Drop xerrors and reflection dependency

Nothing wrong with missinggo.CopyExact -- but fewer dependencies is better IMO.  Also changed String() to use a consistent receiver name -- not a big deal.

diff --git a/peer_protocol/handshake.go b/peer_protocol/handshake.go
index 5e6f123dd99379e8605cdf36419e8d2112e57832..ba81a0cf385974123f5734dd990c6780364009f9 100644 (file)
--- a/peer_protocol/handshake.go
+++ b/peer_protocol/handshake.go
@@ -2,12 +2,11 @@ package peer_protocol
 
 import (
        "encoding/hex"
+       "errors"
        "fmt"
        "io"
+       "strconv"
 
-       "golang.org/x/xerrors"
-
-       "github.com/anacrolix/missinggo/v2"
        "github.com/anacrolix/torrent/metainfo"
 )
 
@@ -34,8 +33,8 @@ type (
        PeerExtensionBits [8]byte
 )
 
-func (me PeerExtensionBits) String() string {
-       return hex.EncodeToString(me[:])
+func (pex PeerExtensionBits) String() string {
+       return hex.EncodeToString(pex[:])
 }
 
 func NewPeerExtensionBytes(bits ...ExtensionBit) (ret PeerExtensionBits) {
@@ -98,7 +97,7 @@ func Handshake(
                // Wait until writes complete before returning from handshake.
                err = <-writeDone
                if err != nil {
-                       err = fmt.Errorf("error writing: %s", err)
+                       err = fmt.Errorf("error writing: %w", err)
                }
        }()
 
@@ -119,16 +118,21 @@ func Handshake(
        var b [68]byte
        _, err = io.ReadFull(sock, b[:68])
        if err != nil {
-               err = xerrors.Errorf("while reading: %w", err)
-               return
+               return res, fmt.Errorf("while reading: %w", err)
        }
        if string(b[:20]) != Protocol {
-               err = xerrors.Errorf("unexpected protocol string")
-               return
+               return res, errors.New("unexpected protocol string")
+       }
+
+       copyExact := func(dst []byte, src []byte) {
+               if dstLen, srcLen := uint64(len(dst)), uint64(len(src)); dstLen != srcLen {
+                       panic("dst len " + strconv.FormatUint(dstLen,10) + " != src len " + strconv.FormatUint(srcLen,10))
+               }
+               copy(dst, src)
        }
-       missinggo.CopyExact(&res.PeerExtensionBits, b[20:28])
-       missinggo.CopyExact(&res.Hash, b[28:48])
-       missinggo.CopyExact(&res.PeerID, b[48:68])
+       copyExact(res.PeerExtensionBits[:], b[20:28])
+       copyExact(res.Hash[:], b[28:48])
+       copyExact(res.PeerID[:], b[48:68])
        // peerExtensions.Add(res.PeerExtensionBits.String(), 1)
 
        // TODO: Maybe we can just drop peers here if we're not interested. This