LRU

An LRU cache for zig projects. Compatible with Zig 0.14.

This code is for my personal use, and works for my purposes. There is no guarantee that it will be suitable and reliable for your purposes. The code is released under the MIT licence, you are free to use it, but strongly urged to fully test that the code functions correctly for your use cases.

How to use

LRU caches are usually expected to automatically free objects when the cache is full. This example demonstrates how to provide an optional callback function to free an object.

/// Implement a `destroy` function.
const Sample = struct {
    age: u8 = 10,
    pub const Self = @This();
    pub fn destroy(self: *Self, gpa: Allocator) void {
        gpa.destroy(self);
    }
};

Create an LRU cache that holds a maximum of 100 objects.

var lru = LRU(u32, *Sample).init(100);
defer lru.deinit(allocator);
// Tell the lru cache to call the destroy function on free:
lru.entry_dealloc = Sample.destroy;

Put and get items from the cache:

const sample = try allocator.create(Sample);
sample.*.age = 20;

const sample2 = try allocator.create(Sample);
sample2.*.age = 30;

try lru.put(allocator, 20, sample);
try lru.put(allocator, 30, sample2);
try lru.put(allocator, 40, sample3);

if(try lru.get(20)) |entry| {
    std.log.info("Age: {d}", .{entry.age});
}

Strings as keys

If you wish to use strings as keys, you can hash your string key into a u64. This is exactly how zigs StringHashMap operates.

var lru = LRU(u64, *Sample).init(100);
defer lru.deinit(allocator);

const key = std.hash.Wyhash.hash(0, "[email protected]");
try lru.put(allocator, key, sample);