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compress/gzip: cleanup gzip package

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Changes made:
* Reader.flg is not used anywhere else other than readHeader and
does not need to be stored.
* Store Reader.digest and Writer.digest as uint32s rather than as
a hash.Hash32 and use the crc32.Update function instead. This simplifies
initialization logic since the zero value of uint32 is the initial
CRC-32 value. There are no performance detriments to doing this since
the hash.Hash32 returned by crc32 simply calls crc32.Update as well.
* s/[0:/[:/            Consistently use shorter notation for slicing.
* s/RFC1952/RFC 1952/  Consistently use RFC notation.

Change-Id: I55416a19f4836cbed943adaa3f672538ea5d166d
Reviewed-on: https://go-review.googlesource.com/21429
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Joe Tsai <joetsai@digital-static.net>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This commit is contained in:
Joe Tsai 2016-04-01 18:11:26 -07:00 committed by Brad Fitzpatrick
parent ac8d97b679
commit 0d40dfa745
3 changed files with 32 additions and 50 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

54
src/compress/gzip/gunzip.go
View File

@ -10,7 +10,6 @@ import (
"bufio" "bufio"
"compress/flate" "compress/flate"
"errors" "errors"
"hash"
"hash/crc32" "hash/crc32"
"io" "io"
"time" "time"
@ -72,9 +71,8 @@ type Reader struct {
Header // valid after NewReader or Reader.Reset Header // valid after NewReader or Reader.Reset
r flate.Reader r flate.Reader
decompressor io.ReadCloser decompressor io.ReadCloser
digest hash.Hash32 digest uint32 // CRC-32, IEEE polynomial (section 8)
size uint32 size uint32 // Uncompressed size (section 2.3.1)
flg byte
buf [512]byte buf [512]byte
err error err error
multistream bool multistream bool
@ -91,7 +89,6 @@ func NewReader(r io.Reader) (*Reader, error) {
z := new(Reader) z := new(Reader)
z.r = makeReader(r) z.r = makeReader(r)
z.multistream = true z.multistream = true
z.digest = crc32.NewIEEE()
if err := z.readHeader(true); err != nil { if err := z.readHeader(true); err != nil {
return nil, err return nil, err
} }
@ -103,11 +100,7 @@ func NewReader(r io.Reader) (*Reader, error) {
// This permits reusing a Reader rather than allocating a new one. // This permits reusing a Reader rather than allocating a new one.
func (z *Reader) Reset(r io.Reader) error { func (z *Reader) Reset(r io.Reader) error {
z.r = makeReader(r) z.r = makeReader(r)
if z.digest == nil { z.digest = 0
z.digest = crc32.NewIEEE()
} else {
z.digest.Reset()
}
z.size = 0 z.size = 0
z.err = nil z.err = nil
z.multistream = true z.multistream = true
@ -157,18 +150,18 @@ func (z *Reader) readString() (string, error) {
// GZIP (RFC 1952) specifies that strings are NUL-terminated ISO 8859-1 (Latin-1). // GZIP (RFC 1952) specifies that strings are NUL-terminated ISO 8859-1 (Latin-1).
if needconv { if needconv {
s := make([]rune, 0, i) s := make([]rune, 0, i)
for _, v := range z.buf[0:i] { for _, v := range z.buf[:i] {
s = append(s, rune(v)) s = append(s, rune(v))
} }
return string(s), nil return string(s), nil
} }
return string(z.buf[0:i]), nil return string(z.buf[:i]), nil
} }
} }
} }
func (z *Reader) read2() (uint32, error) { func (z *Reader) read2() (uint32, error) {
_, err := io.ReadFull(z.r, z.buf[0:2]) _, err := io.ReadFull(z.r, z.buf[:2])
if err != nil { if err != nil {
if err == io.EOF { if err == io.EOF {
err = io.ErrUnexpectedEOF err = io.ErrUnexpectedEOF
@ -179,9 +172,9 @@ func (z *Reader) read2() (uint32, error) {
} }
func (z *Reader) readHeader(save bool) error { func (z *Reader) readHeader(save bool) error {
_, err := io.ReadFull(z.r, z.buf[0:10]) _, err := io.ReadFull(z.r, z.buf[:10])
if err != nil { if err != nil {
// RFC1952 section 2.2 says the following: // RFC 1952, section 2.2, says the following:
// A gzip file consists of a series of "members" (compressed data sets). // A gzip file consists of a series of "members" (compressed data sets).
// //
// Other than this, the specification does not clarify whether a // Other than this, the specification does not clarify whether a
@ -193,16 +186,15 @@ func (z *Reader) readHeader(save bool) error {
if z.buf[0] != gzipID1 || z.buf[1] != gzipID2 || z.buf[2] != gzipDeflate { if z.buf[0] != gzipID1 || z.buf[1] != gzipID2 || z.buf[2] != gzipDeflate {
return ErrHeader return ErrHeader
} }
z.flg = z.buf[3] flg := z.buf[3]
if save { if save {
z.ModTime = time.Unix(int64(get4(z.buf[4:8])), 0) z.ModTime = time.Unix(int64(get4(z.buf[4:8])), 0)
// z.buf[8] is xfl, ignored // z.buf[8] is xfl, ignored
z.OS = z.buf[9] z.OS = z.buf[9]
} }
z.digest.Reset() z.digest = crc32.Update(0, crc32.IEEETable, z.buf[:10])
z.digest.Write(z.buf[0:10])
if z.flg&flagExtra != 0 { if flg&flagExtra != 0 {
n, err := z.read2() n, err := z.read2()
if err != nil { if err != nil {
return err return err
@ -220,7 +212,7 @@ func (z *Reader) readHeader(save bool) error {
} }
var s string var s string
if z.flg&flagName != 0 { if flg&flagName != 0 {
if s, err = z.readString(); err != nil { if s, err = z.readString(); err != nil {
return err return err
} }
@ -229,7 +221,7 @@ func (z *Reader) readHeader(save bool) error {
} }
} }
if z.flg&flagComment != 0 { if flg&flagComment != 0 {
if s, err = z.readString(); err != nil { if s, err = z.readString(); err != nil {
return err return err
} }
@ -238,18 +230,18 @@ func (z *Reader) readHeader(save bool) error {
} }
} }
if z.flg&flagHdrCrc != 0 { if flg&flagHdrCrc != 0 {
n, err := z.read2() n, err := z.read2()
if err != nil { if err != nil {
return err return err
} }
sum := z.digest.Sum32() & 0xFFFF sum := z.digest & 0xFFFF
if n != sum { if n != sum {
return ErrHeader return ErrHeader
} }
} }
z.digest.Reset() z.digest = 0
if z.decompressor == nil { if z.decompressor == nil {
z.decompressor = flate.NewReader(z.r) z.decompressor = flate.NewReader(z.r)
} else { } else {
@ -264,29 +256,27 @@ func (z *Reader) Read(p []byte) (n int, err error) {
} }
n, z.err = z.decompressor.Read(p) n, z.err = z.decompressor.Read(p)
z.digest.Write(p[0:n]) z.digest = crc32.Update(z.digest, crc32.IEEETable, p[:n])
z.size += uint32(n) z.size += uint32(n)
if z.err != io.EOF { if z.err != io.EOF {
// In the normal case we return here. // In the normal case we return here.
return n, z.err return n, z.err
} }
// Finished file; check checksum + size. // Finished file; check checksum and size.
if _, err := io.ReadFull(z.r, z.buf[0:8]); err != nil { if _, err := io.ReadFull(z.r, z.buf[:8]); err != nil {
if err == io.EOF { if err == io.EOF {
err = io.ErrUnexpectedEOF err = io.ErrUnexpectedEOF
} }
z.err = err z.err = err
return n, err return n, err
} }
crc32, isize := get4(z.buf[0:4]), get4(z.buf[4:8]) digest, size := get4(z.buf[:4]), get4(z.buf[4:8])
sum := z.digest.Sum32() if digest != z.digest || size != z.size {
if sum != crc32 || isize != z.size {
z.err = ErrChecksum z.err = ErrChecksum
return n, z.err return n, z.err
} }
z.digest.Reset() z.digest, z.size = 0, 0
z.size = 0
// File is ok; check if there is another. // File is ok; check if there is another.
if !z.multistream { if !z.multistream {

2
src/compress/gzip/gunzip_test.go
View File

@ -411,7 +411,7 @@ Found:
} }
func TestNilStream(t *testing.T) { func TestNilStream(t *testing.T) {
// Go liberally interprets RFC1952 section 2.2 to mean that a gzip file // Go liberally interprets RFC 1952 section 2.2 to mean that a gzip file
// consist of zero or more members. Thus, we test that a nil stream is okay. // consist of zero or more members. Thus, we test that a nil stream is okay.
_, err := NewReader(bytes.NewReader(nil)) _, err := NewReader(bytes.NewReader(nil))
if err != io.EOF { if err != io.EOF {

26
src/compress/gzip/gzip.go
View File

@ -8,7 +8,6 @@ import (
"compress/flate" "compress/flate"
"errors" "errors"
"fmt" "fmt"
"hash"
"hash/crc32" "hash/crc32"
"io" "io"
) )
@ -30,8 +29,8 @@ type Writer struct {
level int level int
wroteHeader bool wroteHeader bool
compressor *flate.Writer compressor *flate.Writer
digest hash.Hash32 digest uint32 // CRC-32, IEEE polynomial (section 8)
size uint32 size uint32 // Uncompressed size (section 2.3.1)
closed bool closed bool
buf [10]byte buf [10]byte
err error err error
@ -66,12 +65,6 @@ func NewWriterLevel(w io.Writer, level int) (*Writer, error) {
} }
func (z *Writer) init(w io.Writer, level int) { func (z *Writer) init(w io.Writer, level int) {
digest := z.digest
if digest != nil {
digest.Reset()
} else {
digest = crc32.NewIEEE()
}
compressor := z.compressor compressor := z.compressor
if compressor != nil { if compressor != nil {
compressor.Reset(w) compressor.Reset(w)
@ -82,7 +75,6 @@ func (z *Writer) init(w io.Writer, level int) {
}, },
w: w, w: w,
level: level, level: level,
digest: digest,
compressor: compressor, compressor: compressor,
} }
} }
@ -113,8 +105,8 @@ func (z *Writer) writeBytes(b []byte) error {
if len(b) > 0xffff { if len(b) > 0xffff {
return errors.New("gzip.Write: Extra data is too large") return errors.New("gzip.Write: Extra data is too large")
} }
put2(z.buf[0:2], uint16(len(b))) put2(z.buf[:2], uint16(len(b)))
_, err := z.w.Write(z.buf[0:2]) _, err := z.w.Write(z.buf[:2])
if err != nil { if err != nil {
return err return err
} }
@ -149,7 +141,7 @@ func (z *Writer) writeString(s string) (err error) {
} }
// GZIP strings are NUL-terminated. // GZIP strings are NUL-terminated.
z.buf[0] = 0 z.buf[0] = 0
_, err = z.w.Write(z.buf[0:1]) _, err = z.w.Write(z.buf[:1])
return err return err
} }
@ -185,7 +177,7 @@ func (z *Writer) Write(p []byte) (int, error) {
z.buf[8] = 0 z.buf[8] = 0
} }
z.buf[9] = z.OS z.buf[9] = z.OS
n, z.err = z.w.Write(z.buf[0:10]) n, z.err = z.w.Write(z.buf[:10])
if z.err != nil { if z.err != nil {
return n, z.err return n, z.err
} }
@ -212,7 +204,7 @@ func (z *Writer) Write(p []byte) (int, error) {
} }
} }
z.size += uint32(len(p)) z.size += uint32(len(p))
z.digest.Write(p) z.digest = crc32.Update(z.digest, crc32.IEEETable, p)
n, z.err = z.compressor.Write(p) n, z.err = z.compressor.Write(p)
return n, z.err return n, z.err
} }
@ -262,8 +254,8 @@ func (z *Writer) Close() error {
if z.err != nil { if z.err != nil {
return z.err return z.err
} }
put4(z.buf[0:4], z.digest.Sum32()) put4(z.buf[:4], z.digest)
put4(z.buf[4:8], z.size) put4(z.buf[4:8], z.size)
_, z.err = z.w.Write(z.buf[0:8]) _, z.err = z.w.Write(z.buf[:8])
return z.err return z.err
} }