cache

A general-purpose cache written in Ecko: in-memory LRU with TTL over an optional disk store. get/set/remember(key, ttl, fn).

ecko get github.com/ecko-lang/cache

import cache

Declares fs:read and fs:write. A capability is only advisory in the manifest: what the package actually gets is the grant you give it when you import it.

Version 0.9.5 - source - MIT.

open(dir, opts = empty_map())

open(dir, opts?) -> a cache handle.

dir empty or null makes the cache memory-only; a path makes it disk-backed, so entries survive across process runs. opts.max caps the in-memory tier (default 1000) and eviction is least-recently-used - an evicted entry is gone from memory but still on disk.

c = cache.open(".ecko-cache", { max: 500 })
mem = cache.open("")               # memory-only

set(c, key, value, ttl = 0)

set(c, key, value, ttl?) -> the value, so it can be used inline.

ttl is in seconds; 0 (the default) never expires. Writes both tiers.

cache.set(c, "board", data, 300)   # five minutes

get(c, key)

get(c, key) -> the value, or null when there is nothing live for key.

Memory first, then disk. An expired entry is deleted and reads as a miss, and a disk hit is promoted back into memory. A hit bumps recency.

has(c, key)

has(c, key) -> whether a live entry exists for key.

Non-mutating, which is the difference from get: it neither bumps recency nor promotes a disk entry into memory, so probing cannot evict anything.

remember(c, key, ttl, producer)

remember(c, key, ttl, producer) -> the cached value, computing it if absent.

On a hit the cached value is returned and producer is never called. On a miss producer() runs once, its result is stored with ttl, and returned.

A cached null reads as a miss, so producer would run again - use set and get directly if null is a value you need to cache.

board = cache.remember(c, "board", 300, fn() http.get(url).body)

delete(c, key)

delete(c, key) -> null. Removes key from both tiers.

clear(c)

clear(c) -> null. Empties the memory tier and removes this cache's own disk files, leaving anything else in the directory alone.