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use std::{
borrow::{Borrow, Cow},
fmt,
string::String as StdString,
};
use crate::{error, Error};
/// An owned structured field value [string].
///
/// Strings may only contain printable ASCII characters (i.e. the range
/// `0x20 ..= 0x7e`).
///
#[derive(Clone, Debug, Default, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct String(StdString);
/// A borrowed structured field value [string].
///
/// Strings may only contain printable ASCII characters (i.e. the range
/// `0x20 ..= 0x7e`).
///
/// This type is to [`String`] as [`str`] is to [`std::string::String`].
///
#[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Hash, ref_cast::RefCastCustom)]
#[repr(transparent)]
pub struct StringRef(str);
struct StringError {
byte_index: usize,
}
impl From<StringError> for Error {
fn from(err: StringError) -> Self {
error::Repr::InvalidCharacter(err.byte_index).into()
}
}
const fn validate(v: &[u8]) -> Result<(), StringError> {
let mut index = 0;
while index < v.len() {
if v[index] < 0x20 || v[index] > 0x7e {
return Err(StringError { byte_index: index });
}
index += 1;
}
Ok(())
}
impl StringRef {
/// An empty `&StringRef`.
pub const EMPTY: &Self = Self::cast("");
#[ref_cast::ref_cast_custom]
const fn cast(v: &str) -> &Self;
/// Creates a `&StringRef` from a `&str`.
///
/// # Errors
/// The error reports the cause of any failed string validation.
#[allow(clippy::should_implement_trait)]
pub fn from_str(v: &str) -> Result<&Self, Error> {
validate(v.as_bytes())?;
Ok(Self::cast(v))
}
/// Creates a `&StringRef`, panicking if the value is invalid.
///
/// This method is intended to be called from `const` contexts in which the
/// value is known to be valid. Use [`StringRef::from_str`] for non-panicking
/// conversions.
#[must_use]
pub const fn constant(v: &str) -> &Self {
match validate(v.as_bytes()) {
Ok(()) => Self::cast(v),
Err(_) => panic!("invalid character for string"),
}
}
/// Returns the string as a `&str`.
#[must_use]
pub fn as_str(&self) -> &str {
&self.0
}
}
impl ToOwned for StringRef {
type Owned = String;
fn to_owned(&self) -> String {
String(self.0.to_owned())
}
fn clone_into(&self, target: &mut String) {
self.0.clone_into(&mut target.0);
}
}
impl Borrow<StringRef> for String {
fn borrow(&self) -> &StringRef {
self
}
}
impl std::ops::Deref for String {
type Target = StringRef;
fn deref(&self) -> &StringRef {
StringRef::cast(&self.0)
}
}
impl From<String> for StdString {
fn from(v: String) -> StdString {
v.0
}
}
impl TryFrom<StdString> for String {
type Error = Error;
fn try_from(v: StdString) -> Result<String, Error> {
validate(v.as_bytes())?;
Ok(String(v))
}
}
impl String {
/// Creates a `String` from a `std::string::String`.
///
/// Returns the original value if the conversion failed.
///
/// # Errors
/// The error reports any problems from failed validation.
pub fn from_string(v: StdString) -> Result<Self, (Error, StdString)> {
match validate(v.as_bytes()) {
Ok(()) => Ok(Self(v)),
Err(err) => Err((err.into(), v)),
}
}
}
/// Creates a `&StringRef`, panicking if the value is invalid.
///
/// This is a convenience free function for [`StringRef::constant`].
///
/// This method is intended to be called from `const` contexts in which the
/// value is known to be valid. Use [`StringRef::from_str`] for non-panicking
/// conversions.
#[must_use]
pub const fn string_ref(v: &str) -> &StringRef {
StringRef::constant(v)
}
impl fmt::Display for StringRef {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
fmt::Display::fmt(self.as_str(), f)
}
}
impl fmt::Display for String {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
<StringRef as fmt::Display>::fmt(self, f)
}
}
macro_rules! impl_eq {
($a: ty, $b: ty) => {
impl PartialEq<$a> for $b {
fn eq(&self, other: &$a) -> bool {
<StringRef as PartialEq>::eq(self, other)
}
}
impl PartialEq<$b> for $a {
fn eq(&self, other: &$b) -> bool {
<StringRef as PartialEq>::eq(self, other)
}
}
};
}
impl_eq!(String, StringRef);
impl_eq!(String, &StringRef);
impl_eq!(Cow<'_, StringRef>, StringRef);
impl_eq!(Cow<'_, StringRef>, &StringRef);
impl<'a> TryFrom<&'a str> for &'a StringRef {
type Error = Error;
fn try_from(v: &'a str) -> Result<&'a StringRef, Error> {
StringRef::from_str(v)
}
}
impl Borrow<str> for String {
fn borrow(&self) -> &str {
self.as_str()
}
}
impl Borrow<str> for StringRef {
fn borrow(&self) -> &str {
self.as_str()
}
}
#[cfg(feature = "arbitrary")]
impl<'a> arbitrary::Arbitrary<'a> for &'a StringRef {
fn arbitrary(u: &mut arbitrary::Unstructured<'a>) -> arbitrary::Result<Self> {
StringRef::from_str(<&str>::arbitrary(u)?).map_err(|_| arbitrary::Error::IncorrectFormat)
}
}
#[cfg(feature = "arbitrary")]
impl<'a> arbitrary::Arbitrary<'a> for String {
fn arbitrary(u: &mut arbitrary::Unstructured<'a>) -> arbitrary::Result<Self> {
<&StringRef>::arbitrary(u).map(ToOwned::to_owned)
}
}
impl Default for &StringRef {
fn default() -> Self {
StringRef::EMPTY
}
}