FingerprintUtil: Add prettifyFingerprint method

Author: vanitasvitae

pg/src/main/java/org/bouncycastle/bcpg/FingerprintUtil.java

@@ -1,6 +1,7 @@
 package org.bouncycastle.bcpg;
 
 import org.bouncycastle.util.Pack;
+import org.bouncycastle.util.encoders.Hex;
 
 public class FingerprintUtil
 {
@@ -112,4 +113,54 @@ public static void writeKeyID(long keyID, byte[] bytes)
     {
         writeKeyID(keyID, bytes, 0);
     }
+
+    public static String prettifyFingerprint(byte[] fingerprint)
+    {
+        String hex = Hex.toHexString(fingerprint);
+        StringBuilder sb = new StringBuilder();
+        switch (hex.length())
+        {
+            case 32:
+                // v3 keys
+                for (int i = 0; i < 4; i++)
+                {
+                    sb.append(hex, i * 4, (i + 1) * 4).append(' ');
+                }
+                sb.append(' ');
+                for (int i = 4; i < 7; i++)
+                {
+                    sb.append(hex, i * 4, (i + 1) * 4).append(' ');
+                }
+                sb.append(hex, 28, 32);
+                return sb.toString();
+            case 40:
+                // v4 keys
+                for (int i = 0; i <= 4; i++)
+                {
+                    sb.append(hex, i * 4, (i + 1) * 4).append(' ');
+                }
+                sb.append(' ');
+                for (int i = 5; i <= 8; i++)
+                {
+                    sb.append(hex, i * 4, (i + 1) * 4).append(' ');
+                }
+                sb.append(hex, 36, 40);
+                return sb.toString();
+            case 64:
+                // v5, v6 keys
+                for (int i = 0; i < 4; i++)
+                {
+                    sb.append(hex, i * 8, (i + 1) * 8).append(' ');
+                }
+                sb.append(' ');
+                for (int i = 4; i < 7; i++)
+                {
+                    sb.append(hex, i * 8, (i + 1) * 8).append(' ');
+                }
+                sb.append(hex, 56, 64);
+                return sb.toString();
+            default:
+                return hex;
+        }
+    }
 }