Generate content addressable locations for shrine uploads.
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README.md

Shrine::Plugins::ContentAddressable

Build Status Gem Version MIT license Maintainability

Generate content addressable locations for shrine uploads.

Installation

Add this line to your application's Gemfile:

gem 'shrine-content_addressable'

And then execute:

$ bundle

Or install it yourself as:

$ gem install shrine-content_addressable

Usage

This plugin depends on the signature plugin:

require 'shrine/plugins/content_addressable'
require 'shrine/plugins/signature'

class MyUploader < Shrine
  plugin :signature
  plugin :content_addressable, hash: :sha256, prefix: '/'
end

Currently you can enter :md5, :sha, :sha256 and :sha512 for hash:. If you have a different algorithm that is correctly supported by the signature plugin, and has a multihash code, add the multihash code mapping:

# Let's say the signature plugin starts supporting blake 2b as :blake2_b,
#   the multihash code is 'blake2b'
plugin :content_addressable, hash: :blake2_b, multihash: 'blake2b'

Your uploaded files will be extended with some multihash capability:

uploader = Uploader.new(:cache)
uploaded_file = uploader.upload(my_file)

uploaded_file.content_addressable # => the content addressable hash, regardless of location
uploaded_file.decode # => the decoded multihash
uploaded_file.digest # => the decoded digest (in bytes. Use .unpack('H*') to turn into hex)
uploaded_file.digest_function # => the digest function used to create the multihash
uploaded_file.to_content_addressable! # => ContentAddressableFile, and auto registers the storage

ContentAddressable IO

Since a content-addressable stored file is the same across whichever storage, it MUST not matter what storage the file is accessed from when it comes to reading. A wrapper is provided so files can be looked up by their content-addressable id / hash, instead of a data hash (default for Shrine).

require 'content_addressable_file'

# You currently need to register the storages, unless you use uploaded_file.to_content_addressable!
ContentAddressableFile.register_storage(lookup, lookup, lookup)

# You can disallow deletion
ContentAddressableFile.register_read_only_storage(lookup, lookup, lookup) 

file = ContentAddressableFile.new(content_addressable_hash)

# Shares the interface with UploadedFile
# => file methods like open, rewind, read, close and eof? are available
# => file.url gives the first url that exists
# => file.exists? is true if it exists in any storage
# => file.delete attempts to delete it from ALL storages 

To reset known storages use:

ContentAddressableFile.reset

Registration is only automatic when using #to_content_addressable!. Do not rely on that behaviour if you're not always uploading files, but trying to retrieve them.

A lookup storage needs to respond to:

lookup = Shrine::Storage::Memory.new
content_addressable = content_addressable_hash

lookup.open(content_addressable) # IO.open
lookup.exists?(content_addressable) # true if storage has it (and can open)

# optional
lookup.url(content_addressable) # url to the io (only if storage has it)
lookup.delete(content_addressable) # delete from storage
lookup.download(content_addressable) # download the io

Note that you input the hash, and not some arbitrary path.

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake test to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in shrine-configurable_storage.gemspec.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at SleeplessByte/shrine-configurable_storage. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.

License

The gem is available as open source under the terms of the MIT License.

Code of Conduct

Everyone interacting in the Shrine::Plugins::ContentAddressable project’s codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.