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//! Structured keys.
use std::borrow::Borrow;
use std::fmt;
/// A type that can be converted into a [`Key`](struct.Key.html).
pub trait ToKey {
/// Perform the conversion.
fn to_key(&self) -> Key;
}
impl<'a, T> ToKey for &'a T
where
T: ToKey + ?Sized,
{
fn to_key(&self) -> Key {
(**self).to_key()
}
}
impl<'k> ToKey for Key<'k> {
fn to_key(&self) -> Key {
Key { key: self.key }
}
}
impl ToKey for str {
fn to_key(&self) -> Key {
Key::from_str(self)
}
}
/// A key in a structured key-value pair.
// These impls must only be based on the as_str() representation of the key
// If a new field (such as an optional index) is added to the key they must not affect comparison
#[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct Key<'k> {
key: &'k str,
}
impl<'k> Key<'k> {
/// Get a key from a borrowed string.
pub fn from_str(key: &'k str) -> Self {
Key { key }
}
/// Get a borrowed string from this key.
pub fn as_str(&self) -> &str {
self.key
}
/// Try get a string borrowed for the `'k` lifetime from this key.
pub fn to_borrowed_str(&self) -> Option<&'k str> {
// NOTE: This API leaves room for keys to be owned
Some(self.key)
}
}
impl<'k> fmt::Display for Key<'k> {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
self.key.fmt(f)
}
}
impl<'k> AsRef<str> for Key<'k> {
fn as_ref(&self) -> &str {
self.as_str()
}
}
impl<'k> Borrow<str> for Key<'k> {
fn borrow(&self) -> &str {
self.as_str()
}
}
impl<'k> From<&'k str> for Key<'k> {
fn from(s: &'k str) -> Self {
Key::from_str(s)
}
}
#[cfg(feature = "std")]
mod std_support {
use super::*;
use std::borrow::Cow;
impl ToKey for String {
fn to_key(&self) -> Key {
Key::from_str(self)
}
}
impl<'a> ToKey for Cow<'a, str> {
fn to_key(&self) -> Key {
Key::from_str(self)
}
}
}
#[cfg(feature = "kv_unstable_sval")]
mod sval_support {
use super::*;
extern crate sval;
extern crate sval_ref;
use self::sval::Value;
use self::sval_ref::ValueRef;
impl<'a> Value for Key<'a> {
fn stream<'sval, S: sval::Stream<'sval> + ?Sized>(
&'sval self,
stream: &mut S,
) -> sval::Result {
self.key.stream(stream)
}
}
impl<'a> ValueRef<'a> for Key<'a> {
fn stream_ref<S: self::sval::Stream<'a> + ?Sized>(
&self,
stream: &mut S,
) -> self::sval::Result {
self.key.stream(stream)
}
}
}
#[cfg(feature = "kv_unstable_serde")]
mod serde_support {
use super::*;
extern crate serde;
use self::serde::{Serialize, Serializer};
impl<'a> Serialize for Key<'a> {
fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
where
S: Serializer,
{
self.key.serialize(serializer)
}
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn key_from_string() {
assert_eq!("a key", Key::from_str("a key").as_str());
}
}