added canonical cbor map key sorting

Author: Sandin

Sources/SwiftCBOR/CBOREncoder.swift

@@ -125,6 +125,24 @@ extension CBOR {
         res.append(contentsOf: arr.flatMap{ return $0.encode() })
         return res
     }
+    
+    // MARK: sortHelper
+
+    public static func keyOrder(a: [UInt8], b: [UInt8]) -> Bool {
+        if a.count == b.count {
+            for (index, byteA) in a.enumerated() {
+                let byteB = b[index]
+                if byteA == byteB {
+                    continue
+                } else {
+                    return byteA < byteB
+                }
+            }
+            return false
+        } else {
+            return a.count < b.count
+        }
+    }
 
     // MARK: - major 5: a map of pairs of data items
 
@@ -133,10 +151,16 @@ extension CBOR {
         res.reserveCapacity(1 + map.count * (MemoryLayout<A>.size + MemoryLayout<B>.size + 2))
         res = map.count.encode()
         res[0] = res[0] | 0b101_00000
-        for (k, v) in map {
-            res.append(contentsOf: k.encode())
-            res.append(contentsOf: v.encode())
+        
+        let sortedEntries = map
+            .map { k, v in (k.encode(), v.encode()) }
+            .sorted { a, b in keyOrder(a: a.0, b: b.0) }
+
+        for (k, v) in sortedEntries {
+            res.append(contentsOf: k)
+            res.append(contentsOf: v)
         }
+        
         return res
     }