Documentation
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Overview ¶
Package sardata implements IO routines for reading and writing various chunks of the SARchive format, including checksums, blocks (table of contents and archive data), and the 'magic' bytes.
Index ¶
- Constants
- func BlockReader(r io.Reader) (io.ReadCloser, error)
- func BlockWriter(w io.Writer, scheme CompressionScheme, level int) (io.WriteCloser, error)
- func ReadMagic(r io.Reader) (version byte, err error)
- func ReadTOC(r io.Reader) (ret *toc.TOC, err error)
- func WriteMagic(w io.Writer) error
- func WriteTOC(w io.Writer, t *toc.TOC, scheme CompressionScheme, level int) (err error)
- type BlockHeader
- type ChecksumScheme
- type CompressionScheme
- type ErrMismatchedChecksum
Constants ¶
const Magic = "SAR"
Magic is the magic bytes which appear at the beginning of a sarchive.
const Version byte = 1
Version is the version of the sarchive format.
Variables ¶
This section is empty.
Functions ¶
func BlockReader ¶
func BlockReader(r io.Reader) (io.ReadCloser, error)
BlockReader expects to read a compressed block from r. If it finds one and knows the compression scheme of the block, it will return a ReadCloser which can be used to read the decompressed data from the block.
func BlockWriter ¶
func BlockWriter(w io.Writer, scheme CompressionScheme, level int) (io.WriteCloser, error)
BlockWriter returns a writer that will compress the data given to it. When the returned writer is closed, a BlockHeader and the compressed data will be written to `w`.
This means that the compressed data is unfortunately buffered in memory so that the length of the compressed data can be calculated to put into the header.
func ReadMagic ¶
ReadMagic reads magic from the reader and checks that it's equal to SAR, and ensures that the file version is <= Version.
Types ¶
type BlockHeader ¶
type BlockHeader struct {
// Length is the number of compressed bytes compose the block, after the end
// of this header.
Length uint64
// Compression indicates the compression decoder scheme that should be used
// for the block.
Compression CompressionScheme
}
BlockHeader is used as the prefix to a block.
type ChecksumScheme ¶
type ChecksumScheme byte
ChecksumScheme are the various checksum types known to the sarchive format.
const ( ChecksumSHA2_256 ChecksumScheme = iota + 1 ChecksumSHA2_512 ChecksumBLAKE2s ChecksumBLAKE2b ChecksumSHA3_256 ChecksumSHA3_512 // Bypasses ALL checksum verification. ChecksumNULL ChecksumScheme = 255 )
These are the available checksum algorithms implemented for sarchives.
func ChecksumReader ¶
func ChecksumReader(r readSeekCloser) (ret io.ReadCloser, c ChecksumScheme, err error)
ChecksumReader returns a ReadCloser which will verify the trailing checksum of the stream contained by readSeekCloser. It assumes the beginning of the checksum range is the current position of the readSeekCloser.
The checksum verification will happen when the returned Reader is Close()'d.
func ParseTrailer ¶
func ParseTrailer(r readSeekCloser) (c ChecksumScheme, h hash.Hash, nominalEnd int64, nominalChecksum []byte, err error)
ParseTrailer seeks to the end of r, parses the checksum trailer, and returns the pertinent details.
Note that nominalEnd is an offset from the beginning of the FILE (not the current position of r!), as defined by io.Seeker.
func (ChecksumScheme) Hash ¶
func (c ChecksumScheme) Hash() hash.Hash
Hash gets the Hash interface associated with this scheme.
func (ChecksumScheme) String ¶
func (i ChecksumScheme) String() string
func (ChecksumScheme) Valid ¶
func (c ChecksumScheme) Valid() error
Valid returns nil iff the ChecksumScheme is valid.
func (ChecksumScheme) Writer ¶
func (c ChecksumScheme) Writer(w io.WriteCloser) io.WriteCloser
Writer converts the provided WriteCloser into a new WriteCloser which will write a checksum footer when it is Close()'d.
type CompressionScheme ¶
type CompressionScheme byte
CompressionScheme indicates the type of compression used in a block, as indicated by that block's BlockHeader.
const ( CompressionNone CompressionScheme = iota + 1 CompressionFlate )
These are the currently supported compressions schemes.
TODO(iannucci): add zstd or brotli as support becomes available.
func (CompressionScheme) Reader ¶
func (c CompressionScheme) Reader(r io.Reader) (io.ReadCloser, error)
Reader returns a new decompressing reader for the given scheme.
func (CompressionScheme) Valid ¶
func (c CompressionScheme) Valid() error
Valid returns a nil err iff this CompressionScheme is valid.
func (CompressionScheme) Writer ¶
func (c CompressionScheme) Writer(w io.Writer, level int) (io.WriteCloser, error)
Writer returns a new compressing writer for the given scheme.
type ErrMismatchedChecksum ¶
type ErrMismatchedChecksum struct {
Scheme ChecksumScheme
Nominal []byte
Actual []byte
}
ErrMismatchedChecksum is returned from ChecksumReader if the checksum doesn't match up.
func (*ErrMismatchedChecksum) Error ¶
func (e *ErrMismatchedChecksum) Error() string
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