Memory Driver

In-memory storage driver for testing and development. Data is stored in RAM and will be lost when the process exits.

Features

• ✅ Fast - No I/O operations, everything in memory
• ✅ Simple - No setup required
• ✅ Testing - Perfect for unit tests with clear() method
• ✅ Development - Quick prototyping without cloud services

Installation

The memory driver is included in @minimajs/disk:

npm install @minimajs/disk
# or
bun add @minimajs/disk

Usage

Basic Usage

import { createMemoryDriver, createDisk } from "@minimajs/disk";

const memoryDriver = createMemoryDriver();
const disk = createDisk({ driver: memoryDriver });

// Use like any other disk
await disk.put("test.txt", "Hello World");
const file = await disk.get("test.txt");

if (file) {
  const text = await file.text();
  console.log(text); // "Hello World"
}

Testing Example

import { createMemoryDriver, createDisk } from "@minimajs/disk";
import { describe, test, beforeEach, afterEach } from "@jest/globals";
import assert from "node:assert/strict";

describe("File Upload Service", () => {
  let memoryDriver;
  let disk;

  beforeEach(() => {
    memoryDriver = createMemoryDriver();
    disk = createDisk({ driver: memoryDriver });
  });

  afterEach(() => {
    // Clear all data after each test
    memoryDriver.clear();
  });

  test("uploads file successfully", async () => {
    const file = await disk.put("uploads/avatar.jpg", imageData);

    assert.ok(await disk.exists("uploads/avatar.jpg"));
    assert.equal(file.size, imageData.byteLength);
  });

  test("copies file", async () => {
    await disk.put("original.txt", "content");
    await disk.copy("original.txt", "copy.txt");

    assert.ok(await disk.exists("original.txt"));
    assert.ok(await disk.exists("copy.txt"));
  });
});

With Public URLs

import { createMemoryDriver, createDisk } from "@minimajs/disk";

const memoryDriver = createMemoryDriver({
  publicUrl: "http://localhost:3000/files",
});

const disk = createDisk({ driver: memoryDriver });

await disk.put("avatar.jpg", imageData);

const url = await disk.url("avatar.jpg");
console.log(url); // http://localhost:3000/files/avatar.jpg

Development Server Example

import { createMemoryDriver, createDisk } from "@minimajs/disk";
import express from "express";

const memoryDriver = createMemoryDriver({
  publicUrl: "http://localhost:3000/uploads",
});

const disk = createDisk({ driver: memoryDriver });

const app = express();

app.post("/upload", async (req, res) => {
  const file = await disk.put("uploads/" + req.file.name, req.file.data);
  res.json({ url: await disk.url(file.href) });
});

app.get("/uploads/:file", async (req, res) => {
  const file = await disk.get("uploads/" + req.params.file);
  if (!file) return res.status(404).send("Not found");

  const stream = file.stream();
  const reader = stream.getReader();

  res.setHeader("Content-Type", file.type);
  res.setHeader("Content-Length", file.size.toString());

  while (true) {
    const { done, value } = await reader.read();
    if (done) break;
    res.write(value);
  }
  res.end();
});

app.listen(3000);

API

createMemoryDriver(options?)

Creates a new memory driver instance.

Options:

• publicUrl?: string - Base URL for generating public URLs (optional)

Returns: MemoryDriver (implements DiskDriver)

Special Methods

clear()

Clears all stored data from memory. Useful for cleanup between tests.

const driver = createMemoryDriver();
driver.clear(); // Remove all files

Comparison with Other Drivers

Feature	Memory	Filesystem	S3
Speed	⚡ Fastest	🚀 Fast	🌐 Network
Persistence	❌ Lost on exit	✅ Persistent	✅ Persistent
Setup	✅ None	✅ Simple	🔧 AWS config
Use Case	Testing	Local files	Production

When to Use

✅ Good For:

• Unit tests
• Integration tests
• Quick prototyping
• Development without cloud setup
• CI/CD pipelines (fast tests)
• Mocking storage in demos

❌ Not Good For:

• Production (data lost on restart)
• Large files (limited by RAM)
• Data persistence requirements
• Multi-process applications
• Distributed systems

Stream Behavior

The memory driver supports multiple stream reads:

const file = await disk.put("test.txt", "Hello World");

// First read - uses stored data
const stream1 = file.stream();
const text1 = await new Response(stream1).text(); // "Hello World"

// Second read - creates new stream from stored data
const stream2 = file.stream();
const text2 = await new Response(stream2).text(); // "Hello World"

Notes

• All data is stored in memory and lost when the process exits
• No file size limits other than available RAM
• Thread-safe within a single Node.js process
• Not shared between processes or instances
• href format: /path/to/file (no protocol prefix)

See Also

• Main Documentation
• Testing Strategies
• Filesystem Driver