plumbing/packfile: add new packfile parser

Signed-off-by: Javi Fontan <jfontan@gmail.com>

2 files changed, 498 insertions, 0 deletions

diff --git a/plumbing/format/packfile/parser.go b/plumbing/format/packfile/parser.go
new file mode 100644
index 0000000..460fc3f
--- /dev/null
+++ b/plumbing/format/packfile/parser.go
@@ -0,0 +1,359 @@
+package packfile
+
+import (
+	"bytes"
+	"errors"
+	"io"
+
+	"gopkg.in/src-d/go-git.v4/plumbing"
+	"gopkg.in/src-d/go-git.v4/plumbing/cache"
+)
+
+// Observer interface is implemented by index encoders.
+type Observer interface {
+	// OnHeader is called when a new packfile is opened.
+	OnHeader(count uint32) error
+	// OnInflatedObjectHeader is called for each object header read.
+	OnInflatedObjectHeader(t plumbing.ObjectType, objSize int64, pos int64) error
+	// OnInflatedObjectContent is called for each decoded object.
+	OnInflatedObjectContent(h plumbing.Hash, pos int64, crc uint32) error
+	// OnFooter is called when decoding is done.
+	OnFooter(h plumbing.Hash) error
+}
+
+// Parser decodes a packfile and calls any observer associated to it. Is used
+// to generate indexes.
+type Parser struct {
+	scanner    *Scanner
+	count      uint32
+	oi         []*objectInfo
+	oiByHash   map[plumbing.Hash]*objectInfo
+	oiByOffset map[int64]*objectInfo
+	hashOffset map[plumbing.Hash]int64
+	checksum   plumbing.Hash
+
+	cache *cache.ObjectLRU
+
+	ob []Observer
+}
+
+// NewParser creates a new Parser struct.
+func NewParser(scanner *Scanner, ob ...Observer) *Parser {
+	return &Parser{
+		scanner: scanner,
+		ob:      ob,
+		count:   0,
+		cache:   cache.NewObjectLRUDefault(),
+	}
+}
+
+// Parse start decoding phase of the packfile.
+func (p *Parser) Parse() (plumbing.Hash, error) {
+	err := p.init()
+	if err != nil {
+		return plumbing.ZeroHash, err
+	}
+
+	err = p.firstPass()
+	if err != nil {
+		return plumbing.ZeroHash, err
+	}
+
+	err = p.resolveDeltas()
+	if err != nil {
+		return plumbing.ZeroHash, err
+	}
+
+	for _, o := range p.ob {
+		err := o.OnFooter(p.checksum)
+		if err != nil {
+			return plumbing.ZeroHash, err
+		}
+	}
+
+	return p.checksum, nil
+}
+
+func (p *Parser) init() error {
+	_, c, err := p.scanner.Header()
+	if err != nil {
+		return err
+	}
+
+	for _, o := range p.ob {
+		err := o.OnHeader(c)
+		if err != nil {
+			return err
+		}
+	}
+
+	p.count = c
+	p.oiByHash = make(map[plumbing.Hash]*objectInfo, p.count)
+	p.oiByOffset = make(map[int64]*objectInfo, p.count)
+	p.oi = make([]*objectInfo, p.count)
+
+	return nil
+}
+
+func (p *Parser) firstPass() error {
+	buf := new(bytes.Buffer)
+
+	for i := uint32(0); i < p.count; i++ {
+		buf.Truncate(0)
+
+		oh, err := p.scanner.NextObjectHeader()
+		if err != nil {
+			return err
+		}
+
+		delta := false
+		var ota *objectInfo
+		switch t := oh.Type; t {
+		case plumbing.OFSDeltaObject, plumbing.REFDeltaObject:
+			delta = true
+
+			var parent *objectInfo
+			var ok bool
+
+			if t == plumbing.OFSDeltaObject {
+				parent, ok = p.oiByOffset[oh.OffsetReference]
+			} else {
+				parent, ok = p.oiByHash[oh.Reference]
+			}
+
+			if !ok {
+				// TODO improve error
+				return errors.New("Reference delta not found")
+			}
+
+			ota = newDeltaObject(oh.Offset, oh.Length, t, parent)
+
+			parent.Children = append(parent.Children, ota)
+		default:
+			ota = newBaseObject(oh.Offset, oh.Length, t)
+		}
+
+		size, crc, err := p.scanner.NextObject(buf)
+		if err != nil {
+			return err
+		}
+
+		ota.Crc32 = crc
+		ota.PackSize = size
+		ota.Length = oh.Length
+
+		if !delta {
+			ota.Write(buf.Bytes())
+			ota.SHA1 = ota.Sum()
+		}
+
+		p.oiByOffset[oh.Offset] = ota
+		p.oiByHash[oh.Reference] = ota
+
+		p.oi[i] = ota
+	}
+
+	checksum, err := p.scanner.Checksum()
+	p.checksum = checksum
+
+	if err == io.EOF {
+		return nil
+	}
+
+	return err
+}
+
+func (p *Parser) resolveDeltas() error {
+	for _, obj := range p.oi {
+		for _, o := range p.ob {
+			err := o.OnInflatedObjectHeader(obj.Type, obj.Length, obj.Offset)
+			if err != nil {
+				return err
+			}
+
+			err = o.OnInflatedObjectContent(obj.SHA1, obj.Offset, obj.Crc32)
+			if err != nil {
+				return err
+			}
+		}
+
+		if !obj.IsDelta() && len(obj.Children) > 0 {
+			var err error
+			base, err := p.get(obj)
+			if err != nil {
+				return err
+			}
+
+			for _, child := range obj.Children {
+				_, err = p.resolveObject(child, base)
+				if err != nil {
+					return err
+				}
+			}
+		}
+	}
+
+	return nil
+}
+
+func (p *Parser) get(o *objectInfo) ([]byte, error) {
+	e, ok := p.cache.Get(o.SHA1)
+	if ok {
+		r, err := e.Reader()
+		if err != nil {
+			return nil, err
+		}
+
+		buf := make([]byte, e.Size())
+		_, err = r.Read(buf)
+		if err != nil {
+			return nil, err
+		}
+
+		return buf, nil
+	}
+
+	// Read from disk
+	if o.DiskType.IsDelta() {
+		base, err := p.get(o.Parent)
+		if err != nil {
+			return nil, err
+		}
+
+		data, err := p.resolveObject(o, base)
+		if err != nil {
+			return nil, err
+		}
+
+		if len(o.Children) > 0 {
+			m := &plumbing.MemoryObject{}
+			m.Write(data)
+			m.SetType(o.Type)
+			m.SetSize(o.Size())
+			p.cache.Put(m)
+		}
+
+		return data, nil
+	}
+
+	data, err := p.readData(o)
+	if err != nil {
+		return nil, err
+	}
+
+	if len(o.Children) > 0 {
+		m := &plumbing.MemoryObject{}
+		m.Write(data)
+		m.SetType(o.Type)
+		m.SetSize(o.Size())
+		p.cache.Put(m)
+	}
+
+	return data, nil
+}
+
+func (p *Parser) resolveObject(
+	o *objectInfo,
+	base []byte) ([]byte, error) {
+
+	if !o.DiskType.IsDelta() {
+		return nil, nil
+	}
+
+	data, err := p.readData(o)
+	if err != nil {
+		return nil, err
+	}
+
+	data, err = applyPatchBase(o, data, base)
+	if err != nil {
+		return nil, err
+	}
+
+	return data, nil
+}
+
+func (p *Parser) readData(o *objectInfo) ([]byte, error) {
+	buf := new(bytes.Buffer)
+
+	// TODO: skip header. Header size can be calculated with the offset of the
+	// next offset in the first pass.
+	p.scanner.SeekFromStart(o.Offset)
+	_, err := p.scanner.NextObjectHeader()
+	if err != nil {
+		return nil, err
+	}
+
+	buf.Truncate(0)
+
+	_, _, err = p.scanner.NextObject(buf)
+	if err != nil {
+		return nil, err
+	}
+
+	return buf.Bytes(), nil
+}
+
+func applyPatchBase(ota *objectInfo, data, base []byte) ([]byte, error) {
+	patched, err := PatchDelta(base, data)
+	if err != nil {
+		return nil, err
+	}
+
+	ota.Type = ota.Parent.Type
+	hash := plumbing.ComputeHash(ota.Type, patched)
+
+	ota.SHA1 = hash
+
+	return patched, nil
+}
+
+type objectInfo struct {
+	plumbing.Hasher
+
+	Offset   int64
+	Length   int64
+	PackSize int64
+	Type     plumbing.ObjectType
+	DiskType plumbing.ObjectType
+
+	Crc32 uint32
+
+	Parent   *objectInfo
+	Children []*objectInfo
+	SHA1     plumbing.Hash
+}
+
+func newBaseObject(offset, length int64, t plumbing.ObjectType) *objectInfo {
+	return newDeltaObject(offset, length, t, nil)
+}
+
+func newDeltaObject(
+	offset, length int64,
+	t plumbing.ObjectType,
+	parent *objectInfo,
+) *objectInfo {
+	children := make([]*objectInfo, 0)
+
+	obj := &objectInfo{
+		Hasher:   plumbing.NewHasher(t, length),
+		Offset:   offset,
+		Length:   length,
+		PackSize: 0,
+		Type:     t,
+		DiskType: t,
+		Crc32:    0,
+		Parent:   parent,
+		Children: children,
+	}
+
+	return obj
+}
+
+func (o *objectInfo) IsDelta() bool {
+	return o.Type.IsDelta()
+}
+
+func (o *objectInfo) Size() int64 {
+	return o.Length
+}
diff --git a/plumbing/format/packfile/parser_test.go b/plumbing/format/packfile/parser_test.go
new file mode 100644
index 0000000..87a8804
--- /dev/null
+++ b/plumbing/format/packfile/parser_test.go
@@ -0,0 +1,139 @@
+package packfile_test
+
+import (
+	"gopkg.in/src-d/go-git.v4/plumbing"
+	"gopkg.in/src-d/go-git.v4/plumbing/format/packfile"
+
+	. "gopkg.in/check.v1"
+	"gopkg.in/src-d/go-git-fixtures.v3"
+)
+
+type ParserSuite struct {
+	fixtures.Suite
+}
+
+var _ = Suite(&ParserSuite{})
+
+func (s *ParserSuite) TestParserHashes(c *C) {
+	f := fixtures.Basic().One()
+	scanner := packfile.NewScanner(f.Packfile())
+
+	obs := new(testObserver)
+	parser := packfile.NewParser(scanner, obs)
+
+	ch, err := parser.Parse()
+	c.Assert(err, IsNil)
+
+	checksum := "a3fed42da1e8189a077c0e6846c040dcf73fc9dd"
+	c.Assert(ch.String(), Equals, checksum)
+
+	c.Assert(obs.checksum, Equals, checksum)
+	c.Assert(int(obs.count), Equals, int(31))
+
+	commit := plumbing.CommitObject
+	blob := plumbing.BlobObject
+	tree := plumbing.TreeObject
+
+	objs := []observerObject{
+		{"e8d3ffab552895c19b9fcf7aa264d277cde33881", commit, 254, 12, 0xaa07ba4b},
+		{"6ecf0ef2c2dffb796033e5a02219af86ec6584e5", commit, 93, 186, 0xf706df58},
+		{"918c48b83bd081e863dbe1b80f8998f058cd8294", commit, 242, 286, 0x12438846},
+		{"af2d6a6954d532f8ffb47615169c8fdf9d383a1a", commit, 242, 449, 0x2905a38c},
+		{"1669dce138d9b841a518c64b10914d88f5e488ea", commit, 333, 615, 0xd9429436},
+		{"a5b8b09e2f8fcb0bb99d3ccb0958157b40890d69", commit, 332, 838, 0xbecfde4e},
+		{"35e85108805c84807bc66a02d91535e1e24b38b9", commit, 244, 1063, 0x780e4b3e},
+		{"b8e471f58bcbca63b07bda20e428190409c2db47", commit, 243, 1230, 0xdc18344f},
+		{"b029517f6300c2da0f4b651b8642506cd6aaf45d", commit, 187, 1392, 0xcf4e4280},
+		{"32858aad3c383ed1ff0a0f9bdf231d54a00c9e88", blob, 189, 1524, 0x1f08118a},
+		{"d3ff53e0564a9f87d8e84b6e28e5060e517008aa", blob, 18, 1685, 0xafded7b8},
+		{"c192bd6a24ea1ab01d78686e417c8bdc7c3d197f", blob, 1072, 1713, 0xcc1428ed},
+		{"d5c0f4ab811897cadf03aec358ae60d21f91c50d", blob, 76110, 2351, 0x1631d22f},
+		{"880cd14280f4b9b6ed3986d6671f907d7cc2a198", blob, 2780, 78050, 0xbfff5850},
+		{"49c6bb89b17060d7b4deacb7b338fcc6ea2352a9", blob, 217848, 78882, 0xd108e1d8},
+		{"c8f1d8c61f9da76f4cb49fd86322b6e685dba956", blob, 706, 80725, 0x8e97ba25},
+		{"9a48f23120e880dfbe41f7c9b7b708e9ee62a492", blob, 11488, 80998, 0x7316ff70},
+		{"9dea2395f5403188298c1dabe8bdafe562c491e3", blob, 78, 84032, 0xdb4fce56},
+		{"dbd3641b371024f44d0e469a9c8f5457b0660de1", tree, 272, 84115, 0x901cce2c},
+		{"a8d315b2b1c615d43042c3a62402b8a54288cf5c", tree, 43, 84375, 0xec4552b0},
+		{"a39771a7651f97faf5c72e08224d857fc35133db", tree, 38, 84430, 0x847905bf},
+		{"5a877e6a906a2743ad6e45d99c1793642aaf8eda", tree, 75, 84479, 0x3689459a},
+		{"586af567d0bb5e771e49bdd9434f5e0fb76d25fa", tree, 38, 84559, 0xe67af94a},
+		{"cf4aa3b38974fb7d81f367c0830f7d78d65ab86b", tree, 34, 84608, 0xc2314a2e},
+		{"7e59600739c96546163833214c36459e324bad0a", blob, 9, 84653, 0xcd987848},
+		{"fb72698cab7617ac416264415f13224dfd7a165e", tree, 6, 84671, 0x8a853a6d},
+		{"4d081c50e250fa32ea8b1313cf8bb7c2ad7627fd", tree, 9, 84688, 0x70c6518},
+		{"eba74343e2f15d62adedfd8c883ee0262b5c8021", tree, 6, 84708, 0x4f4108e2},
+		{"c2d30fa8ef288618f65f6eed6e168e0d514886f4", tree, 5, 84725, 0xd6fe09e9},
+		{"8dcef98b1d52143e1e2dbc458ffe38f925786bf2", tree, 8, 84741, 0xf07a2804},
+		{"aa9b383c260e1d05fbbf6b30a02914555e20c725", tree, 4, 84760, 0x1d75d6be},
+	}
+
+	c.Assert(obs.objects, DeepEquals, objs)
+}
+
+type observerObject struct {
+	hash   string
+	otype  plumbing.ObjectType
+	size   int64
+	offset int64
+	crc    uint32
+}
+
+type testObserver struct {
+	count    uint32
+	checksum string
+	objects  []observerObject
+	pos      map[int64]int
+}
+
+func (t *testObserver) OnHeader(count uint32) error {
+	t.count = count
+	t.pos = make(map[int64]int, count)
+	return nil
+}
+
+func (t *testObserver) OnInflatedObjectHeader(otype plumbing.ObjectType, objSize int64, pos int64) error {
+	o := t.get(pos)
+	o.otype = otype
+	o.size = objSize
+	o.offset = pos
+
+	t.put(pos, o)
+
+	return nil
+}
+
+func (t *testObserver) OnInflatedObjectContent(h plumbing.Hash, pos int64, crc uint32) error {
+	o := t.get(pos)
+	o.hash = h.String()
+	o.crc = crc
+
+	t.put(pos, o)
+
+	return nil
+}
+
+func (t *testObserver) OnFooter(h plumbing.Hash) error {
+	t.checksum = h.String()
+	return nil
+}
+
+func (t *testObserver) get(pos int64) observerObject {
+	i, ok := t.pos[pos]
+	if ok {
+		return t.objects[i]
+	}
+
+	return observerObject{}
+}
+
+func (t *testObserver) put(pos int64, o observerObject) {
+	i, ok := t.pos[pos]
+	if ok {
+		t.objects[i] = o
+		return
+	}
+
+	t.pos[pos] = len(t.objects)
+	t.objects = append(t.objects, o)
+}