4 files changed, 223 insertions, 0 deletions
diff --git a/core/errors.go b/core/errors.go
new file mode 100644
index 0000000..fd1133e
--- /dev/null
+++ b/core/errors.go
@@ -0,0 +1,35 @@
+package core
+
+import "fmt"
+
+type PermanentError struct {
+	err error
+}
+
+func NewPermanentError(err error) *PermanentError {
+	if err == nil {
+		return nil
+	}
+
+	return &PermanentError{err: err}
+}
+
+func (e *PermanentError) Error() string {
+	return fmt.Sprintf("permanent client error: %s", e.err.Error())
+}
+
+type UnexpectedError struct {
+	err error
+}
+
+func NewUnexpectedError(err error) *UnexpectedError {
+	if err == nil {
+		return nil
+	}
+
+	return &UnexpectedError{err: err}
+}
+
+func (e *UnexpectedError) Error() string {
+	return fmt.Sprintf("unexpected client error: %s", e.err.Error())
+}
diff --git a/core/hash.go b/core/hash.go
new file mode 100644
index 0000000..0b6f274
--- /dev/null
+++ b/core/hash.go
@@ -0,0 +1,40 @@
+package core
+
+import (
+	"crypto/sha1"
+	"encoding/hex"
+	"strconv"
+)
+
+// Hash SHA1 hased content
+type Hash [20]byte
+
+// ComputeHash compute the hash for a given ObjectType and content
+func ComputeHash(t ObjectType, content []byte) Hash {
+	h := t.Bytes()
+	h = append(h, ' ')
+	h = strconv.AppendInt(h, int64(len(content)), 10)
+	h = append(h, 0)
+	h = append(h, content...)
+
+	return Hash(sha1.Sum(h))
+}
+
+// NewHash return a new Hash from a hexadecimal hash representation
+func NewHash(s string) Hash {
+	b, _ := hex.DecodeString(s)
+
+	var h Hash
+	copy(h[:], b)
+
+	return h
+}
+
+func (h Hash) IsZero() bool {
+	var empty Hash
+	return h == empty
+}
+
+func (h Hash) String() string {
+	return hex.EncodeToString(h[:])
+}
diff --git a/core/hash_test.go b/core/hash_test.go
new file mode 100644
index 0000000..8c4ed67
--- /dev/null
+++ b/core/hash_test.go
@@ -0,0 +1,35 @@
+package core
+
+import (
+	"testing"
+
+	. "gopkg.in/check.v1"
+)
+
+func Test(t *testing.T) { TestingT(t) }
+
+type HashSuite struct{}
+
+var _ = Suite(&HashSuite{})
+
+func (s *HashSuite) TestComputeHash(c *C) {
+	hash := ComputeHash(BlobObject, []byte(""))
+	c.Assert(hash.String(), Equals, "e69de29bb2d1d6434b8b29ae775ad8c2e48c5391")
+
+	hash = ComputeHash(BlobObject, []byte("Hello, World!\n"))
+	c.Assert(hash.String(), Equals, "8ab686eafeb1f44702738c8b0f24f2567c36da6d")
+}
+
+func (s *HashSuite) TestNewHash(c *C) {
+	hash := ComputeHash(BlobObject, []byte("Hello, World!\n"))
+
+	c.Assert(hash, Equals, NewHash(hash.String()))
+}
+
+func (s *HashSuite) TestIsZero(c *C) {
+	hash := NewHash("foo")
+	c.Assert(hash.IsZero(), Equals, true)
+
+	hash = NewHash("8ab686eafeb1f44702738c8b0f24f2567c36da6d")
+	c.Assert(hash.IsZero(), Equals, false)
+}
diff --git a/core/object.go b/core/object.go
new file mode 100644
index 0000000..4e8a587
--- /dev/null
+++ b/core/object.go
@@ -0,0 +1,113 @@
+package core
+
+import (
+	"bytes"
+	"io"
+)
+
+// Object is a generic representation of any git object
+type Object interface {
+	Type() ObjectType
+	SetType(ObjectType)
+	Size() int64
+	SetSize(int64)
+	Hash() Hash
+	Reader() io.Reader
+	Writer() io.Writer
+}
+
+// ObjectStorage generic storage of objects
+type ObjectStorage interface {
+	New() Object
+	Set(Object) Hash
+	Get(Hash) (Object, bool)
+}
+
+// ObjectType internal object type's
+type ObjectType int8
+
+const (
+	CommitObject   ObjectType = 1
+	TreeObject     ObjectType = 2
+	BlobObject     ObjectType = 3
+	TagObject      ObjectType = 4
+	OFSDeltaObject ObjectType = 6
+	REFDeltaObject ObjectType = 7
+)
+
+func (t ObjectType) String() string {
+	switch t {
+	case CommitObject:
+		return "commit"
+	case TreeObject:
+		return "tree"
+	case BlobObject:
+		return "blob"
+	default:
+		return "-"
+	}
+}
+
+func (t ObjectType) Bytes() []byte {
+	return []byte(t.String())
+}
+
+type RAWObject struct {
+	b []byte
+	t ObjectType
+	s int64
+}
+
+func (o *RAWObject) Type() ObjectType     { return o.t }
+func (o *RAWObject) SetType(t ObjectType) { o.t = t }
+func (o *RAWObject) Size() int64          { return o.s }
+func (o *RAWObject) SetSize(s int64)      { o.s = s }
+func (o *RAWObject) Reader() io.Reader    { return bytes.NewBuffer(o.b) }
+func (o *RAWObject) Hash() Hash           { return ComputeHash(o.t, o.b) }
+func (o *RAWObject) Writer() io.Writer    { return o }
+func (o *RAWObject) Write(p []byte) (n int, err error) {
+	o.b = append(o.b, p...)
+	return len(p), nil
+}
+
+type RAWObjectStorage struct {
+	Objects map[Hash]Object
+	Commits map[Hash]Object
+	Trees   map[Hash]Object
+	Blobs   map[Hash]Object
+}
+
+func NewRAWObjectStorage() *RAWObjectStorage {
+	return &RAWObjectStorage{
+		Objects: make(map[Hash]Object, 0),
+		Commits: make(map[Hash]Object, 0),
+		Trees:   make(map[Hash]Object, 0),
+		Blobs:   make(map[Hash]Object, 0),
+	}
+}
+
+func (o *RAWObjectStorage) New() Object {
+	return &RAWObject{}
+}
+
+func (o *RAWObjectStorage) Set(obj Object) Hash {
+	h := obj.Hash()
+	o.Objects[h] = obj
+
+	switch obj.Type() {
+	case CommitObject:
+		o.Commits[h] = o.Objects[h]
+	case TreeObject:
+		o.Trees[h] = o.Objects[h]
+	case BlobObject:
+		o.Blobs[h] = o.Objects[h]
+	}
+
+	return h
+}
+
+func (o *RAWObjectStorage) Get(h Hash) (Object, bool) {
+	obj, ok := o.Objects[h]
+
+	return obj, ok
+}