Fix varint encoding and decoding

preserves.nimble

@@ -1,6 +1,6 @@
 # Package
 
-version = "20230817"
+version = "20230823"
 author        = "Emery Hemingway"
 description   = "data model and serialization format"
 license       = "Unlicense"

src/preserves.nim

@@ -1,4 +1,4 @@
-# SPDX-FileCopyrightText: 2021 ☭ Emery Hemingway
+# SPDX-FileCopyrightText: ☭ Emery Hemingway
 # SPDX-License-Identifier: Unlicense
 
 import std/[base64, endians, hashes, options, sets, sequtils, streams, strutils, tables, typetraits]
@@ -526,25 +526,23 @@ proc unembed*[E](pr: Preserve[E]): E =
     raise newException(ValueError, "not an embedded value")
   pr.embed
 
-proc writeVarint(s: Stream; n: int) =
+proc writeVarint(s: Stream; n: Natural) =
   var n = n
-  while true:
-    let c = int8(n and 0x7f)
+  while n > 0x7f:
+    s.write(uint8 n or 0x80)
     n = n shr 7
-    if n == 0:
-      s.write((char)c.char)
-      break
-    else:
-      s.write((char)c or 0x80)
+  s.write(uint8 n and 0x7f)
 
-proc readVarint(s: Stream): int =
-  var shift = 0
-  while shift < (9*8):
-    let c = s.readInt8
+proc readVarint(s: Stream): uint =
+  var
+    shift = 0
+    c = uint s.readUint8
+  if c == 0x80: raise newException(ValueError, "invalid Preserves data")
+  while (c and 0x80) == 0x80:
     result = result or ((c and 0x7f) shl shift)
-    if (c and 0x80) == 0:
-      break
     inc(shift, 7)
+    c = uint s.readUint8
+  result = result or (c shl shift)
 
 proc write*[E](str: Stream; pr: Preserve[E]) =
   ## Write the binary-encoding of a Preserves value to a stream.
@@ -792,7 +790,7 @@ proc decode*(dec: var BufferedDecoder; E = void): (bool, Preserve[E]) =
         dec.stream.data.setLen(0)
         dec.appendPosition = 0
         dec.decodePosition = 0
-    except IOError, ValueError:
+    except IOError:
       discard
 
 template preservesRecord*(label: string) {.pragma.}

tests/Tupfile

@@ -1,2 +1,2 @@
 include_rules
-: foreach test_*.nim |> !nim_run |>
+: foreach t*.nim |> !nim_run |>