// Copyright 2009 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 pgzip implements reading and writing of gzip format compressed files,
// as specified in RFC 1952.
//
// This is a drop in replacement for "compress/gzip".
// This will split compression into blocks that are compressed in parallel.
// This can be useful for compressing big amounts of data.
// The gzip decompression has not been modified, but remains in the package,
// so you can use it as a complete replacement for "compress/gzip".
//
// See more at https://github.com/klauspost/pgzip
package pgzip
import (
"bufio"
"errors"
"hash"
"hash/crc32"
"io"
"sync"
"time"
"github.com/klauspost/compress/flate"
)
const (
gzipID1 = 0x1f
gzipID2 = 0x8b
gzipDeflate = 8
flagText = 1 << 0
flagHdrCrc = 1 << 1
flagExtra = 1 << 2
flagName = 1 << 3
flagComment = 1 << 4
)
func makeReader(r io.Reader) flate.Reader {
if rr, ok := r.(flate.Reader); ok {
return rr
}
return bufio.NewReader(r)
}
var (
// ErrChecksum is returned when reading GZIP data that has an invalid checksum.
ErrChecksum = errors.New("gzip: invalid checksum")
// ErrHeader is returned when reading GZIP data that has an invalid header.
ErrHeader = errors.New("gzip: invalid header")
)
// The gzip file stores a header giving metadata about the compressed file.
// That header is exposed as the fields of the Writer and Reader structs.
type Header struct {
Comment string // comment
Extra []byte // "extra data"
ModTime time.Time // modification time
Name string // file name
OS byte // operating system type
}
// A Reader is an io.Reader that can be read to retrieve
// uncompressed data from a gzip-format compressed file.
//
// In general, a gzip file can be a concatenation of gzip files,
// each with its own header. Reads from the Reader
// return the concatenation of the uncompressed data of each.
// Only the first header is recorded in the Reader fields.
//
// Gzip files store a length and checksum of the uncompressed data.
// The Reader will return a ErrChecksum when Read
// reaches the end of the uncompressed data if it does not
// have the expected length or checksum. Clients should treat data
// returned by Read as tentative until they receive the io.EOF
// marking the end of the data.
type Reader struct {
Header
r flate.Reader
decompressor io.ReadCloser
digest hash.Hash32
size uint32
flg byte
buf [512]byte
err error
closeErr chan error
multistream bool
readAhead chan read
roff int // read offset
current []byte
closeReader chan struct{}
lastBlock bool
blockSize int
blocks int
activeRA bool // Indication if readahead is active
mu sync.Mutex // Lock for above
blockPool chan []byte
}
type read struct {
b []byte
err error
}
// NewReader creates a new Reader reading the given reader.
// The implementation buffers input and may read more data than necessary from r.
// It is the caller's responsibility to call Close on the Reader when done.
func NewReader(r io.Reader) (*Reader, error) {
z := new(Reader)
z.blocks = defaultBlocks
z.blockSize = defaultBlockSize
z.r = makeReader(r)
z.digest = crc32.NewIEEE()
z.multistream = true
z.blockPool = make(chan []byte, z.blocks)
for i := 0; i < z.blocks; i++ {
z.blockPool <- make([]byte, z.blockSize)
}
if err := z.readHeader(true); err != nil {
return nil, err
}
return z, nil
}
// NewReaderN creates a new Reader reading the given reader.
// The implementation buffers input and may read more data than necessary from r.
// It is the caller's responsibility to call Close on the Reader when done.
//
// With this you can control the approximate size of your blocks,
// as well as how many blocks you want to have prefetched.
//
// Default values for this is blockSize = 250000, blocks = 16,
// meaning up to 16 blocks of maximum 250000 bytes will be
// prefetched.
func NewReaderN(r io.Reader, blockSize, blocks int) (*Reader, error) {
z := new(Reader)
z.blocks = blocks
z.blockSize = blockSize
z.r = makeReader(r)
z.digest = crc32.NewIEEE()
z.multistream = true
// Account for too small values
if z.blocks <= 0 {
z.blocks = defaultBlocks
}
if z.blockSize <= 512 {
z.blockSize = defaultBlockSize
}
z.blockPool = make(chan []byte, z.blocks)
for i := 0; i < z.blocks; i++ {
z.blockPool <- make([]byte, z.blockSize)
}
if err := z.readHeader(true); err != nil {
return nil, err
}
return z, nil
}
// Reset discards the Reader z's state and makes it equivalent to the
// result of its original state from NewReader, but reading from r instead.
// This permits reusing a Reader rather than allocating a new one.
func (z *Reader) Reset(r io.Reader) error {
z.killReadAhead()
z.r = makeReader(r)
z.digest = crc32.NewIEEE()
z.size = 0
z.err = nil
z.multistream = true
// Account for uninitialized values
if z.blocks <= 0 {
z.blocks = defaultBlocks
}
if z.blockSize <= 512 {
z.blockSize = defaultBlockSize
}
if z.blockPool == nil {
z.blockPool = make(chan []byte, z.blocks)
for i := 0; i < z.blocks; i++ {
z.blockPool <- make([]byte, z.blockSize)
}
}
return z.readHeader(true)
}
// Multistream controls whether the reader supports multistream files.
//
// If enabled (the default), the Reader expects the input to be a sequence
// of individually gzipped data streams, each with its own header and
// trailer, ending at EOF. The effect is that the concatenation of a sequence
// of gzipped files is treated as equivalent to the gzip of the concatenation
// of the sequence. This is standard behavior for gzip readers.
//
// Calling Multistream(false) disables this behavior; disabling the behavior
// can be useful when reading file formats that distinguish individual gzip
// data streams or mix gzip data streams with other data streams.
// In this mode, when the Reader reaches the end of the data stream,
// Read returns io.EOF. If the underlying reader implements io.ByteReader,
// it will be left positioned just after the gzip stream.
// To start the next stream, call z.Reset(r) followed by z.Multistream(false).
// If there is no next stream, z.Reset(r) will return io.EOF.
func (z *Reader) Multistream(ok bool) {
z.multistream = ok
}
// GZIP (RFC 1952) is little-endian, unlike ZLIB (RFC 1950).
func get4(p []byte) uint32 {
return uint32(p[0]) | uint32(p[1])<<8 | uint32(p[2])<<16 | uint32(p[3])<<24
}
func (z *Reader) readString() (string, error) {
var err error
needconv := false
for i := 0; ; i++ {
if i >= len(z.buf) {
return "", ErrHeader
}
z.buf[i], err = z.r.ReadByte()
if err != nil {
return "", err
}
if z.buf[i] > 0x7f {
needconv = true
}
if z.buf[i] == 0 {
// GZIP (RFC 1952) specifies that strings are NUL-terminated ISO 8859-1 (Latin-1).
if needconv {
s := make([]rune, 0, i)
for _, v := range z.buf[0:i] {
s = append(s, rune(v))
}
return string(s), nil
}
return string(z.buf[0:i]), nil
}
}
}
func (z *Reader) read2() (uint32, error) {
_, err := io.ReadFull(z.r, z.buf[0:2])
if err != nil {
return 0, err
}
return uint32(z.buf[0]) | uint32(z.buf[1])<<8, nil
}
func (z *Reader) readHeader(save bool) error {
z.killReadAhead()
_, err := io.ReadFull(z.r, z.buf[0:10])
if err != nil {
return err
}
if z.buf[0] != gzipID1 || z.buf[1] != gzipID2 || z.buf[2] != gzipDeflate {
return ErrHeader
}
z.flg = z.buf[3]
if save {
z.ModTime = time.Unix(int64(get4(z.buf[4:8])), 0)
// z.buf[8] is xfl, ignored
z.OS = z.buf[9]
}
z.digest.Reset()
z.digest.Write(z.buf[0:10])
if z.flg&flagExtra != 0 {
n, err := z.read2()
if err != nil {
return err
}
data := make([]byte, n)
if _, err = io.ReadFull(z.r, data); err != nil {
return err
}
if save {
z.Extra = data
}
}
var s string
if z.flg&flagName != 0 {
if s, err = z.readString(); err != nil {
return err
}
if save {
z.Name = s
}
}
if z.flg&flagComment != 0 {
if s, err = z.readString(); err != nil {
return err
}
if save {
z.Comment = s
}
}
if z.flg&flagHdrCrc != 0 {
n, err := z.read2()
if err != nil {
return err
}
sum := z.digest.Sum32() & 0xFFFF
if n != sum {
return ErrHeader
}
}
z.digest.Reset()
z.decompressor = flate.NewReader(z.r)
z.doReadAhead()
return nil
}
func (z *Reader) killReadAhead() error {
z.mu.Lock()
defer z.mu.Unlock()
if z.activeRA {
if z.closeReader != nil {
close(z.closeReader)
}
// Wait for decompressor to be closed and return error, if any.
e, ok := <-z.closeErr
z.activeRA = false
for blk := range z.readAhead {
if blk.b != nil {
z.blockPool <- blk.b
}
}
if cap(z.current) > 0 {
z.blockPool <- z.current
z.current = nil
}
if !ok {
// Channel is closed, so if there was any error it has already been returned.
return nil
}
return e
}
return nil
}
// Starts readahead.
// Will return on error (including io.EOF)
// or when z.closeReader is closed.
func (z *Reader) doReadAhead() {
z.mu.Lock()
defer z.mu.Unlock()
z.activeRA = true
if z.blocks <= 0 {
z.blocks = defaultBlocks
}
if z.blockSize <= 512 {
z.blockSize = defaultBlockSize
}
ra := make(chan read, z.blocks)
z.readAhead = ra
closeReader := make(chan struct{}, 0)
z.closeReader = closeReader
z.lastBlock = false
closeErr := make(chan error, 1)
z.closeErr = closeErr
z.size = 0
z.roff = 0
z.current = nil
decomp := z.decompressor
go func() {
defer func() {
closeErr <- decomp.Close()
close(closeErr)
close(ra)
}()
// We hold a local reference to digest, since
// it way be changed by reset.
digest := z.digest
var wg sync.WaitGroup
for {
var buf []byte
select {
case buf = <-z.blockPool:
case <-closeReader:
return
}
buf = buf[0:z.blockSize]
// Try to fill the buffer
n, err := io.ReadFull(decomp, buf)
if err == io.ErrUnexpectedEOF {
if n > 0 {
err = nil
} else {
// If we got zero bytes, we need to establish if
// we reached end of stream or truncated stream.
_, err = decomp.Read([]byte{})
if err == io.EOF {
err = nil
}
}
}
if n < len(buf) {
buf = buf[0:n]
}
wg.Wait()
wg.Add(1)
go func() {
digest.Write(buf)
wg.Done()
}()
z.size += uint32(n)
// If we return any error, out digest must be ready
if err != nil {
wg.Wait()
}
select {
case z.readAhead <- read{b: buf, err: err}:
case <-closeReader:
// Sent on close, we don't care about the next results
z.blockPool <- buf
return
}
if err != nil {
return
}
}
}()
}
func (z *Reader) Read(p []byte) (n int, err error) {
if z.err != nil {
return 0, z.err
}
if len(p) == 0 {
return 0, nil
}
for {
if len(z.current) == 0 && !z.lastBlock {
read := <-z.readAhead
if read.err != nil {
// If not nil, the reader will have exited
z.closeReader = nil
if read.err != io.EOF {
z.err = read.err
return
}
if read.err == io.EOF {
z.lastBlock = true
err = nil
}
}
z.current = read.b
z.roff = 0
}
avail := z.current[z.roff:]
if len(p) >= len(avail) {
// If len(p) >= len(current), return all content of current
n = copy(p, avail)
z.blockPool <- z.current
z.current = nil
if z.lastBlock {
err = io.EOF
break
}
} else {
// We copy as much as there is space for
n = copy(p, avail)
z.roff += n
}
return
}
// Finished file; check checksum + size.
if _, err := io.ReadFull(z.r, z.buf[0:8]); err != nil {
z.err = err
return 0, err
}
crc32, isize := get4(z.buf[0:4]), get4(z.buf[4:8])
sum := z.digest.Sum32()
if sum != crc32 || isize != z.size {
z.err = ErrChecksum
return 0, z.err
}
// File is ok; should we attempt reading one more?
if !z.multistream {
return 0, io.EOF
}
// Is there another?
if err = z.readHeader(false); err != nil {
z.err = err
return
}
// Yes. Reset and read from it.
return z.Read(p)
}
func (z *Reader) WriteTo(w io.Writer) (n int64, err error) {
total := int64(0)
for {
if z.err != nil {
return total, z.err
}
// We write both to output and digest.
for {
// Read from input
read := <-z.readAhead
if read.err != nil {
// If not nil, the reader will have exited
z.closeReader = nil
if read.err != io.EOF {
z.err = read.err
return total, z.err
}
if read.err == io.EOF {
z.lastBlock = true
err = nil
}
}
// Write what we got
n, err := w.Write(read.b)
if n != len(read.b) {
return total, io.ErrShortWrite
}
total += int64(n)
if err != nil {
return total, err
}
// Put block back
z.blockPool <- read.b
if z.lastBlock {
break
}
}
// Finished file; check checksum + size.
if _, err := io.ReadFull(z.r, z.buf[0:8]); err != nil {
z.err = err
return total, err
}
crc32, isize := get4(z.buf[0:4]), get4(z.buf[4:8])
sum := z.digest.Sum32()
if sum != crc32 || isize != z.size {
z.err = ErrChecksum
return total, z.err
}
// File is ok; should we attempt reading one more?
if !z.multistream {
return total, nil
}
// Is there another?
err = z.readHeader(false)
if err == io.EOF {
return total, nil
}
if err != nil {
z.err = err
return total, err
}
}
}
// Close closes the Reader. It does not close the underlying io.Reader.
func (z *Reader) Close() error {
return z.killReadAhead()
}