openpgp,buffered-reader: Optimize Vec<u8>::truncate manually

  - On debug builds, Vec<u8>::truncate is very, very slow.  For
    instance, running the decrypt_test_stream test takes 51 seconds on
    my (Neal's) computer using Vec<u8>::truncate and <0.1 seconds using
    `unsafe { v.set_len(len); }`.

    The issue is that the compiler calls drop on every element that is
    dropped, even though a u8 doesn't have a drop implementation.  The
    compiler optimizes this away at high optimization levels, but
    those levels make debugging harder.

1 files changed, 2 insertions, 1 deletions

diff --git a/openpgp/src/armor.rs b/openpgp/src/armor.rs
index 85a0a967..c593fdee 100644
--- a/openpgp/src/armor.rs
+++ b/openpgp/src/armor.rs
@@ -35,6 +35,7 @@ use std::str;
 use std::borrow::Cow;
 use quickcheck::{Arbitrary, Gen};
 
+use crate::vec_truncate;
 use crate::packet::prelude::*;
 use crate::packet::header::BodyLength;
 use crate::packet::header::ctb::{CTBNew, CTBOld};
@@ -931,7 +932,7 @@ fn base64_filter(mut bytes: Cow<[u8]>, base64_data_max: usize,
             (Cow::Borrowed(&s[..base64_len]), unfiltered_complete_len,
              prefix_remaining),
         Cow::Owned(mut v) => {
-            v.truncate(base64_len);
+            vec_truncate(&mut v, base64_len);
             (Cow::Owned(v), unfiltered_complete_len, prefix_remaining)
         }
     }