ContainerRegistry: Represent digest algorithms by an enum

Author: euanh

Sources/ContainerRegistry/ImageReference.swift

@@ -24,7 +24,7 @@ func splitReference(_ reference: String) throws -> (String?, String) {
     // Hostname heuristic: contains a '.' or a ':', or is localhost
     if splits[0] != "localhost", !splits[0].contains("."), !splits[0].contains(":") { return (nil, reference) }
 
-    return (String(splits[0]), String(splits[1]))
+    return ("\(splits[0])", "\(splits[1])")
 }
 
 // Split the name into repository and tag parts
@@ -35,8 +35,8 @@ func parseName(_ name: String) throws -> (ImageReference.Repository, any ImageRe
     let digestSplit = name.split(separator: "@", maxSplits: 1, omittingEmptySubsequences: false)
     if digestSplit.count == 2 {
         return (
-            try ImageReference.Repository(String(digestSplit[0])),
-            try ImageReference.Digest(String(digestSplit[1]))
+            try ImageReference.Repository("\(digestSplit[0])"),
+            try ImageReference.Digest("\(digestSplit[1])")
         )
     }
 
@@ -51,8 +51,8 @@ func parseName(_ name: String) throws -> (ImageReference.Repository, any ImageRe
 
     // assert splits == 2
     return (
-        try ImageReference.Repository(String(tagSplit[0])),
-        try ImageReference.Tag(String(tagSplit[1]))
+        try ImageReference.Repository("\(tagSplit[0])"),
+        try ImageReference.Tag("\(tagSplit[1])")
     )
 }
 
@@ -214,7 +214,19 @@ extension ImageReference {
 
     /// Digest identifies a specific blob by the hash of the blob's contents.
     public struct Digest: Reference, Sendable, Equatable, CustomStringConvertible, CustomDebugStringConvertible {
-        var algorithm: String
+        public enum Algorithm: String, Sendable {
+            case sha256 = "sha256"
+            case sha512 = "sha512"
+
+	    init(fromString rawValue: String) throws {
+                guard let algorithm = Algorithm(rawValue: rawValue) else {
+                    throw RegistryClientError.invalidDigestAlgorithm(rawValue)
+                }
+		self = algorithm
+	    }
+        }
+
+        var algorithm: Algorithm
         var value: String
 
         public enum ValidationError: Error, Equatable {
@@ -230,16 +242,16 @@ extension ImageReference {
             // https://github.com/opencontainers/image-spec/blob/v1.0.1/descriptor.md#sha-256
             let sha256digest = /(sha256):([a-fA-F0-9]{64})/
             if let match = try sha256digest.wholeMatch(in: rawValue) {
-                algorithm = String(match.1)
-                value = String(match.2)
+                algorithm = try Algorithm(fromString: "\(match.1)")
+                value = "\(match.2)"
                 return
             }
 
             // https://github.com/opencontainers/image-spec/blob/v1.0.1/descriptor.md#sha-512
             let sha512digest = /(sha512):([a-fA-F0-9]{128})/
             if let match = try sha512digest.wholeMatch(in: rawValue) {
-                algorithm = String(match.1)
-                value = String(match.2)
+                algorithm = try Algorithm(fromString: "\(match.1)")
+                value = "\(match.2)"
                 return
             }
 

Sources/ContainerRegistry/RegistryClient.swift

@@ -23,6 +23,7 @@ enum RegistryClientError: Error {
     case registryParseError(String)
     case invalidRegistryPath(String)
     case invalidUploadLocation(String)
+    case invalidDigestAlgorithm(String)
 }
 
 extension RegistryClientError: CustomStringConvertible {
@@ -31,6 +32,7 @@ extension RegistryClientError: CustomStringConvertible {
         case let .registryParseError(reference): return "Unable to parse registry: \(reference)"
         case let .invalidRegistryPath(path): return "Unable to construct URL for registry path: \(path)"
         case let .invalidUploadLocation(location): return "Received invalid upload location from registry: \(location)"
+        case let .invalidDigestAlgorithm(digest): return "Invalid or unsupported digest algorithm: \(digest)"
         }
     }
 }

Tests/ContainerRegistryTests/ImageReferenceTests.swift

@@ -293,7 +293,7 @@ struct DigestTests {
     func testParseValidDigest(digest: String, algorithm: String, value: String) throws {
         let parsed = try! ImageReference.Digest(digest)
 
-        #expect(parsed.algorithm == algorithm)
+        #expect("\(parsed.algorithm)" == algorithm)
         #expect(parsed.value == value)
         #expect("\(parsed)" == digest)
     }