fix: write called without restricting size (#4)

This commit reverts the change by switching back to real-time allocated buffer and fixed a bug caused by writing `dupBuf` instead of `dupBuf[:len(b)]`.

Signed-off-by: Gaukas Wang <i@gaukas.wang>

tinygo/v0/examples/reverse/wrapper_transport.go

@@ -1,14 +1,10 @@
 package main
 
 import (
-	"io"
-
 	v0 "github.com/refraction-networking/watm/tinygo/v0"
 	v0net "github.com/refraction-networking/watm/tinygo/v0/net"
 )
 
-var dupBuf []byte = make([]byte, 16384) // 16k buffer for reversing
-
 // type guard: ReverseWrappingTransport must implement [v0.WrappingTransport].
 var _ v0.WrappingTransport = (*ReverseWrappingTransport)(nil)
 
@@ -24,29 +20,27 @@ type ReverseConn struct {
 }
 
 func (rc *ReverseConn) Read(b []byte) (n int, err error) {
-	n, err = rc.Conn.Read(dupBuf)
+	tmpBuf := make([]byte, len(b))
+	n, err = rc.Conn.Read(tmpBuf)
 	if err != nil {
 		return 0, err
 	}
 
-	if n > len(b) {
-		err = io.ErrShortBuffer
-		n = len(b)
-	}
-
 	// reverse all bytes read successfully so far
 	for i := 0; i < n; i++ {
-		b[i] = dupBuf[n-i-1]
+		b[i] = tmpBuf[n-i-1]
 	}
 
 	return n, err
 }
 
 func (rc *ReverseConn) Write(b []byte) (n int, err error) {
+	tmpBuf := make([]byte, len(b))
+
 	// reverse the bytes to be written
 	for i := 0; i < len(b); i++ {
-		dupBuf[i] = b[len(b)-i-1]
+		tmpBuf[i] = b[len(b)-i-1]
 	}
 
-	return rc.Conn.Write(dupBuf)
+	return rc.Conn.Write(tmpBuf[:len(b)])
 }