From 1dec2cdc84a6497c893d84485c6f94589f997215 Mon Sep 17 00:00:00 2001
From: n-peugnet <n.peugnet@free.fr>
Date: Wed, 1 Sep 2021 19:07:49 +0200
Subject: Prepare for delta encoding

---
 chunk.go | 17 +++++++++++++++++
 delta.go | 32 ++++++++++++++++++++++++++++++++
 repo.go  | 18 ++++++++++++++++++
 3 files changed, 67 insertions(+)
 create mode 100644 delta.go

diff --git a/chunk.go b/chunk.go
index 9927c94..3fc9057 100644
--- a/chunk.go
+++ b/chunk.go
@@ -115,3 +115,20 @@ func (c *TempChunk) AppendFrom(r io.Reader) {
 	}
 	c.value = append(c.value, buff...)
 }
+
+type DeltaChunk struct {
+	repo   *Repo
+	source *ChunkId
+	patch  []byte
+	size   int
+}
+
+func (c *DeltaChunk) Reader() ChunkReader {
+	var buff bytes.Buffer
+	c.repo.Patcher().Patch(c.source.Reader(c.repo), &buff, bytes.NewReader(c.patch))
+	return &buff
+}
+
+func (c *DeltaChunk) Len() int {
+	return c.size
+}
diff --git a/delta.go b/delta.go
new file mode 100644
index 0000000..423fb07
--- /dev/null
+++ b/delta.go
@@ -0,0 +1,32 @@
+package main
+
+import (
+	"io"
+
+	"github.com/gabstv/go-bsdiff/pkg/bsdiff"
+	"github.com/gabstv/go-bsdiff/pkg/bspatch"
+)
+
+type DeltaCodec interface {
+	Differ
+	Patcher
+}
+
+type Differ interface {
+	Diff(source io.Reader, target io.Reader, patch io.Writer) error
+}
+
+type Patcher interface {
+	Patch(source io.Reader, target io.Writer, patch io.Reader) error
+}
+
+// TODO: maybe move this in it own file ?
+type Bsdiff struct{}
+
+func (*Bsdiff) Diff(source io.Reader, target io.Reader, patch io.Writer) error {
+	return bsdiff.Reader(source, target, patch)
+}
+
+func (*Bsdiff) Patch(source io.Reader, target io.Writer, patch io.Reader) error {
+	return bspatch.Reader(source, target, patch)
+}
diff --git a/repo.go b/repo.go
index 6f177c2..32666f4 100644
--- a/repo.go
+++ b/repo.go
@@ -48,6 +48,8 @@ type Repo struct {
 	sketchWSize   int
 	sketchSfCount int
 	sketchFCount  int
+	differ        Differ
+	patcher       Patcher
 }
 
 type File struct {
@@ -63,9 +65,19 @@ func NewRepo(path string) *Repo {
 		sketchWSize:   32,
 		sketchSfCount: 3,
 		sketchFCount:  4,
+		differ:        &Bsdiff{},
+		patcher:       &Bsdiff{},
 	}
 }
 
+func (r *Repo) Differ() Differ {
+	return r.differ
+}
+
+func (r *Repo) Patcher() Patcher {
+	return r.patcher
+}
+
 func (r *Repo) Commit(source string) {
 	versions := r.loadVersions()
 	newVersion := len(versions)
@@ -275,6 +287,12 @@ func (r *Repo) findSimilarChunk(chunk Chunk, sketches SketchMap) (*ChunkId, bool
 	return similarChunk, similarChunk != nil
 }
 
+// TODO: encode stream
+func (r *Repo) encodeStream(stream io.Reader, fingerprints FingerprintMap, sketches SketchMap) []Chunk {
+	chunks := r.matchStream(stream, fingerprints)
+	return chunks
+}
+
 func (r *Repo) matchStream(stream io.Reader, fingerprints FingerprintMap) []Chunk {
 	var b byte
 	var chunks []Chunk
-- 
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