From 7e8d7125446bb6e12a056a5a6ca979727790d0df Mon Sep 17 00:00:00 2001
From: Máximo Cuadros <mcuadros@gmail.com>
Date: Thu, 15 Sep 2016 21:20:58 +0200
Subject: dotgit: synced write packfile and index generation

---
 storage/filesystem/internal/dotgit/dotgit.go | 154 +++++++++++++++++++++------
 1 file changed, 122 insertions(+), 32 deletions(-)

(limited to 'storage/filesystem/internal/dotgit/dotgit.go')

diff --git a/storage/filesystem/internal/dotgit/dotgit.go b/storage/filesystem/internal/dotgit/dotgit.go
index cacda68..54113d5 100644
--- a/storage/filesystem/internal/dotgit/dotgit.go
+++ b/storage/filesystem/internal/dotgit/dotgit.go
@@ -8,12 +8,12 @@ import (
 	"io"
 	"os"
 	"strings"
+	"sync/atomic"
 	"time"
 
 	"gopkg.in/src-d/go-git.v4/core"
 	"gopkg.in/src-d/go-git.v4/formats/idxfile"
 	"gopkg.in/src-d/go-git.v4/formats/packfile"
-	"gopkg.in/src-d/go-git.v4/storage/memory"
 	"gopkg.in/src-d/go-git.v4/utils/fs"
 )
 
@@ -227,35 +227,35 @@ func isHexAlpha(b byte) bool {
 }
 
 type PackWriter struct {
-	fs fs.Filesystem
-	sr io.ReadCloser
-	sw io.WriteCloser
-	fw fs.File
-	mw io.Writer
+	Notify func(h core.Hash, i idxfile.Idxfile)
 
+	fs       fs.Filesystem
+	fr, fw   fs.File
+	synced   *syncedReader
 	checksum core.Hash
 	index    idxfile.Idxfile
 	result   chan error
-	Notify   func(h core.Hash, i idxfile.Idxfile)
 }
 
 func newPackWrite(fs fs.Filesystem) (*PackWriter, error) {
-	temp := sha1.Sum([]byte(time.Now().String()))
-	filename := fmt.Sprintf(".%x", temp)
+	seed := sha1.Sum([]byte(time.Now().String()))
+	tmp := fs.Join(objectsPath, packPath, fmt.Sprintf("tmp_pack_%x", seed))
 
-	fw, err := fs.Create(fs.Join(objectsPath, packPath, filename))
+	fw, err := fs.Create(tmp)
 	if err != nil {
 		return nil, err
 	}
 
-	sr, sw := io.Pipe()
+	fr, err := fs.Open(tmp)
+	if err != nil {
+		return nil, err
+	}
 
 	writer := &PackWriter{
 		fs:     fs,
 		fw:     fw,
-		sr:     sr,
-		sw:     sw,
-		mw:     io.MultiWriter(sw, fw),
+		fr:     fr,
+		synced: newSyncedReader(fw, fr),
 		result: make(chan error),
 	}
 
@@ -264,10 +264,12 @@ func newPackWrite(fs fs.Filesystem) (*PackWriter, error) {
 }
 
 func (w *PackWriter) buildIndex() {
-	defer w.sr.Close()
-	o := memory.NewStorage().ObjectStorage()
-	s := packfile.NewScanner(w.sr)
-	d := packfile.NewDecoder(s, o)
+	s := packfile.NewScanner(w.synced)
+	d, err := packfile.NewDecoder(s, nil)
+	if err != nil {
+		w.result <- err
+		return
+	}
 
 	checksum, err := d.Decode()
 	if err != nil {
@@ -287,8 +289,8 @@ func (w *PackWriter) buildIndex() {
 	w.result <- err
 }
 
-func (w *PackWriter) Write(p []byte) (int, error) {
-	return w.mw.Write(p)
+func (w *PackWriter) Write(p []byte) (n int, err error) {
+	return w.synced.Write(p)
 }
 
 func (w *PackWriter) Close() error {
@@ -296,20 +298,18 @@ func (w *PackWriter) Close() error {
 		close(w.result)
 	}()
 
-	if err := w.fw.Close(); err != nil {
-		return err
-	}
-
-	if err := w.sw.Close(); err != nil {
-		return err
-	}
-
-	if err := <-w.result; err != nil {
-		return err
+	pipe := []func() error{
+		func() error { return <-w.result },
+		w.fr.Close,
+		w.fw.Close,
+		w.synced.Close,
+		w.save,
 	}
 
-	if err := w.save(); err != nil {
-		return err
+	for i, f := range pipe {
+		if err := f(); err != nil {
+			return err
+		}
 	}
 
 	if w.Notify != nil {
@@ -342,3 +342,93 @@ func (w *PackWriter) encodeIdx(writer io.Writer) error {
 	_, err := e.Encode(&w.index)
 	return err
 }
+
+type syncedReader struct {
+	w io.Writer
+	r io.ReadSeeker
+
+	blocked, done uint32
+	written, read uint64
+	news          chan bool
+}
+
+func newSyncedReader(w io.Writer, r io.ReadSeeker) *syncedReader {
+	return &syncedReader{
+		w:    w,
+		r:    r,
+		news: make(chan bool),
+	}
+}
+
+func (s *syncedReader) Write(p []byte) (n int, err error) {
+	defer func() {
+		written := atomic.AddUint64(&s.written, uint64(n))
+		read := atomic.LoadUint64(&s.read)
+		if written > read {
+			s.wake()
+		}
+	}()
+
+	n, err = s.w.Write(p)
+	return
+}
+
+func (s *syncedReader) Read(p []byte) (n int, err error) {
+	defer func() { atomic.AddUint64(&s.read, uint64(n)) }()
+
+	s.sleep()
+	n, err = s.r.Read(p)
+	if err == io.EOF && !s.isDone() {
+		if n == 0 {
+			return s.Read(p)
+		}
+
+		return n, nil
+	}
+
+	return
+}
+
+func (s *syncedReader) isDone() bool {
+	return atomic.LoadUint32(&s.done) == 1
+}
+
+func (s *syncedReader) isBlocked() bool {
+	return atomic.LoadUint32(&s.blocked) == 1
+}
+
+func (s *syncedReader) wake() {
+	if s.isBlocked() {
+		//	fmt.Println("wake")
+		atomic.StoreUint32(&s.blocked, 0)
+		s.news <- true
+	}
+}
+
+func (s *syncedReader) sleep() {
+	read := atomic.LoadUint64(&s.read)
+	written := atomic.LoadUint64(&s.written)
+	if read >= written {
+		atomic.StoreUint32(&s.blocked, 1)
+		//	fmt.Println("sleep", read, written)
+		<-s.news
+	}
+
+}
+
+func (s *syncedReader) Seek(offset int64, whence int) (int64, error) {
+	if whence == io.SeekCurrent {
+		return s.r.Seek(offset, whence)
+	}
+
+	p, err := s.r.Seek(offset, whence)
+	s.read = uint64(p)
+
+	return p, err
+}
+
+func (s *syncedReader) Close() error {
+	atomic.StoreUint32(&s.done, 1)
+	close(s.news)
+	return nil
+}
-- 
cgit