Add initializers for ASN1ObjectIdentifier (#56)

* Add initializers for ASN1ObjectIdentifier

* Added comments to public symbols. Updated error name.

* Add new Substring initializer. Refactor UInt Collection initializer.

---------

Co-authored-by: Cory Benfield <[email protected]>

Sources/SwiftASN1/Basic ASN1 Types/ObjectIdentifier.swift

@@ -63,8 +63,9 @@ public struct ASN1ObjectIdentifier: DERImplicitlyTaggable, BERImplicitlyTaggable
         }
     }
 
+    /// An array representing the OID components
     @inlinable
-    var oidComponents: [UInt] {
+    public var oidComponents: [UInt] {
         var content = bytes
         // We have to parse the content. From the spec:
         //
@@ -143,25 +144,72 @@ extension ASN1ObjectIdentifier: Hashable {}
 
 extension ASN1ObjectIdentifier: Sendable {}
 
-extension ASN1ObjectIdentifier: ExpressibleByArrayLiteral {
+extension ASN1ObjectIdentifier {
+    /// Initializes ``ASN1ObjectIdentifier`` from its OID components
+    /// - Parameter elements: The OID components
     @inlinable
-    public init(arrayLiteral elements: UInt...) {
+    public init(elements: some Collection<UInt>) throws {
         var bytes = [UInt8]()
-        var components = elements[...]
-        guard let firstComponent = components.popFirst(), let secondComponent = components.popFirst() else {
-            preconditionFailure("Invalid number of OID components: must be at least two!")
+        var iterator = elements.makeIterator()
+
+        guard let firstComponent = iterator.next(), let secondComponent = iterator.next() else {
+            throw ASN1Error.tooFewOIDComponents(
+                reason: "Invalid number of OID components: must be at least two!"
+            )
         }
 
         let serializedFirstComponent = (firstComponent * 40) + secondComponent
         ASN1ObjectIdentifier._writeOIDSubidentifier(serializedFirstComponent, into: &bytes)
 
-        while let component = components.popFirst() {
+        while let component = iterator.next() {
             ASN1ObjectIdentifier._writeOIDSubidentifier(component, into: &bytes)
         }
         self.bytes = bytes[...]
     }
 }
 
+extension ASN1ObjectIdentifier: ExpressibleByStringLiteral {
+    @inlinable
+    public init(stringLiteral dotRepresentation: String) {
+        // To allow for invalid strings to be tested, parsing is performed in a separate initializer that  `throws`
+        // (this initializer conforms to ExpressibleByStringLiteral so cannot throw)
+        try! self.init(dotRepresentation: dotRepresentation)
+    }
+
+    /// Initializes an instance from a `Substring` containing the dot represented OID
+    /// - Parameter dotRepresentation: The dot represented OID
+    @inlinable
+    public init(dotRepresentation: Substring) throws {
+        let octetArray = dotRepresentation.utf8.split(
+            separator: UInt8(ascii: "."),
+            omittingEmptySubsequences: false
+        )
+
+        try self.init(
+            elements: octetArray.lazy.map { octet in
+                guard let uintOctet = UInt(Substring(octet)) else {
+                    throw ASN1Error.invalidStringRepresentation(reason: "Invalid octet in OID")
+                }
+                return uintOctet
+            }
+        )
+    }
+
+    /// Initializes an instance from a `String` containing the dot represented OID
+    /// - Parameter dotRepresentation: The dot represented OID
+    @inlinable
+    public init(dotRepresentation: String) throws {
+        try self.init(dotRepresentation: Substring(dotRepresentation))
+    }
+}
+
+extension ASN1ObjectIdentifier: ExpressibleByArrayLiteral {
+    @inlinable
+    public init(arrayLiteral elements: UInt...) {
+        try! self.init(elements: elements)
+    }
+}
+
 extension ASN1ObjectIdentifier: CustomStringConvertible {
     @inlinable
     public var description: String {

Sources/SwiftASN1/Errors.swift

@@ -164,6 +164,23 @@ public struct ASN1Error: Error, Hashable, CustomStringConvertible {
             )
         )
     }
+
+    /// Too few OID components were provided. There must be at least two or more.
+    @inline(never)
+    public static func tooFewOIDComponents(
+        reason: String,
+        file: String = #fileID,
+        line: UInt = #line
+    ) -> ASN1Error {
+        return ASN1Error(
+            backing: .init(
+                code: .tooFewOIDComponents,
+                reason: reason,
+                file: file,
+                line: line
+            )
+        )
+    }
 }
 
 extension ASN1Error {
@@ -181,6 +198,7 @@ extension ASN1Error {
             case unsupportedFieldLength
             case invalidPEMDocument
             case invalidStringRepresentation
+            case tooFewOIDComponents
         }
 
         fileprivate var backingCode: BackingCode
@@ -211,6 +229,9 @@ extension ASN1Error {
         /// A string was invalid.
         public static let invalidStringRepresentation = ErrorCode(.invalidStringRepresentation)
 
+        /// Too few OID components were provided. There must be at least two or more.
+        public static let tooFewOIDComponents = ErrorCode(.tooFewOIDComponents)
+
         public var description: String {
             return String(describing: self.backingCode)
         }

Tests/SwiftASN1Tests/ASN1Tests.swift

@@ -1019,6 +1019,46 @@ class ASN1Tests: XCTestCase {
         XCTAssertEqual(s, "ASN1Any([5, 0])")
     }
 
+    func testOIDArrayInitializer() {
+        let oidArray = try! ASN1ObjectIdentifier(elements: [1, 2, 865, 11241, 3])
+        XCTAssertEqual(oidArray.oidComponents, [1, 2, 865, 11241, 3])
+
+        let anotherOidArray = try! ASN1ObjectIdentifier(elements: [1, 2, 865])
+        XCTAssertEqual(anotherOidArray.oidComponents, [1, 2, 865])
+    }
+
+    func testOIDArrayInitializerInvalid() {
+        XCTAssertThrowsError(try ASN1ObjectIdentifier(elements: [1])) { error in
+            XCTAssertEqual((error as? ASN1Error)?.code, .tooFewOIDComponents)
+        }
+
+        XCTAssertThrowsError(try ASN1ObjectIdentifier(elements: [])) { error in
+            XCTAssertEqual((error as? ASN1Error)?.code, .tooFewOIDComponents)
+        }
+    }
+
+    func testOIDStringInitializer() {
+        let oidFromString: ASN1ObjectIdentifier = "1.2.865.11241.3"
+        let oidFromArrayLiteral: ASN1ObjectIdentifier = [1, 2, 865, 11241, 3]
+
+        XCTAssertEqual(oidFromString, oidFromArrayLiteral)
+        XCTAssertEqual(oidFromString.oidComponents, [1, 2, 865, 11241, 3])
+    }
+
+    func testOIDStringInitializerInvalid() {
+        XCTAssertThrowsError(try ASN1ObjectIdentifier(dotRepresentation: "1..2.865.11241.3")) { error in
+            XCTAssertEqual((error as? ASN1Error)?.code, .invalidStringRepresentation)
+        }
+
+        XCTAssertThrowsError(try ASN1ObjectIdentifier(dotRepresentation: "1.2.<invalid>.11241.3")) { error in
+            XCTAssertEqual((error as? ASN1Error)?.code, .invalidStringRepresentation)
+        }
+
+        XCTAssertThrowsError(try ASN1ObjectIdentifier(dotRepresentation: "25")) { error in
+            XCTAssertEqual((error as? ASN1Error)?.code, .tooFewOIDComponents)
+        }
+    }
+
     func testSetOfSingleElement() throws {
         var serializer = DER.Serializer()
         try serializer.serializeSetOf([