2020-01-17 21:57:18 +00:00
|
|
|
// Copyright 2010 The Go Authors. All rights reserved.
|
|
|
|
// Use of this source code is governed by a BSD-style
|
|
|
|
// license that can be found in the LICENSE file.
|
|
|
|
|
|
|
|
package gzip
|
|
|
|
|
|
|
|
import (
|
|
|
|
"errors"
|
|
|
|
"fmt"
|
|
|
|
"hash/crc32"
|
|
|
|
"io"
|
|
|
|
|
|
|
|
"github.com/klauspost/compress/flate"
|
|
|
|
)
|
|
|
|
|
|
|
|
// These constants are copied from the flate package, so that code that imports
|
|
|
|
// "compress/gzip" does not also have to import "compress/flate".
|
|
|
|
const (
|
|
|
|
NoCompression = flate.NoCompression
|
|
|
|
BestSpeed = flate.BestSpeed
|
|
|
|
BestCompression = flate.BestCompression
|
|
|
|
DefaultCompression = flate.DefaultCompression
|
|
|
|
ConstantCompression = flate.ConstantCompression
|
|
|
|
HuffmanOnly = flate.HuffmanOnly
|
|
|
|
|
|
|
|
// StatelessCompression will do compression but without maintaining any state
|
|
|
|
// between Write calls.
|
|
|
|
// There will be no memory kept between Write calls,
|
|
|
|
// but compression and speed will be suboptimal.
|
|
|
|
// Because of this, the size of actual Write calls will affect output size.
|
|
|
|
StatelessCompression = -3
|
|
|
|
)
|
|
|
|
|
|
|
|
// A Writer is an io.WriteCloser.
|
|
|
|
// Writes to a Writer are compressed and written to w.
|
|
|
|
type Writer struct {
|
|
|
|
Header // written at first call to Write, Flush, or Close
|
|
|
|
w io.Writer
|
|
|
|
level int
|
|
|
|
wroteHeader bool
|
|
|
|
compressor *flate.Writer
|
|
|
|
digest uint32 // CRC-32, IEEE polynomial (section 8)
|
|
|
|
size uint32 // Uncompressed size (section 2.3.1)
|
|
|
|
closed bool
|
|
|
|
buf [10]byte
|
|
|
|
err error
|
|
|
|
}
|
|
|
|
|
|
|
|
// NewWriter returns a new Writer.
|
|
|
|
// Writes to the returned writer are compressed and written to w.
|
|
|
|
//
|
|
|
|
// It is the caller's responsibility to call Close on the WriteCloser when done.
|
|
|
|
// Writes may be buffered and not flushed until Close.
|
|
|
|
//
|
|
|
|
// Callers that wish to set the fields in Writer.Header must do so before
|
|
|
|
// the first call to Write, Flush, or Close.
|
|
|
|
func NewWriter(w io.Writer) *Writer {
|
|
|
|
z, _ := NewWriterLevel(w, DefaultCompression)
|
|
|
|
return z
|
|
|
|
}
|
|
|
|
|
|
|
|
// NewWriterLevel is like NewWriter but specifies the compression level instead
|
|
|
|
// of assuming DefaultCompression.
|
|
|
|
//
|
|
|
|
// The compression level can be DefaultCompression, NoCompression, or any
|
|
|
|
// integer value between BestSpeed and BestCompression inclusive. The error
|
|
|
|
// returned will be nil if the level is valid.
|
|
|
|
func NewWriterLevel(w io.Writer, level int) (*Writer, error) {
|
|
|
|
if level < StatelessCompression || level > BestCompression {
|
|
|
|
return nil, fmt.Errorf("gzip: invalid compression level: %d", level)
|
|
|
|
}
|
|
|
|
z := new(Writer)
|
|
|
|
z.init(w, level)
|
|
|
|
return z, nil
|
|
|
|
}
|
|
|
|
|
|
|
|
func (z *Writer) init(w io.Writer, level int) {
|
|
|
|
compressor := z.compressor
|
|
|
|
if level != StatelessCompression {
|
|
|
|
if compressor != nil {
|
|
|
|
compressor.Reset(w)
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
*z = Writer{
|
|
|
|
Header: Header{
|
|
|
|
OS: 255, // unknown
|
|
|
|
},
|
|
|
|
w: w,
|
|
|
|
level: level,
|
|
|
|
compressor: compressor,
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
// Reset discards the Writer z's state and makes it equivalent to the
|
|
|
|
// result of its original state from NewWriter or NewWriterLevel, but
|
|
|
|
// writing to w instead. This permits reusing a Writer rather than
|
|
|
|
// allocating a new one.
|
|
|
|
func (z *Writer) Reset(w io.Writer) {
|
|
|
|
z.init(w, z.level)
|
|
|
|
}
|
|
|
|
|
|
|
|
// writeBytes writes a length-prefixed byte slice to z.w.
|
|
|
|
func (z *Writer) writeBytes(b []byte) error {
|
|
|
|
if len(b) > 0xffff {
|
|
|
|
return errors.New("gzip.Write: Extra data is too large")
|
|
|
|
}
|
|
|
|
le.PutUint16(z.buf[:2], uint16(len(b)))
|
|
|
|
_, err := z.w.Write(z.buf[:2])
|
|
|
|
if err != nil {
|
|
|
|
return err
|
|
|
|
}
|
|
|
|
_, err = z.w.Write(b)
|
|
|
|
return err
|
|
|
|
}
|
|
|
|
|
|
|
|
// writeString writes a UTF-8 string s in GZIP's format to z.w.
|
|
|
|
// GZIP (RFC 1952) specifies that strings are NUL-terminated ISO 8859-1 (Latin-1).
|
|
|
|
func (z *Writer) writeString(s string) (err error) {
|
|
|
|
// GZIP stores Latin-1 strings; error if non-Latin-1; convert if non-ASCII.
|
|
|
|
needconv := false
|
|
|
|
for _, v := range s {
|
|
|
|
if v == 0 || v > 0xff {
|
|
|
|
return errors.New("gzip.Write: non-Latin-1 header string")
|
|
|
|
}
|
|
|
|
if v > 0x7f {
|
|
|
|
needconv = true
|
|
|
|
}
|
|
|
|
}
|
|
|
|
if needconv {
|
|
|
|
b := make([]byte, 0, len(s))
|
|
|
|
for _, v := range s {
|
|
|
|
b = append(b, byte(v))
|
|
|
|
}
|
|
|
|
_, err = z.w.Write(b)
|
|
|
|
} else {
|
|
|
|
_, err = io.WriteString(z.w, s)
|
|
|
|
}
|
|
|
|
if err != nil {
|
|
|
|
return err
|
|
|
|
}
|
|
|
|
// GZIP strings are NUL-terminated.
|
|
|
|
z.buf[0] = 0
|
|
|
|
_, err = z.w.Write(z.buf[:1])
|
|
|
|
return err
|
|
|
|
}
|
|
|
|
|
|
|
|
// Write writes a compressed form of p to the underlying io.Writer. The
|
|
|
|
// compressed bytes are not necessarily flushed until the Writer is closed.
|
|
|
|
func (z *Writer) Write(p []byte) (int, error) {
|
|
|
|
if z.err != nil {
|
|
|
|
return 0, z.err
|
|
|
|
}
|
|
|
|
var n int
|
|
|
|
// Write the GZIP header lazily.
|
|
|
|
if !z.wroteHeader {
|
|
|
|
z.wroteHeader = true
|
|
|
|
z.buf[0] = gzipID1
|
|
|
|
z.buf[1] = gzipID2
|
|
|
|
z.buf[2] = gzipDeflate
|
|
|
|
z.buf[3] = 0
|
|
|
|
if z.Extra != nil {
|
|
|
|
z.buf[3] |= 0x04
|
|
|
|
}
|
|
|
|
if z.Name != "" {
|
|
|
|
z.buf[3] |= 0x08
|
|
|
|
}
|
|
|
|
if z.Comment != "" {
|
|
|
|
z.buf[3] |= 0x10
|
|
|
|
}
|
|
|
|
le.PutUint32(z.buf[4:8], uint32(z.ModTime.Unix()))
|
|
|
|
if z.level == BestCompression {
|
|
|
|
z.buf[8] = 2
|
|
|
|
} else if z.level == BestSpeed {
|
|
|
|
z.buf[8] = 4
|
|
|
|
} else {
|
|
|
|
z.buf[8] = 0
|
|
|
|
}
|
|
|
|
z.buf[9] = z.OS
|
|
|
|
n, z.err = z.w.Write(z.buf[:10])
|
|
|
|
if z.err != nil {
|
|
|
|
return n, z.err
|
|
|
|
}
|
|
|
|
if z.Extra != nil {
|
|
|
|
z.err = z.writeBytes(z.Extra)
|
|
|
|
if z.err != nil {
|
|
|
|
return n, z.err
|
|
|
|
}
|
|
|
|
}
|
|
|
|
if z.Name != "" {
|
|
|
|
z.err = z.writeString(z.Name)
|
|
|
|
if z.err != nil {
|
|
|
|
return n, z.err
|
|
|
|
}
|
|
|
|
}
|
|
|
|
if z.Comment != "" {
|
|
|
|
z.err = z.writeString(z.Comment)
|
|
|
|
if z.err != nil {
|
|
|
|
return n, z.err
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
if z.compressor == nil && z.level != StatelessCompression {
|
|
|
|
z.compressor, _ = flate.NewWriter(z.w, z.level)
|
|
|
|
}
|
|
|
|
}
|
|
|
|
z.size += uint32(len(p))
|
|
|
|
z.digest = crc32.Update(z.digest, crc32.IEEETable, p)
|
|
|
|
if z.level == StatelessCompression {
|
2020-02-10 21:35:08 +00:00
|
|
|
return len(p), flate.StatelessDeflate(z.w, p, false, nil)
|
2020-01-17 21:57:18 +00:00
|
|
|
}
|
|
|
|
n, z.err = z.compressor.Write(p)
|
|
|
|
return n, z.err
|
|
|
|
}
|
|
|
|
|
|
|
|
// Flush flushes any pending compressed data to the underlying writer.
|
|
|
|
//
|
|
|
|
// It is useful mainly in compressed network protocols, to ensure that
|
|
|
|
// a remote reader has enough data to reconstruct a packet. Flush does
|
|
|
|
// not return until the data has been written. If the underlying
|
|
|
|
// writer returns an error, Flush returns that error.
|
|
|
|
//
|
|
|
|
// In the terminology of the zlib library, Flush is equivalent to Z_SYNC_FLUSH.
|
|
|
|
func (z *Writer) Flush() error {
|
|
|
|
if z.err != nil {
|
|
|
|
return z.err
|
|
|
|
}
|
|
|
|
if z.closed || z.level == StatelessCompression {
|
|
|
|
return nil
|
|
|
|
}
|
|
|
|
if !z.wroteHeader {
|
|
|
|
z.Write(nil)
|
|
|
|
if z.err != nil {
|
|
|
|
return z.err
|
|
|
|
}
|
|
|
|
}
|
|
|
|
z.err = z.compressor.Flush()
|
|
|
|
return z.err
|
|
|
|
}
|
|
|
|
|
|
|
|
// Close closes the Writer, flushing any unwritten data to the underlying
|
|
|
|
// io.Writer, but does not close the underlying io.Writer.
|
|
|
|
func (z *Writer) Close() error {
|
|
|
|
if z.err != nil {
|
|
|
|
return z.err
|
|
|
|
}
|
|
|
|
if z.closed {
|
|
|
|
return nil
|
|
|
|
}
|
|
|
|
z.closed = true
|
|
|
|
if !z.wroteHeader {
|
|
|
|
z.Write(nil)
|
|
|
|
if z.err != nil {
|
|
|
|
return z.err
|
|
|
|
}
|
|
|
|
}
|
|
|
|
if z.level == StatelessCompression {
|
2020-02-10 21:35:08 +00:00
|
|
|
z.err = flate.StatelessDeflate(z.w, nil, true, nil)
|
2020-01-17 21:57:18 +00:00
|
|
|
} else {
|
|
|
|
z.err = z.compressor.Close()
|
|
|
|
}
|
|
|
|
if z.err != nil {
|
|
|
|
return z.err
|
|
|
|
}
|
|
|
|
le.PutUint32(z.buf[:4], z.digest)
|
|
|
|
le.PutUint32(z.buf[4:8], z.size)
|
|
|
|
_, z.err = z.w.Write(z.buf[:8])
|
|
|
|
return z.err
|
|
|
|
}
|