Spry: binary encoding and decoding

src/preserves/sprypreserves.nim

@@ -116,20 +116,38 @@ when isMainModule:
 
 proc addPreserves*(spry: Interpreter) =
   nimFunc("parsePreserves"):
-    let str = StringVal(evalArg(spry)).value
-    PreservesNode(preserve: parsePreserves(str))
+    let node = evalArg(spry)
+    if node of StringVal:
+      let str = StringVal(node).value
+      result = PreservesNode(preserve: parsePreserves(str))
+
+  nimFunc("decodePreserves"):
+    let node = evalArg(spry)
+    if node of StringVal:
+      let str = StringVal(node).value
+      result = PreservesNode(preserve: decodePreserves(cast[seq[byte]](str)))
+
+  nimMeth("encodePreserves"):
+    let node = evalArgInfix(spry)
+    if node of PreservesNode:
+      var bin = encode PreservesNode(node).preserve
+      result = newValue(cast[string](bin))
+
   nimFunc("fromPreserves"):
     let node = evalArg(spry)
     if node of PreservesNode:
       let pr = PreservesNode(node).preserve
       return toSpry(pr, spry)
+
   nimMeth("toPreserves"):
     let node = evalArgInfix(spry)
     PreservesNode(preserve: node.toPreserve)
+
   nimMeth("arity"):
     let node = evalArgInfix(spry)
     if node of RecordNode:
       return newValue(pred SeqComposite(node).nodes.len)
+
   nimMeth("label"):
     let node = evalArgInfix(spry)
     if node of RecordNode: