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package index
import (
"bytes"
"crypto/sha1"
"errors"
"hash"
"io"
"sort"
"time"
"github.com/go-git/go-git/v5/utils/binary"
)
var (
// EncodeVersionSupported is the range of supported index versions
EncodeVersionSupported uint32 = 3
// ErrInvalidTimestamp is returned by Encode if a Index with a Entry with
// negative timestamp values
ErrInvalidTimestamp = errors.New("negative timestamps are not allowed")
)
// An Encoder writes an Index to an output stream.
type Encoder struct {
w io.Writer
hash hash.Hash
}
// NewEncoder returns a new encoder that writes to w.
func NewEncoder(w io.Writer) *Encoder {
h := sha1.New()
mw := io.MultiWriter(w, h)
return &Encoder{mw, h}
}
// Encode writes the Index to the stream of the encoder.
func (e *Encoder) Encode(idx *Index) error {
// TODO: support v4
// TODO: support extensions
if idx.Version > EncodeVersionSupported {
return ErrUnsupportedVersion
}
if err := e.encodeHeader(idx); err != nil {
return err
}
if err := e.encodeEntries(idx); err != nil {
return err
}
return e.encodeFooter()
}
func (e *Encoder) encodeHeader(idx *Index) error {
return binary.Write(e.w,
indexSignature,
idx.Version,
uint32(len(idx.Entries)),
)
}
func (e *Encoder) encodeEntries(idx *Index) error {
sort.Sort(byName(idx.Entries))
for _, entry := range idx.Entries {
if err := e.encodeEntry(entry); err != nil {
return err
}
entryLength := entryHeaderLength
if entry.IntentToAdd || entry.SkipWorktree {
entryLength += 2
}
wrote := entryLength + len(entry.Name)
if err := e.padEntry(wrote); err != nil {
return err
}
}
return nil
}
func (e *Encoder) encodeEntry(entry *Entry) error {
sec, nsec, err := e.timeToUint32(&entry.CreatedAt)
if err != nil {
return err
}
msec, mnsec, err := e.timeToUint32(&entry.ModifiedAt)
if err != nil {
return err
}
flags := uint16(entry.Stage&0x3) << 12
if l := len(entry.Name); l < nameMask {
flags |= uint16(l)
} else {
flags |= nameMask
}
flow := []interface{}{
sec, nsec,
msec, mnsec,
entry.Dev,
entry.Inode,
entry.Mode,
entry.UID,
entry.GID,
entry.Size,
entry.Hash[:],
}
flagsFlow := []interface{}{flags}
if entry.IntentToAdd || entry.SkipWorktree {
var extendedFlags uint16
if entry.IntentToAdd {
extendedFlags |= intentToAddMask
}
if entry.SkipWorktree {
extendedFlags |= skipWorkTreeMask
}
flagsFlow = []interface{}{flags | entryExtended, extendedFlags}
}
flow = append(flow, flagsFlow...)
if err := binary.Write(e.w, flow...); err != nil {
return err
}
return binary.Write(e.w, []byte(entry.Name))
}
func (e *Encoder) timeToUint32(t *time.Time) (uint32, uint32, error) {
if t.IsZero() {
return 0, 0, nil
}
if t.Unix() < 0 || t.UnixNano() < 0 {
return 0, 0, ErrInvalidTimestamp
}
return uint32(t.Unix()), uint32(t.Nanosecond()), nil
}
func (e *Encoder) padEntry(wrote int) error {
padLen := 8 - wrote%8
_, err := e.w.Write(bytes.Repeat([]byte{'\x00'}, padLen))
return err
}
func (e *Encoder) encodeFooter() error {
return binary.Write(e.w, e.hash.Sum(nil))
}
type byName []*Entry
func (l byName) Len() int { return len(l) }
func (l byName) Swap(i, j int) { l[i], l[j] = l[j], l[i] }
func (l byName) Less(i, j int) bool { return l[i].Name < l[j].Name }
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