plumbing: TreeWalker performance improvement, bufio pool for objects

Removes path.Clean and path.Join, as they're expensive in comparison to basic
string manipulation that can be used here.

Adds bufio.Buffer pool to be used by tag, tree and commit object decoding.

Signed-off-by: Arran Walker <arran.walker@fiveturns.org>

Author: saracen

plumbing/object/commit.go

@@ -171,7 +171,9 @@ func (c *Commit) Decode(o plumbing.EncodedObject) (err error) {
 	}
 	defer ioutil.CheckClose(reader, &err)
 
-	r := bufio.NewReader(reader)
+	r := bufPool.Get().(*bufio.Reader)
+	defer bufPool.Put(r)
+	r.Reset(reader)
 
 	var message bool
 	var pgpsig bool

plumbing/object/common.go

@@ -0,0 +1,12 @@
+package object
+
+import (
+	"bufio"
+	"sync"
+)
+
+var bufPool = sync.Pool{
+	New: func() interface{} {
+		return bufio.NewReader(nil)
+	},
+}

plumbing/object/tag.go

@@ -93,7 +93,9 @@ func (t *Tag) Decode(o plumbing.EncodedObject) (err error) {
 	}
 	defer ioutil.CheckClose(reader, &err)
 
-	r := bufio.NewReader(reader)
+	r := bufPool.Get().(*bufio.Reader)
+	defer bufPool.Put(r)
+	r.Reset(reader)
 	for {
 		var line []byte
 		line, err = r.ReadBytes('\n')

plumbing/object/tree.go

@@ -230,7 +230,9 @@ func (t *Tree) Decode(o plumbing.EncodedObject) (err error) {
 	}
 	defer ioutil.CheckClose(reader, &err)
 
-	r := bufio.NewReader(reader)
+	r := bufPool.Get().(*bufio.Reader)
+	defer bufPool.Put(r)
+	r.Reset(reader)
 	for {
 		str, err := r.ReadString(' ')
 		if err != nil {
@@ -383,7 +385,7 @@ func NewTreeWalker(t *Tree, recursive bool, seen map[plumbing.Hash]bool) *TreeWa
 // underlying repository will be skipped automatically. It is possible that this
 // may change in future versions.
 func (w *TreeWalker) Next() (name string, entry TreeEntry, err error) {
-	var obj Object
+	var obj *Tree
 	for {
 		current := len(w.stack) - 1
 		if current < 0 {
@@ -403,7 +405,7 @@ func (w *TreeWalker) Next() (name string, entry TreeEntry, err error) {
 			// Finished with the current tree, move back up to the parent
 			w.stack = w.stack[:current]
 			w.base, _ = path.Split(w.base)
-			w.base = path.Clean(w.base) // Remove trailing slash
+			w.base = strings.TrimSuffix(w.base, "/")
 			continue
 		}
 
@@ -419,7 +421,11 @@ func (w *TreeWalker) Next() (name string, entry TreeEntry, err error) {
 			obj, err = GetTree(w.s, entry.Hash)
 		}
 
-		name = path.Join(w.base, entry.Name)
+		if len(w.base) > 0 {
+			name = w.base + "/" + entry.Name
+		} else {
+			name = entry.Name
+		}
 
 		if err != nil {
 			err = io.EOF
@@ -433,9 +439,13 @@ func (w *TreeWalker) Next() (name string, entry TreeEntry, err error) {
 		return
 	}
 
-	if t, ok := obj.(*Tree); ok {
-		w.stack = append(w.stack, &treeEntryIter{t, 0})
-		w.base = path.Join(w.base, entry.Name)
+	if obj != nil {
+		w.stack = append(w.stack, &treeEntryIter{obj, 0})
+		if len(w.base) > 0 {
+			w.base = w.base + "/" + entry.Name
+		} else {
+			w.base = entry.Name
+		}
 	}
 
 	return