feat(driver): new memory-meta driver

[sandros94]

Resolves #583

while experimenting I've noticed that adding metadata's to the default memory drive would introduce even a small amount of overhead (depending on the platform). So instead of modifying the original driver I decided to experiment and then build a new one, for those that are actually interested in it.

It mimics the *time metadata from storages like fs, while supporting ttl (globally and per-key, to circumvent lru-cache limitation) and correctly dispose the setTimeout when the related key gets removed or storage disposed.

I also fixed the base issue that is present in the default memory driver, although I plan to fix it as well in a separate PR

• Implementation
• Tests
• Docs

  This drive aims to be a more advanced version of the memory driver by adding metadata support, while introducing a small overhead and allocation cost.

  By supporting metadata, it allows for features like Time-To-Live (TTL),active by default, and optionally tracking a rough size of the stored data. The TTL can be set per item or globally.

  Each key has its own metadata, that includes:

  • ttl: remaining Time-To-Live in milliseconds, if set during creation.
  • atime: last access time.
  • mtime: last modified time.
  • ctime: last change time.
  • birthtime: Creation time.
  • size: Size in bytes, if enabled.

  ::note
  For memory efficency all *time values are stored in milliseconds since the Unix epoch. But returned as Date when called via getMeta.
  ::

  import { createStorage } from "unstorage";
  import memoryMetaDriver from "unstorage/drivers/memory-meta";
  
  const storage = createStorage({
    driver: memoryMetaDriver({
      base: "my-storage",   // Optional prefix to use for all keys.
      ttl: 1000 * 60 * 60,  // default `undefined`
      ttlAutoPurge: true,   // default `true`
      trackSize: true,      // default `false`
    }),
  });

  Options:

  • base: Optional prefix to use for all keys. Can be used for namespacing.
  • ttl: Default Time-To-Live for all items in milliseconds.
  • ttlAutoPurge: Whether to automatically purge expired items. (default: true)
  • trackSize: Whether to track the size of items in bytes. (default: false)