Crate intern_arc

Library for interning based on stdlib Arc

The design of the hash-based half is taken from the arc-interner crate, with the addition of another half based on BTreeMap. Local benchmarks have shown that hashing is faster for objects below 1kB while tree traversal and comparisons are faster above 1kB (very roughly and broadly speaking).

The main functions exist in three variants:

• intern_hash and friends for when you want to use hashing (or have no Ord instance at hand)
• intern_tree and friends for when you want to use tree map (or have no Hash instance at hand)
• intern and friends to automatically choose based on object size

Within each of these classes, four function exist to ingest data in various forms:

use std::sync::Arc;
use intern_arc::{intern, intern_unsized, intern_boxed, intern_arc};

// for sized types
let a1: Arc<String> = intern("hello".to_owned());

// for unsized non-owned types
let a2: Arc<str> = intern_unsized("hello");

// for unsized owned types
let a3: Arc<str> = intern_boxed(Box::<str>::from("hello"));

// for types with shared ownership
let a4: Arc<str> = intern_arc(Arc::<str>::from("hello"));

Introspection

This library offers some utilities for checking how well it works for a given use-case:

use std::sync::Arc;
use intern_arc::{inspect_hash, num_objects_interned_hash, types_interned};

println!("str: {} objects", num_objects_interned_hash::<str>());

let (hash, tree) = types_interned();
println!("types interned: {} with hashing, {} with trees", hash, tree);

inspect_hash::<[u8], _, _>(|iter| {
    for arc in iter {
        println!("{} x {:?}", Arc::strong_count(&arc), arc);
    }
});

All function exist also with tree suffix instead of hash.

Functions

inspect_hash	Feed an iterator over all interned values for the given type to the given function
inspect_tree	Feed an iterator over all interned values for the given type to the given function
intern	Intern an owned value (will not clone)
intern_arc	Intern a shared-ownership reference (will not clone)
intern_boxed	Intern an owned reference (will not clone)
intern_hash	Intern an owned value using hashing (will not clone)
intern_hash_arc	Intern a shared-ownership reference using hashing (will not clone)
intern_hash_boxed	Intern an owned reference using hashing (will not clone)
intern_hash_unsized	Intern a non-owned reference using hashing (will clone)
intern_tree	Intern an owned value using tree map (will not clone)
intern_tree_arc	Intern a shared-ownership reference using tree map (will not clone)
intern_tree_boxed	Intern an owned reference using tree map (will not clone)
intern_tree_unsized	Intern a non-owned reference using tree map (will clone)
intern_unsized	Intern a non-owned reference (will clone)
num_objects_interned_hash	Perform internal maintenance (removing otherwise unreferenced elements) and return count of elements
num_objects_interned_tree	Perform internal maintenance (removing otherwise unreferenced elements) and return count of elements
types_interned	Number of different types (TypeIds) interned using hashing and tree-based, respectively