> On Dec 12, 2017, at 9:00 AM, Ian Lance Taylor <i...@golang.org> wrote:
> DecodedLen is supposed to be applied to the length of the encoded
> data. RFC 4648 says that the encoded data must be padded to be a
> multiple of 8 bytes.
Yet encoding/hash32 defines a NoPadding constant, the code is filled
with tests for whether the padding has been set to NoPadding, and the package
docs make reference to setting things with NoPadding.
There is a lot of logic for that and it can all be made to work with
--- /usr/local/go/src/encoding/base32/base32.go 2017-08-24 16:50:22.000000000
-0500
+++ base32.go 2017-12-12 11:26:34.000000000 -0600
@@ -499,8 +499,11 @@
// corresponding to n bytes of base32-encoded data.
func (enc *Encoding) DecodedLen(n int) int {
if enc.padChar == NoPadding {
- return n * 5 / 8
+ r := n * 5 / 8
+ if (n*5)%8 != 0 {
+ return r + 1
+ }
+ return r
}
-
return n / 8 * 5
}
> Perhaps DecodedLen should have had an error return, but it's too late
> now.
If you are going to go that route, then it isn’t just DecodedLen that
needs to change. Every block of code like
if enc.padChar == NoPadding { … }
should be removed; NoPadding should not be defined; and the package
documentation must stop claiming this can be set with NoPadding.
Note that encoding without padding works as expected, but that would
have to be removed as well.
Or, we could simply fix the math in that length calculation. It is already part
of a if enc.padChar == NoPadding { } block. It just has a math error.
> There is no correct value to return to for an impossible input,
> so returning 0 seems as good as anything.
I would really hate to have to fork encoding/hash32 for the stuff
that I’m trying to build. Building a zbase32 encoder/decoder was
just a call to base32.NewEncoder(). But now it will have to
be a call to a forked version.
Or a math error could be corrected to get the package to behave
as clearly intended.
Cheers,
-j
--
You received this message because you are subscribed to the Google Groups
"golang-nuts" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to golang-nuts+unsubscr...@googlegroups.com.
For more options, visit https://groups.google.com/d/optout.
smime.p7s
Description: S/MIME cryptographic signature
