update: reduce dynamic allocation

Use a globally allocated buffer when viable.
Reduce static buffer size from 64k to 16k.

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

tinygo/v0/examples/reverse/wrapper_transport.go

@@ -1,10 +1,14 @@
 package main
 
 import (
+ "io"
+
  v0 "github.com/gaukas/watm/tinygo/v0"
  v0net "github.com/gaukas/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)
 
@@ -20,8 +24,15 @@ type ReverseConn struct {
 }
 
 func (rc *ReverseConn) Read(b []byte) (n int, err error) {
- var dupBuf []byte = make([]byte, len(b))
  n, err = rc.Conn.Read(dupBuf)
+ 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++ {
@@ -32,8 +43,6 @@ func (rc *ReverseConn) Read(b []byte) (n int, err error) {
 }
 
 func (rc *ReverseConn) Write(b []byte) (n int, err error) {
- var dupBuf []byte = make([]byte, len(b))
-
  // reverse the bytes to be written
  for i := 0; i < len(b); i++ {
  dupBuf[i] = b[len(b)-i-1]

tinygo/v0/exports.go

@@ -1,6 +1,7 @@
 package v0
 
 import (
+ "bytes"
  "errors"
  "log"
  "os"
@@ -66,15 +67,14 @@ func readConfig() (config []byte, err error) {
  }
 
  // read the config file
- var fileContent []byte = make([]byte, 65536)
- n, err := file.Read(fileContent)
+ buf := new(bytes.Buffer)
+ _, err = buf.ReadFrom(file)
  if err != nil {
- log.Println("readConfig: file.Read:", err)
+ log.Println("readConfig: (*bytes.Buffer).ReadFrom:", err)
  return nil, syscall.EIO
  }
 
- config = make([]byte, n)
- copy(config, fileContent[:n])
+ config = buf.Bytes()
 
  // close the file
  if err := file.Close(); err != nil {

tinygo/v0/worker.go

@@ -34,6 +34,8 @@ var cancelConn v0net.Conn // cancelConn is used to cancel the entire worker.
 
 var workerFn func() int32 = unfairWorker // by default, use unfairWorker
 
+var readBuf []byte = make([]byte, 16384) // 16k buffer for reading
+
 // WorkerFairness sets the fairness of a worker.
 //
 // If sourceConn or remoteConn will not work in non-blocking mode,
@@ -90,7 +92,6 @@ func untilError(f func() error) error {
 //
 // TODO: use poll_oneoff instead of busy polling
 func unfairWorker() int32 {
- var readBuf []byte = make([]byte, 65536)
  for {
  pollFd := []pollFd{
  {
@@ -195,7 +196,6 @@ func unfairWorker() int32 {
 //
 // TODO: use poll_oneoff instead of busy polling
 func fairWorker() int32 {
- var readBuf []byte = make([]byte, 65536)
  for {
  pollFd := []pollFd{
  {
@@ -256,8 +256,8 @@ func fairWorker() int32 {
 }
 
 func copyOnce(dstName, srcName string, dst, src net.Conn, buf []byte) error {
- if buf == nil {
- buf = make([]byte, 65536)
+ if len(buf) == 0 {
+ buf = make([]byte, 16384) // 16k buffer for reading
  }
 
  readN, readErr := src.Read(buf)