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Signed-off-by: Paulo Gomes <paulo.gomes@suse.com>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,231 @@ | ||
| package idxfile | ||
|
|
||
| import ( | ||
| "bufio" | ||
| "bytes" | ||
| "errors" | ||
| "fmt" | ||
| "io" | ||
|
|
||
| format "github.com/go-git/go-git/v5/plumbing/format/config" | ||
| "github.com/go-git/go-git/v5/plumbing/hasher" | ||
| "github.com/go-git/go-git/v5/utils/binary" | ||
| ) | ||
|
|
||
| var ( | ||
| // ErrUnsupportedVersion is returned by Decode when the idx file version | ||
| // is not supported. | ||
| ErrUnsupportedVersion = errors.New("unsupported version") | ||
| // ErrMalformedIdxFile is returned by Decode when the idx file is corrupted. | ||
| ErrMalformedIdxFile = errors.New("malformed IDX file") | ||
| // ErrMemoryIndexInUse is returned when an exclusive lock cannot be acquired | ||
| // for a MemoryIndex. This is likely to happen when the same MemoryIndex is | ||
| // being used concurrently for more than one Decode or Encode operation. | ||
| ErrMemoryIndexLocked = errors.New("memory index is locked") | ||
| ) | ||
|
|
||
| const ( | ||
| fanout = 256 | ||
| magicNumberLength = 4 | ||
| ) | ||
|
|
||
| // Decoder reads and decodes idx files from an input stream. | ||
| type Decoder struct { | ||
| *bufio.Reader | ||
| objectFormat format.ObjectFormat | ||
| version Version | ||
| objectNameLength int | ||
| } | ||
|
|
||
| // TODO: rename and reuse for encoding? Any specific options that would | ||
| // only be for one of those ops? | ||
| type DecoderOptions struct { | ||
| format.ObjectFormat | ||
| } | ||
|
|
||
| // NewDecoder builds a new idx stream decoder, that reads from r. | ||
| func NewDecoder(r io.Reader) (*Decoder, error) { | ||
| return NewDecoderWithOptions(r, DecoderOptions{ObjectFormat: format.SHA1}) | ||
| } | ||
|
|
||
| func NewDecoderWithOptions(r io.Reader, opts DecoderOptions) (*Decoder, error) { | ||
| if r == nil { | ||
| return nil, fmt.Errorf("cannot create decoder: nil reader") | ||
| } | ||
|
|
||
| h, err := hasher.FromObjectFormat(opts.ObjectFormat) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
|
|
||
| return &Decoder{ | ||
| bufio.NewReader(r), | ||
| opts.ObjectFormat, | ||
| VersionNotSet, | ||
| h.Size(), | ||
| }, nil | ||
| } | ||
|
|
||
| var decodeFlow = []func(*MemoryIndex, io.Reader) error{ | ||
| readVersion, | ||
| readFanout, | ||
| readObjectNames, | ||
| readCRC32, | ||
| readOffsets, | ||
| readChecksums, | ||
| } | ||
|
|
||
| // Decode reads from the stream and decode the content into the MemoryIndex struct. | ||
| // It is safe to use a previously used MemoryIndex, as it will be reset before the | ||
| // decoding process. | ||
| func (d *Decoder) Decode(idx *MemoryIndex) error { | ||
| if idx == nil { | ||
| return fmt.Errorf("failed to decode: target index is nil") | ||
| } | ||
|
|
||
| if !idx.m.TryLock() { | ||
| return fmt.Errorf("failed to decode: %w", ErrMemoryIndexLocked) | ||
| } | ||
| defer idx.m.Unlock() | ||
| idx.reset(d.objectNameLength, d.objectFormat) | ||
|
|
||
| if err := validateHeader(idx, d); err != nil { | ||
| return err | ||
| } | ||
|
|
||
| for _, f := range decodeFlow { | ||
| if err := f(idx, d); err != nil { | ||
| return err | ||
| } | ||
| } | ||
|
|
||
| return nil | ||
| } | ||
|
|
||
| func validateHeader(idx *MemoryIndex, r io.Reader) error { | ||
| if _, err := io.ReadFull(r, idx.header[:]); err != nil { | ||
| return err | ||
| } | ||
|
|
||
| if !bytes.Equal(idx.header[:], idxHeader) { | ||
| return ErrMalformedIdxFile | ||
| } | ||
|
|
||
| return nil | ||
| } | ||
|
|
||
| func readVersion(idx *MemoryIndex, r io.Reader) error { | ||
| v, err := binary.ReadUint32(r) | ||
| if err != nil { | ||
| return err | ||
| } | ||
|
|
||
| switch v { | ||
| case uint32(Version2): | ||
| idx.Version = 2 | ||
| case uint32(Version3): | ||
| idx.Version = 3 | ||
| default: | ||
| return ErrUnsupportedVersion | ||
| } | ||
|
|
||
| return nil | ||
| } | ||
|
|
||
| func readFanout(idx *MemoryIndex, r io.Reader) error { | ||
| for k := 0; k < fanout; k++ { | ||
| n, err := binary.ReadUint32(r) | ||
| if err != nil { | ||
| return err | ||
| } | ||
|
|
||
| idx.Fanout[k] = n | ||
| idx.FanoutMapping[k] = noMapping | ||
| } | ||
|
|
||
| return nil | ||
| } | ||
|
|
||
| func readObjectNames(idx *MemoryIndex, r io.Reader) error { | ||
| for k := 0; k < fanout; k++ { | ||
| buckets := idx.Fanout[k] | ||
| if k != 0 { | ||
| buckets -= idx.Fanout[k-1] | ||
| } | ||
|
|
||
| if buckets == 0 { | ||
| continue | ||
| } | ||
|
|
||
| idx.FanoutMapping[k] = len(idx.Names) | ||
|
|
||
| nameLen := int(buckets) * idx.nameLength | ||
| bin := make([]byte, nameLen) | ||
| if _, err := io.ReadFull(r, bin); err != nil { | ||
| return err | ||
| } | ||
|
|
||
| idx.Names = append(idx.Names, bin) | ||
| idx.Offset32 = append(idx.Offset32, make([]byte, buckets*4)) | ||
| idx.CRC32 = append(idx.CRC32, make([]byte, buckets*4)) | ||
| } | ||
| return nil | ||
| } | ||
|
|
||
| func readCRC32(idx *MemoryIndex, r io.Reader) error { | ||
| for k := 0; k < fanout; k++ { | ||
| if pos := idx.FanoutMapping[k]; pos != noMapping { | ||
| if _, err := io.ReadFull(r, idx.CRC32[pos]); err != nil { | ||
| return err | ||
| } | ||
| } | ||
| } | ||
|
|
||
| return nil | ||
| } | ||
|
|
||
| func readOffsets(idx *MemoryIndex, r io.Reader) error { | ||
| var o64cnt int | ||
| for k := 0; k < fanout; k++ { | ||
| if pos := idx.FanoutMapping[k]; pos != noMapping { | ||
| if _, err := io.ReadFull(r, idx.Offset32[pos]); err != nil { | ||
| return err | ||
| } | ||
|
|
||
| for p := 0; p < len(idx.Offset32[pos]); p += 4 { | ||
| if idx.Offset32[pos][p]&(byte(1)<<7) > 0 { | ||
| o64cnt++ | ||
| } | ||
| } | ||
| } | ||
| } | ||
|
|
||
| if o64cnt > 0 { | ||
| idx.Offset64 = make([]byte, o64cnt*8) | ||
| if _, err := io.ReadFull(r, idx.Offset64); err != nil { | ||
| return err | ||
| } | ||
| } | ||
|
|
||
| return nil | ||
| } | ||
|
|
||
| func readChecksums(idx *MemoryIndex, r io.Reader) error { | ||
| if len(idx.PackfileChecksum) == 0 { | ||
| idx.PackfileChecksum = make([]byte, idx.nameLength) | ||
| } | ||
|
|
||
| if _, err := io.ReadFull(r, idx.PackfileChecksum[:]); err != nil { | ||
| return err | ||
| } | ||
|
|
||
| if len(idx.IdxChecksum) == 0 { | ||
| idx.IdxChecksum = make([]byte, idx.nameLength) | ||
| } | ||
|
|
||
| if _, err := io.ReadFull(r, idx.IdxChecksum[:]); err != nil { | ||
| return err | ||
| } | ||
|
|
||
| return nil | ||
| } |
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