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Diffstat (limited to 'activestorage/app/models/active_storage/blob.rb')
| -rw-r--r-- | activestorage/app/models/active_storage/blob.rb | 277 |
1 files changed, 277 insertions, 0 deletions
diff --git a/activestorage/app/models/active_storage/blob.rb b/activestorage/app/models/active_storage/blob.rb new file mode 100644 index 0000000000..6ca7d49bc1 --- /dev/null +++ b/activestorage/app/models/active_storage/blob.rb @@ -0,0 +1,277 @@ +# frozen_string_literal: true + +require "active_storage/downloader" + +# A blob is a record that contains the metadata about a file and a key for where that file resides on the service. +# Blobs can be created in two ways: +# +# 1. Subsequent to the file being uploaded server-side to the service via <tt>create_after_upload!</tt>. +# 2. Ahead of the file being directly uploaded client-side to the service via <tt>create_before_direct_upload!</tt>. +# +# The first option doesn't require any client-side JavaScript integration, and can be used by any other back-end +# service that deals with files. The second option is faster, since you're not using your own server as a staging +# point for uploads, and can work with deployments like Heroku that do not provide large amounts of disk space. +# +# Blobs are intended to be immutable in as-so-far as their reference to a specific file goes. You're allowed to +# update a blob's metadata on a subsequent pass, but you should not update the key or change the uploaded file. +# If you need to create a derivative or otherwise change the blob, simply create a new blob and purge the old one. +class ActiveStorage::Blob < ActiveRecord::Base + require_dependency "active_storage/blob/analyzable" + require_dependency "active_storage/blob/identifiable" + require_dependency "active_storage/blob/representable" + + include Analyzable + include Identifiable + include Representable + + self.table_name = "active_storage_blobs" + + has_secure_token :key + store :metadata, accessors: [ :analyzed, :identified ], coder: ActiveRecord::Coders::JSON + + class_attribute :service + + has_many :attachments + + scope :unattached, -> { left_joins(:attachments).where(ActiveStorage::Attachment.table_name => { blob_id: nil }) } + + before_destroy(prepend: true) do + raise ActiveRecord::InvalidForeignKey if attachments.exists? + end + + class << self + # You can use the signed ID of a blob to refer to it on the client side without fear of tampering. + # This is particularly helpful for direct uploads where the client-side needs to refer to the blob + # that was created ahead of the upload itself on form submission. + # + # The signed ID is also used to create stable URLs for the blob through the BlobsController. + def find_signed(id) + find ActiveStorage.verifier.verify(id, purpose: :blob_id) + end + + # Returns a new, unsaved blob instance after the +io+ has been uploaded to the service. + # When providing a content type, pass <tt>identify: false</tt> to bypass automatic content type inference. + def build_after_upload(io:, filename:, content_type: nil, metadata: nil, identify: true) + new(filename: filename, content_type: content_type, metadata: metadata).tap do |blob| + blob.upload(io, identify: identify) + end + end + + def build_after_unfurling(io:, filename:, content_type: nil, metadata: nil, identify: true) #:nodoc: + new(filename: filename, content_type: content_type, metadata: metadata).tap do |blob| + blob.unfurl(io, identify: identify) + end + end + + # Returns a saved blob instance after the +io+ has been uploaded to the service. Note, the blob is first built, + # then the +io+ is uploaded, then the blob is saved. This is done this way to avoid uploading (which may take + # time), while having an open database transaction. + # When providing a content type, pass <tt>identify: false</tt> to bypass automatic content type inference. + def create_after_upload!(io:, filename:, content_type: nil, metadata: nil, identify: true) + build_after_upload(io: io, filename: filename, content_type: content_type, metadata: metadata, identify: identify).tap(&:save!) + end + + # Returns a saved blob _without_ uploading a file to the service. This blob will point to a key where there is + # no file yet. It's intended to be used together with a client-side upload, which will first create the blob + # in order to produce the signed URL for uploading. This signed URL points to the key generated by the blob. + # Once the form using the direct upload is submitted, the blob can be associated with the right record using + # the signed ID. + def create_before_direct_upload!(filename:, byte_size:, checksum:, content_type: nil, metadata: nil) + create! filename: filename, byte_size: byte_size, checksum: checksum, content_type: content_type, metadata: metadata + end + + # To prevent problems with case-insensitive filesystems, especially in combination + # with databases which treat indices as case-sensitive, all blob keys generated are going + # to only contain the base-36 character alphabet and will therefore be lowercase. To maintain + # the same or higher amount of entropy as in the base-58 encoding used by `has_secure_token` + # the number of bytes used is increased to 28 from the standard 24 + def generate_unique_secure_token + SecureRandom.base36(28) + end + end + + # Returns a signed ID for this blob that's suitable for reference on the client-side without fear of tampering. + # It uses the framework-wide verifier on <tt>ActiveStorage.verifier</tt>, but with a dedicated purpose. + def signed_id + ActiveStorage.verifier.generate(id, purpose: :blob_id) + end + + # Returns the key pointing to the file on the service that's associated with this blob. The key is the + # secure-token format from Rails in lower case. So it'll look like: xtapjjcjiudrlk3tmwyjgpuobabd. + # This key is not intended to be revealed directly to the user. + # Always refer to blobs using the signed_id or a verified form of the key. + def key + # We can't wait until the record is first saved to have a key for it + self[:key] ||= self.class.generate_unique_secure_token + end + + # Returns an ActiveStorage::Filename instance of the filename that can be + # queried for basename, extension, and a sanitized version of the filename + # that's safe to use in URLs. + def filename + ActiveStorage::Filename.new(self[:filename]) + end + + # Returns true if the content_type of this blob is in the image range, like image/png. + def image? + content_type.start_with?("image") + end + + # Returns true if the content_type of this blob is in the audio range, like audio/mpeg. + def audio? + content_type.start_with?("audio") + end + + # Returns true if the content_type of this blob is in the video range, like video/mp4. + def video? + content_type.start_with?("video") + end + + # Returns true if the content_type of this blob is in the text range, like text/plain. + def text? + content_type.start_with?("text") + end + + + # Returns the URL of the blob on the service. This URL is intended to be short-lived for security and not used directly + # with users. Instead, the +service_url+ should only be exposed as a redirect from a stable, possibly authenticated URL. + # Hiding the +service_url+ behind a redirect also gives you the power to change services without updating all URLs. And + # it allows permanent URLs that redirect to the +service_url+ to be cached in the view. + def service_url(expires_in: ActiveStorage.service_urls_expire_in, disposition: :inline, filename: nil, **options) + filename = ActiveStorage::Filename.wrap(filename || self.filename) + + service.url key, expires_in: expires_in, filename: filename, content_type: content_type_for_service_url, + disposition: forced_disposition_for_service_url || disposition, **options + end + + # Returns a URL that can be used to directly upload a file for this blob on the service. This URL is intended to be + # short-lived for security and only generated on-demand by the client-side JavaScript responsible for doing the uploading. + def service_url_for_direct_upload(expires_in: ActiveStorage.service_urls_expire_in) + service.url_for_direct_upload key, expires_in: expires_in, content_type: content_type, content_length: byte_size, checksum: checksum + end + + # Returns a Hash of headers for +service_url_for_direct_upload+ requests. + def service_headers_for_direct_upload + service.headers_for_direct_upload key, filename: filename, content_type: content_type, content_length: byte_size, checksum: checksum + end + + + # Uploads the +io+ to the service on the +key+ for this blob. Blobs are intended to be immutable, so you shouldn't be + # using this method after a file has already been uploaded to fit with a blob. If you want to create a derivative blob, + # you should instead simply create a new blob based on the old one. + # + # Prior to uploading, we compute the checksum, which is sent to the service for transit integrity validation. If the + # checksum does not match what the service receives, an exception will be raised. We also measure the size of the +io+ + # and store that in +byte_size+ on the blob record. The content type is automatically extracted from the +io+ unless + # you specify a +content_type+ and pass +identify+ as false. + # + # Normally, you do not have to call this method directly at all. Use the factory class methods of +build_after_upload+ + # and +create_after_upload!+. + def upload(io, identify: true) + unfurl io, identify: identify + upload_without_unfurling io + end + + def unfurl(io, identify: true) #:nodoc: + self.checksum = compute_checksum_in_chunks(io) + self.content_type = extract_content_type(io) if content_type.nil? || identify + self.byte_size = io.size + self.identified = true + end + + def upload_without_unfurling(io) #:nodoc: + service.upload key, io, checksum: checksum, **service_metadata + end + + # Downloads the file associated with this blob. If no block is given, the entire file is read into memory and returned. + # That'll use a lot of RAM for very large files. If a block is given, then the download is streamed and yielded in chunks. + def download(&block) + service.download key, &block + end + + # Downloads the blob to a tempfile on disk. Yields the tempfile. + # + # The tempfile's name is prefixed with +ActiveStorage-+ and the blob's ID. Its extension matches that of the blob. + # + # By default, the tempfile is created in <tt>Dir.tmpdir</tt>. Pass +tempdir:+ to create it in a different directory: + # + # blob.open(tempdir: "/path/to/tmp") do |file| + # # ... + # end + # + # The tempfile is automatically closed and unlinked after the given block is executed. + # + # Raises ActiveStorage::IntegrityError if the downloaded data does not match the blob's checksum. + def open(tempdir: nil, &block) + ActiveStorage::Downloader.new(self, tempdir: tempdir).download_blob_to_tempfile(&block) + end + + + # Deletes the files on the service associated with the blob. This should only be done if the blob is going to be + # deleted as well or you will essentially have a dead reference. It's recommended to use #purge and #purge_later + # methods in most circumstances. + def delete + service.delete(key) + service.delete_prefixed("variants/#{key}/") if image? + end + + # Deletes the file on the service and then destroys the blob record. This is the recommended way to dispose of unwanted + # blobs. Note, though, that deleting the file off the service will initiate a HTTP connection to the service, which may + # be slow or prevented, so you should not use this method inside a transaction or in callbacks. Use #purge_later instead. + def purge + destroy + delete + rescue ActiveRecord::InvalidForeignKey + end + + # Enqueues an ActiveStorage::PurgeJob to call #purge. This is the recommended way to purge blobs from a transaction, + # an Active Record callback, or in any other real-time scenario. + def purge_later + ActiveStorage::PurgeJob.perform_later(self) + end + + private + def compute_checksum_in_chunks(io) + Digest::MD5.new.tap do |checksum| + while chunk = io.read(5.megabytes) + checksum << chunk + end + + io.rewind + end.base64digest + end + + def extract_content_type(io) + Marcel::MimeType.for io, name: filename.to_s, declared_type: content_type + end + + def forcibly_serve_as_binary? + ActiveStorage.content_types_to_serve_as_binary.include?(content_type) + end + + def allowed_inline? + ActiveStorage.content_types_allowed_inline.include?(content_type) + end + + def content_type_for_service_url + forcibly_serve_as_binary? ? ActiveStorage.binary_content_type : content_type + end + + def forced_disposition_for_service_url + if forcibly_serve_as_binary? || !allowed_inline? + :attachment + end + end + + def service_metadata + if forcibly_serve_as_binary? + { content_type: ActiveStorage.binary_content_type, disposition: :attachment, filename: filename } + elsif !allowed_inline? + { content_type: content_type, disposition: :attachment, filename: filename } + else + { content_type: content_type } + end + end + + ActiveSupport.run_load_hooks(:active_storage_blob, self) +end |