simple_cache - In-Memory LRU Cache for Eiffel

Overview

simple_cache provides a generic in-memory cache with Least Recently Used (LRU) eviction policy for Eiffel applications. It supports optional Time-to-Live (TTL) for automatic entry expiration and tracks cache statistics like hits, misses, and evictions.

Quick Start

Installation

<library name="simple_cache" location="$SIMPLE_CACHE\simple_cache.ecf"/>

Basic Usage

local
    cache: SIMPLE_CACHE [STRING]
do
    -- Create cache with max 100 entries
    create cache.make (100)

    -- Store values
    cache.put ("user:123", "Alice")
    cache.put ("user:456", "Bob")

    -- Retrieve values
    if attached cache.get ("user:123") as name then
        print ("Found: " + name)
    end

    -- Check statistics
    print ("Hit rate: " + (cache.hit_rate * 100).out + "%%")
end

Features

Generic Storage

STRING keys with any value type via SIMPLE_CACHE [G]

LRU Eviction

Automatically removes least recently used entries when full

TTL Support

Optional time-to-live per entry or default expiration

Statistics

Track hits, misses, evictions, and hit rate

Redis Support

SIMPLE_REDIS_CACHE for distributed caching via Redis

Redis Client

SIMPLE_REDIS for low-level Redis commands

TTL (Time-to-Live)

-- Cache with default 1-hour TTL
create cache.make_with_ttl (100, 3600)

-- Store with custom TTL (5 minutes)
cache.put_with_ttl ("temp:xyz", data, 300)

-- Entries automatically expire

Redis Cache

local
    cache: SIMPLE_REDIS_CACHE
do
    create cache.make ("localhost", 6379, 1000)
    if cache.connect then
        cache.put ("user:123", user_json)
        if attached cache.get ("user:123") as data then
            print (data)
        end
        cache.disconnect
    end
end

Redis Client

local
    redis: SIMPLE_REDIS
do
    create redis.make ("localhost", 6379)
    if redis.connect then
        redis.set ("key", "value")
        redis.setex ("temp", 60, "expires in 1 min")
        redis.incr ("counter")
        if redis.ping then
            print ("Connected!")
        end
        redis.disconnect
    end
end

API Reference

make (a_max_size: INTEGER)

create cache.make (100)

Create cache with maximum entries, no expiration.

Require

positive_size: a_max_size > 0

Ensure

max_size_set: max_size = a_max_size

initially_empty: is_empty

make_with_ttl (a_max_size, a_ttl: INTEGER)

create cache.make_with_ttl (100, 3600)

Create cache with maximum entries and default TTL in seconds.

put (a_key: STRING; a_value: G)

cache.put ("user:123", "Alice")

Store value with key. Uses default TTL if set.

get (a_key: STRING): detachable G

if attached cache.get ("user:123") as v then ...

Retrieve value. Returns Void if not found or expired.

Statistics

Feature	Type	Description
`hits`	INTEGER	Cache hit count
`misses`	INTEGER	Cache miss count
`evictions`	INTEGER	LRU eviction count
`hit_rate`	REAL_64	Hit rate (0.0 to 1.0)