Introduce SigningResult class to allow for additional signing information to be returned

sop-java/src/main/java/sop/SigningResult.java

@@ -0,0 +1,50 @@
+// SPDX-FileCopyrightText: 2021 Paul Schaub <vanitasvitae@fsfe.org>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package sop;
+
+/**
+ * This class contains various information about a signed message.
+ */
+public final class SigningResult {
+
+    private final MicAlg micAlg;
+
+    private SigningResult(MicAlg micAlg) {
+        this.micAlg = micAlg;
+    }
+
+    /**
+     * Return a string identifying the digest mechanism used to create the signed message.
+     * This is useful for setting the micalg= parameter for the multipart/signed
+     * content type of a PGP/MIME object as described in section 5 of [RFC3156].
+     *
+     * If more than one signature was generated and different digest mechanisms were used,
+     * the value of the micalg object is an empty string.
+     *
+     * @return micalg
+     */
+    public MicAlg getMicAlg() {
+        return micAlg;
+    }
+
+    public static Builder builder() {
+        return new Builder();
+    }
+
+    public static class Builder {
+
+        private MicAlg micAlg;
+
+        public Builder setMicAlg(MicAlg micAlg) {
+            this.micAlg = micAlg;
+            return this;
+        }
+
+        public SigningResult build() {
+            SigningResult signingResult = new SigningResult(micAlg);
+            return signingResult;
+        }
+    }
+}

sop-java/src/main/java/sop/operation/Sign.java

@@ -8,8 +8,8 @@ import java.io.ByteArrayInputStream;
 import java.io.IOException;
 import java.io.InputStream;
 
-import sop.MicAlg;
 import sop.ReadyWithResult;
+import sop.SigningResult;
 import sop.enums.SignAs;
 import sop.exception.SOPGPException;
 
@@ -55,7 +55,7 @@ public interface Sign {
      * @param data input stream containing data
      * @return ready
      */
-    ReadyWithResult<MicAlg> data(InputStream data) throws IOException, SOPGPException.ExpectedText;
+    ReadyWithResult<SigningResult> data(InputStream data) throws IOException, SOPGPException.ExpectedText;
 
     /**
      * Signs data.
@@ -63,7 +63,7 @@ public interface Sign {
      * @param data byte array containing data
      * @return ready
      */
-    default ReadyWithResult<MicAlg> data(byte[] data) throws IOException, SOPGPException.ExpectedText {
+    default ReadyWithResult<SigningResult> data(byte[] data) throws IOException, SOPGPException.ExpectedText {
         return data(new ByteArrayInputStream(data));
     }
 }