Fix float parsing

src/preserves/private/decoding.nim

@@ -30,24 +30,22 @@ proc decodePreserves*(s: Stream; E = void): Preserve[E] =
     result = decodePreserves(s, E)
     result.embedded = true
   of 0x87:
-    let n = s.readUint8()
+    var N: int
+    let n = int s.readUint8()
     case n
     of 4:
-      when system.cpuEndian == bigEndian:
-        result = Preserve[E](kind: pkFloat, float: s.readFloat32())
-      else:
-        result = Preserve[E](kind: pkFloat)
-        var be = s.readFloat32()
-        swapEndian32(result.float.addr, be.addr)
+      result = Preserve[E](kind: pkFloat)
+      var buf: uint32
+      N = s.readData(addr buf, sizeof(buf))
+      bigEndian32(addr result.float, addr buf)
     of 8:
-      when system.cpuEndian == bigEndian:
-        result = Preserve[E](kind: pkDouble, double: s.readFloat64())
-      else:
-        result = Preserve[E](kind: pkDouble)
-        var be = s.readFloat64()
-        swapEndian64(result.double.addr, be.addr)
+      result = Preserve[E](kind: pkDouble)
+      var buf: uint64
+      N = s.readData(addr buf, sizeof(buf))
+      bigEndian64(addr result.double, addr buf)
     else:
       raise newException(IOError, "unhandled IEEE754 value of " & $n & " bytes")
+    if N != n: raise newException(IOError, "short read")
   of 0xb0:
     var n = int s.readVarint()
     if n <= sizeof(int):

src/preserves/private/parsing.nim

@@ -88,7 +88,7 @@ proc pushHexNibble[T](result: var T; c: char) =
     of '0'..'9': T(ord(c) - ord('0'))
     of 'a'..'f': T(ord(c) - ord('a') + 10)
     of 'A'..'F': T(ord(c) - ord('A') + 10)
-    else: 0
+    else: return
   result = (result shl 4) or n
 
 proc parsePreserves*(text: string): Preserve[void] =