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digitwin/node_modules/cacache/README.md

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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's local cache, but can just as easily be used on its own.

Install

$ npm install --save cacache

Table of Contents

Example

const cacache = require('cacache')
const fs = require('fs')

const tarball = '/path/to/mytar.tgz'
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 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? 🤔

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, and just generally be excellent to each other.

Please refer to the Changelog for project history details, too.

Happy hacking!

API

> cacache.ls(cache) -> Promise<Object>

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 objects as the values.

Example
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
  }
}

> cacache.ls.stream(cache) -> Readable

Lists info for all entries currently in the cache as a single large object.

This works just like ls, except get.info entries are returned as 'data' events on the returned stream.

Example
cacache.ls.stream(cachePath).on('data', console.log)
// Output
{
  key: 'my-thing',
  integrity: 'sha512-BaSe64HaSh',
  path: '.testcache/content/deadbeef', // joined with `cachePath`
  time: 12345698490,
  size: 13423,
  metadata: {
    name: 'blah',
    version: '1.2.3',
    description: 'this was once a package but now it is my-thing'
  }
}

{
  key: 'other-thing',
  integrity: 'whirlpool-WoWSoMuchSupport',
  path: '.testcache/content/bada55',
  time: 11992309289,
  size: 498023984029
}

{
  ...
}

> cacache.get(cache, key, [opts]) -> Promise({data, metadata, integrity})

Returns an object with the cached data, digest, and metadata identified by key. The data property of this object will be a Buffer instance that presumably holds some data that means something to you. I'm sure you know what to do with it! cacache just won't care.

integrity is a Subresource Integrity string. That is, a string that can be used to verify data, which looks like <hash-algorithm>-<base64-integrity-hash>.

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

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 instead.

Example
// Look up by key
cache.get(cachePath, 'my-thing').then(console.log)
// Output:
{
  metadata: {
    thingName: 'my'
  },
  integrity: 'sha512-BaSe64HaSh',
  data: Buffer#<deadbeef>,
  size: 9320
}

// Look up by digest
cache.get.byDigest(cachePath, 'sha512-BaSe64HaSh').then(console.log)
// Output:
Buffer#<deadbeef>

> cacache.get.stream(cache, key, [opts]) -> Readable

Returns a Readable Stream of the cached data identified by key.

If there is no content identified by key, or if the locally-stored data does not pass the validity checksum, an error will be emitted.

metadata and integrity events will be emitted before the stream closes, if you need to collect that extra data about the cached entry.

A sub-function, get.stream.byDigest may be used for identical behavior, except lookup will happen by integrity hash, bypassing the index entirely. This version does not emit the metadata and integrity events at all.

See: options

Example
// Look up by key
cache.get.stream(
  cachePath, 'my-thing'
).on('metadata', metadata => {
  console.log('metadata:', metadata)
}).on('integrity', integrity => {
  console.log('integrity:', integrity)
}).pipe(
  fs.createWriteStream('./x.tgz')
)
// Outputs:
metadata: { ... }
integrity: 'sha512-SoMeDIGest+64=='

// Look up by digest
cache.get.stream.byDigest(
  cachePath, 'sha512-SoMeDIGest+64=='
).pipe(
  fs.createWriteStream('./x.tgz')
)

> cacache.get.info(cache, key) -> Promise

Looks up key in the cache index, returning information about the entry if one exists.

Fields
  • key - Key the entry was looked up under. Matches the key argument.
  • integrity - Subresource Integrity hash for the content this entry refers to.
  • path - Filesystem path where content is stored, joined with cache argument.
  • time - Timestamp the entry was first added on.
  • metadata - User-assigned metadata associated with the entry/content.
Example
cacache.get.info(cachePath, 'my-thing').then(console.log)

// Output
{
  key: 'my-thing',
  integrity: 'sha256-MUSTVERIFY+ALL/THINGS=='
  path: '.testcache/content/deadbeef',
  time: 12345698490,
  size: 849234,
  metadata: {
    name: 'blah',
    version: '1.2.3',
    description: 'this was once a package but now it is my-thing'
  }
}

> cacache.get.hasContent(cache, integrity) -> Promise

Looks up a Subresource Integrity hash in the cache. If content exists for this integrity, it will return an object, with the specific single integrity hash that was found in sri key, and the size of the found content as size. If no content exists for this integrity, it will return false.

Example
cacache.get.hasContent(cachePath, 'sha256-MUSTVERIFY+ALL/THINGS==').then(console.log)

// Output
{
  sri: {
    source: 'sha256-MUSTVERIFY+ALL/THINGS==',
    algorithm: 'sha256',
    digest: 'MUSTVERIFY+ALL/THINGS==',
    options: []
  },
  size: 9001
}

cacache.get.hasContent(cachePath, 'sha521-NOT+IN/CACHE==').then(console.log)

// Output
false
Options
opts.integrity

If present, the pre-calculated digest for the inserted content. If this option is provided and does not match the post-insertion digest, insertion will fail with an EINTEGRITY error.

opts.memoize

Default: null

If explicitly truthy, cacache will read from memory and memoize data on bulk read. If false, cacache will read from disk data. Reader functions by default read from in-memory cache.

opts.size

If provided, the data stream will be verified to check that enough data was passed through. If there's more or less data than expected, insertion will fail with an EBADSIZE error.

> cacache.put(cache, key, data, [opts]) -> Promise

Inserts data passed to it into the cache. The returned Promise resolves with a digest (generated according to opts.algorithms) after the cache entry has been successfully written.

See: options

Example
fetch(
  'https://registry.npmjs.org/cacache/-/cacache-1.0.0.tgz'
).then(data => {
  return cacache.put(cachePath, 'registry.npmjs.org|cacache@1.0.0', data)
}).then(integrity => {
  console.log('integrity hash is', integrity)
})

> cacache.put.stream(cache, key, [opts]) -> Writable

Returns a Writable Stream that inserts data written to it into the cache. Emits an integrity event with the digest of written contents when it succeeds.

See: options

Example
request.get(
  'https://registry.npmjs.org/cacache/-/cacache-1.0.0.tgz'
).pipe(
  cacache.put.stream(
    cachePath, 'registry.npmjs.org|cacache@1.0.0'
  ).on('integrity', d => console.log(`integrity digest is ${d}`))
)
Options
opts.metadata

Arbitrary metadata to be attached to the inserted key.

opts.size

If provided, the data stream will be verified to check that enough data was passed through. If there's more or less data than expected, insertion will fail with an EBADSIZE error.

opts.integrity

If present, the pre-calculated digest for the inserted content. If this option is provided and does not match the post-insertion digest, insertion will fail with an EINTEGRITY error.

algorithms has no effect if this option is present.

opts.integrityEmitter

Streaming only If present, uses the provided event emitter as a source of truth for both integrity and size. This allows use cases where integrity is already being calculated outside of cacache to reuse that data instead of calculating it a second time.

The emitter must emit both the 'integrity' and 'size' events.

NOTE: If this option is provided, you must verify that you receive the correct integrity value yourself and emit an 'error' event if there is a mismatch. ssri Integrity Streams do this for you when given an expected integrity.

opts.algorithms

Default: ['sha512']

Hashing algorithms to use when calculating the subresource integrity digest for inserted data. Can use any algorithm listed in crypto.getHashes() or 'omakase'/'お任せします' to pick a random hash algorithm on each insertion. You may also use any anagram of 'modnar' to use this feature.

Currently only supports one algorithm at a time (i.e., an array length of exactly 1). Has no effect if opts.integrity is present.

opts.memoize

Default: null

If provided, cacache will memoize the given cache insertion in memory, bypassing any filesystem checks for that key or digest in future cache fetches. Nothing will be written to the in-memory cache unless this option is explicitly truthy.

If opts.memoize is an object or a Map-like (that is, an object with get and set methods), it will be written to instead of the global memoization cache.

Reading from disk data can be forced by explicitly passing memoize: false to the reader functions, but their default will be to read from memory.

opts.tmpPrefix

Default: null

Prefix to append on the temporary directory name inside the cache's tmp dir.

> cacache.rm.all(cache) -> Promise

Clears the entire cache. Mainly by blowing away the cache directory itself.

Example
cacache.rm.all(cachePath).then(() => {
  console.log('THE APOCALYPSE IS UPON US 😱')
})

> cacache.rm.entry(cache, key, [opts]) -> Promise

Alias: cacache.rm

Removes the index entry for key. Content will still be accessible if requested directly by content address (get.stream.byDigest).

By default, this appends a new entry to the index with an integrity of null. If opts.removeFully is set to true then the index file itself will be physically deleted rather than appending a null.

To remove the content itself (which might still be used by other entries), use rm.content. Or, to safely vacuum any unused content, use verify.

Example
cacache.rm.entry(cachePath, 'my-thing').then(() => {
  console.log('I did not like it anyway')
})

> cacache.rm.content(cache, integrity) -> Promise

Removes the content identified by integrity. Any index entries referring to it will not be usable again until the content is re-added to the cache with an identical digest.

Example
cacache.rm.content(cachePath, 'sha512-SoMeDIGest/IN+BaSE64==').then(() => {
  console.log('data for my-thing is gone!')
})

> cacache.index.compact(cache, key, matchFn, [opts]) -> Promise

Uses matchFn, which must be a synchronous function that accepts two entries and returns a boolean indicating whether or not the two entries match, to deduplicate all entries in the cache for the given key.

If opts.validateEntry is provided, it will be called as a function with the only parameter being a single index entry. The function must return a Boolean, if it returns true the entry is considered valid and will be kept in the index, if it returns false the entry will be removed from the index.

If opts.validateEntry is not provided, however, every entry in the index will be deduplicated and kept until the first null integrity is reached, removing all entries that were written before the null.

The deduplicated list of entries is both written to the index, replacing the existing content, and returned in the Promise.

> cacache.index.insert(cache, key, integrity, opts) -> Promise

Writes an index entry to the cache for the given key without writing content.

It is assumed if you are using this method, you have already stored the content some other way and you only wish to add a new index to that content. The metadata and size properties are read from opts and used as part of the index entry.

Returns a Promise resolving to the newly added entry.

> cacache.clearMemoized()

Completely resets the in-memory entry cache.

> tmp.mkdir(cache, opts) -> Promise<Path>

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(), which will fix all tmp directory permissions.

If you want automatic cleanup of this directory, use tmp.withTmp()

See: options

Example
cacache.tmp.mkdir(cache).then(dir => {
  fs.writeFile(path.join(dir, 'blablabla'), Buffer#<1234>, ...)
})

> tmp.fix(cache) -> Promise

Sets the uid and gid properties on all files and folders within the tmp folder to match the rest of the cache.

Use this after manually writing files into tmp.mkdir or tmp.withTmp.

Example
cacache.tmp.mkdir(cache).then(dir => {
  writeFile(path.join(dir, 'file'), someData).then(() => {
    // make sure we didn't just put a root-owned file in the cache
    cacache.tmp.fix().then(() => {
      // all uids and gids match now
    })
  })
})

> tmp.withTmp(cache, opts, cb) -> Promise

Creates a temporary directory with tmp.mkdir() and calls cb with it. The created temporary directory will be removed when the return value of cb() resolves, the tmp directory will be automatically deleted once that promise completes.

The same caveats apply when it comes to managing permissions for the tmp dir's contents.

See: options

Example
cacache.tmp.withTmp(cache, dir => {
  return fs.writeFile(path.join(dir, 'blablabla'), 'blabla contents', { encoding: 'utf8' })
}).then(() => {
  // `dir` no longer exists
})
Options
opts.tmpPrefix

Default: null

Prefix to append on the temporary directory name inside the cache's tmp dir.

Subresource Integrity Digests

For content verification and addressing, cacache uses strings following the Subresource Integrity spec. That is, any time cacache expects an integrity argument or option, it should be in the format <hashAlgorithm>-<base64-hash>.

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:

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 to have a richer set of functionality around SRI strings, including generation, parsing, and translating from existing hex-formatted strings.

> cacache.verify(cache, opts) -> Promise

Checks out and fixes up your cache:

  • Cleans up corrupted or invalid index entries.
  • Custom entry filtering options.
  • Garbage collects any content entries not referenced by the index.
  • Checks integrity for all content entries and removes invalid content.
  • Fixes cache ownership.
  • Removes the tmp directory in the cache and all its contents.

When it's done, it'll return an object with various stats about the verification process, including amount of storage reclaimed, number of valid entries, number of entries removed, etc.

Options
opts.concurrency

Default: 20

Number of concurrently read files in the filesystem while doing clean up.

opts.filter

Receives a formatted entry. Return false to remove it. Note: might be called more than once on the same entry.

opts.log

Custom logger function:

  log: { silly () {} }
  log.silly('verify', 'verifying cache at', cache)
Example
echo somegarbage >> $CACHEPATH/content/deadbeef

cacache.verify(cachePath).then(stats => {
  // deadbeef collected, because of invalid checksum.
  console.log('cache is much nicer now! stats:', stats)
})

> cacache.verify.lastRun(cache) -> Promise

Returns a Date representing the last time cacache.verify was run on cache.

Example
cacache.verify(cachePath).then(() => {
  cacache.verify.lastRun(cachePath).then(lastTime => {
    console.log('cacache.verify was last called on' + lastTime)
  })
})