Documentation
¶
Overview ¶
Package xz supports the compression and decompression of xz files. It supports version 1.1.0 of the specification without the non-LZMA2 filters. See http://tukaani.org/xz/xz-file-format-1.1.0.txt
Example ¶
const text = "The quick brown fox jumps over the lazy dog."
var buf bytes.Buffer
// compress text
w, err := NewWriter(&buf)
if err != nil {
log.Fatalf("NewWriter error %s", err)
}
if _, err := io.WriteString(w, text); err != nil {
log.Fatalf("WriteString error %s", err)
}
if err := w.Close(); err != nil {
log.Fatalf("w.Close error %s", err)
}
// decompress buffer and write result to stdout
r, err := NewReader(&buf)
if err != nil {
log.Fatalf("NewReader error %s", err)
}
if _, err = io.Copy(os.Stdout, r); err != nil {
log.Fatalf("io.Copy error %s", err)
}
Output: The quick brown fox jumps over the lazy dog.
Index ¶
Examples ¶
Constants ¶
const ( None byte = 0x0 CRC32 byte = 0x1 CRC64 byte = 0x4 SHA256 byte = 0xa )
Constants for the checksum methods supported by xz.
const HeaderLen = 12
HeaderLen provides the length of the xz file header.
const (
SingleStream = 1 << iota
)
Flags for th Stat function
Variables ¶
This section is empty.
Functions ¶
func NewReader ¶
func NewReader(xz io.Reader) (r io.ReadCloser, err error)
NewReader creates an io.ReadCloser. The function should never fail.
func NewReaderOptions ¶
func NewReaderOptions(xz io.Reader, options ReaderOptions) (r io.ReadCloser, err error)
NewReaderOptions creates an xz reader using the provided configuration. If Workers are larger than one, the LZMA reader will only use single-threaded workers.
func ValidHeader ¶
ValidHeader checks whether data is a correct xz file header. The length of data must be HeaderLen.
Types ¶
type ReaderOptions ¶
type ReaderOptions struct {
// Workers defines the number of readers for parallel reading. The
// default is the value of GOMAXPROCS.
Workers int
// Read a single xz stream from the underlying reader, stop and return
// EOF. No checks are done whether the underlying reader finishes too.
SingleStream bool
// Runs the multiple Workers in LZMA mode. (This is an experimental
// setup is normally not required.)
LZMAParallel bool
// LZMABufferSize provides the buffer size to the LZMA layer. It is only
// required if LZMAParallel is set.
LZMABufferSize int
}
ReaderOptions defines the parameters for the xz reader. The SingleStream parameter requests the reader to assume that the underlying stream contains only a single stream without padding.
The workers variable controls the number of parallel workers decoding the file. It only has an effect if the file was encoded in a way that it created blocks with the compressed size set in the headers. If Workers not 1 the Workers variable in LZMAConfig will be ignored.
func (*ReaderOptions) MarshalJSON ¶
func (cfg *ReaderOptions) MarshalJSON() (p []byte, err error)
MarshalJSON creates the jason structure for a ReaderConfig value.
func (*ReaderOptions) UnmarshalJSON ¶
func (cfg *ReaderOptions) UnmarshalJSON(p []byte) error
UnmarshalJSON parses JSON and sets the ReaderConfig accordingly.
type WriteFlushCloser ¶
type WriteFlushCloser interface {
io.WriteCloser
Flush() error
}
WriteFlushCloser supports the Write, Flush and Close methods.
func NewWriter ¶
func NewWriter(xz io.Writer) (w WriteFlushCloser, err error)
NewWriter creates a new Writer for xz-compressed data. The Writer uses the preset #5. See Preset and NewWriterOptions for changing the parameters.
func NewWriterOptions ¶
func NewWriterOptions(xz io.Writer, options WriterOptions) (w WriteFlushCloser, err error)
NewWriterOptions creates a WriteFlushCloser instance. If multi-threading is requested by a Workers configuration larger than 1, single threading will be requested for the LZMA writer by setting the Workers variable there to 1.
type WriterOptions ¶
type WriterOptions struct {
// WindowSize sets the dictionary size.
WindowSize int
// BufferSize sets the size of the buffer used by the LZ parser.
BufferSize int
// Properties for the LZMA algorithm.
Properties lzma.Properties
// FixedProperties indicate that the Properties is indeed zero
FixedProperties bool
// Number of workers processing data.
Workers int
// LZMAParallel indicates that the parallel execution should be on the
// LZMA level. (This is an experimental setup and should normally not be
// used.)
LZMAParallel bool
// Configuration for the LZ parser.
ParserOptions lz.Configurator
// checksum method: CRC32, CRC64 or SHA256 (default: CRC64)
Checksum byte
// Forces NoChecksum (default: false)
NoChecksum bool
}
WriterOptions describe the parameters for an xz writer. CRC64 is used as the default checksum despite the XZ specification saying a decoder must only support CRC32.
func Preset ¶
func Preset(n int) WriterOptions
Preset returns a WriterConfig with preset parameters. Supported presets are ranging from 1 to 9 from fast to slow with increasing compression rate.
func (*WriterOptions) MarshalJSON ¶
func (opts *WriterOptions) MarshalJSON() (p []byte, err error)
MarshalJSON creates the JSON representation of the WriterOptions value.
func (*WriterOptions) UnmarshalJSON ¶
func (opts *WriterOptions) UnmarshalJSON(p []byte) error
UnmarshalJSON parses a JSON value and set the WriterOptions value accordingly.
Source Files
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Directories
¶
| Path | Synopsis |
|---|---|
|
internal
|
|
|
randtxt
Package randtxt supports the generation of random text using a trigram model for the English language.
|
Package randtxt supports the generation of random text using a trigram model for the English language. |
|
stream
Package stream supports implements Streamers which track the offset in the file and allows the discarding of data.
|
Package stream supports implements Streamers which track the offset in the file and allows the discarding of data. |
|
Package lzma provides support for the encoding and decoding LZMA, LZMA2 and raw LZMA streams without a header.
|
Package lzma provides support for the encoding and decoding LZMA, LZMA2 and raw LZMA streams without a header. |