BufferedDecoder: return Option[Value] from decode

preserves.nimble

@@ -1,6 +1,6 @@
 # Package
 
-version = "20240114"
+version = "20240116"
 author        = "Emery Hemingway"
 description   = "data model and serialization format"
 license       = "Unlicense"

src/preserves/private/decoding.nim

@@ -1,7 +1,7 @@
 # SPDX-FileCopyrightText: ☭ Emery Hemingway
 # SPDX-License-Identifier: Unlicense
 
-import std/[endians, streams, strutils]
+import std/[endians, options, streams, strutils]
 import bigints
 import ./values
 
@@ -163,15 +163,14 @@ proc feed*[T: byte|char](dec: var BufferedDecoder; data: openarray[T]) =
   if data.len > 0:
     dec.feed(unsafeAddr data[0], data.len)
 
-proc decode*(dec: var BufferedDecoder): (bool, Value) =
+proc decode*(dec: var BufferedDecoder): Option[Value] =
   ## Decode from `dec`. If decoding fails the internal position of the
   ## decoder does not advance.
   if dec.appendPosition > 0:
     assert(dec.decodePosition < dec.appendPosition)
     dec.stream.setPosition(dec.decodePosition)
     try:
-      result[1] = decodePreserves(dec.stream)
-      result[0] = true
+      result = dec.stream.decodePreserves.some
       dec.decodePosition = dec.stream.getPosition()
       if dec.decodePosition == dec.appendPosition:
         dec.stream.setPosition(0)

tests/test_buffereddecoder.nim

@@ -1,7 +1,7 @@
 # SPDX-FileCopyrightText: 2021 ☭ Emery Hemingway
 # SPDX-License-Identifier: Unlicense
 
-import std/unittest
+import std/[options, unittest]
 import preserves
 
 suite "BufferedDecoder":
@@ -10,7 +10,6 @@ suite "BufferedDecoder":
     var
       buf = newBufferedDecoder()
       pr = Value(kind: pkByteString, bytes: newSeq[byte](23))
-      ok: bool
     for i, _ in pr.bytes:
       pr.bytes[i] = byte(i)
     let bin = encode(pr)
@@ -19,5 +18,5 @@ suite "BufferedDecoder":
       let j = (i+2) and 0xf
       feed(buf, bin[0..<j])
       feed(buf, bin[j..bin.high])
-      (ok, pr) = decode(buf)
-      assert ok
+      var v = decode(buf)
+      check v.isSome