70 lines
1.8 KiB
Rust
70 lines
1.8 KiB
Rust
// These are helpers for objects that can be borrowed, but can be made owned while changing the type.
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// The difference between e.g. Cow and CloneToOwned, is that we can implement it recursively for owned types.
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//
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// E.g. HashMap<&str, &str> can be converted to HashMap<String, String>.
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//
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// This lets us express types like TorrentMetaInfo<&[u8]> for zero-copy metadata about a bencode buffer in memory,
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// but to have one-line conversion for it into TorrentMetaInfo<Vec<u8>> so that we can store it later somewhere.
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use std::collections::HashMap;
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pub trait CloneToOwned {
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type Target;
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fn clone_to_owned(&self) -> Self::Target;
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}
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impl<T> CloneToOwned for Option<T>
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where
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T: CloneToOwned,
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{
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type Target = Option<<T as CloneToOwned>::Target>;
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fn clone_to_owned(&self) -> Self::Target {
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self.as_ref().map(|i| i.clone_to_owned())
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}
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}
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impl<T> CloneToOwned for Vec<T>
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where
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T: CloneToOwned,
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{
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type Target = Vec<<T as CloneToOwned>::Target>;
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fn clone_to_owned(&self) -> Self::Target {
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self.iter().map(|i| i.clone_to_owned()).collect()
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}
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}
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impl CloneToOwned for u8 {
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type Target = u8;
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fn clone_to_owned(&self) -> Self::Target {
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*self
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}
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}
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impl CloneToOwned for u32 {
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type Target = u32;
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fn clone_to_owned(&self) -> Self::Target {
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*self
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}
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}
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impl<K, V> CloneToOwned for HashMap<K, V>
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where
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K: CloneToOwned,
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<K as CloneToOwned>::Target: std::hash::Hash + Eq,
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V: CloneToOwned,
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{
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type Target = HashMap<<K as CloneToOwned>::Target, <V as CloneToOwned>::Target>;
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fn clone_to_owned(&self) -> Self::Target {
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let mut result = HashMap::with_capacity(self.capacity());
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for (k, v) in self {
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result.insert(k.clone_to_owned(), v.clone_to_owned());
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}
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result
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}
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}
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