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euanheuanh
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ContainerRegistry: Separate registry operations into ImageSource and ImageDestination protocols (#148)
Motivation ---------- Currently, `RegistryClient` handles uploading and downloading container images to and from a registry. In fact, `containertool` creates two clients: one is used only to download images from the source repository, and the other is used only to upload images to the destination. Registries are read/write, but in the future we may need to handle sources of images which are read-only or write-only - for example when writing a container image out to an archive on disk. This change adds two new protocols, splitting up the operations needed to upload and download images. This allows for future clients which cannot handle both sets of operations. Modifications ------------- * Add new `ImageSource` and `ImageDestination` protocols, defining the functions needed to download and upload images, respectively. * Consolidate the `RegistryClient` extensions which implement the `ImageSource` and `ImageDestination` protocols. Result ------ Refactoring. No functional change, but responsibilities of different objects are clearer. Test Plan --------- Existing tests continue to pass.
1 parent 935912e commit cf92449

11 files changed

+515
-291
lines changed

‎Sources/ContainerRegistry/ImageDestination.swift‎

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//===----------------------------------------------------------------------===//
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//
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// This source file is part of the SwiftContainerPlugin open source project
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//
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// Copyright (c) 2025 Apple Inc. and the SwiftContainerPlugin project authors
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// Licensed under Apache License v2.0
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//
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// See LICENSE.txt for license information
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// See CONTRIBUTORS.txt for the list of SwiftContainerPlugin project authors
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//
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// SPDX-License-Identifier: Apache-2.0
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//
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//===----------------------------------------------------------------------===//
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import struct Foundation.Data
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/// A destination, such as a registry, to which container images can be uploaded.
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public protocol ImageDestination {
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/// Checks whether a blob exists.
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///
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/// - Parameters:
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/// - repository: Name of the destination repository.
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/// - digest: Digest of the requested blob.
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/// - Returns: True if the blob exists, otherwise false.
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/// - Throws: If the destination encounters an error.
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func blobExists(
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repository: ImageReference.Repository,
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digest: ImageReference.Digest
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) async throws -> Bool
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/// Uploads a blob of unstructured data.
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///
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/// - Parameters:
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/// - repository: Name of the destination repository.
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/// - mediaType: mediaType field for returned ContentDescriptor.
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/// On the wire, all blob uploads are `application/octet-stream'.
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/// - data: Object to be uploaded.
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/// - Returns: An ContentDescriptor object representing the
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/// uploaded blob.
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/// - Throws: If the upload fails.
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func putBlob(
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repository: ImageReference.Repository,
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mediaType: String,
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data: Data
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) async throws -> ContentDescriptor
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/// Encodes and uploads a JSON object.
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///
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/// - Parameters:
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/// - repository: Name of the destination repository.
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/// - mediaType: mediaType field for returned ContentDescriptor.
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/// On the wire, all blob uploads are `application/octet-stream'.
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/// - data: Object to be uploaded.
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/// - Returns: An ContentDescriptor object representing the
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/// uploaded blob.
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/// - Throws: If the blob cannot be encoded or the upload fails.
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///
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/// Some JSON objects, such as ImageConfiguration, are stored
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/// in the registry as plain blobs with MIME type "application/octet-stream".
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/// This function encodes the data parameter and uploads it as a generic blob.
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func putBlob<Body: Encodable>(
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repository: ImageReference.Repository,
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mediaType: String,
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data: Body
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) async throws -> ContentDescriptor
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/// Encodes and uploads an image manifest.
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///
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/// - Parameters:
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/// - repository: Name of the destination repository.
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/// - reference: Optional tag to apply to this manifest.
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/// - manifest: Manifest to be uploaded.
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/// - Returns: An ContentDescriptor object representing the
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/// uploaded blob.
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/// - Throws: If the blob cannot be encoded or the upload fails.
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///
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/// Manifests are not treated as blobs by the distribution specification.
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/// They have their own MIME types and are uploaded to different
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/// registry endpoints than blobs.
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func putManifest(
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repository: ImageReference.Repository,
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reference: (any ImageReference.Reference)?,
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manifest: ImageManifest
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) async throws -> ContentDescriptor
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}
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extension ImageDestination {
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/// Uploads a blob of unstructured data.
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///
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/// - Parameters:
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/// - repository: Name of the destination repository.
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/// - mediaType: mediaType field for returned ContentDescriptor.
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/// On the wire, all blob uploads are `application/octet-stream'.
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/// - data: Object to be uploaded.
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/// - Returns: An ContentDescriptor object representing the
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/// uploaded blob.
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/// - Throws: If the upload fails.
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public func putBlob(
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repository: ImageReference.Repository,
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mediaType: String = "application/octet-stream",
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data: Data
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) async throws -> ContentDescriptor {
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try await putBlob(repository: repository, mediaType: mediaType, data: data)
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}
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/// Upload an image configuration record to the registry.
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/// - Parameters:
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/// - image: Reference to the image associated with the record.
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/// - configuration: An image configuration record
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/// - Returns: An `ContentDescriptor` referring to the blob stored in the registry.
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/// - Throws: If the blob upload fails.
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///
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/// Image configuration records are stored as blobs in the registry. This function encodes the provided configuration record and stores it as a blob in the registry.
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public func putImageConfiguration(
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forImage image: ImageReference,
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configuration: ImageConfiguration
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) async throws -> ContentDescriptor {
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try await putBlob(
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repository: image.repository,
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mediaType: "application/vnd.oci.image.config.v1+json",
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data: configuration
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)
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}
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}

‎Sources/ContainerRegistry/ImageSource.swift‎

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//===----------------------------------------------------------------------===//
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//
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// This source file is part of the SwiftContainerPlugin open source project
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//
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// Copyright (c) 2025 Apple Inc. and the SwiftContainerPlugin project authors
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// Licensed under Apache License v2.0
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//
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// See LICENSE.txt for license information
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// See CONTRIBUTORS.txt for the list of SwiftContainerPlugin project authors
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//
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// SPDX-License-Identifier: Apache-2.0
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//
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//===----------------------------------------------------------------------===//
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import struct Foundation.Data
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/// A source, such as a registry, from which container images can be fetched.
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public protocol ImageSource {
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/// Fetches a blob of unstructured data.
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///
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/// - Parameters:
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/// - repository: Name of the source repository.
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/// - digest: Digest of the blob.
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/// - Returns: The downloaded data.
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/// - Throws: If the blob download fails.
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func getBlob(
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repository: ImageReference.Repository,
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digest: ImageReference.Digest
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) async throws -> Data
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/// Fetches an image manifest.
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///
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/// - Parameters:
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/// - repository: Name of the source repository.
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/// - reference: Tag or digest of the manifest to fetch.
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/// - Returns: The downloaded manifest.
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/// - Throws: If the download fails or the manifest cannot be decoded.
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func getManifest(
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repository: ImageReference.Repository,
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reference: any ImageReference.Reference
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) async throws -> (ImageManifest, ContentDescriptor)
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/// Fetches an image index.
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///
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/// - Parameters:
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/// - repository: Name of the source repository.
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/// - reference: Tag or digest of the index to fetch.
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/// - Returns: The downloaded index.
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/// - Throws: If the download fails or the index cannot be decoded.
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func getIndex(
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repository: ImageReference.Repository,
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reference: any ImageReference.Reference
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) async throws -> ImageIndex
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/// Fetches an image configuration from the registry.
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///
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/// - Parameters:
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/// - image: Reference to the image containing the record.
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/// - digest: Digest of the configuration object to fetch.
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/// - Returns: The image confguration record.
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/// - Throws: If the download fails or the configuration record cannot be decoded.
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///
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/// Image configuration records are stored as blobs in the registry. This function retrieves
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/// the requested blob and tries to decode it as a configuration record.
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func getImageConfiguration(
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forImage image: ImageReference,
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digest: ImageReference.Digest
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) async throws -> ImageConfiguration
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}

Sources/ContainerRegistry/CheckAPI.swift renamed to Sources/ContainerRegistry/RegistryClient+CheckAPI.swift

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//
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//===----------------------------------------------------------------------===//
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import Foundation
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import struct Foundation.URL
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public extension RegistryClient {
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extension RegistryClient {
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/// Checks whether the registry supports v2 of the distribution specification.
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/// - Returns: an `true` if the registry supports the distribution specification.
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/// - Throws: if the registry does not support the distribution specification.
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static func checkAPI(client: HTTPClient, registryURL: URL) async throws -> AuthChallenge {
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public static func checkAPI(client: HTTPClient, registryURL: URL) async throws -> AuthChallenge {
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// See https://github.com/opencontainers/distribution-spec/blob/main/spec.md#determining-support
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// The registry indicates that it supports the v2 protocol by returning a 200 OK response.

‎Sources/ContainerRegistry/RegistryClient+ImageConfiguration.swift‎

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This file was deleted.

Sources/ContainerRegistry/Blobs.swift renamed to Sources/ContainerRegistry/RegistryClient+ImageDestination.swift

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//
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//===----------------------------------------------------------------------===//
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import Foundation
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import struct Foundation.Data
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import struct Foundation.URL
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import HTTPTypes
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extension RegistryClient {
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extension RegistryClient: ImageDestination {
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// Internal helper method to initiate a blob upload in 'two shot' mode
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func startBlobUploadSession(repository: ImageReference.Repository) async throws -> URL {
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// Upload in "two shot" mode.
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return locationURL
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}
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}
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public extension RegistryClient {
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func blobExists(repository: ImageReference.Repository, digest: ImageReference.Digest) async throws -> Bool {
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/// Checks whether a blob exists.
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///
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/// - Parameters:
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/// - repository: Name of the destination repository.
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/// - digest: Digest of the requested blob.
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/// - Returns: True if the blob exists, otherwise false.
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/// - Throws: If the destination encounters an error.
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public func blobExists(
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repository: ImageReference.Repository,
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digest: ImageReference.Digest
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) async throws -> Bool {
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do {
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let _ = try await executeRequestThrowing(
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.head(repository, path: "blobs/\(digest)"),
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} catch HTTPClientError.unexpectedStatusCode(status: .notFound, _, _) { return false }
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}
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/// Fetches an unstructured blob of data from the registry.
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///
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/// - Parameters:
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/// - repository: Name of the repository containing the blob.
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/// - digest: Digest of the blob.
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/// - Returns: The downloaded data.
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/// - Throws: If the blob download fails.
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func getBlob(repository: ImageReference.Repository, digest: ImageReference.Digest) async throws -> Data {
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try await executeRequestThrowing(
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.get(repository, path: "blobs/\(digest)", accepting: ["application/octet-stream"]),
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decodingErrors: [.notFound]
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)
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.data
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}
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/// Uploads a blob to the registry.
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///
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/// This function uploads a blob of unstructured data to the registry.
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/// - Returns: An ContentDescriptor object representing the
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/// uploaded blob.
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/// - Throws: If the blob cannot be encoded or the upload fails.
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func putBlob(repository: ImageReference.Repository, mediaType: String = "application/octet-stream", data: Data)
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async throws
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-> ContentDescriptor
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{
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public func putBlob(
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repository: ImageReference.Repository,
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mediaType: String = "application/octet-stream",
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data: Data
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) async throws -> ContentDescriptor {
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// Ask the server to open a session and tell us where to upload our data
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let location = try await startBlobUploadSession(repository: repository)
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/// Some JSON objects, such as ImageConfiguration, are stored
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/// in the registry as plain blobs with MIME type "application/octet-stream".
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/// This function encodes the data parameter and uploads it as a generic blob.
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func putBlob<Body: Encodable>(
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public func putBlob<Body: Encodable>(
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repository: ImageReference.Repository,
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mediaType: String = "application/octet-stream",
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data: Body
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)
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async throws -> ContentDescriptor
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{
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) async throws -> ContentDescriptor {
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let encoded = try encoder.encode(data)
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return try await putBlob(repository: repository, mediaType: mediaType, data: encoded)
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}
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/// Encodes and uploads an image manifest.
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///
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/// - Parameters:
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/// - repository: Name of the destination repository.
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/// - reference: Optional tag to apply to this manifest.
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/// - manifest: Manifest to be uploaded.
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/// - Returns: An ContentDescriptor object representing the
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/// uploaded blob.
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/// - Throws: If the blob cannot be encoded or the upload fails.
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///
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/// Manifests are not treated as blobs by the distribution specification.
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/// They have their own MIME types and are uploaded to different
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public func putManifest(
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repository: ImageReference.Repository,
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reference: (any ImageReference.Reference)? = nil,
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manifest: ImageManifest
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) async throws -> ContentDescriptor {
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// See https://github.com/opencontainers/distribution-spec/blob/main/spec.md#pushing-manifests
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let encoded = try encoder.encode(manifest)
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let digest = ImageReference.Digest(of: encoded)
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let mediaType = manifest.mediaType ?? "application/vnd.oci.image.manifest.v1+json"
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let _ = try await executeRequestThrowing(
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.put(
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repository,
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path: "manifests/\(reference ?? digest)",
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contentType: mediaType
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),
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uploading: encoded,
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expectingStatus: .created,
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decodingErrors: [.notFound]
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)
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return ContentDescriptor(
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mediaType: mediaType,
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digest: "\(digest)",
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size: Int64(encoded.count)
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)
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}
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}

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