From f68f07d896a677b4709e1c4be9b07364ff7c385b Mon Sep 17 00:00:00 2001
From: James Hillyerd <james@hillyerd.com>
Date: Sat, 20 Oct 2018 20:33:27 -0700
Subject: [PATCH] file: pool index readers to reduce allocs for #122

---
 pkg/storage/file/fstore.go | 33 ++++++++++++++++++++++++++++-----
 pkg/storage/file/mbox.go   |  4 +++-
 2 files changed, 31 insertions(+), 6 deletions(-)

diff --git a/pkg/storage/file/fstore.go b/pkg/storage/file/fstore.go
index a52bc36..2eb51c9 100644
--- a/pkg/storage/file/fstore.go
+++ b/pkg/storage/file/fstore.go
@@ -7,6 +7,7 @@ import (
 	"io/ioutil"
 	"os"
 	"path/filepath"
+	"sync"
 	"time"
 
 	"github.com/jhillyerd/inbucket/pkg/config"
@@ -40,10 +41,11 @@ func countGenerator(c chan int) {
 // Store implements DataStore aand is the root of the mail storage
 // hiearchy.  It provides access to Mailbox objects
 type Store struct {
-	hashLock   storage.HashLock
-	path       string
-	mailPath   string
-	messageCap int
+	hashLock      storage.HashLock
+	path          string
+	mailPath      string
+	messageCap    int
+	bufReaderPool sync.Pool
 }
 
 // New creates a new DataStore object using the specified path
@@ -60,7 +62,16 @@ func New(cfg config.Storage) (storage.Store, error) {
 				Msg("Error creating dir")
 		}
 	}
-	return &Store{path: path, mailPath: mailPath, messageCap: cfg.MailboxMsgCap}, nil
+	return &Store{
+		path:       path,
+		mailPath:   mailPath,
+		messageCap: cfg.MailboxMsgCap,
+		bufReaderPool: sync.Pool{
+			New: func() interface{} {
+				return bufio.NewReader(nil)
+			},
+		},
+	}, nil
 }
 
 // AddMessage adds a message to the specified mailbox.
@@ -253,6 +264,18 @@ func (fs *Store) mboxFromHash(hash string) *mbox {
 	}
 }
 
+// getPooledReader pulls a buffered reader from the fs.bufReaderPool
+func (fs *Store) getPooledReader(r io.Reader) *bufio.Reader {
+	br := fs.bufReaderPool.Get().(*bufio.Reader)
+	br.Reset(r)
+	return br
+}
+
+// putPooledReader returns a buffered reader to the fs.bufReaderPool
+func (fs *Store) putPooledReader(br *bufio.Reader) {
+	fs.bufReaderPool.Put(br)
+}
+
 // generatePrefix converts a Time object into the ISO style format we use
 // as a prefix for message files.  Note:  It is used directly by unit
 // tests.
diff --git a/pkg/storage/file/mbox.go b/pkg/storage/file/mbox.go
index 8c85145..55f1c9f 100644
--- a/pkg/storage/file/mbox.go
+++ b/pkg/storage/file/mbox.go
@@ -120,7 +120,9 @@ func (mb *mbox) readIndex() error {
 		}
 	}()
 	// Decode gob data
-	dec := gob.NewDecoder(bufio.NewReader(file))
+	br := mb.store.getPooledReader(file)
+	defer mb.store.putPooledReader(br)
+	dec := gob.NewDecoder(br)
 	name := ""
 	if err = dec.Decode(&name); err != nil {
 		return fmt.Errorf("Corrupt mailbox %q: %v", mb.indexPath, err)