats::Subject;
///
/// let s = Subject::from("foo");
/// assert_eq!("foo", s.as_str());
/// ```
#[inline]
pub fn as_str(&self) -> &str {
self
}
/// Turns the `Subject` into a `String`, consuming it.
///
/// Note that this function is not implemented as `From<Subject> for String` as the conversion
/// from the underlying type could involve an allocation. If the `Subject` is owned data, it
/// will not allocate, but if it was constructed from borrowed data, it will.
///
/// # Examples
///
/// ```
/// use async_nats::Subject;
///
/// let s = Subject::from("foo");
/// let sub = s.into_string();
/// ```
pub fn into_string(self) -> String {
// SAFETY: We have guaranteed that the bytes in the `Subject` struct are valid UTF-8.
unsafe { String::from_utf8_unchecked(self.bytes.into()) }
}
}
impl<'a> From<&'a str> for Subject {
fn from(s: &'a str) -> Self {
// Since &str is guaranteed to be valid UTF-8, we can create the Subject instance by copying the contents of the &str
Subject {
bytes: Bytes::copy_from_slice(s.as_bytes()),
}
}
}
impl From<String> for Subject {
fn from(s: String) -> Self {
// Since the input `String` is guaranteed to be valid UTF-8, we can
// safely transmute the internal Vec<u8> to a Bytes value.
let bytes = Bytes::from(s.into_bytes());
Subject { bytes }
}
}
impl AsRef<str> for Subject {
fn as_ref(&self) -> &str {
self
}
}
impl Deref for Subject {
type Target = str;
fn deref(&self) -> &Self::Target {
// SAFETY: It is safe to perform an unchecked conversion from bytes to a string slice
// here because we guarantee that the bytes in the `Subject` struct are valid UTF-8.
// This is enforced during the construction of `Subject` through the `from_static`,
// and `from_utf8` methods. In both cases, the input is either checked for UTF-8 validity or
// known to be valid UTF-8 as a static string.
unsafe { std::str::from_utf8_unchecked(&self.bytes) }
}
}
impl fmt::Display for Subject {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
write!(f, "{}", self.as_str())
}
}
pub trait ToSubject {
fn to_subject(&self) -> Subject;
}
impl ToSubject for Subject {
fn to_subject(&self) -> Subject {
self.to_owned()
}
}
impl ToSubject for &'static str {
fn to_subject(&self) -> Subject {
Subject::from_static(self)
}
}
impl ToSubject for String {
fn to_subject(&self) -> Subject {
Subject::from(self.as_str())
}
}
impl Serialize for Subject {
fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
where
S: serde::Serializer,
{
serializer.serialize_str(self.as_str())
}
}
impl<'de> Deserialize<'de> for Subject {
fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
where
D: serde::Deserializer<'de>,
{
Ok(String::deserialize(deserializer)?.into())
}
}