387 lines
8.5 KiB
Go
387 lines
8.5 KiB
Go
// Copyright 2014-2017 Ulrich Kunitz. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package xz
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import (
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"errors"
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"hash"
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"io"
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"github.com/ulikunitz/xz/lzma"
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)
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// WriterConfig describe the parameters for an xz writer.
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type WriterConfig struct {
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Properties *lzma.Properties
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DictCap int
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BufSize int
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BlockSize int64
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// checksum method: CRC32, CRC64 or SHA256
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CheckSum byte
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// match algorithm
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Matcher lzma.MatchAlgorithm
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}
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// fill replaces zero values with default values.
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func (c *WriterConfig) fill() {
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if c.Properties == nil {
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c.Properties = &lzma.Properties{LC: 3, LP: 0, PB: 2}
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}
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if c.DictCap == 0 {
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c.DictCap = 8 * 1024 * 1024
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}
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if c.BufSize == 0 {
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c.BufSize = 4096
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}
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if c.BlockSize == 0 {
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c.BlockSize = maxInt64
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}
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if c.CheckSum == 0 {
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c.CheckSum = CRC64
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}
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}
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// Verify checks the configuration for errors. Zero values will be
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// replaced by default values.
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func (c *WriterConfig) Verify() error {
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if c == nil {
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return errors.New("xz: writer configuration is nil")
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}
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c.fill()
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lc := lzma.Writer2Config{
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Properties: c.Properties,
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DictCap: c.DictCap,
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BufSize: c.BufSize,
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Matcher: c.Matcher,
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}
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if err := lc.Verify(); err != nil {
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return err
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}
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if c.BlockSize <= 0 {
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return errors.New("xz: block size out of range")
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}
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if err := verifyFlags(c.CheckSum); err != nil {
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return err
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}
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return nil
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}
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// filters creates the filter list for the given parameters.
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func (c *WriterConfig) filters() []filter {
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return []filter{&lzmaFilter{int64(c.DictCap)}}
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}
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// maxInt64 defines the maximum 64-bit signed integer.
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const maxInt64 = 1<<63 - 1
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// verifyFilters checks the filter list for the length and the right
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// sequence of filters.
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func verifyFilters(f []filter) error {
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if len(f) == 0 {
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return errors.New("xz: no filters")
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}
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if len(f) > 4 {
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return errors.New("xz: more than four filters")
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}
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for _, g := range f[:len(f)-1] {
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if g.last() {
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return errors.New("xz: last filter is not last")
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}
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}
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if !f[len(f)-1].last() {
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return errors.New("xz: wrong last filter")
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}
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return nil
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}
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// newFilterWriteCloser converts a filter list into a WriteCloser that
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// can be used by a blockWriter.
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func (c *WriterConfig) newFilterWriteCloser(w io.Writer, f []filter) (fw io.WriteCloser, err error) {
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if err = verifyFilters(f); err != nil {
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return nil, err
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}
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fw = nopWriteCloser(w)
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for i := len(f) - 1; i >= 0; i-- {
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fw, err = f[i].writeCloser(fw, c)
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if err != nil {
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return nil, err
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}
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}
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return fw, nil
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}
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// nopWCloser implements a WriteCloser with a Close method not doing
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// anything.
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type nopWCloser struct {
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io.Writer
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}
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// Close returns nil and doesn't do anything else.
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func (c nopWCloser) Close() error {
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return nil
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}
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// nopWriteCloser converts the Writer into a WriteCloser with a Close
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// function that does nothing beside returning nil.
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func nopWriteCloser(w io.Writer) io.WriteCloser {
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return nopWCloser{w}
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}
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// Writer compresses data written to it. It is an io.WriteCloser.
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type Writer struct {
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WriterConfig
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xz io.Writer
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bw *blockWriter
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newHash func() hash.Hash
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h header
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index []record
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closed bool
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}
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// newBlockWriter creates a new block writer writes the header out.
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func (w *Writer) newBlockWriter() error {
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var err error
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w.bw, err = w.WriterConfig.newBlockWriter(w.xz, w.newHash())
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if err != nil {
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return err
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}
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if err = w.bw.writeHeader(w.xz); err != nil {
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return err
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}
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return nil
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}
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// closeBlockWriter closes a block writer and records the sizes in the
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// index.
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func (w *Writer) closeBlockWriter() error {
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var err error
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if err = w.bw.Close(); err != nil {
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return err
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}
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w.index = append(w.index, w.bw.record())
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return nil
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}
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// NewWriter creates a new xz writer using default parameters.
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func NewWriter(xz io.Writer) (w *Writer, err error) {
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return WriterConfig{}.NewWriter(xz)
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}
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// NewWriter creates a new Writer using the given configuration parameters.
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func (c WriterConfig) NewWriter(xz io.Writer) (w *Writer, err error) {
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if err = c.Verify(); err != nil {
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return nil, err
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}
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w = &Writer{
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WriterConfig: c,
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xz: xz,
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h: header{c.CheckSum},
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index: make([]record, 0, 4),
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}
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if w.newHash, err = newHashFunc(c.CheckSum); err != nil {
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return nil, err
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}
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data, err := w.h.MarshalBinary()
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if _, err = xz.Write(data); err != nil {
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return nil, err
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}
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if err = w.newBlockWriter(); err != nil {
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return nil, err
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}
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return w, nil
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}
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// Write compresses the uncompressed data provided.
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func (w *Writer) Write(p []byte) (n int, err error) {
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if w.closed {
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return 0, errClosed
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}
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for {
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k, err := w.bw.Write(p[n:])
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n += k
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if err != errNoSpace {
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return n, err
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}
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if err = w.closeBlockWriter(); err != nil {
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return n, err
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}
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if err = w.newBlockWriter(); err != nil {
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return n, err
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}
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}
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}
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// Close closes the writer and adds the footer to the Writer. Close
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// doesn't close the underlying writer.
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func (w *Writer) Close() error {
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if w.closed {
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return errClosed
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}
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w.closed = true
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var err error
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if err = w.closeBlockWriter(); err != nil {
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return err
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}
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f := footer{flags: w.h.flags}
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if f.indexSize, err = writeIndex(w.xz, w.index); err != nil {
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return err
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}
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data, err := f.MarshalBinary()
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if err != nil {
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return err
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}
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if _, err = w.xz.Write(data); err != nil {
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return err
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}
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return nil
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}
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// countingWriter is a writer that counts all data written to it.
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type countingWriter struct {
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w io.Writer
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n int64
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}
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// Write writes data to the countingWriter.
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func (cw *countingWriter) Write(p []byte) (n int, err error) {
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n, err = cw.w.Write(p)
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cw.n += int64(n)
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if err == nil && cw.n < 0 {
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return n, errors.New("xz: counter overflow")
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}
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return
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}
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// blockWriter is writes a single block.
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type blockWriter struct {
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cxz countingWriter
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// mw combines io.WriteCloser w and the hash.
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mw io.Writer
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w io.WriteCloser
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n int64
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blockSize int64
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closed bool
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headerLen int
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filters []filter
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hash hash.Hash
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}
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// newBlockWriter creates a new block writer.
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func (c *WriterConfig) newBlockWriter(xz io.Writer, hash hash.Hash) (bw *blockWriter, err error) {
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bw = &blockWriter{
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cxz: countingWriter{w: xz},
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blockSize: c.BlockSize,
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filters: c.filters(),
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hash: hash,
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}
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bw.w, err = c.newFilterWriteCloser(&bw.cxz, bw.filters)
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if err != nil {
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return nil, err
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}
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bw.mw = io.MultiWriter(bw.w, bw.hash)
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return bw, nil
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}
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// writeHeader writes the header. If the function is called after Close
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// the commpressedSize and uncompressedSize fields will be filled.
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func (bw *blockWriter) writeHeader(w io.Writer) error {
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h := blockHeader{
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compressedSize: -1,
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uncompressedSize: -1,
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filters: bw.filters,
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}
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if bw.closed {
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h.compressedSize = bw.compressedSize()
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h.uncompressedSize = bw.uncompressedSize()
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}
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data, err := h.MarshalBinary()
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if err != nil {
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return err
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}
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if _, err = w.Write(data); err != nil {
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return err
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}
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bw.headerLen = len(data)
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return nil
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}
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// compressed size returns the amount of data written to the underlying
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// stream.
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func (bw *blockWriter) compressedSize() int64 {
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return bw.cxz.n
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}
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// uncompressedSize returns the number of data written to the
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// blockWriter
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func (bw *blockWriter) uncompressedSize() int64 {
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return bw.n
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}
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// unpaddedSize returns the sum of the header length, the uncompressed
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// size of the block and the hash size.
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func (bw *blockWriter) unpaddedSize() int64 {
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if bw.headerLen <= 0 {
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panic("xz: block header not written")
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}
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n := int64(bw.headerLen)
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n += bw.compressedSize()
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n += int64(bw.hash.Size())
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return n
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}
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// record returns the record for the current stream. Call Close before
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// calling this method.
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func (bw *blockWriter) record() record {
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return record{bw.unpaddedSize(), bw.uncompressedSize()}
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}
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var errClosed = errors.New("xz: writer already closed")
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var errNoSpace = errors.New("xz: no space")
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// Write writes uncompressed data to the block writer.
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func (bw *blockWriter) Write(p []byte) (n int, err error) {
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if bw.closed {
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return 0, errClosed
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}
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t := bw.blockSize - bw.n
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if int64(len(p)) > t {
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err = errNoSpace
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p = p[:t]
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}
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var werr error
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n, werr = bw.mw.Write(p)
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bw.n += int64(n)
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if werr != nil {
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return n, werr
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}
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return n, err
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}
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// Close closes the writer.
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func (bw *blockWriter) Close() error {
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if bw.closed {
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return errClosed
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}
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bw.closed = true
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if err := bw.w.Close(); err != nil {
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return err
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}
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s := bw.hash.Size()
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k := padLen(bw.cxz.n)
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p := make([]byte, k+s)
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bw.hash.Sum(p[k:k])
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if _, err := bw.cxz.w.Write(p); err != nil {
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return err
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}
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return nil
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}
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