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-rw-r--r--plumbing/format/idxfile/writer.go186
1 files changed, 186 insertions, 0 deletions
diff --git a/plumbing/format/idxfile/writer.go b/plumbing/format/idxfile/writer.go
new file mode 100644
index 0000000..aa919e7
--- /dev/null
+++ b/plumbing/format/idxfile/writer.go
@@ -0,0 +1,186 @@
+package idxfile
+
+import (
+ "bytes"
+ "fmt"
+ "math"
+ "sort"
+ "sync"
+
+ "gopkg.in/src-d/go-git.v4/plumbing"
+ "gopkg.in/src-d/go-git.v4/utils/binary"
+)
+
+// objects implements sort.Interface and uses hash as sorting key.
+type objects []Entry
+
+// Writer implements a packfile Observer interface and is used to generate
+// indexes.
+type Writer struct {
+ m sync.Mutex
+
+ count uint32
+ checksum plumbing.Hash
+ objects objects
+ offset64 uint32
+ finished bool
+ index *MemoryIndex
+ added map[plumbing.Hash]struct{}
+}
+
+// Index returns a previously created MemoryIndex or creates a new one if
+// needed.
+func (w *Writer) Index() (*MemoryIndex, error) {
+ w.m.Lock()
+ defer w.m.Unlock()
+
+ if w.index == nil {
+ return w.createIndex()
+ }
+
+ return w.index, nil
+}
+
+// Add appends new object data.
+func (w *Writer) Add(h plumbing.Hash, pos uint64, crc uint32) {
+ w.m.Lock()
+ defer w.m.Unlock()
+
+ if w.added == nil {
+ w.added = make(map[plumbing.Hash]struct{})
+ }
+
+ if _, ok := w.added[h]; !ok {
+ w.added[h] = struct{}{}
+ w.objects = append(w.objects, Entry{h, crc, pos})
+ }
+
+}
+
+func (w *Writer) Finished() bool {
+ return w.finished
+}
+
+// OnHeader implements packfile.Observer interface.
+func (w *Writer) OnHeader(count uint32) error {
+ w.count = count
+ w.objects = make(objects, 0, count)
+ return nil
+}
+
+// OnInflatedObjectHeader implements packfile.Observer interface.
+func (w *Writer) OnInflatedObjectHeader(t plumbing.ObjectType, objSize int64, pos int64) error {
+ return nil
+}
+
+// OnInflatedObjectContent implements packfile.Observer interface.
+func (w *Writer) OnInflatedObjectContent(h plumbing.Hash, pos int64, crc uint32, _ []byte) error {
+ w.Add(h, uint64(pos), crc)
+ return nil
+}
+
+// OnFooter implements packfile.Observer interface.
+func (w *Writer) OnFooter(h plumbing.Hash) error {
+ w.checksum = h
+ w.finished = true
+ _, err := w.createIndex()
+ if err != nil {
+ return err
+ }
+
+ return nil
+}
+
+// creatIndex returns a filled MemoryIndex with the information filled by
+// the observer callbacks.
+func (w *Writer) createIndex() (*MemoryIndex, error) {
+ if !w.finished {
+ return nil, fmt.Errorf("the index still hasn't finished building")
+ }
+
+ idx := new(MemoryIndex)
+ w.index = idx
+
+ sort.Sort(w.objects)
+
+ // unmap all fans by default
+ for i := range idx.FanoutMapping {
+ idx.FanoutMapping[i] = noMapping
+ }
+
+ buf := new(bytes.Buffer)
+
+ last := -1
+ bucket := -1
+ for i, o := range w.objects {
+ fan := o.Hash[0]
+
+ // fill the gaps between fans
+ for j := last + 1; j < int(fan); j++ {
+ idx.Fanout[j] = uint32(i)
+ }
+
+ // update the number of objects for this position
+ idx.Fanout[fan] = uint32(i + 1)
+
+ // we move from one bucket to another, update counters and allocate
+ // memory
+ if last != int(fan) {
+ bucket++
+ idx.FanoutMapping[fan] = bucket
+ last = int(fan)
+
+ idx.Names = append(idx.Names, make([]byte, 0))
+ idx.Offset32 = append(idx.Offset32, make([]byte, 0))
+ idx.CRC32 = append(idx.CRC32, make([]byte, 0))
+ }
+
+ idx.Names[bucket] = append(idx.Names[bucket], o.Hash[:]...)
+
+ offset := o.Offset
+ if offset > math.MaxInt32 {
+ offset = w.addOffset64(offset)
+ }
+
+ buf.Truncate(0)
+ binary.WriteUint32(buf, uint32(offset))
+ idx.Offset32[bucket] = append(idx.Offset32[bucket], buf.Bytes()...)
+
+ buf.Truncate(0)
+ binary.WriteUint32(buf, uint32(o.CRC32))
+ idx.CRC32[bucket] = append(idx.CRC32[bucket], buf.Bytes()...)
+ }
+
+ for j := last + 1; j < 256; j++ {
+ idx.Fanout[j] = uint32(len(w.objects))
+ }
+
+ idx.Version = VersionSupported
+ idx.PackfileChecksum = w.checksum
+
+ return idx, nil
+}
+
+func (w *Writer) addOffset64(pos uint64) uint64 {
+ buf := new(bytes.Buffer)
+ binary.WriteUint64(buf, pos)
+ w.index.Offset64 = append(w.index.Offset64, buf.Bytes()...)
+
+ index := uint64(w.offset64 | (1 << 31))
+ w.offset64++
+
+ return index
+}
+
+func (o objects) Len() int {
+ return len(o)
+}
+
+func (o objects) Less(i int, j int) bool {
+ cmp := bytes.Compare(o[i].Hash[:], o[j].Hash[:])
+ return cmp < 0
+}
+
+func (o objects) Swap(i int, j int) {
+ o[i], o[j] = o[j], o[i]
+}