plumbing: packfile, read object content only once

Signed-off-by: Miguel Molina <miguel@erizocosmi.co>

2 files changed, 40 insertions, 7 deletions

diff --git a/plumbing/format/packfile/parser.go b/plumbing/format/packfile/parser.go
index beb3e27..581c334 100644
--- a/plumbing/format/packfile/parser.go
+++ b/plumbing/format/packfile/parser.go
@@ -280,14 +280,8 @@ func (p *Parser) resolveDeltas() error {
 		}
 
 		if !obj.IsDelta() && len(obj.Children) > 0 {
-			var err error
-			base, err := p.get(obj)
-			if err != nil {
-				return err
-			}
-
 			for _, child := range obj.Children {
-				if _, err := p.resolveObject(child, base); err != nil {
+				if _, err := p.resolveObject(child, content); err != nil {
 					return err
 				}
 			}
@@ -297,12 +291,18 @@ func (p *Parser) resolveDeltas() error {
 				delete(p.deltas, obj.Offset)
 			}
 		}
+
+		obj.Content = nil
 	}
 
 	return nil
 }
 
 func (p *Parser) get(o *objectInfo) ([]byte, error) {
+	if len(o.Content) > 0 {
+		return o.Content, nil
+	}
+
 	e, ok := p.cache.Get(o.SHA1)
 	// If it's not on the cache and is not a delta we can try to find it in the
 	// storage, if there's one.
@@ -460,6 +460,8 @@ type objectInfo struct {
 	Parent   *objectInfo
 	Children []*objectInfo
 	SHA1     plumbing.Hash
+
+	Content []byte
 }
 
 func newBaseObject(offset, length int64, t plumbing.ObjectType) *objectInfo {
@@ -488,6 +490,12 @@ func newDeltaObject(
 	return obj
 }
 
+func (o *objectInfo) Write(b []byte) (int, error) {
+	o.Content = make([]byte, len(b))
+	copy(o.Content, b)
+	return o.Hasher.Write(b)
+}
+
 func (o *objectInfo) IsDelta() bool {
 	return o.Type.IsDelta()
 }
diff --git a/plumbing/format/packfile/parser_test.go b/plumbing/format/packfile/parser_test.go
index b5d482e..012a140 100644
--- a/plumbing/format/packfile/parser_test.go
+++ b/plumbing/format/packfile/parser_test.go
@@ -168,3 +168,28 @@ func BenchmarkParse(b *testing.B) {
 		})
 	}
 }
+
+func BenchmarkParseBasic(b *testing.B) {
+	if err := fixtures.Init(); err != nil {
+		b.Fatal(err)
+	}
+
+	defer func() {
+		if err := fixtures.Clean(); err != nil {
+			b.Fatal(err)
+		}
+	}()
+
+	f := fixtures.Basic().One()
+	for i := 0; i < b.N; i++ {
+		parser, err := packfile.NewParser(packfile.NewScanner(f.Packfile()))
+		if err != nil {
+			b.Fatal(err)
+		}
+
+		_, err = parser.Parse()
+		if err != nil {
+			b.Fatal(err)
+		}
+	}
+}