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