# cacache [](https://npm.im/cacache) [](https://npm.im/cacache) [](https://travis-ci.org/npm/cacache) [](https://ci.appveyor.com/project/npm/cacache) [](https://coveralls.io/github/npm/cacache?branch=latest)
[`cacache`](https://github.com/npm/cacache) is a Node.js library for managing
local key and content address caches. It's really fast, really good at
concurrency, and it will never give you corrupted data, even if cache files
get corrupted or manipulated.
On systems that support user and group settings on files, cacache will
match the `uid` and `gid` values to the folder where the cache lives, even
when running as `root`.
It was written to be used as [npm](https://npm.im)'s local cache, but can
just as easily be used on its own.
## Install
`$ npm install --save cacache`
## Table of Contents
* [Example](#example)
* [Features](#features)
* [Contributing](#contributing)
* [API](#api)
* [Using localized APIs](#localized-api)
* Reading
* [`ls`](#ls)
* [`ls.stream`](#ls-stream)
* [`get`](#get-data)
* [`get.stream`](#get-stream)
* [`get.info`](#get-info)
* [`get.hasContent`](#get-hasContent)
* Writing
* [`put`](#put-data)
* [`put.stream`](#put-stream)
* [`rm.all`](#rm-all)
* [`rm.entry`](#rm-entry)
* [`rm.content`](#rm-content)
* [`index.compact`](#index-compact)
* [`index.insert`](#index-insert)
* Utilities
* [`clearMemoized`](#clear-memoized)
* [`tmp.mkdir`](#tmp-mkdir)
* [`tmp.withTmp`](#with-tmp)
* Integrity
* [Subresource Integrity](#integrity)
* [`verify`](#verify)
* [`verify.lastRun`](#verify-last-run)
### Example
```javascript
const cacache = require('cacache')
const fs = require('fs')
const cachePath = '/tmp/my-toy-cache'
const key = 'my-unique-key-1234'
// Cache it! Use `cachePath` as the root of the content cache
cacache.put(cachePath, key, '10293801983029384').then(integrity => {
console.log(`Saved content to ${cachePath}.`)
})
const destination = '/tmp/mytar.tgz'
// Copy the contents out of the cache and into their destination!
// But this time, use stream instead!
cacache.get.stream(
cachePath, key
).pipe(
fs.createWriteStream(destination)
).on('finish', () => {
console.log('done extracting!')
})
// The same thing, but skip the key index.
cacache.get.byDigest(cachePath, integrityHash).then(data => {
fs.writeFile(destination, data, err => {
console.log('tarball data fetched based on its sha512sum and written out!')
})
})
```
### Features
* Extraction by key or by content address (shasum, etc)
* [Subresource Integrity](#integrity) web standard support
* Multi-hash support - safely host sha1, sha512, etc, in a single cache
* Automatic content deduplication
* Fault tolerance (immune to corruption, partial writes, process races, etc)
* Consistency guarantees on read and write (full data verification)
* Lockless, high-concurrency cache access
* Streaming support
* Promise support
* Fast -- sub-millisecond reads and writes including verification
* Arbitrary metadata storage
* Garbage collection and additional offline verification
* Thorough test coverage
* There's probably a bloom filter in there somewhere. Those are cool, right? π€
### Contributing
The cacache team enthusiastically welcomes contributions and project participation! There's a bunch of things you can do if you want to contribute! Please don't hesitate to jump in if you'd like to, or even ask us questions if something isn't clear.
All participants and maintainers in this project are expected to follow [Code of Conduct](CODE_OF_CONDUCT.md), and just generally be excellent to each other.
Please refer to the [Changelog](CHANGELOG.md) for project history details, too.
Happy hacking!
### API
#### `
Lists info for all entries currently in the cache as a single large object. Each
entry in the object will be keyed by the unique index key, with corresponding
[`get.info`](#get-info) objects as the values.
##### Example
```javascript
cacache.ls(cachePath).then(console.log)
// Output
{
'my-thing': {
key: 'my-thing',
integrity: 'sha512-BaSe64/EnCoDED+HAsh=='
path: '.testcache/content/deadbeef', // joined with `cachePath`
time: 12345698490,
size: 4023948,
metadata: {
name: 'blah',
version: '1.2.3',
description: 'this was once a package but now it is my-thing'
}
},
'other-thing': {
key: 'other-thing',
integrity: 'sha1-ANothER+hasH=',
path: '.testcache/content/bada55',
time: 11992309289,
size: 111112
}
}
```
#### -`.
If there is no content identified by `key`, or if the locally-stored data does
not pass the validity checksum, the promise will be rejected.
A sub-function, `get.byDigest` may be used for identical behavior, except lookup
will happen by integrity hash, bypassing the index entirely. This version of the
function *only* returns `data` itself, without any wrapper.
See: [options](#get-options)
##### Note
This function loads the entire cache entry into memory before returning it. If
you're dealing with Very Large data, consider using [`get.stream`](#get-stream)
instead.
##### Example
```javascript
// Look up by key
cache.get(cachePath, 'my-thing').then(console.log)
// Output:
{
metadata: {
thingName: 'my'
},
integrity: 'sha512-BaSe64HaSh',
data: Buffer#,
size: 9320
}
// Look up by digest
cache.get.byDigest(cachePath, 'sha512-BaSe64HaSh').then(console.log)
// Output:
Buffer#
```
#### `
Returns a unique temporary directory inside the cache's `tmp` dir. This
directory will use the same safe user assignment that all the other stuff use.
Once the directory is made, it's the user's responsibility that all files
within are given the appropriate `gid`/`uid` ownership settings to match
the rest of the cache. If not, you can ask cacache to do it for you by
calling [`tmp.fix()`](#tmp-fix), which will fix all tmp directory
permissions.
If you want automatic cleanup of this directory, use
[`tmp.withTmp()`](#with-tpm)
See: [options](#tmp-options)
##### Example
```javascript
cacache.tmp.mkdir(cache).then(dir => {
fs.writeFile(path.join(dir, 'blablabla'), Buffer#<1234>, ...)
})
```
#### -`.
One deviation from the current spec is that cacache will support any hash
algorithms supported by the underlying Node.js process. You can use
`crypto.getHashes()` to see which ones you can use.
##### Generating Digests Yourself
If you have an existing content shasum, they are generally formatted as a
hexadecimal string (that is, a sha1 would look like:
`5f5513f8822fdbe5145af33b64d8d970dcf95c6e`). In order to be compatible with
cacache, you'll need to convert this to an equivalent subresource integrity
string. For this example, the corresponding hash would be:
`sha1-X1UT+IIv2+UUWvM7ZNjZcNz5XG4=`.
If you want to generate an integrity string yourself for existing data, you can
use something like this:
```javascript
const crypto = require('crypto')
const hashAlgorithm = 'sha512'
const data = 'foobarbaz'
const integrity = (
hashAlgorithm +
'-' +
crypto.createHash(hashAlgorithm).update(data).digest('base64')
)
```
You can also use [`ssri`](https://npm.im/ssri) to have a richer set of functionality
around SRI strings, including generation, parsing, and translating from existing
hex-formatted strings.
####