1076 lines
27 KiB
Go
1076 lines
27 KiB
Go
// Copyright 2011 The Snappy-Go Authors. All rights reserved.
|
|
// Copyright (c) 2019+ Klaus Post. All rights reserved.
|
|
// Use of this source code is governed by a BSD-style
|
|
// license that can be found in the LICENSE file.
|
|
|
|
package s2
|
|
|
|
import (
|
|
"errors"
|
|
"fmt"
|
|
"io"
|
|
"io/ioutil"
|
|
"math"
|
|
"runtime"
|
|
"sync"
|
|
)
|
|
|
|
// ErrCantSeek is returned if the stream cannot be seeked.
|
|
type ErrCantSeek struct {
|
|
Reason string
|
|
}
|
|
|
|
// Error returns the error as string.
|
|
func (e ErrCantSeek) Error() string {
|
|
return fmt.Sprintf("s2: Can't seek because %s", e.Reason)
|
|
}
|
|
|
|
// NewReader returns a new Reader that decompresses from r, using the framing
|
|
// format described at
|
|
// https://github.com/google/snappy/blob/master/framing_format.txt with S2 changes.
|
|
func NewReader(r io.Reader, opts ...ReaderOption) *Reader {
|
|
nr := Reader{
|
|
r: r,
|
|
maxBlock: maxBlockSize,
|
|
}
|
|
for _, opt := range opts {
|
|
if err := opt(&nr); err != nil {
|
|
nr.err = err
|
|
return &nr
|
|
}
|
|
}
|
|
nr.maxBufSize = MaxEncodedLen(nr.maxBlock) + checksumSize
|
|
if nr.lazyBuf > 0 {
|
|
nr.buf = make([]byte, MaxEncodedLen(nr.lazyBuf)+checksumSize)
|
|
} else {
|
|
nr.buf = make([]byte, MaxEncodedLen(defaultBlockSize)+checksumSize)
|
|
}
|
|
nr.readHeader = nr.ignoreStreamID
|
|
nr.paramsOK = true
|
|
return &nr
|
|
}
|
|
|
|
// ReaderOption is an option for creating a decoder.
|
|
type ReaderOption func(*Reader) error
|
|
|
|
// ReaderMaxBlockSize allows to control allocations if the stream
|
|
// has been compressed with a smaller WriterBlockSize, or with the default 1MB.
|
|
// Blocks must be this size or smaller to decompress,
|
|
// otherwise the decoder will return ErrUnsupported.
|
|
//
|
|
// For streams compressed with Snappy this can safely be set to 64KB (64 << 10).
|
|
//
|
|
// Default is the maximum limit of 4MB.
|
|
func ReaderMaxBlockSize(blockSize int) ReaderOption {
|
|
return func(r *Reader) error {
|
|
if blockSize > maxBlockSize || blockSize <= 0 {
|
|
return errors.New("s2: block size too large. Must be <= 4MB and > 0")
|
|
}
|
|
if r.lazyBuf == 0 && blockSize < defaultBlockSize {
|
|
r.lazyBuf = blockSize
|
|
}
|
|
r.maxBlock = blockSize
|
|
return nil
|
|
}
|
|
}
|
|
|
|
// ReaderAllocBlock allows to control upfront stream allocations
|
|
// and not allocate for frames bigger than this initially.
|
|
// If frames bigger than this is seen a bigger buffer will be allocated.
|
|
//
|
|
// Default is 1MB, which is default output size.
|
|
func ReaderAllocBlock(blockSize int) ReaderOption {
|
|
return func(r *Reader) error {
|
|
if blockSize > maxBlockSize || blockSize < 1024 {
|
|
return errors.New("s2: invalid ReaderAllocBlock. Must be <= 4MB and >= 1024")
|
|
}
|
|
r.lazyBuf = blockSize
|
|
return nil
|
|
}
|
|
}
|
|
|
|
// ReaderIgnoreStreamIdentifier will make the reader skip the expected
|
|
// stream identifier at the beginning of the stream.
|
|
// This can be used when serving a stream that has been forwarded to a specific point.
|
|
func ReaderIgnoreStreamIdentifier() ReaderOption {
|
|
return func(r *Reader) error {
|
|
r.ignoreStreamID = true
|
|
return nil
|
|
}
|
|
}
|
|
|
|
// ReaderSkippableCB will register a callback for chuncks with the specified ID.
|
|
// ID must be a Reserved skippable chunks ID, 0x80-0xfd (inclusive).
|
|
// For each chunk with the ID, the callback is called with the content.
|
|
// Any returned non-nil error will abort decompression.
|
|
// Only one callback per ID is supported, latest sent will be used.
|
|
// You can peek the stream, triggering the callback, by doing a Read with a 0
|
|
// byte buffer.
|
|
func ReaderSkippableCB(id uint8, fn func(r io.Reader) error) ReaderOption {
|
|
return func(r *Reader) error {
|
|
if id < 0x80 || id > 0xfd {
|
|
return fmt.Errorf("ReaderSkippableCB: Invalid id provided, must be 0x80-0xfd (inclusive)")
|
|
}
|
|
r.skippableCB[id-0x80] = fn
|
|
return nil
|
|
}
|
|
}
|
|
|
|
// ReaderIgnoreCRC will make the reader skip CRC calculation and checks.
|
|
func ReaderIgnoreCRC() ReaderOption {
|
|
return func(r *Reader) error {
|
|
r.ignoreCRC = true
|
|
return nil
|
|
}
|
|
}
|
|
|
|
// Reader is an io.Reader that can read Snappy-compressed bytes.
|
|
type Reader struct {
|
|
r io.Reader
|
|
err error
|
|
decoded []byte
|
|
buf []byte
|
|
skippableCB [0xff - 0x80]func(r io.Reader) error
|
|
blockStart int64 // Uncompressed offset at start of current.
|
|
index *Index
|
|
|
|
// decoded[i:j] contains decoded bytes that have not yet been passed on.
|
|
i, j int
|
|
// maximum block size allowed.
|
|
maxBlock int
|
|
// maximum expected buffer size.
|
|
maxBufSize int
|
|
// alloc a buffer this size if > 0.
|
|
lazyBuf int
|
|
readHeader bool
|
|
paramsOK bool
|
|
snappyFrame bool
|
|
ignoreStreamID bool
|
|
ignoreCRC bool
|
|
}
|
|
|
|
// GetBufferCapacity returns the capacity of the internal buffer.
|
|
// This might be useful to know when reusing the same reader in combination
|
|
// with the lazy buffer option.
|
|
func (r *Reader) GetBufferCapacity() int {
|
|
return cap(r.buf)
|
|
}
|
|
|
|
// ensureBufferSize will ensure that the buffer can take at least n bytes.
|
|
// If false is returned the buffer exceeds maximum allowed size.
|
|
func (r *Reader) ensureBufferSize(n int) bool {
|
|
if n > r.maxBufSize {
|
|
r.err = ErrCorrupt
|
|
return false
|
|
}
|
|
if cap(r.buf) >= n {
|
|
return true
|
|
}
|
|
// Realloc buffer.
|
|
r.buf = make([]byte, n)
|
|
return true
|
|
}
|
|
|
|
// Reset discards any buffered data, resets all state, and switches the Snappy
|
|
// reader to read from r. This permits reusing a Reader rather than allocating
|
|
// a new one.
|
|
func (r *Reader) Reset(reader io.Reader) {
|
|
if !r.paramsOK {
|
|
return
|
|
}
|
|
r.index = nil
|
|
r.r = reader
|
|
r.err = nil
|
|
r.i = 0
|
|
r.j = 0
|
|
r.blockStart = 0
|
|
r.readHeader = r.ignoreStreamID
|
|
}
|
|
|
|
func (r *Reader) readFull(p []byte, allowEOF bool) (ok bool) {
|
|
if _, r.err = io.ReadFull(r.r, p); r.err != nil {
|
|
if r.err == io.ErrUnexpectedEOF || (r.err == io.EOF && !allowEOF) {
|
|
r.err = ErrCorrupt
|
|
}
|
|
return false
|
|
}
|
|
return true
|
|
}
|
|
|
|
// skippable will skip n bytes.
|
|
// If the supplied reader supports seeking that is used.
|
|
// tmp is used as a temporary buffer for reading.
|
|
// The supplied slice does not need to be the size of the read.
|
|
func (r *Reader) skippable(tmp []byte, n int, allowEOF bool, id uint8) (ok bool) {
|
|
if id < 0x80 {
|
|
r.err = fmt.Errorf("internal error: skippable id < 0x80")
|
|
return false
|
|
}
|
|
if fn := r.skippableCB[id-0x80]; fn != nil {
|
|
rd := io.LimitReader(r.r, int64(n))
|
|
r.err = fn(rd)
|
|
if r.err != nil {
|
|
return false
|
|
}
|
|
_, r.err = io.CopyBuffer(ioutil.Discard, rd, tmp)
|
|
return r.err == nil
|
|
}
|
|
if rs, ok := r.r.(io.ReadSeeker); ok {
|
|
_, err := rs.Seek(int64(n), io.SeekCurrent)
|
|
if err == nil {
|
|
return true
|
|
}
|
|
if err == io.ErrUnexpectedEOF || (r.err == io.EOF && !allowEOF) {
|
|
r.err = ErrCorrupt
|
|
return false
|
|
}
|
|
}
|
|
for n > 0 {
|
|
if n < len(tmp) {
|
|
tmp = tmp[:n]
|
|
}
|
|
if _, r.err = io.ReadFull(r.r, tmp); r.err != nil {
|
|
if r.err == io.ErrUnexpectedEOF || (r.err == io.EOF && !allowEOF) {
|
|
r.err = ErrCorrupt
|
|
}
|
|
return false
|
|
}
|
|
n -= len(tmp)
|
|
}
|
|
return true
|
|
}
|
|
|
|
// Read satisfies the io.Reader interface.
|
|
func (r *Reader) Read(p []byte) (int, error) {
|
|
if r.err != nil {
|
|
return 0, r.err
|
|
}
|
|
for {
|
|
if r.i < r.j {
|
|
n := copy(p, r.decoded[r.i:r.j])
|
|
r.i += n
|
|
return n, nil
|
|
}
|
|
if !r.readFull(r.buf[:4], true) {
|
|
return 0, r.err
|
|
}
|
|
chunkType := r.buf[0]
|
|
if !r.readHeader {
|
|
if chunkType != chunkTypeStreamIdentifier {
|
|
r.err = ErrCorrupt
|
|
return 0, r.err
|
|
}
|
|
r.readHeader = true
|
|
}
|
|
chunkLen := int(r.buf[1]) | int(r.buf[2])<<8 | int(r.buf[3])<<16
|
|
|
|
// The chunk types are specified at
|
|
// https://github.com/google/snappy/blob/master/framing_format.txt
|
|
switch chunkType {
|
|
case chunkTypeCompressedData:
|
|
r.blockStart += int64(r.j)
|
|
// Section 4.2. Compressed data (chunk type 0x00).
|
|
if chunkLen < checksumSize {
|
|
r.err = ErrCorrupt
|
|
return 0, r.err
|
|
}
|
|
if !r.ensureBufferSize(chunkLen) {
|
|
if r.err == nil {
|
|
r.err = ErrUnsupported
|
|
}
|
|
return 0, r.err
|
|
}
|
|
buf := r.buf[:chunkLen]
|
|
if !r.readFull(buf, false) {
|
|
return 0, r.err
|
|
}
|
|
checksum := uint32(buf[0]) | uint32(buf[1])<<8 | uint32(buf[2])<<16 | uint32(buf[3])<<24
|
|
buf = buf[checksumSize:]
|
|
|
|
n, err := DecodedLen(buf)
|
|
if err != nil {
|
|
r.err = err
|
|
return 0, r.err
|
|
}
|
|
if r.snappyFrame && n > maxSnappyBlockSize {
|
|
r.err = ErrCorrupt
|
|
return 0, r.err
|
|
}
|
|
|
|
if n > len(r.decoded) {
|
|
if n > r.maxBlock {
|
|
r.err = ErrCorrupt
|
|
return 0, r.err
|
|
}
|
|
r.decoded = make([]byte, n)
|
|
}
|
|
if _, err := Decode(r.decoded, buf); err != nil {
|
|
r.err = err
|
|
return 0, r.err
|
|
}
|
|
if !r.ignoreCRC && crc(r.decoded[:n]) != checksum {
|
|
r.err = ErrCRC
|
|
return 0, r.err
|
|
}
|
|
r.i, r.j = 0, n
|
|
continue
|
|
|
|
case chunkTypeUncompressedData:
|
|
r.blockStart += int64(r.j)
|
|
// Section 4.3. Uncompressed data (chunk type 0x01).
|
|
if chunkLen < checksumSize {
|
|
r.err = ErrCorrupt
|
|
return 0, r.err
|
|
}
|
|
if !r.ensureBufferSize(chunkLen) {
|
|
if r.err == nil {
|
|
r.err = ErrUnsupported
|
|
}
|
|
return 0, r.err
|
|
}
|
|
buf := r.buf[:checksumSize]
|
|
if !r.readFull(buf, false) {
|
|
return 0, r.err
|
|
}
|
|
checksum := uint32(buf[0]) | uint32(buf[1])<<8 | uint32(buf[2])<<16 | uint32(buf[3])<<24
|
|
// Read directly into r.decoded instead of via r.buf.
|
|
n := chunkLen - checksumSize
|
|
if r.snappyFrame && n > maxSnappyBlockSize {
|
|
r.err = ErrCorrupt
|
|
return 0, r.err
|
|
}
|
|
if n > len(r.decoded) {
|
|
if n > r.maxBlock {
|
|
r.err = ErrCorrupt
|
|
return 0, r.err
|
|
}
|
|
r.decoded = make([]byte, n)
|
|
}
|
|
if !r.readFull(r.decoded[:n], false) {
|
|
return 0, r.err
|
|
}
|
|
if !r.ignoreCRC && crc(r.decoded[:n]) != checksum {
|
|
r.err = ErrCRC
|
|
return 0, r.err
|
|
}
|
|
r.i, r.j = 0, n
|
|
continue
|
|
|
|
case chunkTypeStreamIdentifier:
|
|
// Section 4.1. Stream identifier (chunk type 0xff).
|
|
if chunkLen != len(magicBody) {
|
|
r.err = ErrCorrupt
|
|
return 0, r.err
|
|
}
|
|
if !r.readFull(r.buf[:len(magicBody)], false) {
|
|
return 0, r.err
|
|
}
|
|
if string(r.buf[:len(magicBody)]) != magicBody {
|
|
if string(r.buf[:len(magicBody)]) != magicBodySnappy {
|
|
r.err = ErrCorrupt
|
|
return 0, r.err
|
|
} else {
|
|
r.snappyFrame = true
|
|
}
|
|
} else {
|
|
r.snappyFrame = false
|
|
}
|
|
continue
|
|
}
|
|
|
|
if chunkType <= 0x7f {
|
|
// Section 4.5. Reserved unskippable chunks (chunk types 0x02-0x7f).
|
|
// fmt.Printf("ERR chunktype: 0x%x\n", chunkType)
|
|
r.err = ErrUnsupported
|
|
return 0, r.err
|
|
}
|
|
// Section 4.4 Padding (chunk type 0xfe).
|
|
// Section 4.6. Reserved skippable chunks (chunk types 0x80-0xfd).
|
|
if chunkLen > maxChunkSize {
|
|
// fmt.Printf("ERR chunkLen: 0x%x\n", chunkLen)
|
|
r.err = ErrUnsupported
|
|
return 0, r.err
|
|
}
|
|
|
|
// fmt.Printf("skippable: ID: 0x%x, len: 0x%x\n", chunkType, chunkLen)
|
|
if !r.skippable(r.buf, chunkLen, false, chunkType) {
|
|
return 0, r.err
|
|
}
|
|
}
|
|
}
|
|
|
|
// DecodeConcurrent will decode the full stream to w.
|
|
// This function should not be combined with reading, seeking or other operations.
|
|
// Up to 'concurrent' goroutines will be used.
|
|
// If <= 0, runtime.NumCPU will be used.
|
|
// On success the number of bytes decompressed nil and is returned.
|
|
// This is mainly intended for bigger streams.
|
|
func (r *Reader) DecodeConcurrent(w io.Writer, concurrent int) (written int64, err error) {
|
|
if r.i > 0 || r.j > 0 || r.blockStart > 0 {
|
|
return 0, errors.New("DecodeConcurrent called after ")
|
|
}
|
|
if concurrent <= 0 {
|
|
concurrent = runtime.NumCPU()
|
|
}
|
|
|
|
// Write to output
|
|
var errMu sync.Mutex
|
|
var aErr error
|
|
setErr := func(e error) (ok bool) {
|
|
errMu.Lock()
|
|
defer errMu.Unlock()
|
|
if e == nil {
|
|
return aErr == nil
|
|
}
|
|
if aErr == nil {
|
|
aErr = e
|
|
}
|
|
return false
|
|
}
|
|
hasErr := func() (ok bool) {
|
|
errMu.Lock()
|
|
v := aErr != nil
|
|
errMu.Unlock()
|
|
return v
|
|
}
|
|
|
|
var aWritten int64
|
|
toRead := make(chan []byte, concurrent)
|
|
writtenBlocks := make(chan []byte, concurrent)
|
|
queue := make(chan chan []byte, concurrent)
|
|
reUse := make(chan chan []byte, concurrent)
|
|
for i := 0; i < concurrent; i++ {
|
|
toRead <- make([]byte, 0, r.maxBufSize)
|
|
writtenBlocks <- make([]byte, 0, r.maxBufSize)
|
|
reUse <- make(chan []byte, 1)
|
|
}
|
|
// Writer
|
|
var wg sync.WaitGroup
|
|
wg.Add(1)
|
|
go func() {
|
|
defer wg.Done()
|
|
for toWrite := range queue {
|
|
entry := <-toWrite
|
|
reUse <- toWrite
|
|
if hasErr() || entry == nil {
|
|
if entry != nil {
|
|
writtenBlocks <- entry
|
|
}
|
|
continue
|
|
}
|
|
if hasErr() {
|
|
writtenBlocks <- entry
|
|
continue
|
|
}
|
|
n, err := w.Write(entry)
|
|
want := len(entry)
|
|
writtenBlocks <- entry
|
|
if err != nil {
|
|
setErr(err)
|
|
continue
|
|
}
|
|
if n != want {
|
|
setErr(io.ErrShortWrite)
|
|
continue
|
|
}
|
|
aWritten += int64(n)
|
|
}
|
|
}()
|
|
|
|
defer func() {
|
|
if r.err != nil {
|
|
setErr(r.err)
|
|
} else if err != nil {
|
|
setErr(err)
|
|
}
|
|
close(queue)
|
|
wg.Wait()
|
|
if err == nil {
|
|
err = aErr
|
|
}
|
|
written = aWritten
|
|
}()
|
|
|
|
// Reader
|
|
for !hasErr() {
|
|
if !r.readFull(r.buf[:4], true) {
|
|
if r.err == io.EOF {
|
|
r.err = nil
|
|
}
|
|
return 0, r.err
|
|
}
|
|
chunkType := r.buf[0]
|
|
if !r.readHeader {
|
|
if chunkType != chunkTypeStreamIdentifier {
|
|
r.err = ErrCorrupt
|
|
return 0, r.err
|
|
}
|
|
r.readHeader = true
|
|
}
|
|
chunkLen := int(r.buf[1]) | int(r.buf[2])<<8 | int(r.buf[3])<<16
|
|
|
|
// The chunk types are specified at
|
|
// https://github.com/google/snappy/blob/master/framing_format.txt
|
|
switch chunkType {
|
|
case chunkTypeCompressedData:
|
|
r.blockStart += int64(r.j)
|
|
// Section 4.2. Compressed data (chunk type 0x00).
|
|
if chunkLen < checksumSize {
|
|
r.err = ErrCorrupt
|
|
return 0, r.err
|
|
}
|
|
if chunkLen > r.maxBufSize {
|
|
r.err = ErrCorrupt
|
|
return 0, r.err
|
|
}
|
|
orgBuf := <-toRead
|
|
buf := orgBuf[:chunkLen]
|
|
|
|
if !r.readFull(buf, false) {
|
|
return 0, r.err
|
|
}
|
|
|
|
checksum := uint32(buf[0]) | uint32(buf[1])<<8 | uint32(buf[2])<<16 | uint32(buf[3])<<24
|
|
buf = buf[checksumSize:]
|
|
|
|
n, err := DecodedLen(buf)
|
|
if err != nil {
|
|
r.err = err
|
|
return 0, r.err
|
|
}
|
|
if r.snappyFrame && n > maxSnappyBlockSize {
|
|
r.err = ErrCorrupt
|
|
return 0, r.err
|
|
}
|
|
|
|
if n > r.maxBlock {
|
|
r.err = ErrCorrupt
|
|
return 0, r.err
|
|
}
|
|
wg.Add(1)
|
|
|
|
decoded := <-writtenBlocks
|
|
entry := <-reUse
|
|
queue <- entry
|
|
go func() {
|
|
defer wg.Done()
|
|
decoded = decoded[:n]
|
|
_, err := Decode(decoded, buf)
|
|
toRead <- orgBuf
|
|
if err != nil {
|
|
writtenBlocks <- decoded
|
|
setErr(err)
|
|
entry <- nil
|
|
return
|
|
}
|
|
if !r.ignoreCRC && crc(decoded) != checksum {
|
|
writtenBlocks <- decoded
|
|
setErr(ErrCRC)
|
|
entry <- nil
|
|
return
|
|
}
|
|
entry <- decoded
|
|
}()
|
|
continue
|
|
|
|
case chunkTypeUncompressedData:
|
|
|
|
// Section 4.3. Uncompressed data (chunk type 0x01).
|
|
if chunkLen < checksumSize {
|
|
r.err = ErrCorrupt
|
|
return 0, r.err
|
|
}
|
|
if chunkLen > r.maxBufSize {
|
|
r.err = ErrCorrupt
|
|
return 0, r.err
|
|
}
|
|
// Grab write buffer
|
|
orgBuf := <-writtenBlocks
|
|
buf := orgBuf[:checksumSize]
|
|
if !r.readFull(buf, false) {
|
|
return 0, r.err
|
|
}
|
|
checksum := uint32(buf[0]) | uint32(buf[1])<<8 | uint32(buf[2])<<16 | uint32(buf[3])<<24
|
|
// Read content.
|
|
n := chunkLen - checksumSize
|
|
|
|
if r.snappyFrame && n > maxSnappyBlockSize {
|
|
r.err = ErrCorrupt
|
|
return 0, r.err
|
|
}
|
|
if n > r.maxBlock {
|
|
r.err = ErrCorrupt
|
|
return 0, r.err
|
|
}
|
|
// Read uncompressed
|
|
buf = orgBuf[:n]
|
|
if !r.readFull(buf, false) {
|
|
return 0, r.err
|
|
}
|
|
|
|
if !r.ignoreCRC && crc(buf) != checksum {
|
|
r.err = ErrCRC
|
|
return 0, r.err
|
|
}
|
|
entry := <-reUse
|
|
queue <- entry
|
|
entry <- buf
|
|
continue
|
|
|
|
case chunkTypeStreamIdentifier:
|
|
// Section 4.1. Stream identifier (chunk type 0xff).
|
|
if chunkLen != len(magicBody) {
|
|
r.err = ErrCorrupt
|
|
return 0, r.err
|
|
}
|
|
if !r.readFull(r.buf[:len(magicBody)], false) {
|
|
return 0, r.err
|
|
}
|
|
if string(r.buf[:len(magicBody)]) != magicBody {
|
|
if string(r.buf[:len(magicBody)]) != magicBodySnappy {
|
|
r.err = ErrCorrupt
|
|
return 0, r.err
|
|
} else {
|
|
r.snappyFrame = true
|
|
}
|
|
} else {
|
|
r.snappyFrame = false
|
|
}
|
|
continue
|
|
}
|
|
|
|
if chunkType <= 0x7f {
|
|
// Section 4.5. Reserved unskippable chunks (chunk types 0x02-0x7f).
|
|
// fmt.Printf("ERR chunktype: 0x%x\n", chunkType)
|
|
r.err = ErrUnsupported
|
|
return 0, r.err
|
|
}
|
|
// Section 4.4 Padding (chunk type 0xfe).
|
|
// Section 4.6. Reserved skippable chunks (chunk types 0x80-0xfd).
|
|
if chunkLen > maxChunkSize {
|
|
// fmt.Printf("ERR chunkLen: 0x%x\n", chunkLen)
|
|
r.err = ErrUnsupported
|
|
return 0, r.err
|
|
}
|
|
|
|
// fmt.Printf("skippable: ID: 0x%x, len: 0x%x\n", chunkType, chunkLen)
|
|
if !r.skippable(r.buf, chunkLen, false, chunkType) {
|
|
return 0, r.err
|
|
}
|
|
}
|
|
return 0, r.err
|
|
}
|
|
|
|
// Skip will skip n bytes forward in the decompressed output.
|
|
// For larger skips this consumes less CPU and is faster than reading output and discarding it.
|
|
// CRC is not checked on skipped blocks.
|
|
// io.ErrUnexpectedEOF is returned if the stream ends before all bytes have been skipped.
|
|
// If a decoding error is encountered subsequent calls to Read will also fail.
|
|
func (r *Reader) Skip(n int64) error {
|
|
if n < 0 {
|
|
return errors.New("attempted negative skip")
|
|
}
|
|
if r.err != nil {
|
|
return r.err
|
|
}
|
|
|
|
for n > 0 {
|
|
if r.i < r.j {
|
|
// Skip in buffer.
|
|
// decoded[i:j] contains decoded bytes that have not yet been passed on.
|
|
left := int64(r.j - r.i)
|
|
if left >= n {
|
|
tmp := int64(r.i) + n
|
|
if tmp > math.MaxInt32 {
|
|
return errors.New("s2: internal overflow in skip")
|
|
}
|
|
r.i = int(tmp)
|
|
return nil
|
|
}
|
|
n -= int64(r.j - r.i)
|
|
r.i = r.j
|
|
}
|
|
|
|
// Buffer empty; read blocks until we have content.
|
|
if !r.readFull(r.buf[:4], true) {
|
|
if r.err == io.EOF {
|
|
r.err = io.ErrUnexpectedEOF
|
|
}
|
|
return r.err
|
|
}
|
|
chunkType := r.buf[0]
|
|
if !r.readHeader {
|
|
if chunkType != chunkTypeStreamIdentifier {
|
|
r.err = ErrCorrupt
|
|
return r.err
|
|
}
|
|
r.readHeader = true
|
|
}
|
|
chunkLen := int(r.buf[1]) | int(r.buf[2])<<8 | int(r.buf[3])<<16
|
|
|
|
// The chunk types are specified at
|
|
// https://github.com/google/snappy/blob/master/framing_format.txt
|
|
switch chunkType {
|
|
case chunkTypeCompressedData:
|
|
r.blockStart += int64(r.j)
|
|
// Section 4.2. Compressed data (chunk type 0x00).
|
|
if chunkLen < checksumSize {
|
|
r.err = ErrCorrupt
|
|
return r.err
|
|
}
|
|
if !r.ensureBufferSize(chunkLen) {
|
|
if r.err == nil {
|
|
r.err = ErrUnsupported
|
|
}
|
|
return r.err
|
|
}
|
|
buf := r.buf[:chunkLen]
|
|
if !r.readFull(buf, false) {
|
|
return r.err
|
|
}
|
|
checksum := uint32(buf[0]) | uint32(buf[1])<<8 | uint32(buf[2])<<16 | uint32(buf[3])<<24
|
|
buf = buf[checksumSize:]
|
|
|
|
dLen, err := DecodedLen(buf)
|
|
if err != nil {
|
|
r.err = err
|
|
return r.err
|
|
}
|
|
if dLen > r.maxBlock {
|
|
r.err = ErrCorrupt
|
|
return r.err
|
|
}
|
|
// Check if destination is within this block
|
|
if int64(dLen) > n {
|
|
if len(r.decoded) < dLen {
|
|
r.decoded = make([]byte, dLen)
|
|
}
|
|
if _, err := Decode(r.decoded, buf); err != nil {
|
|
r.err = err
|
|
return r.err
|
|
}
|
|
if crc(r.decoded[:dLen]) != checksum {
|
|
r.err = ErrCorrupt
|
|
return r.err
|
|
}
|
|
} else {
|
|
// Skip block completely
|
|
n -= int64(dLen)
|
|
r.blockStart += int64(dLen)
|
|
dLen = 0
|
|
}
|
|
r.i, r.j = 0, dLen
|
|
continue
|
|
case chunkTypeUncompressedData:
|
|
r.blockStart += int64(r.j)
|
|
// Section 4.3. Uncompressed data (chunk type 0x01).
|
|
if chunkLen < checksumSize {
|
|
r.err = ErrCorrupt
|
|
return r.err
|
|
}
|
|
if !r.ensureBufferSize(chunkLen) {
|
|
if r.err != nil {
|
|
r.err = ErrUnsupported
|
|
}
|
|
return r.err
|
|
}
|
|
buf := r.buf[:checksumSize]
|
|
if !r.readFull(buf, false) {
|
|
return r.err
|
|
}
|
|
checksum := uint32(buf[0]) | uint32(buf[1])<<8 | uint32(buf[2])<<16 | uint32(buf[3])<<24
|
|
// Read directly into r.decoded instead of via r.buf.
|
|
n2 := chunkLen - checksumSize
|
|
if n2 > len(r.decoded) {
|
|
if n2 > r.maxBlock {
|
|
r.err = ErrCorrupt
|
|
return r.err
|
|
}
|
|
r.decoded = make([]byte, n2)
|
|
}
|
|
if !r.readFull(r.decoded[:n2], false) {
|
|
return r.err
|
|
}
|
|
if int64(n2) < n {
|
|
if crc(r.decoded[:n2]) != checksum {
|
|
r.err = ErrCorrupt
|
|
return r.err
|
|
}
|
|
}
|
|
r.i, r.j = 0, n2
|
|
continue
|
|
case chunkTypeStreamIdentifier:
|
|
// Section 4.1. Stream identifier (chunk type 0xff).
|
|
if chunkLen != len(magicBody) {
|
|
r.err = ErrCorrupt
|
|
return r.err
|
|
}
|
|
if !r.readFull(r.buf[:len(magicBody)], false) {
|
|
return r.err
|
|
}
|
|
if string(r.buf[:len(magicBody)]) != magicBody {
|
|
if string(r.buf[:len(magicBody)]) != magicBodySnappy {
|
|
r.err = ErrCorrupt
|
|
return r.err
|
|
}
|
|
}
|
|
|
|
continue
|
|
}
|
|
|
|
if chunkType <= 0x7f {
|
|
// Section 4.5. Reserved unskippable chunks (chunk types 0x02-0x7f).
|
|
r.err = ErrUnsupported
|
|
return r.err
|
|
}
|
|
if chunkLen > maxChunkSize {
|
|
r.err = ErrUnsupported
|
|
return r.err
|
|
}
|
|
// Section 4.4 Padding (chunk type 0xfe).
|
|
// Section 4.6. Reserved skippable chunks (chunk types 0x80-0xfd).
|
|
if !r.skippable(r.buf, chunkLen, false, chunkType) {
|
|
return r.err
|
|
}
|
|
}
|
|
return nil
|
|
}
|
|
|
|
// ReadSeeker provides random or forward seeking in compressed content.
|
|
// See Reader.ReadSeeker
|
|
type ReadSeeker struct {
|
|
*Reader
|
|
readAtMu sync.Mutex
|
|
}
|
|
|
|
// ReadSeeker will return an io.ReadSeeker and io.ReaderAt
|
|
// compatible version of the reader.
|
|
// If 'random' is specified the returned io.Seeker can be used for
|
|
// random seeking, otherwise only forward seeking is supported.
|
|
// Enabling random seeking requires the original input to support
|
|
// the io.Seeker interface.
|
|
// A custom index can be specified which will be used if supplied.
|
|
// When using a custom index, it will not be read from the input stream.
|
|
// The ReadAt position will affect regular reads and the current position of Seek.
|
|
// So using Read after ReadAt will continue from where the ReadAt stopped.
|
|
// No functions should be used concurrently.
|
|
// The returned ReadSeeker contains a shallow reference to the existing Reader,
|
|
// meaning changes performed to one is reflected in the other.
|
|
func (r *Reader) ReadSeeker(random bool, index []byte) (*ReadSeeker, error) {
|
|
// Read index if provided.
|
|
if len(index) != 0 {
|
|
if r.index == nil {
|
|
r.index = &Index{}
|
|
}
|
|
if _, err := r.index.Load(index); err != nil {
|
|
return nil, ErrCantSeek{Reason: "loading index returned: " + err.Error()}
|
|
}
|
|
}
|
|
|
|
// Check if input is seekable
|
|
rs, ok := r.r.(io.ReadSeeker)
|
|
if !ok {
|
|
if !random {
|
|
return &ReadSeeker{Reader: r}, nil
|
|
}
|
|
return nil, ErrCantSeek{Reason: "input stream isn't seekable"}
|
|
}
|
|
|
|
if r.index != nil {
|
|
// Seekable and index, ok...
|
|
return &ReadSeeker{Reader: r}, nil
|
|
}
|
|
|
|
// Load from stream.
|
|
r.index = &Index{}
|
|
|
|
// Read current position.
|
|
pos, err := rs.Seek(0, io.SeekCurrent)
|
|
if err != nil {
|
|
return nil, ErrCantSeek{Reason: "seeking input returned: " + err.Error()}
|
|
}
|
|
err = r.index.LoadStream(rs)
|
|
if err != nil {
|
|
if err == ErrUnsupported {
|
|
// If we don't require random seeking, reset input and return.
|
|
if !random {
|
|
_, err = rs.Seek(pos, io.SeekStart)
|
|
if err != nil {
|
|
return nil, ErrCantSeek{Reason: "resetting stream returned: " + err.Error()}
|
|
}
|
|
r.index = nil
|
|
return &ReadSeeker{Reader: r}, nil
|
|
}
|
|
return nil, ErrCantSeek{Reason: "input stream does not contain an index"}
|
|
}
|
|
return nil, ErrCantSeek{Reason: "reading index returned: " + err.Error()}
|
|
}
|
|
|
|
// reset position.
|
|
_, err = rs.Seek(pos, io.SeekStart)
|
|
if err != nil {
|
|
return nil, ErrCantSeek{Reason: "seeking input returned: " + err.Error()}
|
|
}
|
|
return &ReadSeeker{Reader: r}, nil
|
|
}
|
|
|
|
// Seek allows seeking in compressed data.
|
|
func (r *ReadSeeker) Seek(offset int64, whence int) (int64, error) {
|
|
if r.err != nil {
|
|
if !errors.Is(r.err, io.EOF) {
|
|
return 0, r.err
|
|
}
|
|
// Reset on EOF
|
|
r.err = nil
|
|
}
|
|
|
|
// Calculate absolute offset.
|
|
absOffset := offset
|
|
|
|
switch whence {
|
|
case io.SeekStart:
|
|
case io.SeekCurrent:
|
|
absOffset = r.blockStart + int64(r.i) + offset
|
|
case io.SeekEnd:
|
|
if r.index == nil {
|
|
return 0, ErrUnsupported
|
|
}
|
|
absOffset = r.index.TotalUncompressed + offset
|
|
default:
|
|
r.err = ErrUnsupported
|
|
return 0, r.err
|
|
}
|
|
|
|
if absOffset < 0 {
|
|
return 0, errors.New("seek before start of file")
|
|
}
|
|
|
|
if !r.readHeader {
|
|
// Make sure we read the header.
|
|
_, r.err = r.Read([]byte{})
|
|
if r.err != nil {
|
|
return 0, r.err
|
|
}
|
|
}
|
|
|
|
// If we are inside current block no need to seek.
|
|
// This includes no offset changes.
|
|
if absOffset >= r.blockStart && absOffset < r.blockStart+int64(r.j) {
|
|
r.i = int(absOffset - r.blockStart)
|
|
return r.blockStart + int64(r.i), nil
|
|
}
|
|
|
|
rs, ok := r.r.(io.ReadSeeker)
|
|
if r.index == nil || !ok {
|
|
currOffset := r.blockStart + int64(r.i)
|
|
if absOffset >= currOffset {
|
|
err := r.Skip(absOffset - currOffset)
|
|
return r.blockStart + int64(r.i), err
|
|
}
|
|
return 0, ErrUnsupported
|
|
}
|
|
|
|
// We can seek and we have an index.
|
|
c, u, err := r.index.Find(absOffset)
|
|
if err != nil {
|
|
return r.blockStart + int64(r.i), err
|
|
}
|
|
|
|
// Seek to next block
|
|
_, err = rs.Seek(c, io.SeekStart)
|
|
if err != nil {
|
|
return 0, err
|
|
}
|
|
|
|
r.i = r.j // Remove rest of current block.
|
|
r.blockStart = u - int64(r.j) // Adjust current block start for accounting.
|
|
if u < absOffset {
|
|
// Forward inside block
|
|
return absOffset, r.Skip(absOffset - u)
|
|
}
|
|
if u > absOffset {
|
|
return 0, fmt.Errorf("s2 seek: (internal error) u (%d) > absOffset (%d)", u, absOffset)
|
|
}
|
|
return absOffset, nil
|
|
}
|
|
|
|
// ReadAt reads len(p) bytes into p starting at offset off in the
|
|
// underlying input source. It returns the number of bytes
|
|
// read (0 <= n <= len(p)) and any error encountered.
|
|
//
|
|
// When ReadAt returns n < len(p), it returns a non-nil error
|
|
// explaining why more bytes were not returned. In this respect,
|
|
// ReadAt is stricter than Read.
|
|
//
|
|
// Even if ReadAt returns n < len(p), it may use all of p as scratch
|
|
// space during the call. If some data is available but not len(p) bytes,
|
|
// ReadAt blocks until either all the data is available or an error occurs.
|
|
// In this respect ReadAt is different from Read.
|
|
//
|
|
// If the n = len(p) bytes returned by ReadAt are at the end of the
|
|
// input source, ReadAt may return either err == EOF or err == nil.
|
|
//
|
|
// If ReadAt is reading from an input source with a seek offset,
|
|
// ReadAt should not affect nor be affected by the underlying
|
|
// seek offset.
|
|
//
|
|
// Clients of ReadAt can execute parallel ReadAt calls on the
|
|
// same input source. This is however not recommended.
|
|
func (r *ReadSeeker) ReadAt(p []byte, offset int64) (int, error) {
|
|
r.readAtMu.Lock()
|
|
defer r.readAtMu.Unlock()
|
|
_, err := r.Seek(offset, io.SeekStart)
|
|
if err != nil {
|
|
return 0, err
|
|
}
|
|
n := 0
|
|
for n < len(p) {
|
|
n2, err := r.Read(p[n:])
|
|
if err != nil {
|
|
// This will include io.EOF
|
|
return n + n2, err
|
|
}
|
|
n += n2
|
|
}
|
|
return n, nil
|
|
}
|
|
|
|
// ReadByte satisfies the io.ByteReader interface.
|
|
func (r *Reader) ReadByte() (byte, error) {
|
|
if r.err != nil {
|
|
return 0, r.err
|
|
}
|
|
if r.i < r.j {
|
|
c := r.decoded[r.i]
|
|
r.i++
|
|
return c, nil
|
|
}
|
|
var tmp [1]byte
|
|
for i := 0; i < 10; i++ {
|
|
n, err := r.Read(tmp[:])
|
|
if err != nil {
|
|
return 0, err
|
|
}
|
|
if n == 1 {
|
|
return tmp[0], nil
|
|
}
|
|
}
|
|
return 0, io.ErrNoProgress
|
|
}
|
|
|
|
// SkippableCB will register a callback for chunks with the specified ID.
|
|
// ID must be a Reserved skippable chunks ID, 0x80-0xfd (inclusive).
|
|
// For each chunk with the ID, the callback is called with the content.
|
|
// Any returned non-nil error will abort decompression.
|
|
// Only one callback per ID is supported, latest sent will be used.
|
|
// Sending a nil function will disable previous callbacks.
|
|
// You can peek the stream, triggering the callback, by doing a Read with a 0
|
|
// byte buffer.
|
|
func (r *Reader) SkippableCB(id uint8, fn func(r io.Reader) error) error {
|
|
if id < 0x80 || id >= chunkTypePadding {
|
|
return fmt.Errorf("ReaderSkippableCB: Invalid id provided, must be 0x80-0xfe (inclusive)")
|
|
}
|
|
r.skippableCB[id-0x80] = fn
|
|
return nil
|
|
}
|