From 459343932d9673fc69ce1363ccb70d5f78f2e3e7 Mon Sep 17 00:00:00 2001
From: n-peugnet <n.peugnet@free.fr>
Date: Thu, 7 Oct 2021 11:56:37 +0200
Subject: fix storeDelta by keeping previous raw bytes

this ensures that the last patch is created on top of the previous one.
This way we know that it will be correctly applied on loadDelta

Also directly write to wrapper instead of using an intermediate buffer.
---
 delta/delta.go |  7 ++++---
 repo/repo.go   | 42 ++++++++++++++++++++++++------------------
 2 files changed, 28 insertions(+), 21 deletions(-)

diff --git a/delta/delta.go b/delta/delta.go
index 439da1d..4be57c2 100644
--- a/delta/delta.go
+++ b/delta/delta.go
@@ -1,6 +1,7 @@
 package delta
 
 import (
+	"fmt"
 	"io"
 
 	"github.com/gabstv/go-bsdiff/pkg/bsdiff"
@@ -44,15 +45,15 @@ func (Fdelta) Diff(source io.Reader, target io.Reader, patch io.Writer) error {
 func (Fdelta) Patch(source io.Reader, target io.Writer, patch io.Reader) error {
 	sourceBuf, err := io.ReadAll(source)
 	if err != nil {
-		return err
+		return fmt.Errorf("source read all: %s", err)
 	}
 	patchBuf, err := io.ReadAll(patch)
 	if err != nil {
-		return err
+		return fmt.Errorf("patch read all: %s", err)
 	}
 	targetBuf, err := fdelta.Apply(sourceBuf, patchBuf)
 	if err != nil {
-		return err
+		return fmt.Errorf("apply patch: %s", err)
 	}
 	_, err = target.Write(targetBuf)
 	return err
diff --git a/repo/repo.go b/repo/repo.go
index ab96dbe..678b091 100644
--- a/repo/repo.go
+++ b/repo/repo.go
@@ -79,7 +79,9 @@ type Repo struct {
 	fingerprints      FingerprintMap
 	sketches          SketchMap
 	recipe            []Chunk
+	recipeRaw         []byte
 	files             []File
+	filesRaw          []byte
 	chunkCache        cache.Cacher
 	chunkReadWrapper  utils.ReadWrapper
 	chunkWriteWrapper utils.WriteWrapper
@@ -334,31 +336,30 @@ func concatFiles(files *[]File, stream io.WriteCloser) {
 	*files = actual
 }
 
-func storeDelta(prev interface{}, curr interface{}, dest string, differ delta.Differ, wrapper utils.WriteWrapper) {
-	var prevBytes, currBytes, deltaBytes bytes.Buffer
+func storeDelta(prevRaw []byte, curr interface{}, dest string, differ delta.Differ, wrapper utils.WriteWrapper) {
+	var prevBuff, currBuff bytes.Buffer
 	var encoder *gob.Encoder
 	var err error
 
-	encoder = gob.NewEncoder(&prevBytes)
-	if err = encoder.Encode(prev); err != nil {
-		logger.Panic(err)
+	if len(prevRaw) == 0 {
+		encoder = gob.NewEncoder(&prevBuff)
+		if err = encoder.EncodeValue(reflect.ValueOf(curr)); err != nil {
+			logger.Panic(err)
+		}
+	} else {
+		prevBuff = *bytes.NewBuffer(prevRaw)
 	}
-	encoder = gob.NewEncoder(&currBytes)
+	encoder = gob.NewEncoder(&currBuff)
 	if err = encoder.Encode(curr); err != nil {
 		logger.Panic(err)
 	}
-	if err = differ.Diff(&prevBytes, &currBytes, &deltaBytes); err != nil {
-		logger.Panic(err)
-	}
-
 	file, err := os.Create(dest)
 	if err != nil {
 		logger.Panic(err)
 	}
 	out := wrapper(file)
-	n, err := io.Copy(out, &deltaBytes)
-	if err != nil {
-		logger.Panic(n, err)
+	if err = differ.Diff(&prevBuff, &currBuff, out); err != nil {
+		logger.Panic(err)
 	}
 	if err = out.Close(); err != nil {
 		logger.Panic(err)
@@ -368,7 +369,7 @@ func storeDelta(prev interface{}, curr interface{}, dest string, differ delta.Di
 	}
 }
 
-func loadDeltas(target interface{}, versions []string, patcher delta.Patcher, wrapper utils.ReadWrapper, name string) {
+func loadDeltas(target interface{}, versions []string, patcher delta.Patcher, wrapper utils.ReadWrapper, name string) []byte {
 	var prev bytes.Buffer
 	var encoder *gob.Encoder
 	var err error
@@ -396,24 +397,29 @@ func loadDeltas(target interface{}, versions []string, patcher delta.Patcher, wr
 		if err = in.Close(); err != nil {
 			logger.Panic(err)
 		}
+		if err = file.Close(); err != nil {
+			logger.Panic(err)
+		}
 	}
+	ret := prev.Bytes()
 	decoder := gob.NewDecoder(&prev)
 	if err = decoder.Decode(target); err != nil {
 		logger.Panic(err)
 	}
+	return ret
 }
 
 // storeFileList stores the given list in the repo dir as a delta against the
 // previous version's one.
 func (r *Repo) storeFileList(version int, list []File) {
 	dest := filepath.Join(r.path, fmt.Sprintf(versionFmt, version), filesName)
-	storeDelta(r.files, list, dest, r.differ, r.chunkWriteWrapper)
+	storeDelta(r.filesRaw, list, dest, r.differ, r.chunkWriteWrapper)
 }
 
 // loadFileLists loads incrementally the file lists' delta of each given version.
 func (r *Repo) loadFileLists(versions []string) {
 	var files []File
-	loadDeltas(&files, versions, r.patcher, r.chunkReadWrapper, filesName)
+	r.filesRaw = loadDeltas(&files, versions, r.patcher, r.chunkReadWrapper, filesName)
 	r.files = files
 }
 
@@ -735,12 +741,12 @@ func (r *Repo) restoreStream(stream io.WriteCloser, recipe []Chunk) {
 
 func (r *Repo) storeRecipe(version int, recipe []Chunk) {
 	dest := filepath.Join(r.path, fmt.Sprintf(versionFmt, version), recipeName)
-	storeDelta(r.recipe, recipe, dest, r.differ, r.chunkWriteWrapper)
+	storeDelta(r.recipeRaw, recipe, dest, r.differ, r.chunkWriteWrapper)
 }
 
 func (r *Repo) loadRecipes(versions []string) {
 	var recipe []Chunk
-	loadDeltas(&recipe, versions, r.patcher, r.chunkReadWrapper, recipeName)
+	r.recipeRaw = loadDeltas(&recipe, versions, r.patcher, r.chunkReadWrapper, recipeName)
 	for _, c := range recipe {
 		if rc, isRepo := c.(RepoChunk); isRepo {
 			rc.SetRepo(r)
-- 
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