1 files changed, 261 insertions, 0 deletions
diff --git a/vendor/github.com/klauspost/compress/zstd/decodeheader.go b/vendor/github.com/klauspost/compress/zstd/decodeheader.go
new file mode 100644
index 000000000..6a5a2988b
--- /dev/null
+++ b/vendor/github.com/klauspost/compress/zstd/decodeheader.go
@@ -0,0 +1,261 @@
+// Copyright 2020+ Klaus Post. All rights reserved.
+// License information can be found in the LICENSE file.
+
+package zstd
+
+import (
+	"encoding/binary"
+	"errors"
+	"io"
+)
+
+// HeaderMaxSize is the maximum size of a Frame and Block Header.
+// If less is sent to Header.Decode it *may* still contain enough information.
+const HeaderMaxSize = 14 + 3
+
+// Header contains information about the first frame and block within that.
+type Header struct {
+	// 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
+
+	// 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.
+		OK bool
+
+		// Is this the last block of a frame?
+		Last bool
+
+		// Is the data compressed?
+		// If true CompressedSize will be populated.
+		// Unfortunately DecompressedSize cannot be determined
+		// without decoding the blocks.
+		Compressed bool
+
+		// DecompressedSize is the expected decompressed size of the block.
+		// Will be 0 if it cannot be determined.
+		DecompressedSize int
+
+		// CompressedSize of the data in the block.
+		// Does not include the block header.
+		// Will be equal to DecompressedSize if not Compressed.
+		CompressedSize int
+	}
+
+	// If set there is a checksum present for the block content.
+	// The checksum field at the end is always 4 bytes long.
+	HasCheckSum bool
+}
+
+// Decode the header from the beginning of the stream.
+// This will decode the frame header and the first block header if enough bytes are provided.
+// It is recommended to provide at least HeaderMaxSize bytes.
+// If the frame header cannot be read an error will be returned.
+// 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 {
+	_, err := h.DecodeAndStrip(in)
+	return err
+}
+
+// DecodeAndStrip will decode the header from the beginning of the stream
+// and on success return the remaining bytes.
+// This will decode the frame header and the first block header if enough bytes are provided.
+// It is recommended to provide at least HeaderMaxSize bytes.
+// If the frame header cannot be read an error will be returned.
+// 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) DecodeAndStrip(in []byte) (remain []byte, err error) {
+	*h = Header{}
+	if len(in) < 4 {
+		return nil, io.ErrUnexpectedEOF
+	}
+	h.HeaderSize += 4
+	b, in := in[:4], in[4:]
+	if string(b) != frameMagic {
+		if string(b[1:4]) != skippableFrameMagic || b[0]&0xf0 != 0x50 {
+			return nil, ErrMagicMismatch
+		}
+		if len(in) < 4 {
+			return nil, io.ErrUnexpectedEOF
+		}
+		h.HeaderSize += 4
+		h.Skippable = true
+		h.SkippableID = int(b[0] & 0xf)
+		h.SkippableSize = binary.LittleEndian.Uint32(in)
+		return in[4:], nil
+	}
+
+	// Read Window_Descriptor
+	// https://github.com/facebook/zstd/blob/dev/doc/zstd_compression_format.md#window_descriptor
+	if len(in) < 1 {
+		return nil, io.ErrUnexpectedEOF
+	}
+	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 nil, errors.New("reserved bit set on frame header")
+	}
+
+	if !h.SingleSegment {
+		if len(in) < 1 {
+			return nil, 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)
+		h.WindowSize = windowBase + windowAdd
+	}
+
+	// Read Dictionary_ID
+	// https://github.com/facebook/zstd/blob/dev/doc/zstd_compression_format.md#dictionary_id
+	if size := fhd & 3; size != 0 {
+		if size == 3 {
+			size = 4
+		}
+		if len(in) < int(size) {
+			return nil, io.ErrUnexpectedEOF
+		}
+		b, in = in[:size], in[size:]
+		h.HeaderSize += int(size)
+		switch len(b) {
+		case 1:
+			h.DictionaryID = uint32(b[0])
+		case 2:
+			h.DictionaryID = uint32(b[0]) | (uint32(b[1]) << 8)
+		case 4:
+			h.DictionaryID = uint32(b[0]) | (uint32(b[1]) << 8) | (uint32(b[2]) << 16) | (uint32(b[3]) << 24)
+		}
+	}
+
+	// Read Frame_Content_Size
+	// https://github.com/facebook/zstd/blob/dev/doc/zstd_compression_format.md#frame_content_size
+	var fcsSize int
+	v := fhd >> 6
+	switch v {
+	case 0:
+		if h.SingleSegment {
+			fcsSize = 1
+		}
+	default:
+		fcsSize = 1 << v
+	}
+
+	if fcsSize > 0 {
+		h.HasFCS = true
+		if len(in) < fcsSize {
+			return nil, io.ErrUnexpectedEOF
+		}
+		b, in = in[:fcsSize], in[fcsSize:]
+		h.HeaderSize += int(fcsSize)
+		switch len(b) {
+		case 1:
+			h.FrameContentSize = uint64(b[0])
+		case 2:
+			// When FCS_Field_Size is 2, the offset of 256 is added.
+			h.FrameContentSize = uint64(b[0]) | (uint64(b[1]) << 8) + 256
+		case 4:
+			h.FrameContentSize = uint64(b[0]) | (uint64(b[1]) << 8) | (uint64(b[2]) << 16) | (uint64(b[3]) << 24)
+		case 8:
+			d1 := uint32(b[0]) | (uint32(b[1]) << 8) | (uint32(b[2]) << 16) | (uint32(b[3]) << 24)
+			d2 := uint32(b[4]) | (uint32(b[5]) << 8) | (uint32(b[6]) << 16) | (uint32(b[7]) << 24)
+			h.FrameContentSize = uint64(d1) | (uint64(d2) << 32)
+		}
+	}
+
+	// Frame Header done, we will not fail from now on.
+	if len(in) < 3 {
+		return in, nil
+	}
+	tmp := in[:3]
+	bh := uint32(tmp[0]) | (uint32(tmp[1]) << 8) | (uint32(tmp[2]) << 16)
+	h.FirstBlock.Last = bh&1 != 0
+	blockType := blockType((bh >> 1) & 3)
+	// find size.
+	cSize := int(bh >> 3)
+	switch blockType {
+	case blockTypeReserved:
+		return in, nil
+	case blockTypeRLE:
+		h.FirstBlock.Compressed = true
+		h.FirstBlock.DecompressedSize = cSize
+		h.FirstBlock.CompressedSize = 1
+	case blockTypeCompressed:
+		h.FirstBlock.Compressed = true
+		h.FirstBlock.CompressedSize = cSize
+	case blockTypeRaw:
+		h.FirstBlock.DecompressedSize = cSize
+		h.FirstBlock.CompressedSize = cSize
+	default:
+		panic("Invalid block type")
+	}
+
+	h.FirstBlock.OK = true
+	return in, nil
+}
+
+// AppendTo will append the encoded header to the dst slice.
+// There is no error checking performed on the header values.
+func (h *Header) AppendTo(dst []byte) ([]byte, error) {
+	if h.Skippable {
+		magic := [4]byte{0x50, 0x2a, 0x4d, 0x18}
+		magic[0] |= byte(h.SkippableID & 0xf)
+		dst = append(dst, magic[:]...)
+		f := h.SkippableSize
+		return append(dst, uint8(f), uint8(f>>8), uint8(f>>16), uint8(f>>24)), nil
+	}
+	f := frameHeader{
+		ContentSize:   h.FrameContentSize,
+		WindowSize:    uint32(h.WindowSize),
+		SingleSegment: h.SingleSegment,
+		Checksum:      h.HasCheckSum,
+		DictID:        h.DictionaryID,
+	}
+	return f.appendTo(dst), nil
+}