flow_lib/utils/

extensions.rs

/*
Copyright (c) 2017 http-rs authors

Permission is hereby granted, free of charge, to any
person obtaining a copy of this software and associated
documentation files (the "Software"), to deal in the
Software without restriction, including without
limitation the rights to use, copy, modify, merge,
publish, distribute, sublicense, and/or sell copies of
the Software, and to permit persons to whom the Software
is furnished to do so, subject to the following
conditions:

The above copyright notice and this permission notice
shall be included in all copies or substantial portions
of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
DEALINGS IN THE SOFTWARE.
*/

use std::any::{Any, TypeId};
use std::collections::HashMap;
use std::fmt;
use std::hash::{BuildHasherDefault, Hasher};

type AnyMap = HashMap<TypeId, Box<dyn Any + Send + Sync>, BuildHasherDefault<IdHasher>>;

#[derive(Default)]
struct IdHasher(u64);

impl Hasher for IdHasher {
    fn write(&mut self, _: &[u8]) {
        unreachable!("TypeId calls write_u64");
    }

    #[inline]
    fn write_u64(&mut self, id: u64) {
        self.0 = id;
    }

    #[inline]
    fn finish(&self) -> u64 {
        self.0
    }
}

#[derive(Default)]
pub struct Extensions {
    // If extensions are never used, no need to carry around an empty HashMap.
    // That's 3 words. Instead, this is only 1 word.
    map: Option<Box<AnyMap>>,
}

impl Extensions {
    /// Create an empty `Extensions`.
    #[inline]
    pub fn new() -> Extensions {
        Extensions { map: None }
    }

    /// Insert a type into this `Extensions`.
    ///
    /// If a extension of this type already existed, it will
    /// be returned.
    ///
    /// # Example
    ///
    /// ```
    /// use flow_lib::utils::Extensions;
    /// let mut ext = Extensions::new();
    /// assert!(ext.insert(5i32).is_none());
    /// assert!(ext.insert(4u8).is_none());
    /// assert_eq!(ext.insert(9i32), Some(5i32));
    /// ```
    pub fn insert<T: Send + Sync + 'static>(&mut self, val: T) -> Option<T> {
        self.map
            .get_or_insert_with(Box::<HashMap<TypeId, Box<dyn Any + Send + Sync>, BuildHasherDefault<IdHasher>>>::default)
            .insert(TypeId::of::<T>(), Box::new(val))
            .and_then(|boxed| {
                (boxed as Box<dyn Any + 'static>)
                    .downcast()
                    .ok()
                    .map(|boxed| *boxed)
            })
    }

    /// Get a reference to a type previously inserted on this `Extensions`.
    ///
    /// # Example
    ///
    /// ```
    /// use flow_lib::utils::Extensions;
    /// let mut ext = Extensions::new();
    /// assert!(ext.get::<i32>().is_none());
    /// ext.insert(5i32);
    ///
    /// assert_eq!(ext.get::<i32>(), Some(&5i32));
    /// ```
    pub fn get<T: Send + Sync + 'static>(&self) -> Option<&T> {
        self.map
            .as_ref()
            .and_then(|map| map.get(&TypeId::of::<T>()))
            .and_then(|boxed| (&**boxed as &(dyn Any + 'static)).downcast_ref())
    }

    /// Get a mutable reference to a type previously inserted on this `Extensions`.
    ///
    /// # Example
    ///
    /// ```
    /// use flow_lib::utils::Extensions;
    /// let mut ext = Extensions::new();
    /// ext.insert(String::from("Hello"));
    /// ext.get_mut::<String>().unwrap().push_str(" World");
    ///
    /// assert_eq!(ext.get::<String>().unwrap(), "Hello World");
    /// ```
    pub fn get_mut<T: Send + Sync + 'static>(&mut self) -> Option<&mut T> {
        self.map
            .as_mut()
            .and_then(|map| map.get_mut(&TypeId::of::<T>()))
            .and_then(|boxed| (&mut **boxed as &mut (dyn Any + 'static)).downcast_mut())
    }

    /// Remove a type from this `Extensions`.
    ///
    /// If a extension of this type existed, it will be returned.
    ///
    /// # Example
    ///
    /// ```
    /// use flow_lib::utils::Extensions;
    /// let mut ext = Extensions::new();
    /// ext.insert(5i32);
    /// assert_eq!(ext.remove::<i32>(), Some(5i32));
    /// assert!(ext.get::<i32>().is_none());
    /// ```
    pub fn remove<T: Send + Sync + 'static>(&mut self) -> Option<T> {
        self.map
            .as_mut()
            .and_then(|map| map.remove(&TypeId::of::<T>()))
            .and_then(|boxed| {
                (boxed as Box<dyn Any + 'static>)
                    .downcast()
                    .ok()
                    .map(|boxed| *boxed)
            })
    }

    /// Clear the `Extensions` of all inserted extensions.
    ///
    /// # Example
    ///
    /// ```
    /// use flow_lib::utils::Extensions;
    /// let mut ext = Extensions::new();
    /// ext.insert(5i32);
    /// ext.clear();
    ///
    /// assert!(ext.get::<i32>().is_none());
    /// ```
    #[inline]
    pub fn clear(&mut self) {
        if let Some(ref mut map) = self.map {
            map.clear();
        }
    }

    /// Check whether the extension set is empty or not.
    ///
    /// # Example
    ///
    /// ```
    /// use flow_lib::utils::Extensions;
    /// let mut ext = Extensions::new();
    /// assert!(ext.is_empty());
    /// ext.insert(5i32);
    /// assert!(!ext.is_empty());
    /// ```
    #[inline]
    pub fn is_empty(&self) -> bool {
        self.map.as_ref().is_none_or(|map| map.is_empty())
    }

    /// Get the numer of extensions available.
    ///
    /// # Example
    ///
    /// ```
    /// use flow_lib::utils::Extensions;
    /// let mut ext = Extensions::new();
    /// assert_eq!(ext.len(), 0);
    /// ext.insert(5i32);
    /// assert_eq!(ext.len(), 1);
    /// ```
    #[inline]
    pub fn len(&self) -> usize {
        self.map.as_ref().map_or(0, |map| map.len())
    }

    /// Extends `self` with another `Extensions`.
    ///
    /// If an instance of a specific type exists in both, the one in `self` is overwritten with the
    /// one from `other`.
    ///
    /// # Example
    ///
    /// ```
    /// use flow_lib::utils::Extensions;
    /// let mut ext_a = Extensions::new();
    /// ext_a.insert(8u8);
    /// ext_a.insert(16u16);
    ///
    /// let mut ext_b = Extensions::new();
    /// ext_b.insert(4u8);
    /// ext_b.insert("hello");
    ///
    /// ext_a.extend(ext_b);
    /// assert_eq!(ext_a.len(), 3);
    /// assert_eq!(ext_a.get::<u8>(), Some(&4u8));
    /// assert_eq!(ext_a.get::<u16>(), Some(&16u16));
    /// assert_eq!(ext_a.get::<&'static str>().copied(), Some("hello"));
    /// ```
    pub fn extend(&mut self, other: Self) {
        if let Some(other) = other.map {
            if let Some(map) = &mut self.map {
                map.extend(*other);
            } else {
                self.map = Some(other);
            }
        }
    }
}

impl fmt::Debug for Extensions {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("Extensions").finish()
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_extensions() {
        #[derive(Debug, PartialEq)]
        struct MyType(i32);

        let mut extensions = Extensions::new();

        extensions.insert(5i32);
        extensions.insert(MyType(10));

        assert_eq!(extensions.get(), Some(&5i32));
        assert_eq!(extensions.get_mut(), Some(&mut 5i32));

        assert_eq!(extensions.remove::<i32>(), Some(5i32));
        assert!(extensions.get::<i32>().is_none());

        assert_eq!(extensions.get::<bool>(), None);
        assert_eq!(extensions.get(), Some(&MyType(10)));
    }
}