diff options
Diffstat (limited to 'vendor/github.com/klauspost/compress/zstd/decodeheader.go')
| -rw-r--r-- | vendor/github.com/klauspost/compress/zstd/decodeheader.go | 84 |
1 files changed, 56 insertions, 28 deletions
diff --git a/vendor/github.com/klauspost/compress/zstd/decodeheader.go b/vendor/github.com/klauspost/compress/zstd/decodeheader.go index 69736e8d..5022e71c 100644 --- a/vendor/github.com/klauspost/compress/zstd/decodeheader.go +++ b/vendor/github.com/klauspost/compress/zstd/decodeheader.go @@ -5,6 +5,7 @@ package zstd import ( "bytes" + "encoding/binary" "errors" "io" ) @@ -15,18 +16,50 @@ const HeaderMaxSize = 14 + 3 // Header contains information about the first frame and block within that. type Header struct { - // Window Size the window of data to keep while decoding. - // Will only be set if HasFCS is false. - WindowSize uint64 + // SingleSegment specifies whether the data is to be decompressed into a + // single contiguous memory segment. + // It implies that WindowSize is invalid and that FrameContentSize is valid. + SingleSegment bool - // Frame content size. - // Expected size of the entire frame. - FrameContentSize uint64 + // WindowSize is the window of data to keep while decoding. + // Will only be set if SingleSegment is false. + WindowSize uint64 // Dictionary ID. // If 0, no dictionary. DictionaryID uint32 + // HasFCS specifies whether FrameContentSize has a valid value. + HasFCS bool + + // FrameContentSize is the expected uncompressed size of the entire frame. + FrameContentSize uint64 + + // Skippable will be true if the frame is meant to be skipped. + // This implies that FirstBlock.OK is false. + Skippable bool + + // SkippableID is the user-specific ID for the skippable frame. + // Valid values are between 0 to 15, inclusive. + SkippableID int + + // SkippableSize is the length of the user data to skip following + // the header. + SkippableSize uint32 + + // HeaderSize is the raw size of the frame header. + // + // For normal frames, it includes the size of the magic number and + // the size of the header (per section 3.1.1.1). + // It does not include the size for any data blocks (section 3.1.1.2) nor + // the size for the trailing content checksum. + // + // For skippable frames, this counts the size of the magic number + // along with the size of the size field of the payload. + // It does not include the size of the skippable payload itself. + // The total frame size is the HeaderSize plus the SkippableSize. + HeaderSize int + // First block information. FirstBlock struct { // OK will be set if first block could be decoded. @@ -51,17 +84,9 @@ type Header struct { CompressedSize int } - // Skippable will be true if the frame is meant to be skipped. - // No other information will be populated. - Skippable bool - // If set there is a checksum present for the block content. + // The checksum field at the end is always 4 bytes long. HasCheckSum bool - - // If this is true FrameContentSize will have a valid value - HasFCS bool - - SingleSegment bool } // Decode the header from the beginning of the stream. @@ -71,39 +96,46 @@ type Header struct { // If there isn't enough input, io.ErrUnexpectedEOF is returned. // The FirstBlock.OK will indicate if enough information was available to decode the first block header. func (h *Header) Decode(in []byte) error { + *h = Header{} if len(in) < 4 { return io.ErrUnexpectedEOF } + h.HeaderSize += 4 b, in := in[:4], in[4:] if !bytes.Equal(b, frameMagic) { if !bytes.Equal(b[1:4], skippableFrameMagic) || b[0]&0xf0 != 0x50 { return ErrMagicMismatch } - *h = Header{Skippable: true} + if len(in) < 4 { + return io.ErrUnexpectedEOF + } + h.HeaderSize += 4 + h.Skippable = true + h.SkippableID = int(b[0] & 0xf) + h.SkippableSize = binary.LittleEndian.Uint32(in) return nil } + + // Read Window_Descriptor + // https://github.com/facebook/zstd/blob/dev/doc/zstd_compression_format.md#window_descriptor if len(in) < 1 { return io.ErrUnexpectedEOF } - - // Clear output - *h = Header{} fhd, in := in[0], in[1:] + h.HeaderSize++ h.SingleSegment = fhd&(1<<5) != 0 h.HasCheckSum = fhd&(1<<2) != 0 - if fhd&(1<<3) != 0 { return errors.New("reserved bit set on frame header") } - // Read Window_Descriptor - // https://github.com/facebook/zstd/blob/dev/doc/zstd_compression_format.md#window_descriptor if !h.SingleSegment { if len(in) < 1 { return io.ErrUnexpectedEOF } var wd byte wd, in = in[0], in[1:] + h.HeaderSize++ windowLog := 10 + (wd >> 3) windowBase := uint64(1) << windowLog windowAdd := (windowBase / 8) * uint64(wd&0x7) @@ -120,9 +152,7 @@ func (h *Header) Decode(in []byte) error { return io.ErrUnexpectedEOF } b, in = in[:size], in[size:] - if b == nil { - return io.ErrUnexpectedEOF - } + h.HeaderSize += int(size) switch size { case 1: h.DictionaryID = uint32(b[0]) @@ -152,9 +182,7 @@ func (h *Header) Decode(in []byte) error { return io.ErrUnexpectedEOF } b, in = in[:fcsSize], in[fcsSize:] - if b == nil { - return io.ErrUnexpectedEOF - } + h.HeaderSize += int(fcsSize) switch fcsSize { case 1: h.FrameContentSize = uint64(b[0]) |