plumbing/packfile: PACK encoder (#131)

* plumbing/packfile: PACK encoder

- Added simple PACK encoder, deltas not supported by now

* Requested changes

* Requested changes

* Requested changes

1 files changed, 140 insertions, 0 deletions

diff --git a/plumbing/format/packfile/encoder_test.go b/plumbing/format/packfile/encoder_test.go
new file mode 100644
index 0000000..729843d
--- /dev/null
+++ b/plumbing/format/packfile/encoder_test.go
@@ -0,0 +1,140 @@
+package packfile
+
+import (
+	"bytes"
+
+	"gopkg.in/src-d/go-git.v4/fixtures"
+	"gopkg.in/src-d/go-git.v4/plumbing"
+	"gopkg.in/src-d/go-git.v4/storage/memory"
+
+	. "gopkg.in/check.v1"
+)
+
+type EncoderSuite struct {
+	fixtures.Suite
+	buf   *bytes.Buffer
+	store *memory.Storage
+	enc   *Encoder
+}
+
+var _ = Suite(&EncoderSuite{})
+
+func (s *EncoderSuite) SetUpTest(c *C) {
+	s.buf = bytes.NewBuffer(nil)
+	s.store = memory.NewStorage()
+	s.enc = NewEncoder(s.buf, s.store)
+}
+
+func (s *EncoderSuite) TestCorrectPackHeader(c *C) {
+	hash, err := s.enc.Encode([]plumbing.Hash{})
+	c.Assert(err, IsNil)
+
+	hb := [20]byte(hash)
+
+	// PACK + VERSION + OBJECTS + HASH
+	expectedResult := []byte{'P', 'A', 'C', 'K', 0, 0, 0, 2, 0, 0, 0, 0}
+	expectedResult = append(expectedResult, hb[:]...)
+
+	result := s.buf.Bytes()
+
+	c.Assert(result, DeepEquals, expectedResult)
+}
+
+func (s *EncoderSuite) TestCorrectPackWithOneEmptyObject(c *C) {
+	o := &plumbing.MemoryObject{}
+	o.SetType(plumbing.CommitObject)
+	o.SetSize(0)
+	_, err := s.store.SetObject(o)
+	c.Assert(err, IsNil)
+
+	hash, err := s.enc.Encode([]plumbing.Hash{o.Hash()})
+	c.Assert(err, IsNil)
+
+	// PACK + VERSION(2) + OBJECT NUMBER(1)
+	expectedResult := []byte{'P', 'A', 'C', 'K', 0, 0, 0, 2, 0, 0, 0, 1}
+	// OBJECT HEADER(TYPE + SIZE)= 0001 0000
+	expectedResult = append(expectedResult, []byte{16}...)
+
+	// Zlib header
+	expectedResult = append(expectedResult,
+		[]byte{120, 156, 1, 0, 0, 255, 255, 0, 0, 0, 1}...)
+
+	// + HASH
+	hb := [20]byte(hash)
+	expectedResult = append(expectedResult, hb[:]...)
+
+	result := s.buf.Bytes()
+
+	c.Assert(result, DeepEquals, expectedResult)
+}
+
+func (s *EncoderSuite) TestMaxObjectSize(c *C) {
+	o := s.store.NewObject()
+	o.SetSize(9223372036854775807)
+	o.SetType(plumbing.CommitObject)
+	_, err := s.store.SetObject(o)
+	c.Assert(err, IsNil)
+	hash, err := s.enc.Encode([]plumbing.Hash{o.Hash()})
+	c.Assert(err, IsNil)
+	c.Assert(hash.IsZero(), Not(Equals), true)
+}
+
+func (s *EncoderSuite) TestDecodeEncodeDecode(c *C) {
+	fixtures.Basic().ByTag("packfile").Test(c, func(f *fixtures.Fixture) {
+		scanner := NewScanner(f.Packfile())
+		storage := memory.NewStorage()
+
+		d, err := NewDecoder(scanner, storage)
+		c.Assert(err, IsNil)
+
+		ch, err := d.Decode()
+		c.Assert(err, IsNil)
+		c.Assert(ch, Equals, f.PackfileHash)
+
+		commitIter, err := d.o.IterObjects(plumbing.AnyObject)
+		c.Assert(err, IsNil)
+
+		objects := []plumbing.Object{}
+		hashes := []plumbing.Hash{}
+		err = commitIter.ForEach(func(o plumbing.Object) error {
+			objects = append(objects, o)
+			hash, err := s.store.SetObject(o)
+			hashes = append(hashes, hash)
+
+			return err
+
+		})
+		c.Assert(err, IsNil)
+		_, err = s.enc.Encode(hashes)
+		c.Assert(err, IsNil)
+
+		scanner = NewScanner(s.buf)
+		storage = memory.NewStorage()
+		d, err = NewDecoder(scanner, storage)
+		c.Assert(err, IsNil)
+		_, err = d.Decode()
+		c.Assert(err, IsNil)
+
+		commitIter, err = d.o.IterObjects(plumbing.AnyObject)
+		c.Assert(err, IsNil)
+		obtainedObjects := []plumbing.Object{}
+		err = commitIter.ForEach(func(o plumbing.Object) error {
+			obtainedObjects = append(obtainedObjects, o)
+
+			return nil
+		})
+		c.Assert(err, IsNil)
+		c.Assert(len(obtainedObjects), Equals, len(objects))
+
+		equals := 0
+		for _, oo := range obtainedObjects {
+			for _, o := range objects {
+				if o.Hash() == oo.Hash() {
+					equals++
+				}
+			}
+		}
+
+		c.Assert(len(obtainedObjects), Equals, equals)
+	})
+}